People don’t usually consider washers a type of gasket, but depending on how they’re being used, that’s exactly what they might be. This blog discusses what washer gaskets do and what to consider when selecting material for them.
Washers for Sealing
A washer is a ring of material under the head of a bolt or under a nut. In fastening applications it’s job is to spread the load being applied. A washer gasket is a ring of gasket material placed under a bolt head or nut. Gasket material isn’t a good load spreader because it’s soft and compressible, but it can have three other functions:
- Seal against fluids
- Dampen transmission of noise and vibration
- Prevent galvanic corrosion
Another way washers, felt washers specifically, are used is to lubricate a rod or shaft passing through the washer. This works because felt washers are very good at retaining oil.
Washer Gasket Material Options
Like any gasket, a washer gasket has to take up deformations in the surfaces it’s sealing. This requires compressibility. Recovery, or resistance to compression set, may be another useful property if the bolt is likely to get hot and expand.
Other selection criteria relate to the media being sealed and the environment the washer gasket will go into. This means looking at characteristics like tolerance to oils, acids and alkalies, and UV and ozone. Then consider temperature, both of the media and the environment.
For dampening applications the vibration-attenuating properties of the material are what matter most. This is where a knowledgeable supplier can be a big help.
Galvanic corrosion occurs when metals with different electrolytic compatibilities come into contact in the presence of moisture. For this type of application the washer gasket’s job is to be an insulator between the two metals.
Depending on the application and the temperature range needed, good material choices can be:
- PTFE
- Neoprene
- EPDM
- Silicone
- NBR
- SBR
Advice From Hennig Gasket & Seals
With many different materials to choose from, deciding which is best for an application can be quite daunting. A risk-free approach is to consult the specialists at Hennig. Contact us today.
