gas locker drainage (sorry if this has been answered before)

Yes, it will, but that mechanism does not assist a vent-less gas locker to empty significantly, and if it did, you have still added weight to my assertion that the box does not need a vent!
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I find all this interesting regarding the vent...These rules stem from the BSS requirements and in those there is NO requirement for the locker to have a lid....just gas tight container to a certain height above the top of the cylinder so in fact in effect the top of the locker is the vent....How does this play in all this molecular movement...Do the butane molecules act as good boys and never climb over the edge unless too many arrive for the drain to cope with?????
 
Hi Bilgediver,
I've never read the BSS requirements, but from your sentence I think I see a contradiction between a gas tight locker and one open at the top.
Personally I wouldn't read your statement as gas tight UP to a certain height above the bottle but - to paraphrase - gas tight with a gas tight lid a certain clearance above the bottle.

The only example I can think of where an open vessel is used offhand is a drycleaning tank we used to have where I work, where cooling coils were used to recondense the trike before it could escape. the result was a roiling grey cloud in a tank.

For a gas like butane or propane there WILL be diffusion out of an open topped locker unless the drain is huge and teh leak is small. And even then, theoretically, some molecules will "climb out".
 
[ QUOTE ]
I find all this interesting regarding the vent

[/ QUOTE ] I must admit that I thought there was a requirement for a vent. At least I thought it was a requirement if the locker was totally gas tight apart from the drain. It was when I tried to find the relevant section in the BSS that I realised I was wrong!
However I knew I had seen something somewhere about a vent, and that it was not entirely a figment of my imagination. I am sure this is not the only place I have seen it but this (very comprehensive) diagram to show the requirements to produce a safe system does show a vent. I comes from PBO from a few years ago, but at the moment I cannot find the original to get a date, and was IIRC produced by Peter Spreadborough, PBO's gas expert, from the Southampton Calor Centre.

363128ec.jpg


Personally, and it is just my personal opinion, I think that the gas locker should be completely sealed, with a gas tight lid and have over board vent as well as a drain. I really cannot see that an open topped locker, as allowed by the BSS, is satisfactory although I am prepared not to fight the case for a vent.
That might seem that I am both saying that gas will flow out of a bottom drain and also escape via the top by diffusion. In reality I think that is exactly what will happen. I can only assume that the people responsible for the BSS believe that the number of bad boys who climb over the edge will be so small as to not be a potential danger. In the event of a very serious leak occurring I am sure their beliefs are wrong.

PS one day I'll get my own gas locker sorted out!
 
I agree it looks unclear, but I was told when BSS inspected last year that ordinary GRP was not acceptable. The gas box had to be steel, or fire-resistant GRP.

S18 of the BSS
"
18 All LPG systems must be designed, installed and maintained in a way that minimises the risks of explosion or of fire starting and spreading."

S 7.4.5/R
"Cylinder lockers must be constructed of materials that are either the same material and thickness of the surrounding hull structure; or,metal of minimum thickness of approximately 1mm; or, 1/4 in. FRP of minimum thickness of approximately 5mm (1/4 in) thickness."

But the CALOR site has the following:
"Cylinder locker/housing construction
Some protection against gas cylinders overheating can be achieved by ensuring that any gas cylinder locker or housing has a fire resistance of 30 minutes.
There are several accepted ways of achieving this fire resistance for cylinder lockers or cylinder housings:
they must be constructed of metal at least 0.9mm (0.03ins) thick, with continuously welded or brazed joints
they must be made of fibre reinforced plastics (FRP) of minimum thickness 5mm (0.2ins)
they must be made of materials with a fire resistance of 30 minutes, in accordance with BS 476-20.

Calor sell marine gas lockers made only of "fire retardant GRP"

I think there's a lack of clarity and precision in the subject, so many thanks for identifying the acronymic anomaly.
 
That locker is the system I would install with both a high level and low level vent and sealed lid.

The high level vent serves duel purpose in that it helps with a circulation which would help this diffusion process and also in the event of a hose failing in the locker would help get rid of the higher volumes of leakage.

The BSS requirements only really deal with low levels of leakage otherwise molecules can climb over the edge into the bilges /forums/images/graemlins/smile.gif
 
Hi Bilgediver,
I've never read the BSS requirements, but from your sentence I think I see a contradiction between a gas tight locker and one open at the top.
Personally I wouldn't read your statement as gas tight UP to a certain height above the bottle but - to paraphrase - gas tight with a gas tight lid a certain clearance above the bottle.

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I havn t read it in ages however I Quote below the relevant bit....


Quote BSS

Or, for cylinder lockers:

Cylinders can be secured in a suitable cylinder locker, which must be gas
tight to the height of the regulator and valve. To help keep the lockers gas
tight they must be designed to only open from the top.
Cylinder valves, regulators and other components in the lockers can be
damaged if boating equipment, such as mooring pins, are thrown in. Damaged gas components could quickly leak, leading to a serious fire or
explosion potentially. To minimise the risk of this happening cylinder lockers
must have a lid or cover to protect the cylinders, low pressure regulators
and associated equipment from mechanical damage.
To prevent gas, which has escaped in the cylinder locker, from entering the
interior of the boat LPG must be able to drain effectively from the lowest
point of the cylinder locker to a point outside the hull, above the waterline.
Boats manufactured before 3 January 2000, which have a cylinder locker
drain as near as practical to the bottom of the cylinder locker, are exempt
from this part of this Standard. [7.2]

Unquote

What I have seen accepted are open topped steel lockers a few inches higher than the actual bottle and fitted with the bottom drain???? I am somewhat surprised however this does not seem contradict the BSS rules!!!!

Southampton CAlor sell basic lockers for both calor and Gaz bottles and do them for single and twin bottle installations. These can be difficult to install in some older boats with lower cockpits as this puts the drain very low in the boat and the lockers subject to flooding when heeled.

Like Alf I believe that both a high level and low level drain should be employed to give the molecule migration a boost!
 
Thanks for the extract Bilgediver.

"Cylinders can be secured in a suitable cylinder locker, which must be gas tight to the height of the regulator and valve. To help keep the lockers gas tight they must be designed to only open from the top."

"gas tight to the height of the regulator and valve" - ambiguous cr*p!

It just goes to show that specifications can be written by idiots and interpreted by idiot inspectors.
God knows I've seen enough of them!

In the end it is opinion engineering. I have no problem with a vent as long as it is swan-necked and vents overboard.

My original point was that, in my opinion, the OPs gas box was fit for purpose without needing a vent.
 
[ QUOTE ]
I have no problem with a vent as long as it is swan-necked and vents overboard.

[/ QUOTE ]

Why swan necked?
 
[ QUOTE ]
Why swan necked

[/ QUOTE ] It confuses the bad molecules trying to get out the wrong way.. they cant see any light so they get lost. /forums/images/graemlins/grin.gif

May also stop water getting in!
 
I realise that that's the idea, but does it matter? There's a drain at the bottom to let it out again.
The illustration you showed earlier didn't show a swan neck.
Just curious, don't suppose it's a big issue.

Molecules these days eh! They weren't like that in my day. Wandering around aimlessly. What they need is National Service....that'll teach them what direction to go in. /forums/images/graemlins/wink.gif
 
Just being thorough!
Would you design a system where there was a potential for water ingress, when a simple bend in a pipe would virtually eliminate the problem?
Of couse, while I was about it I should specify a flame arrestor on the vent.


In fact I really need to put a flare stack fifteen metres out from the boat with a gas sensor and an igniter system.

But then I need a warning strobe for low flying aircraft.

And maybe an offshore support vessel standing by 24/7

But no! emissions regulations! I really need a screw compressor package to recompress any leakage, cool it and send it back to the gas bottle. - 5 tonnes, over £1M...
Need to work to NORSOK spec. if I'm going to go to Norway - that'll add another 1/4 Mill...

Have I taken this too far? /forums/images/graemlins/wink.gif
 
[ QUOTE ]
The illustration you showed earlier didn't show a swan neck

[/ QUOTE ] No I know but i did not draw it! Done by a gas man who possibly is not a boat owner

I do agree though that a swan neck is a sensible thing to include. You dont really want water entering the locker.
See the mentions early in the thread of a sump and rusty stains where the drain exits
 
Re: gas locker holes.

Well, that's made up my mind.

I will definitely install a goose neck and a flame arrestor..........if I ever fit a vent!

I must get around to fitting a bubble leak detector though.
 
Re: gas locker holes.

Actually I was half in jest over the flame arrestor - suggest a loose wad of brass wool up the swan neck would suffice.
Just make sure you don't completely block the vent.
 
Re: gas locker holes.

[ QUOTE ]
Actually I was half in jest over the flame arrestor -

[/ QUOTE ]

So was I!
I haven't got a vent and it would be very difficult to fit one so I won't be bothering. Not ideal, but there it is. /forums/images/graemlins/wink.gif
 
It just goes to show that specifications can be written by idiots and interpreted by idiot inspectors.
God knows I've seen enough of them!

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Took the words out of my mouth.......So ambiguous that just about anything could be argued fills the bill resulting in different surveyors coming up with different interpretations....Unfortunately some surveyors of non river boats look at the BSS as an oracle on such matters yet demand a higher technical standard than the BSS demands!!!
 
NORSOK spec.
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Don t go there.....You ll need a locker to take the 10 tons of documentation covering material specs...test certification.... and dnv certificates.... Been there got the tee shirt!!!!
 
Re: gas locker holes.

I must get around to fitting a bubble leak detector though.
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And if fitting bulkhead connectors then as these introduce a whole host of compression joints to leak at your pleasure then drill the bulkhead connections through clearance size for your pipe and thread a single continuous length right through!!! No joints!!
 
[ QUOTE ]
NORSOK spec.
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Don t go there.....You ll need a locker to take the 10 tons of documentation covering material specs...test certification.... and dnv certificates.... Been there got the tee shirt!!!!

[/ QUOTE ]

Grumble grumble, Duplex stainless... mutter mutter, no instruments below eye level.... Gnash gnash, no manual lift over 25 kg...... computerised docs in weird markup languages... AAArrgghhh....
Oh you got me started!!
(WELL drifted thread!)
 
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