Does Avgas eat any kind of o-ring?

[Chris M]

My very tiny club uses a manual hand crank on a 500 gal tank to refill our two airplanes. For some reason the pump seems to eat seals at an alarming rate. One of our members thinks it's due to side loads on the handle (which is entirely possible, it's a good reach to get on top of the tank so you're working from an odd angle). I'm not aware of any rubber o-ring material that would be incompatible with 100LL but thought I would see if anyone here had experienced something like this.

In the future we may go to a battery powered 12V pump with a solar panel and battery tender. It would definitely be a nice upgrade.

[ahramin]

Yes absolutely avgas will eat o-rings. Before using any o-ring I let it sit in avgas overnight and then check it to make sure it isn't flaking. I'm sure someone else here can tell you what types of rubber are ok and what types aren't.

[Meecka]

This might help:

http://www.fluidseals.com.au/o-ring_app ... _guide.php

[iflyforpie]

In aviation, o-rings are specific to the application. Fuel and hydraulic fluids use different specs. Even 5606 and Skydrol o-rings are incompatible.

Incorrect installation wil also result in problems (twisted, not lubricated, no backup rings, wrong size, damaged groove, wrong shape or thickness, rough handling, expired shelf life).

[CID]

Yes absolutely avgas will eat o-rings. Before using any o-ring I let it sit in avgas overnight and then check it to make sure it isn't flaking. I'm sure someone else here can tell you what types of rubber are ok and what types aren't.

Wow.

[Heliian]

It may not be the type of material used but the application. The seals are lubricated by the medium (fuel in this case), which will evaporate quickly and leave the seals dry, next time you crank, the dry seal gets damaged and so on until it leaks. A proper pump will help you in this case as it sounds like you may be using one designed for oil or more slick products.

[PilotDAR]

Heliian makes a valid point, are you sure that an O ring is the proper type of seal? My hand pump has a leather packing, which is compressed around the piston rod by tightening a gland nut. It does not mind operating dry a few strokes, until the fuel comes up to wet it.

There are certainly right and wrong O rings for gasoline, though generally, any O ring intended for gasoline these days, should tolerate Avgas okay. A Senior Cessna Engineer told me that when Cessna changed their line fuel from 100/130 to 100LL, all the new planes weeped fuel. They had to replace O rings throughout the fuel system, and sourced them from automotive suppliers, as the automotive gasoline O rings could tolerate the higher aromatics now in the 100LL. This was also my experience, when we started using Mogas, we just replaced the original O rings with new, and problem solved...

[niss]

It does not mind operating dry a few strokes, until the fuel comes up to wet it.

[GyvAir]

That's NOT what she said...

[hoserjoe]

Dupont Viton fluoropolymer elastomer o-rings resist fuel and acids better than any other types, in my experience. Believe it or not, there are companies that specialize in o-rings, with excellent customer service, and Google will help you.

[Strega]

I think you need to hire an AME that will rebuild the fuel pump for you,, otherwise, it will not be safe.

They might charge you a lot, but in the end, you will know that it was done correctly.

[DonutHole]

What you really need is a real engineer to design a pump that doesn't use orings.