Raising gas locker floor

[36national]

dunno if you asking me but ill answer anyway, with a full water tank and too much junk on the roof (usual) then the vent is on the waterline. My boat is deep drafted so im often more or less aground when moored especially  in  unfamiliar places. If a pound goes down or i get washed into the bank the boat will start to adopt a jaunty angle which may mean that the vent goes underwater. hence i raised it. 

[David Mack]

23 minutes ago, Tracy D'arth said:

I am amazed that a plywood platform with unventilated space beneath, sealed with combustible sealant, as part of a gas locker ever past BSS examination.

I agree. There's no way to guarantee that the seal to the gas locker is perfect, so gas could accumulate in the void. Granted it is difficult to see a situation where a gas/air mixture in the void might get ignited, but all the same I think this should be a BSC failure.

 

I think your BSC examiner could also fail the use of plywood on the basis that your gas locker is supposed to be constructed of non-combustible material.

[Tracy D'arth]

2 minutes ago, David Mack said:

I agree. There's no way to guarantee that the seal to the gas locker is perfect, so gas could accumulate in the void. Granted it is difficult to see a situation where a gas/air mixture in the void might get ignited, but all the same I think this should be a BSC failure.

 

I think your BSC examiner could also fail the use of plywood on the basis that your gas locker is supposed to be constructed of non-combustible material.

That's what I thought too.

[dmr]

10 minutes ago, 36national said:

dunno if you asking me but ill answer anyway, with a full water tank and too much junk on the roof (usual) then the vent is on the waterline. My boat is deep drafted so im often more or less aground when moored especially  in  unfamiliar places. If a pound goes down or i get washed into the bank the boat will start to adopt a jaunty angle which may mean that the vent goes underwater. hence i raised it. 

 

I was really asking the OP. We have a big water tank so when its full the gas locker vents are almost on the waterline so any little waves will get in. A few very turbulent locks even get water in through the scuppers onto the well deck.

 

............Dave

[Alan de Enfield]

5 minutes ago, David Mack said:

I think your BSC examiner could also fail the use of plywood on the basis that your gas locker is supposed to be constructed of non-combustible material.

 

or, if it constructed from wood must have a FRP lining (section 7:4:5)

 

Also, any void beneath the locker floor MUST be FILLED with an LPG resistant material (section 7:3:2)

Edited July 14, 2021 by Alan de Enfield

[36national]

22 minutes ago, dmr said:

Is the locker floor permanently below the water line or does it just get a bit wet from time to time due to little waves or turbulent locks etc?

 

Many, probably most, gas lockers get a bit wet. Derust the floor if required and paint it with a good epoxy and live with it. Don't worry about it, just do a good check for rust every year or two.

Any sort of false floor including leveling compounds is a BIG risk. Unless it is 100% watertight, and I stress 100%, then water will get trapped below it and rust out the steel floor where you can not see what is going on.

 

............Dave

yes i agree and i ve never been happy with what ive done. ( i hope this comes across from my post) Which is why i made it easy (ish) to remove and inspect the space below. but a vent which can go below the waterline is definately not safe and so far no one has posted a better solution

what is an FRP lining?

 

[nb Innisfree]

In the early 60s I worked on a building where cement grout was beaten to a froth and poured onto the concrete flat roof to act as insulation, sort of a hard foam, it was then covered in asphalt. Maybe it could be used with thick blacking instead of asphalt, much lighter than concrete and waterproofing could be added to the 'foam' when aerating it. 

[PeterF]

FRP = fibre reinforced plastic = glass fibre & resin

[dmr]

9 minutes ago, 36national said:

yes i agree and i ve never been happy with what ive done. ( i hope this comes across from my post) Which is why i made it easy (ish) to remove and inspect the space below. but a vent which can go below the waterline is definately not safe and so far no one has posted a better solution

what is an FRP lining?

 

 

Modifying the round drain holes to be vertical slots is often suggested as a good way to keep a clear drain even when a bit under water. In my case the drains are never continuously below the water line so I don't worry about it.

[36national]

yes and looking at section 7.4.5 it seems that if i cut a 1mm thick sheet of "metal" and lay that on the floor then my gas locker is compliant

[36national]

and lets face it thats a box ticking exercise. If i had a wooden boat then my gas locker could be all wood and according to section 7.4.5 it would be safe !

 

[Alan de Enfield]

7 minutes ago, 36national said:

yes and looking at section 7.4.5 it seems that if i cut a 1mm thick sheet of "metal" and lay that on the floor then my gas locker is compliant

 

And fill any void (as detailed above) and weld it into the locker. I doubt that just laying it on the floor is going to 'get a pass'

 

 

2 minutes ago, 36national said:

and lets face it thats a box ticking exercise. If i had a wooden boat then my gas locker could be all wood and according to section 7.4.5 it would be safe !

 

 

I doubt it. It would need to have evidence that it was gas tight on all joints.

 

Our gas locker is FRP lined to comply.

Edited July 14, 2021 by Alan de Enfield

[Tracy D'arth]

With a bow gas locker there is usually a drain on both sides of the hull. If the locker takes water occasionally when heeling, it will vent any gas on the opposite side.

Has it been established that vents under water do not allow gas to escape?

David Piper hulls and some others do not have holes. With the locker low in the stern deck it is always wet at the bottom so it has a slot some 100mm long to ensure that there is always a vent despite the floor of the locker often being some 50mm below water level.

[36national]

the reasoning behind doing what ive done is that i can still inspect the original floor of the locked. welding a bit in makes this impossible.

section 7.4.5 states that a repair must be seam welded or braised. This is a modification not a repair point of pedantry ill concede but definately not a repair. 

section 7.4.5 also states that the gas locker must be constructed of the same material and thickness as the surrounding hull structure. if wooden hull then wooden locker is safe on a more sensible note if i get some fibre reinforced plastic and seal it in with LPG resistant sealant then this makes it compliant ?

 

i think it can be safely assumed that vents underwater will not allow gas to escape
 

 

[Alan de Enfield]

2 minutes ago, 36national said:

the reasoning behind doing what ive done is that i can still inspect the original floor of the locked. welding a bit in makes this impossible.

section 7.4.5 states that a repair must be seam welded or braised. This is a modification not a repair point of pedantry ill concede but definately not a repair. 

section 7.4.5 also states that the gas locker must be constructed of the same material and thickness as the surrounding hull structure. if wooden hull then wooden locker is safe on a more sensible note if i get some fibre reinforced plastic and seal it in with LPG resistant sealant then this makes it compliant ?

 

 

 

Is your boat wooden ?

[36national]

my gas locker does run  the width of the boat it is on the starboard side

no but thats not really the point the point is how can a wooden locker be safe on a wooden boat but not on a steel boat

 

[36national]

sorry meant does NOT run the width of the boat 

 

[Alan de Enfield]

4 minutes ago, 36national said:

no but thats not really the point the point is how can a wooden locker be safe on a wooden boat but not on a steel boat

 

Fair question - why not ask C&RT / BSS

 

You don't really expect any sort of consistency from C&RT (do you ?)

[system 4-50]

For reference: Ordinary house bricks are porous. Engineering bricks have neglible porousity.

[Tacet]

1 hour ago, Alan de Enfield said:

 

Also, any void beneath the locker floor MUST be FILLED with an LPG resistant material (section 7:3:2)

7.3.2 does not require that. It only relates to the gas locker - not to any void beneath its floor.  Plenty of boats have gas lockers on the back deck - and the engine holes beneath are not filled!

[system 4-50]

2 hours ago, 36national said:

 

reading back through this thread what is this "the LPG hoses have to drain down towards the cylinders ? I was unaware of this 

 

Specifically the High Pressure hoses should drain towards the bottle.

There are some threads on this but I can't think of suitable search word.

The bottle contains some water as well as gas.  The exiting gas or a condensation type of effect can get this water into the hoses. If the hoses drain down to the bottle the water will eventually run back into the bottle. If they don't they run into the regulator which does it no good and into your gas lines and fouls up your appliances.  This is not clean water, it is black.

DAMHIKT. 

This is not a regulation, it is merely good practice for reliable gas usage.

If you buy some autochangeover regulators like I did, you get a document telling you about this.

[ditchcrawler]

1 hour ago, 36national said:

 i think it can be safely assumed that vents underwater will not allow gas to escape

If that's the case then you need to slot up above the water level.

[36national]

section 7.3.2 does not require that.  It relates specifically to areas IN the gas locker not BELOW the gas locker. theres an important and logical difference 

[David Mack]

I'm sure that in the past I have come across low-decked tug style boats with the gas bottles in the bow locker, where the only way to fit the bottles in below the deck hatch was to have the locker floor well below water level, with a long vertical slot for the drain, and the bottles permanently sitting in a few inches of water.  Not sure the BSS would allow that now!

[36national]

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Posted 2 minutes ago

I'm sure that in the past I have come across low-decked tug style boats with the gas bottles in the bow locker, where the only way to fit the bottles in below the deck hatch was to have the locker floor well below water level, with a long vertical slot for the drain, and the bottles permanently sitting in a few inches of water.  Not sure the BSS would allow that now!

 

 

I think The BSS  would for a couple of reasons. there is nothing in section 7 of the BSS to prevent it. And (dont start a sentence with a conjunciton) it is not actually dangerous from the point of view of gas build-up  and explosion. Of course it does mean that if the floor of your wet locker corrodes (as it will) and then rusts through (as it will without careful maintenence) then there is a direct route for water to flow from the canal, into your bilge thus lowering the boat in the water enabling more water to flow from the canal, into your bilge and then guess what youre sunk. However that is not a BSS issue and if youre aware that the botom of  your wet lockers is below the waterline then it is a copeable with issue. Frankly if I was designing a boat then wet lockers would be banned verboten and to all extents done away with but lots of boats have em. Isnt there a BSS examiner on here who can settle this ? I got a pound of flesh spare ( more than one actually)