Sealer for diesel tank ftgs

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colinmi

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Valves on the bottom of my stainless tanks were fitted with PTFE tape. They weeped a bit. Not a lot but enought to be a nuisance.

Have drained the tanks and and taken the fittings off. Now I need to know what to refit them with. They are 1/2 inch bst.

Thanks Colin
 
I would of thought PTFE tape would be the correct thing to use or you can buy PTFE liquid now i use that at work and always seems to seal frist time. the only problem with it you cant pack out a thread to get a valve in a certian position like you can with the tape.
 
[ QUOTE ]
Valves on the bottom of my stainless tanks were fitted with PTFE tape. They weeped a bit. Not a lot but enought to be a nuisance.

[/ QUOTE ] It depends on the thread on the fitting you are screwing in, If it is a parallel thread then the seal should not be on the threads themselves. The fitting should tighten down on to a joint washer etc.
If it is a tapered thread into a parallel female thread (a common but not ideal practice) then tape or a pipe jointing comound is necessary. A gasket cement may not be adequate.
 
PTFE will degrade with diesel. I used a compound called Red Hawk which a plumber friend gave me which is designed for diesel.
 
[ QUOTE ]
PTFE will degrade with diesel

[/ QUOTE ] That is something I have not heard before. About the only thing i can find any reference to is that fluorocarbons can cause swelling of ptfe. Fragments of ptfe could lodge in injectors if used downstream of all the fitters but that's not going to be a problem at the fuel tank.

Also drawn a blank on Red Hawk. Stag jointing pastes are suitable for use with diesel.
 
Well, always pleased to try and help. I've just been round to my engineer to see who made the Red Hawk. He finished that off and had trouble getting more so he got "Heldite" jointing compound. This is for petrol, diesel, lubricating and transmission oils. It is made by Heldite Ltd in Houndslow. Tel 0181 577 9157/9257. I hope this helps.
My comment about PTFE degrading with diesel is based on what several engineers have told me viz that it makes a seal to start with but in a short time it will start weeping. At least I know someone is reading my posts.
 
[ QUOTE ]
"Heldite" jointing compound

[/ QUOTE ] Yes I came across that while looking for jointing compounds in general. 4 suppliers in Scotland.

<span style="color:white"> ~~~~~~~~~~~~~~~ </span> Heldite

I suspect the trouble with ptfe tape is not that it degrades in contact with diesel, in fact I am sure it does not, is that people tend to use too much and you end up with a joint where there is no metal to metal contact at all. With a bit of vibration the tape compresses slightly and then it weeps and once diesel starts weeping nothing seems to stop it.

Tapered male to parallel female joints are perhaps not ideal for diesel (we'll they are not ideal anyway, just commonly used and perfectly satisfactory for water) Even Heldite is not sold as a jointing compound for these joints.

The joints in the diesel system would be much better if they were proper parallel to parallel joints with annealed copper joint washers.
 
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