Inspection hatch in polyethylene diesel tank

J

jwilson

Well-Known Member
Joined
22 Jul 2006
Messages
6,227
Visit site
jwilson said:
I am contemplating fitting an FLB Inspection Hatch in a PE diesel tank (the original fit in a Jeanneau SO35) - http://www.tek-group.co.uk/acatalog/Inspection_Hatches.html or http://www.wema.no/publish_files/FLB-1_-_163120.pdf?PHPSESSID=54fffcbdf7baf3f6d7bd6727bee8a58f

The tank is relatively thin plastic, maybe 4-5mm thick. Has anyone else used these hatches - and did they ever leak? It will be in the top of the tank, and I do need to fill the tank to full regularly.
Click to expand...

Looks OK but I would be worried that the 'O' ring wont stay in position when tightened up. It would be better if the 'O' ring was located in a groove to retain it in position. How flat is the top of your tank? Speak to TekTank for advise, they are helpful.
 
Works fine on my diesel tank. I've had need to use it a couple of times; it's a minor faff undoing the bolt all the way and wiggling the whole caboodle through the hole, but it's not actually difficult.

Someone did post here a while ago about how unhappy he was with one mounted on the side of a holding tank; something to do with loo paper getting caught on the bolt! Not a problem with a diesel tank, I hope.

Fleur - the O ring sits in a groove in the hatch. It tends to drop out as you manoeuvre the thing around to get it out of the hole, but it's easy to put back in before closing the hatch.

Pete
 
If you really don't need it don't do it polyethylene is an absolute nightamre to repair if it all goes wrong. Diesel is terrible stuff and is very difficult to seal.

I tried to repair a heater fuel pickup that was leaking using a Wema sender flange and the diesel seeped past the screws, ended up having to have a patch welded over the holes.

So if you don't really need it leave well alone, if you do Tek Tanks told me they pressure test them to 4 bar so it should be ok but hey the sender flange should have been ok as well.

PE is also a right pain to drill it melts easily and snatches the hole saw.
 
Last edited:
davidwf said:
If you really don't need it don't do it polyethylene is an absolute nightamre to repair if it all goes wrong. Diesel is terrible stuff and is very difficult to seal.

I tried to repair a heater fuel pickup that was leaking using a Wema sender flange and the diesel seeped past the screws, ended up having to have a patch welded over the holes.

So if you don't really need it leave well alone, if you do Tek Tanks told me they pressure test them to 4 bar so it should be ok but hey the sender flange should have been ok as well.

PE is also a right pain to drill it melts easily and snatches the hole saw.
Click to expand...

you sure that wasn't 4 psi.......... 4 bar is a lot for a tank?
 
davidwf said:
If you really don't need it don't do it polyethylene is an absolute nightamre to repair if it all goes wrong. Diesel is terrible stuff and is very difficult to seal.

I tried to repair a heater fuel pickup that was leaking using a Wema sender flange and the diesel seeped past the screws, ended up having to have a patch welded over the holes.

So if you don't really need it leave well alone, if you do Tek Tanks told me they pressure test them to 4 bar so it should be ok but hey the sender flange should have been ok as well.

PE is also a right pain to drill it melts easily and snatches the hole saw.
Click to expand...

I really need to do it - or at least do something! The existing pipe inlets on Jeanneaus are small S/S fittings attached with 4 self-tappers each around small (maybe 20mm) holes in the tank top, once they have been removed and refitted the screws don't grip well enough to seal the gasket down. For two years both a local diesel engineer and myself have had half a dozen goes at resealing, using various sealants as well as gaskets - everything we try eventually starts to leak again, as the self-tappers just don't bite any more, even in a larger size.

Unfortunately Jeanneau do not use nice thick Tek-Tanks - quite thin black flexible polyethlene moulded in a perfect shape to fit the hull.

I have a Plan B of getting special C-shaped thick washers with tapped holes made up than can be finangled into the tiny holes to allow long machine screws to replace the self-tappers, but it's going to be an awkward job. Also if anyone then undoes the screws thinking there are captive nuts, the tapped washers will be at the bottom of the tank. Putting an access hatch in will let me use machine scews easily, and also let me check for any muck in the tank after 6 years.
 
Plan C of course would be to get Tek Tanks to make you a new one - they'll be able to match the shape of the old close enough. They will charge handsomely for doing it though, so I can understand trying plans A and B first.

Pete
 
Diesel tank

Yes you do need to have access to the bottom of the tank for cleaning.
Regarding the washers with tapped holes you might consider making a ring of SS larger than the size of the ring of screws drill and tap this ring. If you cut a slot through the ring you should be able to get it in through the smaller hole. ie instead of 4 tapped washers use one piece of metal with holes tapped in the right places.
Buy yourself an appropriate sized tap and drill that really is the easy part. good luck olewill
 
jwilson said:
I have a Plan B of getting special C-shaped thick washers with tapped holes made up than can be finangled into the tiny holes to allow long machine screws to replace the self-tappers, but it's going to be an awkward job. Also if anyone then undoes the screws thinking there are captive nuts, the tapped washers will be at the bottom of the tank. Putting an access hatch in will let me use machine scews easily, and also let me check for any muck in the tank after 6 years.
Click to expand...


Understand now, this sounds very similar to what I tried with the Wema flange, unfortunately the diesel seeped up the screw holes so I ended up with 6 seeping holes not one. If you do go down this route I suggest tapping the holes so that the screws are a really tight fit in the plastic prior to picking up the washer. The flange I used was the stainless steel one at the top http://www.wema.no/?page=417&show=435 I then had a pickup pipe weleded into a 1 1/4 BSP blanking plug that went in the centre.

You could also go down the route I went and get a plastic welder to weld a patch over the exsisting hole to give you a new and much thicker area for the self tappers to bite into. Looks messy as PE waxs when melted so hard to smooth but it does work.

I cannot load the pictures but you can see what I did on this thread,

http://www.ybw.com/forums/showthread.php?t=293260
 
Last edited:
William_H said:
Yes you do need to have access to the bottom of the tank for cleaning.
Regarding the washers with tapped holes you might consider making a ring of SS larger than the size of the ring of screws drill and tap this ring. If you cut a slot through the ring you should be able to get it in through the smaller hole. ie instead of 4 tapped washers use one piece of metal with holes tapped in the right places.
Buy yourself an appropriate sized tap and drill that really is the easy part. good luck olewill
Click to expand...
That was exactly what I had in mind, though I'll get someone to make the two pieces for me. http://www.wema.no/publish_files/FLS-U-163303.jpg shows a similar C-shape but with 5 holes.

To the suggestion of Tek-tanks making a replacement tank, the shape is really quite horribly complex to be made out of flat welded sheets as Tek-Tanks do.
 
Last edited:
Bobobolinsky said:
What about riv nuts with a washer below
Click to expand...

I just don't see how these rivnuts would grip in a thinnish sheet of (diesel-oil-lubricated) polyethylene. If I could get access below to put a washer in I wouldn't have a problem with ordinary nuts and bolts - I could compress a rubber gasket properly tight and seal threads with Hylomar/Loctite or similar.
 
You must log in or register to reply here.

Share this page

Top