당신은 주제를 찾고 있습니까 “pure vs purge oil mist lubrication – LOMA AIR + OIL MIST LUBRICATION SYSTEM“? 다음 카테고리의 웹사이트 https://chewathai27.com/you 에서 귀하의 모든 질문에 답변해 드립니다: https://chewathai27.com/you/blog. 바로 아래에서 답을 찾을 수 있습니다. 작성자 Loma centralized lubrication system 이(가) 작성한 기사에는 조회수 893회 및 좋아요 15개 개의 좋아요가 있습니다.
Although pure mist has been utilized on sleeve bearings and gears, applying oil mist in a purge mist application is easier and cheaper. Many of the benefits of pure mist are not available from a purge mist system.Pure Oil Mist or Dry Sump Lubrication describes the lubrication of rolling element bearings without an oil sump or grease in the bearing housing; the oil mist is the only means of lubrication for the bearings. Oil mist is an aerosol of oil particles that are 1 to 3 μ in size.Properly installed oil mist systems offer the following advantages: No oil changes and reduced maintenance requirements. Reduced lubricant consumption (up to 70 percent compared to sump lubrication) Lower friction and reduced bearing temperatures.
Table of Contents
pure vs purge oil mist lubrication 주제에 대한 동영상 보기
여기에서 이 주제에 대한 비디오를 시청하십시오. 주의 깊게 살펴보고 읽고 있는 내용에 대한 피드백을 제공하세요!
d여기에서 LOMA AIR + OIL MIST LUBRICATION SYSTEM – pure vs purge oil mist lubrication 주제에 대한 세부정보를 참조하세요
pure vs purge oil mist lubrication 주제에 대한 자세한 내용은 여기를 참조하세요.
Oil Mist Lubrication System (With PDF) – What Is Piping
Pure & Purge Mist Lubrication. Pure Mist Lubrication System-. The bearing is lubricated by oil mist, not oil. Bearings can run 10-15 degC cooler with pure …
Source: whatispiping.com
Date Published: 6/10/2021
View: 8286
Oil Mist lubrication system – Dropsa
The following diagrams indicate the difference between PURE and PURGE, as shown in the below images. PURE OIL MIST LUBRICATION In a Pure Oil …
Source: www.dropsa.com
Date Published: 6/9/2022
View: 8981
GETTING THE FACTS ON OIL MIST LUBRICATION … – CORE
There are two methods of applying oil mist: dry sump or pure mist and wet sump or purge mist. The dry sump and wet sump terms are not to be confused with dry …
Source: core.ac.uk
Date Published: 2/27/2022
View: 913
Oil Mist Systems In The Plant-Wide Lubrication Of General …
Wet sump (“purge mist”) vs. dry sump (“pure mist”) In the wet sump method, a liqu oil level is maintained and the mist fills the housing …
Source: www.efficientplantmag.com
Date Published: 4/18/2021
View: 2249
Oil Mist Lubrication
Figure 1: Pure oil mist in centrifugal pump. Note the collecting bottle at bottom of pump bearing housing. Figure 2: Purge mist applied on steam turbine …
Source: sicelub.com
Date Published: 4/7/2022
View: 9007
Proper Application of Pure Oil Mist Lubrication in Refinery …
Oil mist supply pipes were already installed for purge mist, and he correctly surmised that it would be better to avo the traditional oil ring …
Source: www.pumpsandsystems.com
Date Published: 7/26/2022
View: 6411
Oil mist lubrication – Pump Industry Magazine
Pure Oil Mist or Dry Sump Lubrication describes the lubrication of rolling element bearings without an oil sump or grease in the bearing …
Source: www.pumpindustry.com.au
Date Published: 4/11/2022
View: 1180
Oil Mist Lubrication System – Thai
Oil Mist purge over oil level in housing with slight positive pressure to keep oil free from contamination. … Continuously coats all internal surfaces with …
Source: www.longwinthai.com
Date Published: 11/3/2021
View: 4531
주제와 관련된 이미지 pure vs purge oil mist lubrication
주제와 관련된 더 많은 사진을 참조하십시오 LOMA AIR + OIL MIST LUBRICATION SYSTEM. 댓글에서 더 많은 관련 이미지를 보거나 필요한 경우 더 많은 관련 기사를 볼 수 있습니다.
주제에 대한 기사 평가 pure vs purge oil mist lubrication
- Author: Loma centralized lubrication system
- Views: 조회수 893회
- Likes: 좋아요 15개
- Date Published: 2020. 8. 13.
- Video Url link: https://www.youtube.com/watch?v=Gm_B7VzLjpw
What is pure oil mist?
Pure Oil Mist or Dry Sump Lubrication describes the lubrication of rolling element bearings without an oil sump or grease in the bearing housing; the oil mist is the only means of lubrication for the bearings. Oil mist is an aerosol of oil particles that are 1 to 3 μ in size.
What are the advantages of mist lubrication system?
Properly installed oil mist systems offer the following advantages: No oil changes and reduced maintenance requirements. Reduced lubricant consumption (up to 70 percent compared to sump lubrication) Lower friction and reduced bearing temperatures.
How does mist lubrication system work?
Oil Mist is a centralized system in which the energy of compressed gas, usually air taken from the plant supply, is used to atomize oil. Oil is then conveyed by the air in a low pressure distribution system to multiple points of lubricant application. The compressed air is passed through a venturi.
Which type of lubrication system is used in two stock engine?
In two-stroke engines, mist lubrication is used where crankcase lubrication is not suitable. In a two-stroke engine, as the charge is compressed in the crankcase, it is not possible to have the lubricating oil in the sump. Hence, mist lubrication is adopted in practice.
Where is oil mist lubrication used?
Oil mist applications are bearings of all types and gears that are located in rotating equipment found in process industries. The most common applications for oil mist lubrication in the HPI are pumps and motors. Pillow block bearings, turbines and gear boxes are also common applications but not in the same quantities.
How do you use hair oil mist?
Dry oils sprays release the oil as a mist to make it easy to apply evenly throughout your hair. Most products will give specific instructions on the back of the container. As a general guideline, you can hold the can 8 to 10 inches from your hair and spray your hair evenly.
What are the two types of lubrication system?
There are three different types of lubrication: boundary, mixed and full film. Each type is different, but they all rely on a lubricant and the additives within the oils to protect against wear. Full-film lubrication can be broken down into two forms: hydrodynamic and elastohydrodynamic.
What is oil mist in engine?
Oil Mist is created in the crankcase when the lubricating oil is splashed by moving and rotating parts of the engine. This oil mist reduces the flash point of the oil, allowing it to catch fire in presence of a hot spot.
What is oil mist separator?
An Oil Mist Separator, also called Oil Mist Eliminator or demister, is the technical term for a filter system that is used where power generating engines or turbines operate, for example in power plants and refineries. To ensure trouble-free operation, the turbine bearings are lubricated with oil.
What kind of oil do you use in an air Oiler?
Use only clean oil, SAE 10 or lighter is best.
What is mist feed?
Scotts Osmocote Mist+Feed for Indoor Plants is a ready to use mist that is rapidly absorbed by leaves to help you grow beautiful green, glossy foliage and protect from the dry environments found in our homes.
Which lubrication system is generally used?
In most automobiles, which lubrication system is commonly used? Explanation: Pressure type lubrication is used commonly in most automobiles. In this system, oil is drawn in from the sump and forced to all the main bearings of the crankshaft through distributing channels.
What are the different types of lubricant?
There are three main types of lubricants: oil-based, water-based, and silicone-based. The best lubricant for women depends on their needs.
What are the 4 main parts in a lubrication system?
What are the components of a lubrication system? Oil pan, pickup tube, oil pump, pressure relief valve, oil filter, spurt holes and galleries, and sump.
How is oil mist formed?
Formation of Oil Mist
Oil mist may form when high pressure fuel oil, lubricating oil, hydraulic oil, or other oil is sprayed through a narrow crack, or when leaked oil connects with a high temperature surface, vaporizes, and comes in contact with low air temperature.
What is oil mist separator?
An Oil Mist Separator, also called Oil Mist Eliminator or demister, is the technical term for a filter system that is used where power generating engines or turbines operate, for example in power plants and refineries. To ensure trouble-free operation, the turbine bearings are lubricated with oil.
What is a Reclassifier?
Silencer/reclassifiers are integral silencer and oil separation devices. When installed at the exhaust ports of pneumatic valves they reduce exhaust noise and capture lubricants contained in the exhausting air. They are used on valve-cylinder applications and on air tools with piped exhausts.
What is ring lubrication?
Definition of ring lubrication
: lubrication of a shaft bearing by means of a ring riding on the shaft in rotation and bringing up oil from a well into which it dips.
Oil Mist Lubrication in the Hydrocarbon Processing Industry
A survey on oil mist usage in U.S. refineries found that almost 50 percent of the refineries use oil mist lubrication extensively. The survey was based on large-scale systems with a fully monitored oil mist generator (OMG), which serves multiple pumps and drivers. The average pump population per system is 30 to 50 pumps and drivers, usually pure mist or dry sump applications.
Major oil companies were the first to adopt and use oil mist. Now many of the smaller and even the independent refineries recognize the benefits of oil mist lubrication and are using it to achieve improved reliability with their smaller workforces.
What is Oil Mist and How it Works
Oil mist is an aerosol. It is not a Volatile Organic Compound (VOC) or a vapor. It is a mixture of one part oil to 200,000 equal parts of air. It is a lean mixture that will not support combustion and will not explode. The appearance of oil mist resembles cigarette smoke or steam drifting from a pump or motor through a vent line. Using oil mist lubrication, a typical application in the hydrocarbon processing industry will reduce oil consumption up to 40 percent over the traditional oil sump method of lubrication.
Oil Mist System
Oil mist is generated by passing high velocity air over or through an orifice that pulls oil into the air stream. The high velocity air shatters the oil into particle sizes of one to three microns, thus the resemblance to cigarette smoke. Airflow transports these small oil particles through a piping system to the equipment to be lubricated.
Prior to being applied to a bearing, the small particles of oil are passed through an orifice, reclassifier or mist fitting, causing the small particles to impinge on each other and grow in size. The heavier particles are then large enough to wet the surfaces and provide adequate lubrication for most rolling element bearings. It is excellent lubrication for bearings operating at 1,800 to 3,600 rpm and it is often the preferred method of lubrication for bearings operating in the 10,000 to 15,000 rpm range where splash lubrication is ineffective.
Because an oil mist system has no moving parts, there is little chance of failure. The only requirements for generating oil mist are clean air and clean oil. The electric monitors control and help maintain a constant mist density. Many systems without electrical devices are in operation, and may be serving critical equipment. There are numerous systems in refineries serving 30 to 50 pumps in pure mist applications that do not have the redundant or backup units.
Pure Oil Mist
Currently, there is only one OSHA regulation concerning oil mist: “Oil mist cannot contain more than five mg of oil per cubic meter of air that a person can be exposed to in an eight-hour period.” At this time, there are no other laws, regulations or mandates from the government controlling the use of oil mist lubrication.
Benefits of Oil Mist Lubrication
With the hydrocarbon processing industry (HPI) consolidating to reduce cost, the trend to improve machinery reliability is a top priority. The companies using oil mist lubrication see the mean-time-between-repair (MTBR) increase from 24 to 36 months up to 48 to 60 months. With the average repair cost per pump between $5,000 and $10,000, the reduced repair costs attributed to oil mist lubrication can have a dramatic impact on a refinery’s bottom line.
Oil mist lubrication provides a number of important benefits, including:
Reduced bearing failures
Decreased manpower for lubrication tasks
Elimination of oil changes
Reduced fire risk
Improved mechanical seal life
The reduction of the work force in many plants has stimulated the discussion of oil mist in maintenance meetings. The oil mist system allows the reduced staff to spend less time on the tasks of lubrication and more time on high priority tasks, while lubrication is provided in the right amount at the right time. Other possible cost credits include the reduction in fire incidents, mechanical seal failures and exposure to hazardous chemicals.
Maintenance people often ask how oil mist can reduce mechanical seal failures when oil mist is not directly applied to the seals. It is common for an oil mist salesman to hear “We don’t have bearing failures. Mechanical seal failures are more common.” Consider this: With the bearing attached to the same shaft as the mechanical seal, and because everything affects the mechanical seal, it is safe to assume that when bearings last longer mechanical seals will last longer. The same is true when pump failures cause exposure to chemicals; by reducing the number of pump failures, the chance of exposure is reduced.
One of the most favorable benefits of pure oil mist lubrication is that it reduces the operating temperature of the bearing it lubricates, typically 20ºF to 35ºF (-6ºC to 2ºC). Heat is generated by friction created from rolling the bearing through an oil sump at a high speed. When the oil sump is drained away, there is no oil to generate heat and no sump in which to retain it, so the temperature drops. With every 10ºF (5.6ºC) reduction in temperature, the bearing fatigue life is increased by 11 percent.
See Results of Oil Mist Case Study
Oil mist lubrication, while often superior to the traditional oil sump lubrication, not only lubricates equipment during operation but it also protects and preserves internal components (bearings and gears) when equipment is idle. Idle or spare equipment is subject to surface corrosion on internal components due to the ingress of atmospheric moisture, and the possibility of fretting wear caused by ground vibration.
Idle equipment will experience thermal cycling, or breathing contaminated air as temperature changes, many times throughout a 24-hour period. This causes the surrounding atmosphere to enter the bearing or gear cavity. The atmosphere may be laden with moisture, dust or even acid fumes, depending upon the contaminant within the environment. The atmospheric contaminants accumulate on machine surfaces, causing corrosion and reducing equipment life.
In contrast, oil mist builds a slight positive pressure, approximately 0.25 inches water, in the cavity. This pressure prevents the intrusion of the airborne contaminants, and internal surfaces and components are coated with a protective film of oil. The oil film on internal components guards against corrosion, and protects against fretting wear by creating a thin film of separation.
Many facilities now use oil mist storage systems to protect and preserve equipment stored in warehouses. Large-scale storage yards with oil mist are also used in grass-roots plants during the construction phase to protect equipment over extended periods of time. Equipment such as pumps, motors, turbines, diesel engines, large lube oil skids, vertical sump pumps and gearboxes may be stored on a single mist system.
A refinery built in Thailand a few years ago used oil mist storage and experienced only one failure during plant startup. Conversely, refineries not using oil mist storage may experience numerous failures during equipment testing and startup.
Most Common Equipment Applications and How to Apply Oil Mist
The most common application for oil mist is the typical overhung process pump. Pumps are the workhorses in the HPI and are subjected to harsh chemicals, extreme temperatures, long intervals between oil changes, high thrust loads and other conditions for which they were not designed.
For years, maintenance/reliability engineers have experimented with how to apply oil mist, and have been pushing the pump manufacturers to adapt their equipment for oil mist. API 610 8th Edition Pump Standards now embrace oil mist lubrication. Standards of applying oil mist are gaining ground and making the process even more successful.
Motors are an excellent opportunity for oil mist lubrication, but because the rotors, stators and bearings are housed together, it is not an easy application. Oil in the windings is not the problem; it’s the housekeeping situation that makes the application less desirable on motors. In recent years, motor manufacturers have responded to the market’s wishes by researching the use of oil mist lubrication on motors.
As a result, housekeeping has greatly improved. Oil mist is a vast improvement over the traditional grease lubrication found on most motors. With oil mist, the bearing receives a fresh, clean, continuous supply of oil versus a single greasing at the factory or repair shop and infrequent applications of lubricant thereafter.
Pillow block bearings are also candidates for oil mist lubrication because they are normally lubricated with grease or a small oil sump. Grease and the oil baths both retain heat which increases operating temperature. Or, the small lubricant supply may become contaminated from the environment. Both heat and contaminants reduce bearing life.
Two common problems with grease lubrication are overlubrication and underlubrication. Applying the right amount of lubricant at the right time is difficult unless the grease is applied with an automatic system. Set up to control the frequency and amount of grease applied, the automated system can eliminate human error. Mist provides a constant supply of lubricant to properly lubricate the bearings.
Most pumps, motors and pillow block bearings with rolling element bearings have oil mist applied as pure mist or dry sump lubrication. Ideally, oil mist is applied in the upper quadrant on one side of the bearing and exits through a vent or drain from a low point on the opposite side. This means that the oil mist is the only source of lubrication, because there is no oil sump or grease to provide lubrication. Lubricating bearings with oily air may sound risky, but in many applications it has proven itself superior to the oil sump and grease lubrication.
Another way to apply oil mist is purge mist or wet sump lubrication. This requires an oil sump to be maintained in the bearing housing. The oil mist is applied as a purge above the oil level to prevent the intrusion of airborne contaminates. This method is commonly used on sleeve or plain bearings and in gearboxes. Small steam turbines with sleeve bearings are excellent applications due to the steam in the vicinity of the bearing housings. Cooling tower gearboxes also benefit from purge mist or wet sump oil mist due to the harsh (wet) environment around the gearbox.
Sleeve bearings and gears have too much surface area requiring lubrication to make them candidates for pure mist. Although pure mist has been utilized on sleeve bearings and gears, applying oil mist in a purge mist application is easier and cheaper. Many of the benefits of pure mist are not available from a purge mist system.
Limitations and Disadvantages of Oil Mist Lubrication
The main limitations and/or disadvantages of oil mist lubrication are the lack of knowledge about the operation and the application of oil mist. Because airflow delivers the oil mist (oil particles) to the point of lubrication, the suspension of the oil particles is important. Gravity has an effect on the oil particles, causing them to settle if they do not arrive at the point of lubrication within approximately five minutes. With the mist traveling at a velocity of 20 ft./sec., it can easily reach from the point of origin to the point of lubrication.
Distance is the easy part when designing an oil mist system. Achieving the proper pipe slope and pipe diameters is also critical to receiving benefits from the system. Pipe fitters and instrument personnel must route pipe and tubing according to the oil mist system’s requirements. Therefore, choose the installers of your oil mist system carefully.
Users need to be aware of and avoid overzealous application of oil mist. It is a common belief that “if a little oil does a little good, then a lot of oil will do a lot of good.” Oversizing of the reclassifier or mist fitting to improve lubrication has little or no impact on improving bearing life.
In fact, when oil is seen dripping from the equipment, it is due to improper sizing of the reclassifiers and not calibrating the OMG to the designed oil consumption. Oversized reclassifiers and overzealous application can cause a system that would normally consume one gallon of oil per day to consume three or four gallons of oil per day.
Cost/Benefit Comparison to Other Single-Point Lubrication Devices
As a rule, automated lubrication systems have established their value to industry. Although there may be areas of overlap, one type of system generally cannot be used in place of another. The exception to this rule is the air/oil system commonly used in place of a grease system. The most common types of automated systems are grease, circulating oil, oil mist, air/oil and the high-pressure compressor systems.
Grease is used in several applications, ranging from the manually operated grease gun to the injector system, the single-line system and the dual-line system. The grease gun is the most common application method. It is typically preferred when only a few points require lubrication or when management does not want to spend the money for an automatic system.
A grease gun delivers grease in three ways:the right amount, too much and too little. Too much and too little are not good for the equipment. Getting the right amount of grease requires someone well-trained in knowing how much grease is required on each piece of equipment and how to apply it. A grease gun is the least expensive method of applying grease, but how does it affect machinery reliability?
Injector systems are common on air-cooled heat exchangers and sump pumps found in most refineries. Single-line and dual-line systems can serve these same applications; the main differences are features and pricing.
Circulation oil systems have also established their place, not overlapping where other systems can be used. The air/oil system, common to the steel industry, does not have much application in the HPI.
When comparing lubricating systems, an oil mist system is by far the easiest system to maintain; repairs are relatively simple. Maintenance normally consists of changing filters and doing walk-down inspections to look for broken or leaking lines. Repairs often involve a simple replacement of components in the oil mist unit or replacing a broken line.
The least expensive way to lubricate process pumps is with an oil sump to get started, but considering the total life cycle cost, the oil sump leaves a lot to be desired.
These systems vary in price from a few hundred dollars to $100,000 or more, depending on the number of lube points being served. The bottom line is: When reliability is of utmost importance and when your business relies on rotating equipment and bearings that require lubrication, an automated system may be required.
Reference:
1. Nelik, Lev. (1993). Bearing Life Extension and Reliability Features of Modern ANSI Pumps. Second International Conference on Improving Pump Reliability in Petroleum Refineries and Chemical and Natural Gas Plants.
About the Author
Oil mist lubrication
By Don Ehlert, Total Lubrication Management and Marty Williams
Oil mist is an ideal method of lubrication for rotating equipment in geographic regions that are windy, hot, humid, cold, damp, and dusty or anywhere that air borne particulates and moisture contamination may be present. Improving equipment reliability translates into a safer and more reliable plant with more production of product. Oil mist lubrication impedes the ingress of air borne contaminates, delivers clean oil and provides a dramatic impact on equipment MTBR (Mean Time Between Repair). One Australian refinery with approximately 500 pumps uses oil mist with excellent results.
Pure Oil Mist or Dry Sump Lubrication describes the lubrication of rolling element bearings without an oil sump or grease in the bearing housing; the oil mist is the only means of lubrication for the bearings. Oil mist is an aerosol of oil particles that are 1 to 3 μ in size. These small particles are referred to as dry mist; they are too small to lubricate contacting surfaces such as rolling element bearings. The dry mist, 1 to 3 μ sizes, allows the particles to be transported throughout a piping distribution system for lubrication of bearings in rotating equipment with an air flow up to 180 metres away from the oil mist generator, OMG (Oil Mist Generator). Ambient temperature swings have minimal impact on mist density after it leaves the OMG; provided the oil consumption rate is calibrated and proper flow rate is maintained, allowing it to be used in both hot and cold climates. Quality synthetic oils, PAO (Polyalphaolefin) or Diester, are recommended for use when ambient temperatures fall below 4° C (40° F). When mineral oils are used they must be paraffin free to prevent plugging of the reclassifier orifices. Reclassifiers are orifice fittings that convert the dry mist to wet mist, particle sizes larger than 15 μ and greater, for lubrication of the bearings rolling elements. Converting the dry mist to wet mist takes place by increasing the velocity of the small particles through the orifice where they coalesce, impinge on each other, and grow in size. These larger particles then wet out on surfaces and provide a clean, continuous supply of fresh oil. Oil particles that do not grow in size are vented away from the equipment housing and are referred to as stray mist. The loss of oil mist to individual or multiple pieces of equipment does not mean an immediate equipment failure. Should the oil mist system fail or header line breaks; it is recommended that normal system operation should be reinstated prior to the end of the current maintenance shift; within four (4) hours. It is not to be set aside for the next maintenance shift. There are only two items that can completely stop the generation of oil mist; the loss of air and/or oil. Electrical power is not required to generate oil mist. Clean, dry instrument air is required for the generation of oil mist; should the instrument air system fail the entire plant/unit will be shutting down and lubrication will not be an issue. The average oil mist system consumes approximately four litres, (one gallon), of oil in a 24 hour period. For large scale systems the OMG normally has a misting chamber that holds 23 to 34 litres (6 to 9 gallons) of oil with a bulk supply of 284 to 416 litres (75 to 110 gallons) standing by for refilling the misting chamber; the chances of running out of oil are extremely remote.
When applying oil mist to new or rebuilt equipment that may have dry bearings, without any lubricant on them, it is recommended that oil mist lines should be connected immediately after the machine is set in place to allow oil mist to coat the bearings prior to start-up. Equipment coming from a staging or storage area where bearing preservation was not provided is likely to have corrosion or particulate accumulation on the surfaces and bearing failure could be imminent with any method of lubrication.
Benefits of Pure Oil Mist
Pure oil mist is the ultimate oil filter as it breaks oil down to particle sizes of 1 to 3 μ. Larger particles that may bond with solid particulates or water are too heavy for transport throughout the distribution system and fall out of suspension.
The results are a continuous film of fresh clean oil being supplied to bearing surfaces in a pressurized/aerosol form. The bearing housings internal pressure is maintained at approximately 0.125 PSI which inhibits thermal cycling and/or the ingress of external air borne contaminates i.e. dust and moisture. The overall result is bearings without an oil sump operate up to 10° C (30° F) cooler with no recirculation of hot or contaminated oil. Oil mist not only lubricates the operating equipment; it also protects and preserves the standby or idle equipment insuring optimum bearing conditions when service is required. Using pure oil mist means a longer MTBR, mean time between repair, lower life cycle cost, reduced man hours for lubrication tasks, less equipment repairs, less oil inventory on site, less safety incidents due to mechanical seal failures which are initiated by premature bearing failure and less failures that may result in a fire.
Pure Oil Mist on pumps
Current API 610 pump specifications require that pumps shall have NPT (National Pipe Thread) connections outboard of the bearings. This allows oil mist to be applied into a central connection point between the bearings with venting outboard of the bearings or apply oil mist outboard of the bearings and venting out the bottom drain port as shown in figure 1. Either way insures that oil mist will pass through the bearings from side to side before exiting the bearing housing. The arrangement shown is the preferred method of lubrication as it allows the reclassifier to be sized for the individual bearings which is superior to having a single reclassifier serving both the thrust and radial bearings. When retrofitting oil mist to existing or older pumps the illustration shown is recommended when pumps are operating at 3000 RPM or higher and Kw is150 (200 HP) or greater. A single oil mist application point located in the middle point of the bearing housing is acceptable when operating less than 3000 RPM and Kw is less than 150 Kw (200HP) when lip or labyrinth seals are used. When bearing isolators are used two mist application points are mandatory. Oil mist lubricates pumps in operation and it protects and preserves the internal bearing surfaces from corrosion or false bernelling when sitting idle. Oil mist protects equipment 24/7 in all climates and conditions. Experience from many facilities has proven that pure oil mist is beneficial to rotating equipment reliability. User experience indicates that equipment having sat idle in excess of twelve months have been started without incident. There were no changes in vibration readings from when the machines had previously been in operation.
Pure Oil Mist pillow block bearings
Pillow block bearings are commonly lubricated with grease or an oil sump and these types of bearings are commonly used on FD (Forced Draft) or ID (Induced Draft) fans, figure 3. Grease becomes contaminated over time due to the natural process of bearing operation. Grease, like oil, requires changing at regular intervals and in un-spared equipment this may not be an option. The contaminated lubricant then becomes a rubbing compound that severely shortens the life of the bearings rolling elements. Idle bearings are subject to lubricant contamination from thermal cycling, condensation, wash down water and other forces that apply pressure, even a small amount, to the bearing housing seals. Keeping contaminates out is virtually impossible when oil sump is the norm; however the slight pressure created by the oil mist assists in keeping the bearing housing free of debris and moisture. Applying pure oil mist on pillow block bearings is very effective and inexpensive when the oil mist system is already in place for the surrounding equipment such as the pumps and motors.
When a large scale system is not in the immediate area a small modular unit may be used with excellent results. Modular units may be so basic that only a clean instrument air supply is required for operation, figure 4. These units are ideal for isolated equipment such as tank farm pumps or fan bearings where a larger system is not justified. A notable benefit of the oil mist system is the elimination of oil containers sitting around the machines which promotes cross contamination of lubricants and contamination from outside sources.
As a final point, any machine with rolling element bearings has the potential to be successfully lubricated with oil mist lubrication. Refinery experience demonstrated that bearing life is extended well past normal expectations; in many cases exceeding 130,000 hours in service with no degradation of the bearing structure. Special applications require a good understanding of oil mist and should not be attempted before seeking advice from qualified personnel. When properly applied oil mist will move equipment reliability to a much higher level.
About the Authors
Don Ehlert is currently Manager for EPC Sales at Total Lubrication Management Co., a Colfax Fluid Handling Company, located in Houston, TX. His current responsibilities include providing technical training and sales presentations. Don is also responsible for quotation assemblies for both domestic and foreign engineering companies and end users. He provides technical support to oil mist user’s world wide.
Since joining TLM in 1984, he has filled positions in equipment assembly, field maintenance, field installation, field management, sales and sales management. He has been instrumental with the development of oil mist related products and accessories for special applications.
Marty Williams started life as a Maintenance Technician in the mid-seventies at a major oil refinery in the UK, progressed through the ranks leaving in 1989 as a Maintenance Supervisor to emigrate to Australia.
He started at a major oil & gas facility in Western Australia in 1990 as a Maintenance Supervisor until 2000 when he was seconded to SRC in Singapore for nine months as a Reliability Engineer. On his return to Australia he became part of the Reliability Group working on all aspects of refinery machinery reliability. He introduced oil mist lubrication to the refinery in 2000 being the SPA for the project and has installed a total of thirteen oil mist systems covering the majority of rotating equipment and is now Machinery Engineer at the facility.
Find Chemicals And Plastics Related Companies In The Pump Industry Capability Guide
Guidelines for Oil Mist Lubrication
With improvements in oil formulations, oil mist lubrication systems are becoming increasingly popular in a variety of applications where only limited oil feed supply is required.
Examples include bearings of electric motors, pumps and compressors in many oil refineries and petrochemical plants1; gears, cams, chains and sliding surfaces of machines in steel and paper mills; construction equipment and an increasing range of other industrial applications.2
Compact mist supply units are also available for use with electric motors, machine tool spindles and similar local applications.
Oil mist systems present an attractive alternative both to grease at low-to-moderate speeds and to circulating oil systems for high speeds and high temperatures. Properly installed oil mist systems offer the following advantages:
No oil changes and reduced maintenance requirements
Reduced lubricant consumption (up to 70 percent compared to sump lubrication)
Lower friction and reduced bearing temperatures
Mist delivery pressure blocks entrance of contaminants
Less wear and increased life of machine elements
Lower capital costs
Newer air/oil systems are used in steel mills as alternatives to oil mist.3 To minimize loss of stray mist to the surrounding environment, liquid oil is injected from a positive displacement pump directly into the air stream. The oil, injected at time intervals, is then propelled by the air stream along the feed line as droplets in a spiral motion to enter a bearing as an oil spray.
Mist Supply
Oil mist is an aerosol mixture of very small oil droplets (one to five microns) suspended in air with the appearance of smoke. This mist is generated by passing compressed air through a venturi or vortex to siphon oil from a small central reservoir (Figure 1).4
Figure 1. Basic Oil Mist Generators
Pressure of this inlet air is regulated to properly deliver the oil. Droplets larger than about five to seven microns are not easily transported by the air stream, therefore, they are typically intercepted by a baffle for return to the reservoir.
Figure 2. Components of a Typical Oil Mist System
Figure 2 illustrates the main components of a typical oil mist system.2 It includes a pressure-controlled, filtered air supply, heaters to stabilize the air and reservoir oil temperatures at 130° to 170°F, a mist generator and distribution piping or tubing.
The initial dry mist generated then flows at 15 to 20 feet/second at distances up to 1,000 feet or more through pipes, tubing and hoses for delivery from headers commonly maintained at the pressure of a 20-inch water column (0.7 psi, 5 kPa).6 If the mist stream becomes turbulent above about 24 feet/second, mist droplets strike wall surfaces hard enough to stick and prematurely drop out of the mist stream.
The first 50 feet of a delivery header should be sloped back to the mist generator to return any droplets dropping out of the mist stream. Any longer feed manifolds and auxiliary headers should then be sloped either to drains or back to the generator to avoid low spots where trapped oil would interfere with mist flow.
Mist Delivery
Orifice fittings to meter mist supply to individual machine elements involve one of the three types of classifiers in Figure 3.
Figure 3. Classifier Fittings to Agglomerate Fine
Oil Particles in Dry Mist to Larger Droplets in
Wet Mist at Lubrication Points
A mist fitting consists of a simple metering orifice for delivering a fine wet spray with minimum condensation. As this fine spray then encounters rolling-motion elements – such as in ball or roller bearings, gears, chain or cams – the fine oil particles are agglomerated by the turbulence action and the larger wet droplets deposit as lubricating films.
The mist is commonly fed into the bearing housing on one side of the row of balls or rollers and is discharged from the opposite side (Figure 4).
Figure 4. Representative Mist Flow Pattern for
Ball and Roller Bearings
Spray and condensing fittings are used for sliding-motion elements. The major difference between the two types is how long mist particles are maintained at high velocity under turbulent flow conditions to promote agglomeration of the fine oil particles in the dry mist feed. To lubricate sliding surfaces, journal bearings and the like, the resulting wet spray then runs down adjacent surfaces in arrangements such as those shown in Figure 5.
Figure 5. Mist Lubrication of Plain Bearings
Oil Requirements
Table 1 provides a guide for the quantity of oil normally fed to various machine elements for moderate service requirements.4
This information pertains to horizontal shafts with unidirectional load, bearings in any position with oil retained by seals, or porous metal or other self-lubricated bearings. Feed rates in Table 1 should be doubled for heavy-duty service, oscillating bearings, unsealed bearings subject to shock load with constantly shifting load zone, preloaded bearings and nonhorizontal shafts.5 Special considerations are needed from related experience or supplier information for surface speeds over 600 feet/minute.
Lube system suppliers, machinery builders and lubricant suppliers should also be consulted for appropriate feed rates and lubricant specifications because requirements vary for individual installations and may double for speeds, loads and temperatures above those in conventional factory applications.
Two examples drawn from experience under mild operating conditions illustrate the small amount of oil sometimes needed by bearings. A ball bearing in a 10-horsepower electric motor ran satisfactorily for several weeks at 3,600 rpm with a single drop of SAE 10 oil.
In another case, the 9-inch journal of a wick-oiled railroad locomotive propulsion motor ran without failure for one hour at 600 rpm after the lubricating wick was removed. Small porous metal bushings and oil-impregnated polymer bearings are often used for the life of appliances with no additional lubrication. In general, oil volumes given in Table 1 provide suitable excess for reliable operation.7
Machine
Element
(fitting type) Oil Mist
cubic feet/minute Ball and roller
bearings
(spray and mist) DR/40 D=shaft diameter, inches;
R=number of rows of balls or rollers Plain bearings
(condensing and
spray) LD/100 L=axial length, inches;
D=shaft diameter, inches Gears (spray)
Spur
Worm F(D 1+D 2+D n)/160
F(D 1+0.5D 2)/80 F=face width, inches; D 1=pitch
diameter of small gear or worm gear,
inches; D 2=pitch diameter of large gear,
inches; D n=pitch diameter of additional
gears, inches
Cams (spray) FD/400 F=face width, inches;
D=max. diameter of cam, inches Chain (spray)
Power
Silent
Conveyor PDRS0.5/31,000
WDS0.5/600,000
W(D+0.033L)/170 P=pitch of chain or sprocket, inches;
D=pitch diameter of small sprocket or
drive sprocket, inches; R=number of rows
of chain rollers; W=chain width, inches;
S=rpm of small sprocket; L=chain length,
inches Slides and gibs
(condensing) A/800 A=max. contact area, square inches Ways
(condensing) A/400
A=max. contact area, square inches For mist feed with a standard density of about 0.4 in3 of oil per hour/cubic feet of air per minute. Table 1. Oil Mist Requirements for
Moderate Operating Conditions
Oil selection is normally made to satisfy lubrication requirements of the most demanding machine elements. While ISO viscosity grades up to 1,000 and higher can be used, many mist systems employ a mineral gear oil in the ISO VG68 to VG460 viscosity range (68 to 460 cSt at 40°C) with anticorrosion, antiwear, and extreme pressure properties.
Past problems with wax and additive separation from mist oils are now avoided by using naphthenic base stocks, and by not using oil additives that might be deposited upon encountering water contamination.
Mist oils also contain special additives to improve atomization, promote condensation on rotating surfaces, and to reduce fogging and stray mist in the surroundings. These mist formulations typically provide 20 to 30 percent more usable oil delivery than normal mineral oils. Automotive engine oils should not be used because their mistability varies widely.
With their lower lubrication needs, ball bearings in electric motors and related pumps commonly employ a bearing oil of 100 to 150 cSt (at 40°C) for summer use and 32 cSt for colder months.
Minimum cubic feet/minute of mist to be fed to each bearing is specified by U.S. Motors as D (inches shaft diameter) x R (rows of balls)/20 using mist of approximately 0.4 to 0.65 cubic inches of oil/hour/standard cubic feet per minute (scfm) of air flow.
Limitations
While mist systems have dramatically reduced maintenance and operating problems, establishing flow rates in a system has proved troublesome and the following details commonly need attention:
The air stream in feed lines must be kept laminar, below approximately 24 feet/second, because turbulence causes oil particles to impact the pipe wall and be removed from the air stream before reaching delivery points. At abnormally low velocities, on the other hand, oil droplets may also settle out prematurely.
Performance is sensitive to temperature. Even when not required by viscosity considerations, heaters are often employed to stabilize the oil/air ratio under widely varying ambient temperatures. When used, air heaters are usually accompanied by oil reservoir heaters.
Spray mist involves environmental hazards. Vent lines are needed at lubrication points for collecting stray mist which has not been classified. OSHA requirements state that in an eight-hour period, a person can be exposed to no more than five milligrams of oil per cubic meter of air.
References
Ehlert, D. “Oil Mist Lubrication in the Hydrocarbon Processing Industry.” Machinery Lubrication, May-June 2004. Bloch, H. and Shamim, A. Oil Mist Lubrication: Practical Applications. Fairmont Press, Inc., Lilburn, Georgia. 1998. Schrama, R. “Oil Mist vs. Air-Oil for Consumable Lubrication Systems.” Lubrication Engineering, Vol. 49, p. 9-17. 1993. Reiber, S. “Oil Mist Lubrication.” CRC Tribology Data Handbook. E. Booser (editor), CRC Press LLC. 1997. Alemite Corporation. Oil Mist Application Manual. Charlotte, North Carolina. 2004. Towne, C. “Practical Experience with Oil Mist Lubrication.” Lubrication Engineering, Vol. 39, p. 496-502. 1983. Khonsari, M. and Booser, E. Applied Tribology – Bearing Design and Lubrication. Wiley & Sons, New York. 2001.
About the Author
About the Author
Oil Mist Lubrication
History Of Oil Mist Lubrication
The Oil Mist principle was developed by a bearing manufacturer in Europe during the 1930s. The problem that nurtured this development was the inability to satisfactorily lubricate high-speed spindle bearings on grinders and similar equipment. The speed of these bearing was too high for grease lubrication, and liquid oil generated too much heat through fluid friction, necessitating an expensive recirculating system. Continuous thin-film lubrication with Oil Mist provided a solution. The purging and slight cooling effects of the carrier air gave additional benefits. The Oil Mist generator resulted later from this development and used a small amount of air to produce a dense concentration of small oil particles. About 97% of these particles could be transmitted to the bearings without condensing in the piping, regardless of the distance of the bearings from the Oil Mist generator itself.
In 1958, air heaters were developed because it was discovered that, by heating the air used to generate Oil Mist, oils of just about any viscosity could be atomized. Many applications, subject to extremes in ambient temperature, use air heaters to ensure a constant oil/air ratio regardless of the oil viscosity. Today Oil Mist is still used to lubricate high speed spindles in grinders. Included in the increasing range of Oil Mist applications are systems applied to all types of other machine tools, web and sheet processing equipment, belt and chain conveyors rolling mills, vibrators, crushers, centrifuges, kilns, pulverizers, ball mills, dryers and liquid processing pumps.
Mist Generator Systems
Oil Mist is a centralized system in which the energy of compressed gas, usually air taken from the plant supply, is used to atomize oil. Oil is then conveyed by the air in a low pressure distribution system to multiple points of lubricant application.
The compressed air is passed through a venturi. Oil, siphoned from a reservoir by the air flow, is atomized into a fine spray. Baffles downstream from the venturi nozzle causing the larger oil particles to coalesce and return to the reservoir. The remaining air-oil-mixture is Oil Mist. Oil Mist contains oil particles (droplets) averaging about 1-1/2 microns in diameter (.00006 inches), which can be conveyed through distribution piping (mist manifold), at velocities up to 24 feet per second, to application fittings (mist fittings which meter oil to bearing housings). Air-borne oil particles are then “wetted out” by impinging upon bearing surfaces rotating at sufficient speed to cause adherence and the formation of larger drop sizes. Because there are no moving parts in the basis Oil Mist generator system, and because the system pressure is very low (manifold pressures from 5 to 40 inches of water), it is a reliable lubrication method. Also, the system can be interlocked with machine operation or an alarm system to ensure proper functioning. Note that, even when malfunctions occur, most bearings will operate for hours on an existing film of lubricant.
Principle Of Oil Mist Generation
Advantages Of Oil Mist
This system is ideal in that a metered amount of oil (approaching optimum) can be provided to the bearing for proper lubricity. Lubricant friction itself is virtually eliminated. Keep in mind that grease is used only as a “carrier” for those oils within it which provide lubricity. Other than that, it is an impediment to rotation, causes frictional heat, can carry and recycle abrasive particles to the bearing, and doesn’t guarantee good dispersion (i.e., coating of all surfaces of the bearing at all times to prevent corrosion).
The oil mist provides a flushing action with fresh, clean lubricant and acts in a slight manner as a bearing coolant. The carrier air used to distribute the oil provides additional benefits in that it maintains bearing housings under slight positive pressure and the “outward” air flow prevents the entrance of contaminants. Where mist systems run continuously – and when motors are inoperative – problems with condensation reaching bearing surfaces are eliminated.
Maintenance “human factor” problems are reduced: Over-greasing, lack of replenishment of the proper grease and the right amount at the right time.
Our Position: Product Modifications
It has been determined that our horizontal ball bearing motors are compatible with oil mist systems, keeping in mind the following necessary features and modifications:
“Regreasable” motor construction. Open bearings with bearing caps. LUBRIFLUSH or straight-through lube system. Grease inlet in upper bracket quadrant (standard). Grease (condensate) drain near 6 o’clock position. This maintains a “dry sump” system and minimized accumulation of churning of oil. Drain should not be located directly in air flow from fan (copper or galvanized steel tube extensions should be supplied where this is the case). Grease inlet hole threads must accommodate standard mist fittings (1/8 and ¼ inch present standard generally suitable but check particular mist generator supplier for specific size and thread). Vents should be about twice the area of inlets. Winding treatments used for CORRO-DUTY® and VPI are suitable. EXAR 150 leads must be used. Silicon rubber should be avoided due to potential swelling. (Very small particles of mist will enter the motor regardless of bearing caps, seals, etc.). Motors should be supplied with grease intact, for protection during shipping and storage. Before connecting to a mist generation system, vents (grease drain hole) must be opened. Then the grease inlet channel should be cleared with clean, dry, low pressure compressed air so that mist will flow into the bearing cavity.
These features are reflected in the following chart:
NEMA Frame – CORRO-DUTY® Motors
(Except Hazardous Duty)
Frame Cast Iron
Bearing
Cap Bearings Mist Inlet Mist Outlet Insulation
& Leads 140 Construction not suitable 180 Add Bearing Caps Modify To Open Bearings Check
Mist
Supplier
For Hole
Size &
Thread SE & PE
Bracket
Grease Drain
to be at 6 0’Clock Standard
Winding
Treatment Use EXAR 150
Leads or an
Equivalent Impervious
to Oil 210 250 280 320 360 400 440
*Add Vent Extension.
At the present time we will supply modified TEFC motors which are compatible with Oil Mist systems, but will not provide system components or assume total system responsibility.
As a motor supplier, our position is that the bearing must “see” a proper flow, mixture and quality of mist. There should be no pre-condensation of the mist waxing of the lubricant (clogged nozzles) etc.
General guidelines are as follows:
Flow (CFM) should follow the relationship –
CFM = DR/20
D = Shaft Diameter (inches)
R = Rows of balls
20 = Constant for heavy service (use 40 for moderate service)
Note, however, that a conservative standard of 0.4 CFM has been used successfully for most NEMA frames.
Mixture should be:
Oil / air ratio = .4 to .65 cubic inches oil / hour / CFM air
Lubricant:
Use a quality bearing oil formulated for oil mist lubrication, 600 SSU viscosity at 100ºF for summer months or 150 SSU at 100ºF for colder months.
Note that the system should be designed such that bearing cavity pressure will be approximately 5 inches of water minimum. This will prevent contaminants from entering this cavity.
Also note that bearing rolling elements must have a velocity of 200 linear feet per minute minimum when mist fitting is used in order for oil particles to “wet out” as they impinge upon ball surfaces.
Liability:
Since we have no control over lubrication other than the initial amount of grease and since this grease is eventually purged by the mist, we should provide a conditional statement to our Warranty similar to the following:
“The mist system must provide a minimum of CFM flow to each bearing per the relationship of 0.05 D (shaft diameter inches) x R (rows of balls). Mixture of mist should be approximately 0.4 to 0.65 cubic inches of oil / hour / CRM air. A quality bearing oil must be used and have 600 SSU viscosity (100ºF) in summer or 150 SSU viscosity (100ºF) in colder months. The mist generate must be run continuously when the motor is inoperative. Also, the system should have adequate alarms to flag a malfunction and effect shutdown of the motor.”
This statement is at present a general guideline only and may change as we gain experience and/or propose motors for specific applications.
Vertical Motors:
Currently vertical motors are not approved for oil mist lubrication. Further lab testing and/or prototyping in the field may be required. In the interim, however, refer any inquires of significant volume to our headquarters office in St. Louis.
[Solved] In two-stroke engines, the type of lubrication system employ
Concept:
The function of a lubrication system is to provide a sufficient quantity of cool, filtered oil to give positive and adequate lubrication to all the moving parts of an engine. The various lubrication systems used for internal combustion engines may be classified as:
Mist lubrication system
Wet sump lubrication system
Dry sump lubrication system
Mist lubrication system:
In two-stroke engines, mist lubrication is used where crankcase lubrication is not suitable. In a two-stroke engine, as the charge is compressed in the crankcase, it is not possible to have the lubricating oil in the sump. Hence, mist lubrication is adopted in practice. In such engines, the lubricating oil is mixed with the fuel, the usual ratio being 3% to 6%. The oil and fuel mixture is inducted through the carburetor.
Wet sump lubrication system:
In the wet sump system, the bottom of the crankcase contains an oil pan or sump from which the lubricating oil is pumped to various engine components by a pump. After lubricating these parts, the oil flows back to the sump by gravity. There are three varieties in the wet-sump lubrication system.
the splash system
the splash and pressure system
the pressure feed system
Dry Sump Lubrication System:
In this, the supply of oil is carried in an external tank. An oil pump draws oil from the supply tank and circulates it under pressure to the various bearings of the engine.
Oil Mist Lubrication System (With PDF) – What Is Piping
An oil mist lubrication system is the widely used bearing lubrication. A centralized lubrication system generates and automatically delivers the lubricant to machinery bearings to keep it lubricated for making moving parts reliable. The fine mixture of oil and air that is generated is called oil-mist. Oil -mist lubrication ensures a high standard of lubrication as and when required and prevents the ingress of contaminants to the bearing housing.
Various Type of Lubrication
Splash Lubrication
Grease Lubrication
Forced Lubrication
Solid Lubrication
Mist Lubrication
Oil Mist System is a means of generating and transporting a finely dispersed oil mist from a central location to individual bearing housings.
The oil mist system uses compressed air to atomize oil into micron-size particles which can be effectively moved to lubrication points up to 600 feet (180 meters) through Pipes & Tubes
One Oil Mist system can provide lubrication to 60 pumps and their drivers with approximate oil consumption of one gallon (3.8L) of oil per 24 hours.
Typical Oil Mist System
Refer to Fig. 1 which shows a typical oil mist lubrication system used for industrial application.
Fig. 1: Typical Oil Mist System
Types of Oil Mist Lubrication System
The oil mist lubrication system can be categorized into the following types.
Open Loop System (Fig. 2)
Closed-Loop System (Fig. 2)
Dry Sump (Pure Mist-Fig. 3)
Wet Sump (Purge Mist-Fig. 3)
Fig. 2: Open and Closed Loop Mist Lubrication System
Pure & Purge Mist Lubrication
Pure Mist Lubrication System-
The bearing is lubricated by oil mist, not oil.
Bearings can run 10-15 degC cooler with pure mist as compared to sump lubrication.
The bearing housing is pressurized by continuous oil mist flow, then external contaminants (dust, moisture…) are excluded.
Centrally controlled hence attention for oil level is not required individually.
Purge Mist Lubrication System-
The bearing is lubricated by oil, not oil mist.
The bearing housing is pressurized by continuous oil mist flow, then external contaminants (dusts, moisture…) are excluded.
Here mist purges the bearing housing and provide partial fresh Makeup oil.
Oil level must be checked and maintained for each equipment.
Fig. 3 below shows typical pure and purge mist lubrication systems.
Fig. 3: Pure and Purge Mist Lubrication
Components of Oil-Mist Lubrication Systems
The major components of an oil-mist lubrication systems are listed below:
Oil mist generator- the heart of the oil mist lubrication system, compressed air is passed through venturi or vortex to produce the oil-mist mixture.
the heart of the oil mist lubrication system, compressed air is passed through venturi or vortex to produce the oil-mist mixture. Oil mist cabinet- Stainless steel cabinet.
Stainless steel cabinet. Reclassifiers- Controls the mist flow to applicable points. Bearing type, shaft speed, and diameter dictate the sizing of reclassifiers.
Controls the mist flow to applicable points. Bearing type, shaft speed, and diameter dictate the sizing of reclassifiers. Air- Clean and Dry air free from toxic, corrosive, and flammable elements.
Clean and Dry air free from toxic, corrosive, and flammable elements. Air Filter at the air inlet.
at the air inlet. Air regulator to control supply air pressure
to control supply air pressure Air Pre-Heater-For cold climates to maintain the air temperature
While selecting the oil for oil-mist lubrication system, the following factors need to be considered:
Oil Viscosity at the operating temperature
Pour point
Surface tension
Solidification tendency of the oil at low ambient temperatures
How does oil mist Lubrication lubricates the bearing?
The following figure (Fig. 4) shows the working of the oil-mist lubrication system to enhance bearing life.
Fig. 4: Working of Oil-Mist Lubrication System
Mist Lubrication Suitability
Rolling element and sliding contact bearings can be lubricated with Oil Mist either Pure or Purge type.
Oil mist is used to lubricate rolling element bearings of all types. Ball & Roller bearings are generally applied with Pure Mist Lubrication.
When sliding contact bearings are used, oil mist alone does no provide complete lubrication & hence, an oil level is maintained in the bearing housing and is called Purge Mist Lubrication.
Advantages of Oil Mist Lubrication System
Oil mist lubrication system offers various advantages over the other lubrication systems as listed below
Prevent the dust/moisture ingress into bearing housing, due to pressurized system
Increased Bearing Life
Lower friction and thus reduced bearing temperatures
Reduced maintenance, reduced handling, and spillage.
As the bearings operate in a thin film of oil, so less power is required.
Reduced Oil consumption (40% less & 50% of it can be recovered)
More environmentally friendly than the conventional lubrication system.
As the oil on the bearings is always new, it provides better lubricant properties.
In technical papers released by end-users and bearing manufacturers, as well as in university research, bearings lubricated with oil mist have a longer life than bearings lubricated with oil sump or grease. Users report from a 50% to 90% reduction in lubrication-related bearing failures.
Finally, it is economic to use.
Disadvantages of Oil Mist Lubrication System
Even though mist lubrication systems have various advantages and reduce reduce maintenance and operating problems, still there are few disadvantages of this system such as
Oil Mist lubrication system
What is Oil Mist lubrication?
Oil mist lubrication is an advanced centralized lubrication solution comprised of the production and distribution of a continuous flow of atomized Oil particles. These particles are delivered directly to the bearing and metal surfaces, for a high quality, cost-effective lubrication solution.
Oil mist is a mixture of clean, dry Air and Oil (Nebol), a lubricant that is designed to deliver a precise amount of pressurized oil to bearings and metal surfaces, ensuring proper lubrication.
This type of application is specifically designed by DropsA for Oil refineries as it is common that greenfield initiatives for oil refineries specify an oil mist lubrication system for bothpumps and motor bearings.
How does oil mist lubrication work?
During the refining process of oil, a process pump, which is used to transfer oil, must be lubricated with Nebol (mist system)that is specifically designed for each refinery. After determining the best position for the Nebol OMG (oil mist generator) the proper amount of oil mist is determined and transferred to the lubrication points.
The oil mist cabinet generator consists of:
– Vortex or Venturi mix header
– Control panel that can communicate with customer’s DCS, communicating alarms
– Heaters for Oil and Air
– Reservoir and upon request, backup units
– EX certified parts
Furthermore, the oil mist system is composed of the following accessories and components:
– Mist manifold: Utilized to evenly divide the mist from the main line. Normally, it is placed above the pumps and can be used to lubricate up to 8 lubrication points.
– Reclassifiers: Lubrication devices used to conjoin and increase the size of oil particles.
– Auxiliary manual pump: In a closed loop system the lubricant must be returned to the main station. A manual pump can help facilitate this process.
How Oil Mist is generated
Oil mist, which is the mixture of clean, dry air and oil, is generated by an innovative vortex generator. This technology mixes a specific amount of oil from the highest velocity point of the vortex maximizing the acceleration of the particles into the vortex’s center.
At the outlet of the vortex, a rapid decompression zone initially removes large particles by forcing them to coalesce in a static area of the exhaust cone. The remaining aerosol is rotated in a controlled deceleration process in the exhaust cone utilizing the coanda effect accompanied by a specific surface finish used to help further reduce the particle size into sub-micron particles.
A final coalescing plate is used to collect large particles that are subsequently recycled.
The two types of application
The Oil mist lubrication system can be either open or closed loop depending on customer’s requirements. However, in either system It is necessary to calculate the mist flow to each of the lubricating points.
Some points can be PURE, and some can bePURGE. The following diagrams indicate the difference between PURE and PURGE, as shown in the below images.
PURE OIL MIST LUBRICATION
In a Pure Oil Mist application, the oil mist manifolds allow the visual monitoring of the condensed oil as it collects in the drop pipe. This allows the operators to drain the manifold when required.
• Oil Mist Manifold: allows the visual monitoring of the condensed oil as it collects in the drop pipe. This allows the operators to drain the manifold when required.
• Oil Mist Fitting (Reclassifiers): converts small particles of dry mist into larger particles (wet mist) which is used to lubricate surfaces.
• Oil Mist Sight Glass: sight glass allows easy observation of water, or other contaminants, in the bearing housing. Additionally, the sight glass allows venting of oil mist from the closed bearing housing.
• Collection Container:allows the collection of liquid oil from the bearing housing generated from the condensation of oil mist. Allows excess oil to be drained into a separate container.
PURGE OIL MIST LUBRICATION
• Oil Mist Manifold: Allows the visual monitoring of the condensed oil as it collects in the drop pipe. This allows the operators to drain the manifold when required.
• Oil Mist Fitting (Reclassifier): Converts small particles of dry mist into larger particles (wet mist) which is used to create positive pressure inside the bearing housing.
• Oil Mist/Vent/Fill: Allows the Mist to enter the bearing housing while letting it vent at the same time. Also allows filling of oil without disturbing the Oil mist and venting processes.
• Oil Level Sight Indicator: Sight Indicator allows easy observation of the oil level in the pump as well as maintaining the oil level to prevent overfilling of the bearing housing.
• Oil Mist Sight Glass: Sight glass allows easy observation of water, or other contaminants, in the bearing housing.
• Collection container: Allows excess oil from the sight Level Indicator to be drained, maintaining proper oil level inside the bearing housing. Allows excess oil to be drained into a separate container.
Benefits of Oil Mist lubrication
Oil Mist Systems In The Plant-Wide Lubrication Of General Purpose Machinery
Plant-wide oil mist systems have been in use in numerous reliability-minded refineries and petrochemical plants since the mid-1960s. The 8th (2000) and subsequent editions of the API-610 Standard for centrifugal pumps also have described advantageous application parameters for oil mist. In the United States, Canada, South America, the Middle East and Pacific Rim countries, oil mist lubrication has matured to the point where major design contractors now are specifying these types of plant-wide systems quite extensively.
Oil mist is easily controlled & appliedModern plants use oil mist as the lube application of choice. Plant-wide pipe headers distribute the mist to a wide variety of users. Oil mist is easily produced in an oil mist generator console (Fig. 1) and its flow to bearings is not difficult to control. Flow, of course, is a function of orifice (“reclassifier”) size and piping (“header”) pressure. Unless plugged by an unsuitable (e.g., an elevated pour point) lubricant, reclassifiers have a fixed flow area that is selected based on bearing size criteria.
Depending on make and system provider, header pressures range from 20″-35″ (500-890 mm) of H2O. Modern units are provided with controls and instrumentation that will maintain these settings without difficulty. It should be noted, however, that mixing ratios—typically 160,000 to about 200,000 volumes of air per volume of oil—are frequently incorrect on oldstyle mist generators that incorporate gaskets and O-rings in the mixing head, unless these elastomers have been periodically replaced or properly serviced.
Comparing plants with non-optimized mist entry (Fig. 2) to equipment bearing housings with their modern optimized counterparts (Fig. 3), lubricant and air consumption are about 40% less for plants that have implemented the superior mist entry and vent locations of Fig. 3. This has been reported in the cited references and is implied in API-610 8th Edition (2000) and later standards.
Forward-looking plants have used the API method, i.e. Fig. 3, since the mid-1970s. These plants had recognized that mist entering at locations far from the bearings could have difficulty overcoming bearing windage effects. Windage is most often produced by the diagonally-oriented ball cages in angular contact bearings. If such windage were produced by the left row of the thrust bearing in Fig. 2, the mist would take the preferential path straight to the vent exit at the bottom of the bearing housing and insufficient amounts of oil mist would reach the bearing rolling elements.
A larger quantity of oil mist or specially designed “directional” reclassifiers will be needed with certain bearing types unless the API method is used. This latter method will overcome windage, the flow-induced action induced by the skewed cages.
Environmental & health concerns
For decades, environmental and health concerns related to oil mist have been addressed by using oil formulations that are neither toxic nor carcinogenic. Such formulations are available to responsible users. Appropriate lubricants also have been formulated for minimum stray mist emissions. These, too, are readily available to responsible users.
Stray mist emissions can be kept to very low values by installing suitable magnetically-closed dual-face bearing housing seals (Fig. 4, also Ref.1). Unlike old-style labyrinth or other housing seals that allow highly undesirable communication between housing interior and ambient air, face-type devices seal off this contamination route.
Closed oil mist systems also are available—and have been since first being applied in the Swiss textile industry in the late 1950s. Today, closed systems are in use at several U.S. petrochemical plants. They allow an estimated 99% of the lube oil to be recovered and reused. Closed systems emit no oil mist into the environment and are available to environmentally conscious users.
Header temperature & size
Temperature never has been an issue for properly designed systems. Once a mist or aerosol of suitably low particle size has been produced—and particle size is influenced by the temperature constancy of both air and oil in the static mixing head—the oil mist will migrate to all points of application in non-insulated headers at low velocity.
Ambient temperature has little influence on mist quality and effectiveness. Mist temperatures in headers have ranged from well below freezing in North America to over 122 F (50 C) in the Middle East. Regardless of geographic location, conscientiously engineered systems will incorporate both oil and air heaters, since these are needed to maintain constant and optimized air/oil mixing ratios. The heaters must have low-watt density (low power input per square inch of surface area) in order to prevent overheating of the oil. Users that try to save money by omitting heaters or using undersized headers will not be able to realize the greatest life cycle cost benefits from their assets.
Using undersized headers may increase the flow velocity to the point where the small oil globules suspended in the carrier air experience too many collisions. They may thus agglomerate into droplets large enough to fall out of suspension, causing excessively lean mist to arrive at the point to be lubricated.
Wet sump (“purge mist”) vs. dry sump (“pure mist”)
In the wet sump method, a liquid oil level is maintained and the mist fills the housing space above the liquid oil. Wet sump (also called “purge” mist) is essentially “old technology”— and primarily used with sleeve bearing-equipped pumps and blowers(Figs. 5 and 6).
Dry sump oil mist describes the application method whereby no liquid oil level is maintained in the bearing housing. (This principle was illustrated earlier in Figs. 2 and 3.) Pumps lubricated in dry-sump fashion are depicted in Figs. 7 and 8. Here, lubrication is provided entirely by oil mist migrating through the bearing.
The application of dry sump oil mist is advantageous for a number of reasons. Among these, we find lower bearing temperatures, the presence of nothing but uncontaminated oil mist and the exclusion of external contaminants. However, one important, but often overlooked, reason involves oil rings (Fig. 9)—or rather the fact that no oil rings are used with this application method.
Oil rings often represent outdated 18th century technology as they were developed for slow-speed machinery during the Industrial Revolution. Elimination of oil rings is one of the many keys to improved reliability of virtually any type or style of bearing. Oil rings are known to have journal surface velocity limitations, sometimes as low as 2000 fpm, or 10 m/s. So as not to “run downhill,” which might cause the rings to make frictional contact and slow down, ring-lubricated shaft systems would have to be installed with near-perfect horizontal orientation.
Furthermore, frictional contact often results in abrasive wear and the wear products certainly contaminate the oil. Oil rings will malfunction unless they are machined concentric within close tolerances. They suffer from limitations in allowable depth of immersion and, to operate as intended, need narrowly defined and controlled oil viscosity.
Experience with modern oil mist systems
Actual statistics from a world-scale facility convey an accurate picture of the value of properly applied oil mist technology. This petrochemical plant went on-stream in 1978 with 17 oil mist systems providing dry sump oil mist to virtually every one of the many hundreds of pumps and electric motors in the facility. As stated previously, with the dry sump (“pure”) method per current API recommendation, the oil mist is introduced at a location that guarantees its flow through the bearings and to an appropriate vent location. There are neither oil rings nor any other provisions for the introduction of liquid oil on pumps and motors with rolling element bearings at the plant.
Over a period of 14 years, one qualified contract worker serviced these systems by visiting the plant one day each month. In this 14-year time period, there was only one single malfunction; it involved a defective float switch in one of the 17 systems. The incident caused a string of pumps to operate (and operate without inducing even one bearing failure!) for eight hours. In 1992, the combined availability and reliability of oil mist systems at this U.S. Gulf Coast plant was calculated to be 99.99962%.
Concluding comments
Being aware of the relative unreliability of conventional lubricant application methods involving oil rings and certain constant level lubricators (Fig. 10), knowledgeable reliability professionals can attest to the utility and overall advantages of properly engineered dry sump oil mist systems. Certainly, the known advantages of properly engineered oil mist systems far outweigh the actual or perceived disadvantages. It is unfortunate that much information to the contrary is either anecdotal or pertains to systems that were not correctly designed, installed, maintained and/or upgraded as new technology became available.
Only dry-sump applications will lubricate, preserve and protect both operating and stand-by rolling element bearings. At all times, only fresh oil will reach the bearings. In many instances, bearing operating temperatures with dry sump oil mist lubrication are 10 or even 20 F degrees (6 or 12 C degrees) lower than with wet sump lubrication.
Industry experience with dry-sump oil mist systems is well documented [Refs. 1, 2 & 3] and its superiority over both conventionally applied liquid oil and wet sump oil mist lube applications has been solidly established.
Regrettably, there are still entire plants that try to get by on wet sump oil mist. Wet sump lubrication makes economic sense on sleeve bearings only. Here, its only function is the exclusion of atmospheric contaminants. It does so by existing at a pressure slightly above that of the surrounding ambient air. Often, the wet sump oil level is expected to be maintained by an externally mounted constant level lubricator. However, due to the slight pressurization, and on bearing housings equipped with traditional open-to-atmosphere constant level lubricators [Ref. 2], the oil level in the bearing housing will now be below the oil level in the lubricator. Keep in mind that fully pressure-balanced constant level lubricators will be more reliable than many other wet sump lubrication alternatives available today.
References:
Bloch, H.P., and Shammim, A.; Oil Mist Lubrication, Practical Applications, 1998, The Fairmont Press, Inc., Lilburn, GA, ISBN 0-88173-256-7 Bloch, H.P., “Case Study in Reliability Implementation,” Hydrocarbon Processing, August, 2002 Bloch, Heinz P. and Alan Budris, Pump User’s Handbook: Life Extension, 2006, The Fairmont Press, Inc., Lilburn, GA, ISBN 0-88173-517-5
Contributing editor Heinz Bloch is the author of 17 comprehensive textbooks and over 340 other publications on machinery reliability and lubrication. He can be contacted directly at: [email protected]
Proper Application of Pure Oil Mist Lubrication in Refinery Pumping Systems
European Oil Refinery “X” was about to commission a plant-wide oil mist lubrication system, i.e., a setup that combines 200,000 volumes of clean, dry carrier air with one volume of lubricating oil. The resulting oil mist or “oil fog” flows in suitably sized headers and branch pipes to the many pump and electric motor bearings in modern “best-of-class” user plants. Although oil mist lubrication has been successfully used at hundreds of refineries, the lead reliability engineer (RE) at Refinery X had two questions.
Oil Mist for Plain Bearings
His first question referred to an old research article that dealt with the use of oil mist in plain bearings. The article explained how, to be applied to plain bearings, the mist must be converted (reclassified) to air-free liquid oil and applied approximately 10 to 30 millimeters upstream of the plain bearing. The liquid oil is then allowed to flow into the sleeve bearing. The RE was considering oil mist in plain steam turbine bearings after first converting the mist into large oil droplets, or even an oil spray. Oil mist supply pipes were already installed for purge mist, and he correctly surmised that it would be better to avoid the traditional oil ring and sump arrangement if possible. Accordingly, he inquired if he could extract (reclassify) most of the fresh oil from the oil mist and use the oil for lubricating the turbine’s plain bearings. The leftover lean oil mist would still be in the bearing housing and keep out dust and moisture-laden ambient air.
In our answer we mentioned that reclassified oil mist was well researched as a means of lubricating plain bearings in machine tools in the late 1950s. But there are more reliable ways to lubricate plain bearings in small- to mid-sized steam turbines in the hydrocarbon processing industry (HPI). In plain bearings and with the use of conversion (reclassifying) fittings, owners have to consider all the influencing factors around these bearings. Heat removal is one of the primary reasons for the oil. Hence, the flow rate of this reclassified liquid oil must equal the originally specified mass flow. Determining equivalency would be required. An oil mist feed for application and reclassification at plain bearings is cost-justified in relatively few cases.
Are There Temperature Limits?
The RE’s second question related to Reference 2, where he noted our words about the “myth” of a limiting product temperature when applying pure oil mist to rolling element bearings in process pumps. The RE said, “Our specification allows installing pure mist in pumps with product temperatures ranging from 120 C to 250 C, as long as a fan is installed on the pump shaft. Above 250 C the specification disallows pure mist and, instead, requires purge mist (wet sump). The very existence of a temperature limit set by certain design contractors is something I have difficulty understanding. At present, I am attempting to maximize the use of pure oil mist (dry sump) in the plant instead of the purge oil mist (wet sump) that had been widely used at our facility in the past.”
We agreed and confirmed that the world’s best refineries use pure oil mist on many of their thousands of rolling element bearings. Except for a few applications in small steam turbines, or as a floating “blanket” in the space above the conventional oil level in bearing housings with sleeve-bearings (plain bearings), one does not use purge mist. Pure oil mist (dry sump) excels in rolling element bearings and has been in use at refineries owned by BP, Exxon, Chevron, Shell and others for more than 40 years. So that specification at this RE’s plant makes no sense. It will be easy to verify 40 years of good experience in pipe-still bottoms pumps and other hot services with pumpage/product temperatures as high as 400 C.
Years ago, there was a preference to move ambient air across the bearing housing. Since then, however, synthetic lubricants have become widely available. In closed oil mist systems, the coalesced oil is collected after it has passed through the bearings toward a drain port near the low point of the bearing housing. Moreover, refineries have applied pure oil mist in conjunction with appropriate synthetic lubricants (Poly-Alpha-Olefin “PAO” or PAO/Dibasic Ester–based mixtures) for decades, and no cooling off is needed. Therefore, fans are no longer used.
What if There Are Hot Bearings?
If hot bearings are encountered with oil mist, we view this as a sure sign of overloaded bearings, incorrectly installed bearings, incorrect bearing fit or incorrect lubricant viscosity. When bearing temperatures exceed 210 F, remember all failures of rolling element bearings in process pumps are attributable to one of four contributors: force, reactive environment, time and temperature, or FRETT.
Still, the RE wrote he would be grateful for another point of view. In his opinion, his employer could decide to install pure oil mist regardless of fluid temperatures. While he (correctly) reasoned that pure oil mist was the right lubricant application mode in pumps where field measurements of the bearing operating temperature did not exceed 190 F (88 C), he wanted assurances about pure mist working well in high temperature pumps.
Our full answer again confirmed there are many hundreds of pumps in service with pumping temperatures of 740 F (approximately 400 C). They are lubricated with pure oil mist and some of these pumps have been in highly successful service for well over 40 years. Many of these are in operation for six or seven years before being dismantled for precautionary inspections.
Image 1. A circulating oil system can be used to upgrade to superior bearing lubrication in mid-size machines (Courtesy of AESSEAL, Inc, Rotherham, UK, and Rockford, TN) Image 1. A circulating oil system can be used to upgrade to superior bearing lubrication in mid-size machines (Courtesy of AESSEAL, Inc, Rotherham, UK, and Rockford, TN)
Again referring to the RE’s point, we re-affirmed another fact: an American Petroleum Institute (API) pump with rolling element bearings and a pumping temperature of 400 C on pure oil mist will absolutely and unequivocally operate with greater probability of long bearing life than the same pump operated with risky oil rings and a “standard” liquid oil sump. However, removing oil rings and using an auxiliary pump-around unit (see Image 1) would match pure oil mist for long-term lubrication effectiveness in critical hot-service process pumps.
A recent case in the Middle East claimed a hot service pump with a 190 F (88 C) bearings required liquid mineral oil lubrication. But the REs likely overlooked an excessive interference fit between bearing inner rings and shafts.
The pump at issue had its stainless steel shaft thermally expanding 17 percent more than a typical ferrous tool steel shaft. The stainless steel shaft aggravated the interference fit issue. The troubles at that location had nothing to do with oil mist and were solely the result of human error, perhaps misinformation. Reading and acting on information from a $25 text would have saved a fortune. Ref. 1 qualifies as such a text.1
Final advice: Start by reviewing the evidence that pure oil mist works efficiently on hundreds of hot service pumps. Therefore, if it doesn’t work at Refinery X, we must find out and isolate what people at that refinery are doing differently. If oil mist works well on hundreds of seemingly identical pumps elsewhere, the problem must be with us, or with our plant.
References
1. Bloch, Heinz P., “Pump Wisdom: Problem Solving for Operators and Specialists,” (2011) John Wiley & Sons,
2. Bloch, Heinz P., “Petrochemical Machinery Insights,” (2016) Elsevier Publishing Company
Oil mist lubrication
By Don Ehlert, Total Lubrication Management and Marty Williams
Oil mist is an ideal method of lubrication for rotating equipment in geographic regions that are windy, hot, humid, cold, damp, and dusty or anywhere that air borne particulates and moisture contamination may be present. Improving equipment reliability translates into a safer and more reliable plant with more production of product. Oil mist lubrication impedes the ingress of air borne contaminates, delivers clean oil and provides a dramatic impact on equipment MTBR (Mean Time Between Repair). One Australian refinery with approximately 500 pumps uses oil mist with excellent results.
Pure Oil Mist or Dry Sump Lubrication describes the lubrication of rolling element bearings without an oil sump or grease in the bearing housing; the oil mist is the only means of lubrication for the bearings. Oil mist is an aerosol of oil particles that are 1 to 3 μ in size. These small particles are referred to as dry mist; they are too small to lubricate contacting surfaces such as rolling element bearings. The dry mist, 1 to 3 μ sizes, allows the particles to be transported throughout a piping distribution system for lubrication of bearings in rotating equipment with an air flow up to 180 metres away from the oil mist generator, OMG (Oil Mist Generator). Ambient temperature swings have minimal impact on mist density after it leaves the OMG; provided the oil consumption rate is calibrated and proper flow rate is maintained, allowing it to be used in both hot and cold climates. Quality synthetic oils, PAO (Polyalphaolefin) or Diester, are recommended for use when ambient temperatures fall below 4° C (40° F). When mineral oils are used they must be paraffin free to prevent plugging of the reclassifier orifices. Reclassifiers are orifice fittings that convert the dry mist to wet mist, particle sizes larger than 15 μ and greater, for lubrication of the bearings rolling elements. Converting the dry mist to wet mist takes place by increasing the velocity of the small particles through the orifice where they coalesce, impinge on each other, and grow in size. These larger particles then wet out on surfaces and provide a clean, continuous supply of fresh oil. Oil particles that do not grow in size are vented away from the equipment housing and are referred to as stray mist. The loss of oil mist to individual or multiple pieces of equipment does not mean an immediate equipment failure. Should the oil mist system fail or header line breaks; it is recommended that normal system operation should be reinstated prior to the end of the current maintenance shift; within four (4) hours. It is not to be set aside for the next maintenance shift. There are only two items that can completely stop the generation of oil mist; the loss of air and/or oil. Electrical power is not required to generate oil mist. Clean, dry instrument air is required for the generation of oil mist; should the instrument air system fail the entire plant/unit will be shutting down and lubrication will not be an issue. The average oil mist system consumes approximately four litres, (one gallon), of oil in a 24 hour period. For large scale systems the OMG normally has a misting chamber that holds 23 to 34 litres (6 to 9 gallons) of oil with a bulk supply of 284 to 416 litres (75 to 110 gallons) standing by for refilling the misting chamber; the chances of running out of oil are extremely remote.
When applying oil mist to new or rebuilt equipment that may have dry bearings, without any lubricant on them, it is recommended that oil mist lines should be connected immediately after the machine is set in place to allow oil mist to coat the bearings prior to start-up. Equipment coming from a staging or storage area where bearing preservation was not provided is likely to have corrosion or particulate accumulation on the surfaces and bearing failure could be imminent with any method of lubrication.
Benefits of Pure Oil Mist
Pure oil mist is the ultimate oil filter as it breaks oil down to particle sizes of 1 to 3 μ. Larger particles that may bond with solid particulates or water are too heavy for transport throughout the distribution system and fall out of suspension.
The results are a continuous film of fresh clean oil being supplied to bearing surfaces in a pressurized/aerosol form. The bearing housings internal pressure is maintained at approximately 0.125 PSI which inhibits thermal cycling and/or the ingress of external air borne contaminates i.e. dust and moisture. The overall result is bearings without an oil sump operate up to 10° C (30° F) cooler with no recirculation of hot or contaminated oil. Oil mist not only lubricates the operating equipment; it also protects and preserves the standby or idle equipment insuring optimum bearing conditions when service is required. Using pure oil mist means a longer MTBR, mean time between repair, lower life cycle cost, reduced man hours for lubrication tasks, less equipment repairs, less oil inventory on site, less safety incidents due to mechanical seal failures which are initiated by premature bearing failure and less failures that may result in a fire.
Pure Oil Mist on pumps
Current API 610 pump specifications require that pumps shall have NPT (National Pipe Thread) connections outboard of the bearings. This allows oil mist to be applied into a central connection point between the bearings with venting outboard of the bearings or apply oil mist outboard of the bearings and venting out the bottom drain port as shown in figure 1. Either way insures that oil mist will pass through the bearings from side to side before exiting the bearing housing. The arrangement shown is the preferred method of lubrication as it allows the reclassifier to be sized for the individual bearings which is superior to having a single reclassifier serving both the thrust and radial bearings. When retrofitting oil mist to existing or older pumps the illustration shown is recommended when pumps are operating at 3000 RPM or higher and Kw is150 (200 HP) or greater. A single oil mist application point located in the middle point of the bearing housing is acceptable when operating less than 3000 RPM and Kw is less than 150 Kw (200HP) when lip or labyrinth seals are used. When bearing isolators are used two mist application points are mandatory. Oil mist lubricates pumps in operation and it protects and preserves the internal bearing surfaces from corrosion or false bernelling when sitting idle. Oil mist protects equipment 24/7 in all climates and conditions. Experience from many facilities has proven that pure oil mist is beneficial to rotating equipment reliability. User experience indicates that equipment having sat idle in excess of twelve months have been started without incident. There were no changes in vibration readings from when the machines had previously been in operation.
Pure Oil Mist pillow block bearings
Pillow block bearings are commonly lubricated with grease or an oil sump and these types of bearings are commonly used on FD (Forced Draft) or ID (Induced Draft) fans, figure 3. Grease becomes contaminated over time due to the natural process of bearing operation. Grease, like oil, requires changing at regular intervals and in un-spared equipment this may not be an option. The contaminated lubricant then becomes a rubbing compound that severely shortens the life of the bearings rolling elements. Idle bearings are subject to lubricant contamination from thermal cycling, condensation, wash down water and other forces that apply pressure, even a small amount, to the bearing housing seals. Keeping contaminates out is virtually impossible when oil sump is the norm; however the slight pressure created by the oil mist assists in keeping the bearing housing free of debris and moisture. Applying pure oil mist on pillow block bearings is very effective and inexpensive when the oil mist system is already in place for the surrounding equipment such as the pumps and motors.
When a large scale system is not in the immediate area a small modular unit may be used with excellent results. Modular units may be so basic that only a clean instrument air supply is required for operation, figure 4. These units are ideal for isolated equipment such as tank farm pumps or fan bearings where a larger system is not justified. A notable benefit of the oil mist system is the elimination of oil containers sitting around the machines which promotes cross contamination of lubricants and contamination from outside sources.
As a final point, any machine with rolling element bearings has the potential to be successfully lubricated with oil mist lubrication. Refinery experience demonstrated that bearing life is extended well past normal expectations; in many cases exceeding 130,000 hours in service with no degradation of the bearing structure. Special applications require a good understanding of oil mist and should not be attempted before seeking advice from qualified personnel. When properly applied oil mist will move equipment reliability to a much higher level.
About the Authors
Don Ehlert is currently Manager for EPC Sales at Total Lubrication Management Co., a Colfax Fluid Handling Company, located in Houston, TX. His current responsibilities include providing technical training and sales presentations. Don is also responsible for quotation assemblies for both domestic and foreign engineering companies and end users. He provides technical support to oil mist user’s world wide.
Since joining TLM in 1984, he has filled positions in equipment assembly, field maintenance, field installation, field management, sales and sales management. He has been instrumental with the development of oil mist related products and accessories for special applications.
Marty Williams started life as a Maintenance Technician in the mid-seventies at a major oil refinery in the UK, progressed through the ranks leaving in 1989 as a Maintenance Supervisor to emigrate to Australia.
He started at a major oil & gas facility in Western Australia in 1990 as a Maintenance Supervisor until 2000 when he was seconded to SRC in Singapore for nine months as a Reliability Engineer. On his return to Australia he became part of the Reliability Group working on all aspects of refinery machinery reliability. He introduced oil mist lubrication to the refinery in 2000 being the SPA for the project and has installed a total of thirteen oil mist systems covering the majority of rotating equipment and is now Machinery Engineer at the facility.
Find Chemicals And Plastics Related Companies In The Pump Industry Capability Guide
Oil Mist Lubrication System
Oil Mist Lubrication System
LubriMist® Oil Mist Systems
An oil mist system is a centralized lubrication system that generates, conveys and automatically delivers lubricant to machinery bearings. It is a system that has few moving parts making it very reliable. The lean mixture of oil and air produced by the generator is known as oil mist. The oil particles form a stable suspension that can be conveyed considerable distance (180 meters) through piping and tubing to the point requiring lubrication. Oil mist is a proven technology and it provides many advantages over conventional lubrication techniques such as oil splash and grease.
Applications and Use
Oil mist is used to lubricate rolling element bearings of all types. The most common applications in refineries and petrochemical plants are the bearings in pumps and their electric motor drivers. In addition, oil mist is used to purge gearboxes and the bearing houses of small steam turbines using sleeve bearings. Oil mist systems have been used in the hydrocarbon processing industry since the late 1960’s with widespread use in many areas of the world commencing in the 1980’s.
Financial Benefits
Oil mist systems are justified for economic reasons. It has been documented in technical papers released by users, by bearing manufacturers and in publications on university research that bearings lubricated with oil mist have longer life than bearings lubricated with oil sump or grease. Users claim from 50% to 90% reduction in lubrication related bearing failures when oil mist is used. A bearing failure can lead to an equipment overhaul costing $5,000 to $10,000, not including lost production. Reduction in seal failures has also been documented with the use of oil mist. The savings result in payback on the investment in less than two years and this combined with twenty-year life and low system operating cost means oil mist is a high-return, low-risk project.
Reasons for Superior Performance
• Bearings run cooler, typically on the order of 10 C. Lower bearing operating temperature means longer life.
• Oil mist lubrication is contaminant free. Studies have shown that it is common to have high contamination levels in oil sumps even though bearing housing seals are in place and recommended oil change intervals are followed. This contamination is not present with oil mist.
• External contaminants such as water vapor and particulate matter are excluded from the bearing housing because the mist system operates at positive pressure.
• The internal surfaces of the bearing housing are always coated with oil so there is no possibility for corrosion. This also applies to stand-by equipment meaning back-up machinery is ready for operation.
Oil Mist and Industry Specifications
The American Petroleum Institute (API) and the Process Industry Practices (PIP) group have taken a position that supports the use of oil mist. In their “Recommended Practices for Machinery Installation and Installation Design” specification (API RP-686, PIP REIIE 686), oil mist systems are prominently described. In the API specification for pump design (API-610) oil mist lubrication is included as a means for lubrication.
Pure Oil Mist Application for Pump API and Motor
• Pure Oil Mist provides the lubrication, continually supplies to bearing.
• Bearing run cooler typically 10 C, lower friction, less heat generation.
• Wear Particles are Continuously Washed from The Bearing Surface.
Purge Oil Mist Application for Turbine
• Oil Mist purge over oil level in housing with slight positive pressure to keep oil free from contamination.
• Continuously coats all internal surfaces with Lubricant to anti corrosive agent.
Oil Mist Equipment Designs and Certifications
The microprocessor controlled central consoles are easily tied into DCS systems. In addition, consoles that are third party approved for NEC and IEC hazardous area classifications are available. It is not necessary to carry out special designs for particular projects as the vendor equipment is already approved for use in hazardous cl assified areas.
Machinery Manufactures
As the use of oil mist has grown around the world, pump and electric motor manufacturers have incorporated bearing housing designs for oil mist lubrication. Pump and electric motor manufacturers that have a significant presence in the hydrocarbon processing industry supply equipment ready for oil mist lubrication. API-610 gives them clear standards for use of oil mist with pumps. The procedures for converting from grease lubricated motor bearings to oil mist are also readily available and easily adapted.
Oil mist lubrication is a proven technology that delivers both financial and environmental benefits. Equipment failures are reduced lowering operating and maintenance costs. Consumption and discharge of lube oil is also reduced with oil mist. Financial payback on the investment in oil mist systems is quick and low risk. Leading vendors of oil mist systems have the experience and knowledge for the successful application of oil mist to machinery in the hydrocarbon processing industry. The use of oil mist lubrication is becoming a preferred approach to bearing lubrication by many of the leading companies in this industry.
키워드에 대한 정보 pure vs purge oil mist lubrication
다음은 Bing에서 pure vs purge oil mist lubrication 주제에 대한 검색 결과입니다. 필요한 경우 더 읽을 수 있습니다.
이 기사는 인터넷의 다양한 출처에서 편집되었습니다. 이 기사가 유용했기를 바랍니다. 이 기사가 유용하다고 생각되면 공유하십시오. 매우 감사합니다!
사람들이 주제에 대해 자주 검색하는 키워드 LOMA AIR + OIL MIST LUBRICATION SYSTEM
- 동영상
- 공유
- 카메라폰
- 동영상폰
- 무료
- 올리기
LOMA #AIR #+ #OIL #MIST #LUBRICATION #SYSTEM
YouTube에서 pure vs purge oil mist lubrication 주제의 다른 동영상 보기
주제에 대한 기사를 시청해 주셔서 감사합니다 LOMA AIR + OIL MIST LUBRICATION SYSTEM | pure vs purge oil mist lubrication, 이 기사가 유용하다고 생각되면 공유하십시오, 매우 감사합니다.
