Gas Alarm

[duncan99210]

Commonly available alarms are for Carbon Monoxide (CO) which as mentioned above is the killer, lighter than air thus the alarm needs siting at head height or above. Carbon Dioxide (CO2) is heavier than air, is not poisonous and there are no commonly available alarms for it.
CO will kill is relatively low concentrations: levels above 70ppm will cause symptoms (headache, drowsiness) above 150ppm will cause death. CO kills boaters far too frequently, usually from engine exhaust fumes entering the boat.
Of note is that the CO sensor will often alarm when it detects hydrogen coming off a cooking battery. So, if you get an alarm in the middle of the night, no engine running, it probably cooked batteries.

 

[pvb]

However, some years ago, a liveaboard barge, up by Fishermans Wharf, in Penryn , Falmouth.
Exploded , during the night, killing a whole family & destroying a load of buisinesses.
There was one surviving daughter, who had been at a sleepover, with her friends !
I have no idea, what happened to her, afterwards !
So, yes, even at. 66, I am paranoid, about. turning gas on & off !

That was in 1998. The people were liveaboards, and may not have turned their gas off at the canister. If you turn yours off when not needed, you're not in danger.

 

[zoidberg]

If you're vaguely sensible in your use of LPG, and turn things off properly, what's the risk?

'Vaguely' is IMHO insufficient. Spilled LPG is explosive; it maims and kills. It requires a more focused management than 'vaguely'.

Does copper pipe suddenly fracture under zero pressure? Do fittings suddenly unscrew themselves?

Yes, it does. Vibration does that.

In the past decade - on 'other people's boats' - I've experienced a copper pipe, a diesel return line, fracturing due to being inadequately supported/inspected/maintained as well as two copper gas supply pipes splitting. One was certainly due to a 'bending moment' being applied by the short flexible hose to the cooker. Another was in a run inside a cabinet where a drawer impacted the supporting clip ( at the rear ) every time it was forced shut, compressing it and splitting the pipe. That was a 'small leak' which only came to light after a Bubble Tester device - not original fit - was used to confirm a leak existed.

A match would also have confirmed the existence of a leak!

 

[awol]

My gas alarm started sounding for no reason - conclusion a week after removing gas bottle - so for no other reason than I could, I sluiced the sensor head with IPA (no, not beer!) and let it dry off. Normal service was resumed - unlit gas lighter activated it, wafting air calmed it down. I replaced the sensor anyway. Warning: your experience may vary!

 

[pvb]

In the past decade - on 'other people's boats' - I've experienced a copper pipe, a diesel return line, fracturing due to being inadequately supported/inspected/maintained as well as two copper gas supply pipes splitting. One was certainly due to a 'bending moment' being applied by the short flexible hose to the cooker. Another was in a run inside a cabinet where a drawer impacted the supporting clip ( at the rear ) every time it was forced shut, compressing it and splitting the pipe.

You'll recall that I also said "Unless your gas installation is very amateurish, there's no danger."

 

[zoidberg]

You'll recall that I also said "Unless your gas installation is very amateurish, there's no danger."

I'm thinking you wholly miss the point.

I had no reason - nor inclination - to consider blaming the initial installation as 'amateurish'. The point is that, without meticulous and regular competent inspection and maintenance, what WAS a sound installation can and, sooner or later does, turn into a LETHAL one.

I've sailed 'Other People's Boats' for many years, as crew and as delivery skipper, and I believe I haven't been on one where the owner had completed a 'meticulous and regular competent inspection' that current year, or the previous one. I have found, f'r 'zample, a regulator so corroded it couldn't be closed off. It was in a gas locker notionally venting overside, BUT the drain holes were completely blocked with debris, and there was about 2" water inside. The leaking gas was, of course, finding its way into the engine bilge.....

I sailed a couple of time on HMASTY 'Lord Trenchard' when she was new, and learned the implemented gas safety procedures were of 'Gold Standard'. I was shocked to learn just a few years ago that a gas explosion at Poople had blown the back end off and, with it, the skipper's legs. More shocking still, the MAIB report pointed to failures in the detailed maintenance routines.. That changed my 'complacent' approach.

I now use an approach similar to that appropriate to handling armaments.

 

[pvb]

I sailed a couple of time on HMASTY 'Lord Trenchard' when she was new, and learned the implemented gas safety procedures were of 'Gold Standard'. I was shocked to learn just a few years ago that a gas explosion at Poople had blown the back end off and, with it, the skipper's legs. More shocking still, the MAIB report pointed to failures in the detailed maintenance routines.. That changed my 'complacent' approach.

The "Lord Trenchard" explosion is often quoted as an example of how supposedly dangerous LPG is on boats. But the MAIB report highlighted numerous errors:-

* the gas bottle connection hadn't been properly tightened
* the gas locker wasn't gas-tight, as it should have been
* the gas alarm system didn't work
* the procedure for testing the gas alarm was incorrect
* the use of bilge pumps to clear gas in the bilges was insufficient.

With such a catalogue of basic errors, it's a wonder nobody was killed.

There are very few LPG explosions on boats. The "Lord Trenchard" was in 2015. The "Harlequin" explosion mentioned earlier in this thread was in 1998. Properly installed, inspected and maintained, LPG is safe for use.

 

[Graham376]

......... That was a 'small leak' which only came to light after a Bubble Tester device - not original fit - was used to confirm a leak existed.

I have a bubble leak detector but, they will only show a leak after them, not in the line before or regulator. Used to have a regulator with pressure gauge attached, similar to the one on Amazon which has the advantage when bottle turned off, of detecting a leak anywhere in the system - Campingaz Universal safety regulator 50 mbar with Pressure Gauge with Release Valve 32422: Amazon.co.uk: Sports & Outdoors

 

[michael_w]

Campingaz Universal safety regulator 50 mbar with Pressure Gauge with Release Valve 32422: Amazon.co.uk: Sports & Outdoors

This regulator works at too high a pressure. Modern regulators supply gas at 30mbar. Older propane ones 37mbar and butane 28mbar. There would be a serious risk of flame lift-off with 50mbar.

The only leak detector that really works is a manometer, with an appropriate test point.

 

[pvb]

My boat came with a GOK Marine 30mbar "Annex M" regulator, with a pressure gauge.

 

[Graham376]

Campingaz Universal safety regulator 50 mbar with Pressure Gauge with Release Valve 32422: Amazon.co.uk: Sports & Outdoors

This regulator works at too high a pressure. Modern regulators supply gas at 30mbar. Older propane ones 37mbar and butane 28mbar. There would be a serious risk of flame lift-off with 50mbar.

The only leak detector that really works is a manometer, with an appropriate test point.

I hadn't noticed the pressure on that particular one but, as pvb says, there are others available. Manometers are OK but have to be dug out and connected every time you want to check so unlikely to be used very often (if ever), whereas without any work, a fitted pressure gauge will slowly drop in pressure if there's a leak, whenever the bottle is turned off - exactly like the manometer. (when working on district service for the gas board, I used manometers several times/day for 5 days/week ) .

 

[pvb]

Y'know, there are some points of agreement there. Can we declare 'a draw' and move on?

I take exception to the fact that you have edited your quote of my post to include wording I didn't intend.

 

[zoidberg]

Well, Miss Prissy, I have moved on.

You can remain where you are, pouting at the screen and practising little hissy fits...

 

[greeny]

Gas valves leaking in a vented gas locker won't be dangerous. Rubber hoses are date-stamped and we all know to check them routinely. Regulators are in vented gas lockers so leakage isn't dangerous. Unless your gas installation is very amateurish, there's no danger.

Really? It takes a confident man to say NO danger.