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can i use a standard non return valve as a fuel tank breather?
daniel mason - 29/1/11 at 10:15 PM

as above is a standard none return valve ok as a fuel tank breather/vent? they dont let liquid through unless under pressure so it would seem they are ok?

daviep - 29/1/11 at 10:53 PM

quote:
Originally posted by daniel mason
as above is a standard none return valve ok as a fuel tank breather/vent? they dont let liquid through unless under pressure so it would seem they are ok?


What exactly is a "standard" non return valve and why would it let flow through under pressure?

Cheers
Davie

prawnabie - 29/1/11 at 11:02 PM

The "proper" one is available from merlin or think automotive - it is a two way valve that lets the tank suck air in and vent air out whilst not letting fluid out in the event of a roll

daniel mason - 29/1/11 at 11:06 PM

i mean a non return valve. it wont let fuel through unless its pressurised so in the event of a roll it would not leak. it would not suck air back in though,but obviously would let it out!

daviep - 29/1/11 at 11:21 PM

quote:
Originally posted by daniel mason
i mean a non return valve. it wont let fuel through unless its pressurised so in the event of a roll it would not leak. it would not suck air back in though,but obviously would let it out!


Sorry I'm lost

A non return valve allows flow in one direction and stops it in the other regardless of pressure in either direction.

Sorry not to be any help

Davie

daniel mason - 29/1/11 at 11:25 PM

it does allow flow in one direction, but the one i have only allows prssurised flow in one direction! i have seen those on merlin and cant see what they do, that mine doesnt?

Davegtst - 29/1/11 at 11:25 PM

You really need it to vent air both ways but not let fuel escape. As you are using driving using fuel you will be creating a vacuum in the tank so you would need air to enter the tank to stop this. On hot days petrol will expand which can create large ammounts of pressure in the tank. If the tank is not vented when you open the cap you may get covered in petrol as the gases rush to get out.

daniel mason - 29/1/11 at 11:38 PM

ah! thats the response i was after. my valve is no good then. i bought it from cbs and it said it can be used as a fuel tank breather. but its not the same as the merlin ones! cheers mate

daviep - 30/1/11 at 10:17 AM

quote:
Originally posted by daniel mason
it does allow flow in one direction, but the one i have only allows prssurised flow in one direction! i have seen those on merlin and cant see what they do, that mine doesnt?


That's much clearer, what you have is pressure relief valve.

Davie

RazMan - 30/1/11 at 10:40 AM

I have used a couple of these on my tanks ....

Fuel tank cap breather Gold KTM petrol vent UK Seller on eBay (end time 20-Feb-11 18:46:49 GMT)


The valve allows air into the tank but stops fuel escaping - not perfect but definitely more Locost than the Merlin solution


[Edited on 30-1-11 by RazMan]

daviep - 30/1/11 at 12:56 PM

The other truly locost option is a piece of hose. If the breather connection is on the top of the tank at the front you need to bend the hose through 180 degrees and run it down to the bottom of the tank at the back then bend it through 90 degrees and run it across to the other side of the car.

Kind of like this (excuse my crap paint skills )

Davie