Gas Locker Skin Fitting Drain

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Pete735

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I've fitted a gas locker and associated pipework to comply with current regulations, but am left with one problem. Stern is a sugar scoop and angled at 60 degrees to horizontal where drain needs to be. I bought a standard straight plastic skin fitting (type that has both 19mm and 25mm hose tail - I'm using 25mm) and cut hole in the stern only to realise that the plastic pipe from fitting to the gas locker drain, angles downwards prior to going upwards to the actual gas locker. As such this will fill with rain water over time and block the pipe.

I intend having the system inspected and to hopefully get the necessary certification, but clearly not with this setup.

I've made up 2 angled pieces of tube so that the skin fitting comes out horizontally, but there is not enough thread on the fitting to put the locking nut on, so that's out. alternatively, I could use just one angled piece of tube and sikaflex the whole assembly in, but my preferred choice is to use a lock nut

I've looked around all the usual sites trying to find a 25mm skin fitting that is angled at 45 degrees (in white plastic to match other stern fittings), but come up with nothing.

Only option I can think of currently is having one made in stainless , but I would prefer the white plastic option for neatness.

I cannot believe I'm the only person ever to come across this issue, just wondered if anyone has used/found an angled skin fitting - 90 degrees are available, but not suitable in this situation - or devised another option?

Thanks for any help offered.
 
I'd not bother with a skin fitting, but simply sikaflex the pipe horizontally in the hole, trim it off and cover it with a small clamshell vent. It'll look neat and won't allow water to accumulate in the pipe.
 
Pete735 said:
I've fitted a gas locker and associated pipework to comply with current regulations, but am left with one problem. Stern is a sugar scoop and angled at 60 degrees to horizontal where drain needs to be. I bought a standard straight plastic skin fitting (type that has both 19mm and 25mm hose tail - I'm using 25mm) and cut hole in the stern only to realise that the plastic pipe from fitting to the gas locker drain, angles downwards prior to going upwards to the actual gas locker. As such this will fill with rain water over time and block the pipe.
.
Click to expand...

An expensive solution....The exhaust hose would be good too :D

http://www.ebay.co.uk/itm/QUALITY-S...A%2BFICS%2BUFI&otn=21&pmod=271019358856&ps=54
 
rob2 said:
In the event of a gas escape, it should blow the pipe clear!
Click to expand...

Not all gas leaks are under pressure, though - in fact I'd guess it's less common than a small dribble.

I'm surprised that a 90-degree bend can't be used, though, even if it's angled off to one side rather than upwards.

Pete
 
When I did mine, I laid up a bit of glass/epoxy around a piece of pipe, cut the end off flush and epoxied it into a slanty hole in the transom.
I did consider taking it out through the hull, to avoid rust stains on the transom from gas bottles.
 
Hmmm - yes a very slow leak won't blow the pipe clear, athough a full scale escape will. I'm not entirely sure I got the correct angles into my head from the OP's description - was the transom at 30 deg to the vertical? Anything that will truly drain clear cannot take a nut on the reverse, so something akin to the Eberspacher exhaust type fitting will have to be screwed through the flange. The only other way would be to have two linked drains, the upper one with a tee-piece behind it and the lower one with a 90 deg bend. The upper one would drain down to the lower one so that any gas could escape through the upper one or is at least limited to the volume of the pipe between the two. More complexity though in a fit and forget system, not good.

My own gas locker has two holes directly out through the bottom of the hull, which create fountains when the stern slams, so the bottles rust badly. I like the idea of clam shells to prevent water ingress. The size of drains recommended nowadays are to cope with a bottle bursting not just a slow leak, so I guess mine are too small at around half an inch dia. each.

Rob.
 
rob2 said:
Hmmm - yes a very slow leak won't blow the pipe clear, athough a full scale escape will. I'm not entirely sure I got the correct angles into my head from the OP's description - was the transom at 30 deg to the vertical? Anything that will truly drain clear cannot take a nut on the reverse, so something akin to the Eberspacher exhaust type fitting will have to be screwed through the flange. The only other way would be to have two linked drains, the upper one with a tee-piece behind it and the lower one with a 90 deg bend. The upper one would drain down to the lower one so that any gas could escape through the upper one or is at least limited to the volume of the pipe between the two. More complexity though in a fit and forget system, not good.

My own gas locker has two holes directly out through the bottom of the hull, which create fountains when the stern slams, so the bottles rust badly. I like the idea of clam shells to prevent water ingress. The size of drains recommended nowadays are to cope with a bottle bursting not just a slow leak, so I guess mine are too small at around half an inch dia. each.

Rob.
Click to expand...

Interesting idea to fit two draiins. Provided the upper one was at the right height for a fall all the way from the gas locker the lower one could be quite low as it would not matter if some seawater got in at times.

IIRC The recommended minimum size of the drains depends on the total of the gas bottle sizes in the locker. To be found any way in the Boat safety scheme document. (12mm /½ inch diameter is acceptable up to 18kg of gas but 19mm /¾ inch is best practice)

Not so sure that they will cope with a gas bottle bursting. I hope I'm not on a boat when that happens :eek:

You are not suggesting are you that your drains are below the waterline ??
 
No, not below the waterline - that would never work. My drains are around six inches above the waterline when at rest but of course they dip into the quarter wave rather frequently and any hard slamming will cause a fountain inside the locker.

Rob.
 
ghostlymoron said:
Why take it out through the stern? If out through either side, you wouldn't have the problem.
Click to expand...

Except that one will be uphill, and the other underwater when sailing.
TBH, i think it's all a bit unsound anyway, unless your locker lid is well sealed, the gap around the lid probably adds up to a lot more than a 3/4 in drain. A slow leak will probably tend to sink and go down the drain, but any big leak will spill out the top too.
 
Yes, I believe that in a major incident gas will force its way out through the lid - even those wgich meet the MCA coding as sealed. Can't remember the expansion from liquid to gas, greater with propane than butane, but it's going to breach anything but the most serious seal unless the drains are capable of relieving the pressure and I'm pretty sure most aren't.

So I would prioritise good drains and a risk assessment of what happens if gas goes over the top. An opening hatch in the cockpit to the aft cabin or quarter berth is a risk when open, which is likely when you're sleeping. All of this comes back to the issue of good gas management. Regular maintenance of the fittings - particularly in the locker and turning off the bottle when not in use.

Rob.
 
Can't remember the expansion from liquid to gas, greater with propane than butane
Click to expand...

FWIW 1 mole of a gas at ambient temperature and pressure is approx 25 litres (22.4 litres at STP )

A mole of propane is 44 grams. A mole of butane is 58 grams.
 
Thanks for all the comments, I think I'll go with either sikaflex or epoxy to attach the skin fitting to the angled piece of tube and fix the tube/skin fitting to the hull the same way.

As understand it, the drain is to take care of tiny leaks, as anything substantial will I hope be pretty obvious, if not via the smell then vapour appearing from the top of the gas locker!

As Rob says, good practise takes a lot of beating and we do turn the gas off at the bottle before settling in for the night - a pain when you wake up and it's raining though. Plus I'm intending to get a carbon monoxide detector to complete the exercise.
 
A CO detector is a great idea to make sure you don't poison yourself when burning gas, but only a gas detector will alert you to a gas leak long before it reaches an explosive level. I believe there is one dual sensor made.

A bit of rain in the morning is fine on a warm charter, it's a free shower, but in the UK I know some folk who make up a Thermos of coffee for the morning and foresake tea when rain is forecast! Trouble is you still need the gas for the porrage and toast.

Rob.
 
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