A rubber washer is defined as a thin disk made of rubber with a hole in the middle. The washer is normally used to support the weight of a threaded fastener. It is also used as a spacer, spring, wear pad, pre-load indicating device as well as locking device. Washers are made of various materials like metal, plastic, rubber. A common material is rubber. Rubber washers are used in taps or valves where they act as the seal that prevents or closes the flow of liquid or gas. All washers have an outer diameter (OD) about twice their inside diameter (ID). Rubber gaskets which are used in taps to stop the flow of water are also sometimes referred to as washers because they look similar. But, washers and gaskets are usually made differently and designed for different functions.

Types of rubber used in rubber washers

• Neoprene
• Styrene Butadiene Rubber (SBR)
• Ethylene Propylene Diene Monomer (EPM, EPDM)
• Silicone Rubber (SiR)
• Nitrile Rubber (NBR)
• Fluoroelastomers (FKM)/Viton

Buying tips for rubber washers Following are the specifications which should be looked for before buying rubber washers: Material Type Outside Diameter Inside Diameter Thickness

Features of rubber washers
Rubber materials are preferred for washers because of rubber's

• Innate flexibility
• Pliability
• Conformability
• Most rubber grades are as thin as 0.016" to 0.250" thickness.
• It is also measured in terms of hardness (durometer) as soft as 30 and as hard as 90 duro.
• Materials are also available as continuous rolls or cut-to-size.

Flange Washers
Rubber washers are widely used for sealing of flanges. It is estimated that around 50 to 80% of all leaks in flanges are caused by insufficient bolt pre load. The bolts are usually all tightened to a given aim pre load. At this original pre load the bolt has a certain amount of stretch and the process fluid heats up the flange and gasket after some time causing them to expand more than the bolts. This leads to loosening of the grip. Flange Washers are effective because they add deflection to the fastening system. The use of flange washers has a positive impact overall on the performance of a live loaded flange joint.
Flange rubber washers are used in

• Flanges where failure could cause a safety problem.
• Joints that see wide fluctuations in temperature.
• One or more of the flange components are subject to yielding like vibration, gasket creep, bolt creep, or elastic interaction.
• The flange has a long history of maintenance problems.
• Flange joints which develop leaks on account of various reasons like differential thermal expansion, bolt creep and vibration.

Uses of Flange Washers
Flange Washers are designed to serve the following purposes:

• To maintain sufficient bolt tension.
• To maintain gasket pressure by compensating for gasket relaxation, bolt creep, and differential expansion during temperature/pressure changes.
• Flange washers maintain the high loads necessary to keep flange joints tight and leak free.
• Flange Washers prevent damage to bolts and gaskets.