Please note that under most circumstances, you will not need to measure the oil seal itself. To size the seal correctly, you just need to know the shaft diameter, bore diameter, and bore depth of the equipment that you took the seal out of.  

One situation in which you might need to measure the seal itself however, is if you are trying to verify its manufactured size. The most important dimensions on an oil seal are the ID (inner diameter), OD (outer diameter), and width. We do not recommend trying to measure the ID of the seal, as it is very difficult to do without stretching or altering the lip. The OD of the seal can be measured most accurately with a special piece of equipment called a pi tape. The pi tape is able to take into account any out-of-round condition with the seal that a pair of calipers might not. The width of the seal can be measured with a pair of calipers, taking a few measurements around the whole diameter.  

How to Measure Metric Oil Seals?

Metric Oil seals will usually have the sizes written on it, for example 20 40 10 written on the seal tells us it will be a 20mm Inside Diameter (ID) a 40mm Outside Diameter (OD) and 10mm Wide/Thick.

If nothing is printed on the seal you would just need to take Vernier etc and measure the ID,OD and Width.

You may also see letters on the seal, if it has TC this means it is a Double Lip (R23) seal or if SC is written on it this means a Single Lip (R21)

Ways to Measure and Choose Oil Seals for Industrial Applications

Oil seals are used in several industrial applications to protect shafts and bearings from oil, grease, contamination, and dirt. They comprise an outer and an inner circular rings. The outer ring or disk is made of metal, while the inner one is made of rubber and hence is flexible. It is stuck onto the outer ring with the help of a chemical adhesive. There are oil seals with single lip as well double lips. The sizes of these seals depend on application requirement, and hence it is measure the inner and outer diameters, width, and so on. Also, it is crucial to choose the right type of oil seal for every application. This post discusses the way to measure and choose the oil seal for your application.

How to Choose the Right Oil Seal Type?

You may have to choose or identify the oil seal type in case of either a new equipment fitment or as a replacement for the damaged one. Here are a few pointers to identify the right seal type.

• Primarily, there are single lip and double lip oil seals. The single lip is the immersed at the bottom for which the inner diameter needs to be considered.
• Double lip oil seals have an extra lip at the top which protects from external contamination, dirt, and so on.
• Pressing along the line of the inner diameter at the top may help determine whether the oil seal is single lip or double lip.
• Check the code of the lip seal given by the manufacturer or look for a reference guide for further information regarding the oil seal type. This is because there are several types of single lip as well as double lip seals with varied configurations such as type A, B, or C single lip and type BO, ADL, double lip, and so on.
• Type B seals have their outer diameter made of metal, while in case of type A it is made of rubber. In type C, there is reinforced metal added for structural stability. Likewise, there are several types of materials and their permutations and combinations.
• All of these oil seals based on their materials have specific physical and chemical properties, and accordingly find applications in diverse industries. For instance, type C single lip offers structural stability and hence finds use in heavy engineering. Type A made of rubber has amazing resistance to heat, chemicals, and so on. Hence, they find application in industries where there is exposure to chemicals, abrasion, and elevated temperatures.
• Before you choose the type of oil seal, it is essential to measure it, which is discussed in the next section.

How to Measure Oil Seals?

Oil seals are typically used as seals in moving parts that prevent friction as well as mixing of liquids or other elements. The oil seeps between the lip and shaft and that lifts up the lip. This creates the required gap between the lip and shaft as they should never come in contact with each other. This is basic working mechanism of oil seals. When replacing these oil seals, it is essential to measure them since they have different dimensions based on the application they are fitted in. Here are some pointers regarding their measurement.

• While visual inspection may offer some clue, it may not be accurate. Hence, measuring the inner and outer diameter with the help of calipers is important.
• Their measurement is much like O-rings, wherein, height, lip, type, inner and outer diameter are important factors. Material is also a factor to be considered although it cannot be measured.
• Take at least three readings, preferably with a Vernier caliper. Consider the average reading if there is negligible difference among the values.
• Measure the bearings and also consider the gaps.

Related Post

If you want to buy automotive oil seals or industrial oil seals these identification pointers may be useful. However, ensure you source them from reliable manufacturers and suppliers that can ensure leak proof seals. If you are looking for food or pharmaceutical applications, ensure the industrial oil seals are FDA approved. SSP Manufacturing Inc. has a market presence of more than three decades and offer premium quality custom oil seals for a number of industrial applications.