1 reply to this topic

[Zir Ferz]

Hi,

I have to purchase pressure/vacuum relief valves for a carbon steel tank storing crude oil. The manufacturer offers two different types of seals material, teflon or viton so I was wondering which one is better for my application?

Thanks!

[proinwv]

Viton is a fuel resistant elastomer designed for high temperature. In a PV vent it likely will be effective down to about +10 F, and be too stiff for sealing below that. I would still confirm its chem resistance to your product. Buna-N compounds have much better temperature capabilities at low temps. Sometimes, when an elastomer is seated for long periods it can tend to stick to the seat. Seat design has an effect on this as well as the product in contact and temperatures.

Teflon is generally unaffected by fuels and most products. It has a wide temp range and when there is a properly designed seal/seat arrangement, it will seal well in a PV vent application. It is more resistant to the seat freezing in cold weather. Not being an elastomer, it is not as flexible as an elastomer, such as Viton. I like Teflon for the non-stick properties.

As I said the seat/seal interface design is important. Plastic seats can be superior to metal seats.

I suggest that you have a good conversation with tech people at the vent manufacturer. Look at a couple of vent manufacturers too. Also consider if the seat is reasonably protected from sticking due to ice formation, if that is a consideration. Be aware that PV vents do not seal well over time.