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Crystalline residue on top of waste tank


T and H

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When I first worked offshore all our hydraulic lines were 316 stainless pipe but after about 20 years we had loads of failures where the pipe was supported in plastic Storff clamps. Eventually all stainless pipe was removed and replaced with Cunifer piping. Where the pipe was it the open it was fine just inside the clips.

 

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On 11/12/2017 at 13:44, ditchcrawler said:

When I first worked offshore all our hydraulic lines were 316 stainless pipe but after about 20 years we had loads of failures where the pipe was supported in plastic Storff clamps. Eventually all stainless pipe was removed and replaced with Cunifer piping. Where the pipe was it the open it was fine just inside the clips.

 

 

Isn't that what was used for better quality replacement brake pipes back in the 70s? (Better than steel that is.) A copper-like material IIRC. 

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20 minutes ago, Mike the Boilerman said:

 

Isn't that what was used for better quality replacement brake pipes back in the 70s? (Better than steel that is.) A copper-like material IIRC. 

Which had huge problems with ’spark pitting’ due to the earthing onto the car chassis / body when the static electricity, due to the flow of fuel / Brake fluid reached certain levels.

We were involved in the development of ‘electrically conductive plastics’ for the manufacture of  the plastic brake & fuel pipe clips, which stopped the build up of static, hence reduced the pitting of the fuel pipes and reduced the risk of fire/explosion.

XXXX (USA) had a big problem with vehicle fires and after an analysis of the cost/benefits decided that it would be cheaper to pay out on the few deaths that had happened, & may happen in the future, rather than recall many millions of vehicles. The ‘electrically conductive’ clips were introduced on a ‘rolling programme’.

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If your st/steel tank was manufactured in the same way as the one I removed from our boat, it will already have flaws from manufacture.

A lot of these tanks are TIG welded but are not purged internally with the welding gas during construction (i.e. filled with argon gas etc.) down to cost probably, or corner cutting.

This leads to the inside face of the weld turning to oxidised metal. Instead of a nice weld.

The  heat produced during the welding also removes the protective coating off the stainless.

The coating can be brought back by pickling the weld using floric acid, unfortunately this cannot be done on the inside of the tank unless the whole tank is submerged in a solution, so most of them don't get done. And it wouldn't work on the oxidised metal of the weld if not purged in the first place.

To make things worse, the hydrogen sulphide gas produced in your poo tank is a heavy gas so builds up in the tank and is only pushed out when the loo is flushed, it is a highly corrosive gas and will attack the unprotected stainless steel. Hence your pinholes.

If there was cross contamination of the steel  (sparks from grinders used on mild steel as mentioned earlier ) stuck on as well, they will cause corrosion if not removed and the area cleaned and pickled.

So if the steel used to construct your tank had any overspray from a grinder on it, on the inside surface of the tank (where the atmosphere is bad ) that would lead to corrosion.

Hope this was informative.

Edited by Bazza954
added summat.
  • Greenie 1
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  • 2 weeks later...

Very informative!! Really interesting. Thanks so much for your replies everyone. We have learned a lot!!! And would never use a steel tank again!

If anyone is interested in an update... the bitumen product did work but in the end we decided that since the cabin was in chaos anyway we should bite the bullet and replace the tank. We fitted a new plastic one from Lee san and (touch wood) it is perfect. 

Thanks again!

5D35D5C8-9948-49B4-A801-F3B52B315164.jpeg

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6 minutes ago, T and H said:

Very informative!! Really interesting. Thanks so much for your replies everyone. We have learned a lot!!! And would never use a steel tank again!

If anyone is interested in an update... the bitumen product did work but in the end we decided that since the cabin was in chaos anyway we should bite the bullet and replace the tank. We fitted a new plastic one from Lee san and (touch wood) it is perfect. 

Thanks again!

5D35D5C8-9948-49B4-A801-F3B52B315164.jpeg

Spirit level?

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On 11/12/2017 at 14:18, Mike the Boilerman said:

 

Isn't that what was used for better quality replacement brake pipes back in the 70s? (Better than steel that is.) A copper-like material IIRC. 

Yep, Cunifer is the Tubing that should be used on Diesel Fuel Pipe work for Boats , Especially for Rigid connections on Engines ,more Durable and  Resistant to Fracturing.

Edited by cereal tiller
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Strewth! What a kerfuffle.

Still it could be worse, it could be happening to me.

It's good to be reminded why I went from Integral Steel Holding Tank to ...... GRP Holding Tank to ...... Cassette Potty and then last year made the ultimate decision to upgrade to a couple of camping toilets (buckets with seats).

  • Greenie 1
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31 minutes ago, zenataomm said:

It's good to be reminded why I went from Integral Steel Holding Tank to ...... GRP Holding Tank to ...... Cassette Potty and then last year made the ultimate decision to upgrade to a couple of camping toilets (buckets with seats).

..so you finally got to a composting toilet then?

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