Oil Seal Overview

Oil seals, often called a rotary shaft seal or grease seal, closes the gap between stationary and moving components in mechanical equipment — most often rotating shafts — helping prevent lubricant escape and stopping harmful materials, such as dirt, from moving in through the clearance. Oil seals are most commonly used in gearboxes, hydraulic cylinders, and related components.

SHOP FOR OIL SEALS

Oil Seal Part Number System

Global O-Ring and Seal’s oil seal part numbers are designed to describe the seal size, style, and material composition. When searching for oil seals via our online store, you will not only be presented with your selection but with comparable oil seals of the same dimensions. There are often viable style substitutions which are functionally compatible, but with additional features.

As an example, this oil seal has a Shaft Size of 4″, a Bore Size of 5.000″, a Width Size of .375″, a Style of TB2, and is made of Viton material.

OS/MOS: Designates if dimensions are displayed in inches or millimeters.

Shaft, Bore, Width: Dimensions displayed are actual size, rather than nominal.

Style: 2-5 characters in length (see our style chart at the bottom for details).

Material: There are several material options. Nitrile (Blank) Viton (V), Silicone (S), EPDM (E), Carboxylated Nitrile (X), HNBR (H), Polyacrylate (P), and Teflon (T).

Selecting the Right Oil Seal

Beyond selecting the correct size, the three primary selection criteria are Material, Lip and Case. If you have an oil seal you’d like custom designed and made, send us your specifications through our Oil Seal Design Form.

Material Selection:

Material selection is important to the life of a radial shaft seal. The elastomer’s resistance to temperature, abrasion, chemicals, weather, sunlight and ozone can affect a profile’s longevity and performance. The two most prevalent materials are Nitrile and Viton. See our Oil Seal Materials page for details on compounds and chemical compatibility.

The durometer of an oil seal is typically dependent on the material it is made with. Common oil seal materials along with their durometers are as follows:

  • Nitrile (NBR) Oil Seal: 70 durometer (+/- 5)
  • Viton (FKM) Oil Seal: 75 durometer (+/- 5)
  • Polyacrylate (PA) Oil Seal: 75 durometer (+/- 5)
  • Silicone Oil Seal: 80 durometer (+/- 5)

Lip Selection:

Lip selection is driven by the media type, shaft speed, pressure, temperature and contamination parameters. The media used in the majority of applications is either oil or grease. Lip designs generally include a spring when the media is oil because of its higher viscosity as compared to grease. There is also a double spring design when there is media on both sides of the oil seal. Lip designs can also include a secondary lip which purpose is to mitigate particulates from reaching the sealing lip.

‘S’ Lip – single lip with spring. The spring is to ensure sealing of oils versus grease. Used in more benign environments.
‘T’ Lip – dual lip with spring. The lip design includes a secondary dust lip to minimize particulates from entering the sealing region. This is the most common lip design.
‘V’ Lip – single lip without spring. This lip is designed for grease applications because the high viscosity of grease does not require a spring
‘K’ Lip – dual lip without a spring. This lip is designed for grease applications and include a secondary dust lip to minimize particulates from entering the sealing region.
‘D’ Lip – dual lip and dual spring lip. This lip is designed when there is media on both sides of the oil seal.

Case Selection:

The most common and cost effective case materials are stamped from cold rolled carbon steel. The steel is then phosphate coated to aid in the molding process and to help eliminate corrosion during storage. A simply ‘L’ shaped geometry is the most cost effective case design but a number of case geometries are available to improve rigidity, positioning and removability. oil seal cases can also include rubber molded options which address such factors as corrosion, vibration and sealing characteristics.

  • B2 Case – The most economical design and popular design (simple ‘L’ shape). It has a metal outside diameter.
  • A2 Case– The A2 design also has a metal outside diameter but includes an inner case which provide structural rigidity. This case design is used when the diameter of the seal is larger and rigidity is required to maintain structural integrity during installation.
  • C Case– The outside of this case is rubber coated. This design is often used when a seal will be removed frequently or if sealing of bore and oil seal is of concern.
  • B Case– The B design is the same as the B2 except that a rubber inner coating is added to protect case from media.
  • BR Case– The BR design is same as B with additional rubber coating on the leading edge of the case. This additional rubber coating is to ensure sealing when the oil seal is seated in the groove.

Size Selection:

The oil seal size is specified by three dimensions: the rotating shaft diameter, the housing bore diameter, and the width (thickness). Because an oil seal’s purpose, correct size is critical to performance. The inside diameter of an oil seal is sized slightly smaller than the shaft diameter in order to seal lubricants inside and prevent harmful contaminants from entering. Oil seals are offered in both metric and inch sizes to ensure the correct fit. Below are the core 25 oil seal styles:

Oil Seal Style Substitutions

Oil Seals offer numerous style options. With the most popular styles, each can be categorized as Good, Better and Best. The manufacturer most often uses a Good (or Better) solution which was the most economical version that would perform to specifications. When replacing that Oil Seal, you can use the exact style or choice a Better or Best solution if your exact style is not in stock. In the charts below, you can always move up to Better and Best styles which can be substituted. Our goal is to provide our customers with the best product fast so we will stock the Better and Best styles and price them competitively.

Exhibit 1:

Exhibit 2:

Exhibit 3:

Additional Oil Seal Options:

In addition to the Material, Lip, and Case selections, you can select to have a Stainless Steel Case and a Stainless Steel Spring. In those cases you will find an additional indicator in the part number.

Installing an Oil Seal

Choosing the correct oil seal for your application is important. It is just as important that oil seals are installed properly, in which our step-by-step guide can be viewed here. Doing so ensures your desired oil seal fits and performs as intended.

Oil Seal Style Cross Reference Table

Oil seals are produced by a variety of manufacturers from around the globe. Part numbers vary greatly with manufacturers, so we have created a quick cross reference guide to cross oil seal lip and case designs. Sizing and material selection can be made on our ecommerce site or provide to an Inside Sales person when placing an order. See chart below:

Global O-Ring and Seal Case Design Lip Design Timken (National) SKF/CR Harwal Garlock Dichtomatik (TCM)
SC Rubber OD Single Lip w/ Spring 35 HMS5 A 92 SC
TC Rubber OD Double Lip w/ Spring 32 HMSA10 ADL 94 TC
VC Rubber OD Single Lip, No Spring 34 HM4 AO 91 VC
KC Rubber OD Double Lip, No Spring N/A N/A N/A N/A KC
DC Rubber OD Two Spring Lips N/A N/A DC N/A DC
SB Metal OD, Rubber ID Single Lip w/ Spring N/A HDS1/HDS2 SM 76 SM
TB Metal OD, Rubber ID Double Lip w/ Spring N/A N/A TM 78 TM
VB Metal OD, Rubber ID Single Lip, No Spring N/A N/A VM 71 VM
KB Metal OD, Rubber ID Double Lip, No Spring N/A N/A KM N/A KM
DB Metal OD, Rubber ID Two Spring Lips N/A N/A N/A N/A DM
SB2 Metal OD Single Lip w/ Spring 48 CRW1 B 76 SB
TB2 Metal OD Double Lip w/ Spring 47, 69 CRWA1 BDL 78 TB
VB2 Metal OD Single Lip, No Spring 44 HM14 BO 71 VB
KB2 Metal OD Double Lip, No Spring 49 N/A BODL N/A KB
DB2 Metal OD Two Spring Lips N/A N/A DB N/A DB
SBR Metal OD, Rubber ID, and Nose Single Lip w/ Spring 35 N/A N/A N/A SZ
TBR Metal OD, Rubber ID, and Nose Double Lip w/ Spring 33 N/A N/A N/A TZ
VBR Metal OD, Rubber ID, and Nose Single Lip, No Spring 31 N/A VZ N/A VZ
KBR Metal OD, Rubber ID, and Nose Double Lip, No Spring N/A N/A N/A N/A KZ
DBR Metal OD, Rubber ID, and Nose Two Spring Lips N/A N/A N/A N/A N/A
SA2 Metal OD w/ Reinforcing Plate Single Lip w/ Spring 45 CRWH1 C 50 SA
TA2 Metal OD w/ Reinforcing Plate Double Lip w/ Spring 41, 70 CRWHA1 CDL N/A TA
VA2 Metal OD w/ Reinforcing Plate Single Lip, No Spring N/A N/A CO 63 VA
KA2 Metal OD w/ Reinforcing Plate Double Lip, No Spring N/A N/A CODL 63 KA
DA2 Metal OD w/ Reinforcing Plate Two Spring Lips 75 N/A DA N/A DA