Large Diameter O Rings? The 61 Top Answers

There are several ways to check your ring size. If you don’t have an existing ring to measure, or you think your ring size may have changed, you can have your ring size checked professionally and accurately by visiting us in our stores.

If you shop online or prefer to find your ring measurements at home, use our printable ring size chart.

Another easy way to check your ring size from home is to measure the inside diameter of a properly fitting ring you already own and then refer to our size chart to convert that measurement to your ring size. Make sure you use a ruler with millimeter measurements, then place your ring on the ruler and measure the inside of the circle – in other words, the part that touches your finger. Check for correctness.

O-Ring Basics – Measure.

The O-ring, a round mechanical seal that prevents gas or liquid from passing through an orifice. A marvel of engineering, if you will. However, they are not perfect and can wear out over time and need replacing, so finding the right size is important. We’ve put together some easy-to-follow instructions to get you just the right size for the job.

The three D’s of the O-ring

There are three dimensions you need to get the perfectly sized o-ring for your application. These are the outside diameter (OD), inside diameter (ID) and the all-important cross section. Sounds easy and honestly it is. All measurements should be recorded in millimeters. Begin by laying the ring on a flat, clean surface.

OD – Use a ruler or tape to measure the distance from one side of the outside edge to the other.

ID – Repeat this but measure from one inside edge to the other.

CS – Place the o-ring in a caliper and lightly clamp the jaws. Be very gentle now, don’t squeeze it.

Write down all three measurements, don’t forget in millimeters, and Bob is your uncle. “Ah, but I don’t have a caliper,” I hear you say, and that’s no problem. There is a very simple formula that we can use to calculate the CS when you have both ID and OD. In fact, as long as you have two of the three dimensions, there is a handy formula to help you work out the other.

O-rings – the magic formula

The cross section is equal to the outside diameter minus the inside diameter divided by two. Or in equation terms CS=(OD-ID)÷2

The outside diameter is equal to the inside diameter plus twice the cross section or OD = ID+(CS x 2)

The inside diameter is equal to the outside diameter minus twice the cross section or ID = OD-(CS x 2)

If your o-ring is cut or torn, we can still fix it. Measure the length and cross section of the ring. Then divide the length by π (3.142), which gives the circumference. Take the cross section out of it to give you the inside diameter.

length ÷ π = circumference.

Scope – CS = ID

If you don’t have a ruler or really don’t feel like measuring it yourself, then give us one and our knowledgeable sales team will do the hard work for you.

February 23, 2018

By: Chett Norton, C.E.T. and Sylvia Flegg, Head of Marketing

Gaskets come in all shapes and sizes: round, oval, rectangular, etc. Accurate measurement size is important as it ensures the gasket is seated properly and does not interfere with installation. In addition, measurement is managed by QC to ensure the gasket meets either customer specifications or the tolerances set by specific standards for cut gaskets such as ASME B16.21 and EN1514-1. To illustrate some of these points, I’m going to give you two specific examples of what to measure and what to avoid.

Ring seals are fairly easy to measure as you only need to check two measurements: inside diameter (ID) and outside diameter (OD). Ring gaskets are commonly used in raised face (RF) flanges because the gasket is centered in the bolts. In general, the use of ring gaskets in full face flanges is not recommended as they are thinner and more fragile. Because the O.D. of the ring seal is not flush with the edge of the flange, any deflection of the flange (flange rotation) caused by tightening bolts can cause serious damage.

Full face gaskets are a bit more difficult to measure as there are five things you need to check correctly: Inside Diameter (ID), Outside Diameter (OD), Bolt Circle Diameter (BCD), Bolt Hole Diameter and the total number of bolt holes.

Full face gaskets are commonly found in flat flanges but are also occasionally used in edgewise (RF) flanges. For ease of use in RF flanges, installers place the gasket between the two flanges and insert two or more screws to align the gasket prior to installation. Although using a full face gasket in an HF flange makes installation more expensive, it minimizes improper gasket centering and eases the installation process.

measurement methods

The most common hand tool used for measuring is a tape measure or ruler. Both can easily allow the person to check the inside and outside diameter of the seal by visually checking the measurement increments on the tool. Bolt holes and the bolt circle diameter of a gasket are a bit trickier; However, with a little practice, consistent measurements can be achieved. These types of measurement tools should not be used when high precision measurements are required.

Vernier calipers are another hand tool that is far more accurate than rulers and tape measures. The digital display allows measurements in increments as small as 0.001 inch. Vernier calipers are available in different size ranges. So if you have a range of gasket sizes to measure, there’s a good chance you might need two or three sets to cover the full size range you need.

The two methods I’ve listed above both share one major drawback in terms of measurement – human error. When trying to measure gaskets, they can become “ovoid” or oval. The easy way to eliminate this error is to use a jig or pass/fail jig that allows you to seat the gasket without having to physically measure it. If the seal fits, it passes, and if the seal does not, it is rejected. The downside to this type of retainer is that it can be expensive to manufacture and you will need a retainer for each individual seal size.

So there you have it! I hope this gives you an idea of ​​what to look for or what to consider when determining gasket measurement.

Keep the liquid between the tubes until next time!

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[PDF] Available o-ring tool sizes

AS568 is the aerospace size standard for O-rings from the Society of Automotive Engineers. The SAE Aerospace Standard (AS) specifies the inside diameters, cross-sections, tolerances, and size identification codes (prime numbers) for O-rings used in sealing applications and straight-threaded tube fitting gland seals. Please add the material and hardness information to select a correct o-ring. Please see the gland design to design a suitable gland for these o-rings.

Metric O-Ring Size Chart Search our metric o-ring size chart to view common metric o-ring sizes and to order o-rings from the world’s largest inventory network. Thousands of popular metric o-rings and non-standard metric sized o-rings are available in stock. Custom o-rings are available upon request and can typically be made in a matter of weeks with no tooling costs.

Choose Marco Rubber & Plastics For more than 40 years, Marco Rubber & Plastics has provided custom and standard O-rings and other sealing solutions to a variety of industries. With millions of products produced and shipped annually, we are the experts your business needs to ensure your application’s success. Explore standard size o-ring sizes below.

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If you would like to discuss your special application with a product expert, call us today at 603-468-3600. Download size table as PDF

O-rings come in a variety of colors and it is important to understand what these colors mean as the O-rings you choose will affect your overall process application.

Finally, different O-ring colors are used to make it easier to distinguish between different materials.

Specialist Sealing Products can supply a range of O-Rings in any color and in a range of materials.

The good news is that we can order our o-rings directly online HERE; However, if you have specific questions about O-Rings, their color and materials, call us on 01535 274 776 or visit this page to learn more about O-Rings.

Yellow, black and green o-rings

Black o-rings

Manufactured from EPDM, black o-rings are best suited for applications such as heating, fire protection, drinking water and sanitary water.

They comply with the EN 681-1 standard and are equipped with the patented SECURFRABO system security.

They also withstand minimum temperatures of -10 degrees and maximum temperatures of over 110 degrees.

Yellow o-rings

Manufactured from HNBR, find yellow o-rings for gas applications that comply with the EN 549 standard.

These norms are also shared, i. H. EN 681-1 yellow O-ring for water and EN 549 yellow O-ring suitable for gas.

Patented security system SECURFRABO.

The minimum temperature of the yellow O-rings for water and gas can reach -20 degrees, with a maximum temperature of +95 degrees.

For such O-rings, which are only gas, the minimum temperatures reach -20 degrees, and their maximum temperature can reach +70 degrees.

Green o-rings

Manufactured from FKM materials, these o-rings perform perfectly at high temperatures and changing stress levels – making them ideal for systems such as solar.

Their maximum temperatures reach 160 degrees but can briefly reach 200 degrees if needed.

O-ring color coded

O-Ring Color/O-Ring Material

Black/FFKM, NBR, EPDM, Viton, Alfas, Neoprene

Green/HNBR, HSN, Viton

Blue/Fluoro Silicone

Hi-Vis Green/NBR

Brown/Viton

Red/Silicone, PFAS, TES

Clear/Urethane

White/NBR, Viton, Silicone, EPDM, PTFE

Yellow/NBR

Each O-ring material offers different properties, making it suitable for different applications and processes. It is important to choose the most suitable material to achieve the best seal for your application.

Various O-ring compounds are recommended for sealing as new and innovative materials are identified and used as suitable sealing products.

As mentioned earlier, color coding O-rings in this way has allowed the industry to distinguish between different types of materials and most importantly, improve their visibility in applications.

Colored dots can also sometimes be applied to o-ring lots to help you with your own inventory.

Keep everything organized and in a systematic order. (Note: These markings are not permanent and are for your own information only).

SSP can assist with color coding if you wish to include this item in your o-ring order.

Difference between black o-rings and green o-rings

Black o-rings are primarily made of neoprene or nitrile, or in some cases a mixture of the two materials. Black O-rings were primarily the only colored O-rings prior to 1987; However, as new materials entered the market, different colors were required to identify the different materials used, mark their visibility and allow companies to verify their suitability for specific and different applications. Black o-rings are most commonly used for car air conditioning systems.

Green O-Rings are Hydrogenated Nitrile, also known as Highly Saturated Nitrile or better known as HNBR. These o-rings have the green color molded into their rubber and were introduced with refrigerant 134a, which is suitable for high temperatures and alternating loads.

There is a call to simplify o-ring color selection; For now, however, these colors provide a clear picture of the changes taking place.

Specialist Sealing Products offers a range of o-rings and can assist with color coding for inventory management. Our knowledgeable, experienced and friendly team will be happy to help you find the most suitable o-ring material for your application.

Call us today on 01535 274 776 or visit our stock pages online to find out more. Click the button below.

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