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Did I remember to turn off the gas?

capnsensible

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Joined
15 Mar 2007
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31,203
Location
Atlantic
I sailed on 'Trenchard', several times, and other Service boats. Around part of that time, the pro skipper was John Reeve - an ex- Nimrod OCU nav/instructor, assessor for the RAF's 'Mates and Skippers Tickets', and leading light/originator in the RIN's Small Craft Group - who was a consumate seaman. In 'Mentor Mode', he showed me the multiple gas safety systems and procedures installed in 'Trenchard' ( and other boats ) and 'dinned into' me the perceived risks of accumulating gas leaks. He and I, as Service aircrew, lived with explosive materials and were well aware of the vital need for unrelaxed vigilance.

I followed his guidance on the use and management of boaty gas systems for many years, content that I 'had that box ticked'. Reports of the gas explosion on 'Trenchard' at Poole Town Quay shocked me.

What I took from the MAIB report was that I could not rely on others, whose knowledge and degree of conscientiousness I could not guarantee. I've sailed many boats over the past 50 years or so. Very rarely have I witnessed an owner 'religiously' close a supply cock then let the gas in the flexible tube and burner extinguish itself by combustion. Very rarely have I observed a crewmember ensure a lit gas burner is shut off safe before making and distributing the tea. Frequently have I witnessed a gusty wind down the companionway blow out the gas flame - and the user leave it like that for a while until he'd completed something else he was doing.....

I've examined enough cracked and brittle rubber supply hoses years past their replacement date, enough corroded regulators that cannot be shut off, enough inadequately-supported brittle copper tubing to have my suspicions about 'others' cavalier approach roundly validated, over and again.

Gas can kill.

It is/can be lethally explosive, and vanishing-few on here seem to treat it with the requisite caution.

I'm wary of gas in boats. I'm wary of fuel leaks. I'm wary of fools....
Excellent post from the front line. Understanding how organisations respond to incidents is important. Every single sailor who reads this forum is one step away from a careless moment that puts their name in an MAIB report. Which I sincerely hope will never happen. And without the support of such an organisation.

Unlike my friend John, who died as a result is a gas explosion on his yacht. No one will ever know how that happened.

The fact that such incidents are thankfully rare points to how dangerous substances can be used safely by people of all levels of experience. Designer, manufacturers and builders should take credit for that.
 

mjcoon

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Joined
18 Jun 2011
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3,472
Location
Berkshire, UK
Why do the manufacturers of gas detectors require that the sensors are placed low in bilges?
Because if there is a density gradient it will be that way round and at depth is where there will be the least movement and thus least active dilution. None of that implies that is where all the gas is!
 

penfold

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Joined
25 Aug 2003
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4,545
Location
On the Clyde
The distribution of the gasses in the atmosphere is really not a strong function of height and amounts to damn all over a one or two metre height difference. Think about it: the CO2 from your breathing doesn't asphyxiate the dog, but his farts - certainly much denser than CO2 - can nigh asphyxiate you even when you're standing up!
HS2 and other sulphides which create the pong are marginally heavier than air, but most dogs wag their tail with delight and this causes rapid mixing and distribution; brownian motion and/or diffusion probably deals with the rest.
 

JumbleDuck

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8 Aug 2013
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23,588
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SW Scotland
I always thought that it wasn't due to density of the atmosphere but that due to the lighter molecules of hydrogen and helium a much greater proportion, despite being well down the tail of the Maxwell-Boltzman distribution, have velocity sufficient to escape the earth's gravity - aka escape velocity.
It;'s because they are lighter that they can get the velocity they need to escape when whacked (technical term) by larger molecules.
 

JumbleDuck

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8 Aug 2013
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23,588
Location
SW Scotland
There is no 'they'. An incident happened on one yacht 22 years ago. For some reason, you seem to want to use this as a stick to beat service sailing. You alone know why.
We all know why, because it's in the MAIB report. Sloppy maintenance, sloppy operation and a fundamental belief that following ticklist would keep everyone safe.
 
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Boathook

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5 Oct 2001
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4,916
Location
Surrey & boat in Dorset. Both have pubs
The way to get rid of it is with the manual bilge pump: don't turn anything electric on or off if you suspect a gas leak.
The best way I was taught is to lift the floor boards and fan the area with something like a chopping board with all hatches, etc open. LPG is only just heavier than air and it is soon shifted / diluted.
 

JumbleDuck

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8 Aug 2013
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23,588
Location
SW Scotland
HS2 and other sulphides which create the pong are marginally heavier than air, but most dogs wag their tail with delight and this causes rapid mixing and distribution; brownian motion and/or diffusion probably deals with the rest.
Is it not a mercaptan which gives the pong to "our" LPG? That's what they use in autogas, and because it doesn't get burned in the engine, LPG exhaust smells like ... LPG, which can give rise to all sorts of misunderstandings
 

jdc

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Joined
1 Dec 2007
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1,581
Location
Falmouth
It;'s because they are lighter that they can get the velocity they need to escape when whacked (technical term) by larger molecules.
Many 'thanks' for defining that that technical term - There's a good chance we both attended the same 1st year thermodynamics lectures in the Clarendon!
 

JumbleDuck

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8 Aug 2013
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Location
SW Scotland
Many 'thanks' for defining that that technical term - There's a good chance we both attended the same 1st year thermodynamics lectures in the Clarendon!
I was across the road in the Thom Building, but spent a few years of my life in the Clarendon later on ...
 

zoidberg

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Joined
12 Nov 2016
Messages
4,238
Just as an aside...... :)

More years ago than I want to remember, I had to 'navigate' a Canberra B2 back from an extended stay on Cyprus. French ATCOs were doing their usual summer 'work to rule'/buggeration and in a complicated complication my pilot packed our baggage into the aircraft while I attended to our flight plan in the Ops Block a mile away. It emerged he'd packed our ~15 demijohns of 'Keo' Cyprus Brandy ( for squadron parties to come ) sideways in the bombaimer's nose-space, jammed in horizontally with our small suitcases.

An hour and a half later, up around 45,000 feet and heading west for Malta, the tranquillity was disturbed by a series of unusual 'pops'. There was a distinct air of 'What the....' followed by a thick, dense smell I indentified as sweet alcohol..... then the realisation that some of the demijohns had popped their corks in the much-reduced cabin pressurisation, and that some gallons of Keo brandy were swilling around in the nose-space. The smell told me that our cabin airspace was now a mix enriched by our oxygen and our alcohol - in some unknown concentration, explosive!

We didn't dare throw a switch, alter trim, change frequency on the radios in case a tiny unguarded spark set off an almighty 'bang'.... until we were down well below 10,000 above Malta/Luqa airfield and could depressurise and vent the noxious miasma.

Of course, the long after-landing 'taxi' in >40C heat just made the 'Sunday morning pub' stench much worse, as the Maltese ground crew who opened the door-hatch illustrated as he recoiled in disgust. It took us hours and a dozen rolls of absorbent paper towel to mop up the spillage, and that aircraft reeked for months afterwards.

I'm a bit precious about gas leaks.....
 
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kof

Active member
Joined
8 May 2018
Messages
123
Jeez. All these stories make me glad I went all electric galley - no gas down below and upstairs the only gas is on the bbq.
 

mjcoon

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18 Jun 2011
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3,472
Location
Berkshire, UK
The best way I was taught is to lift the floor boards and fan the area with something like a chopping board with all hatches, etc open. LPG is only just heavier than air and it is soon shifted / diluted.
I'm sure I've read about using a bucket, just as if 'twere water...
 
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