Did I remember to turn off the gas?

[capnsensible]

Read the report into the incident.

So you have never sailed on a service yacht. Ok.

I posted the link to the report. I've read it many times. It was, at one time, mandatory reading for Visiting Skippers.

I know someone who was onboard.

I know more about routines on service yachts than will ever be in one report. However, it was a very useful document to help further gas safety in all aspects of commercial and leisure sailing.

Where does your information come from that it needs 'a huge amount of pumping to remove a tiny amount of gas'?

Have you ever had a gas leak on a yacht and if so, how did you deal with it? Was it caused by someone making a mistake, or by someone who 'couldn't be bothered'?

 

[pvb]

So you have never sailed on a service yacht. Ok.

Correct.

Where does your information come from that it needs 'a huge amount of pumping to remove a tiny amount of gas'?

From section 2.8 of the Trenchard report (which you'll know as you've apparently read it many times). It says "The volume of gas handled this way is very limited in comparison to the total volume of the major compartments of the vessel. Depending on the number of pump strokes, the likely volume of gas or air pumped from a compartment by the bilge pump would be a few litres. However, the volume of the compartments served by the same bilge pump could be measured in cubic metres. Even recognising that LPG is heavier than air and accumulates in the lowest part of a compartment, the volume of air/gas which would need to be pumped to remove any significant accumulation is likely to be large. Although this volume might not need to be the total compartment volume, it will probably be many times the volume pumped, even by 50 strokes of the bilge pump. These bilge pumping procedures may be suitable for clearing a small accumulation of gas resulting from lighting a cooker. They are not adequate, however, for clearing a large accumulation of gas which might result from a fault in the system. They may also have the undesirable effect of giving crews a false sense of security. JSASTC should set out these limitations in its vessels’ operational documentation which is available to all skippers and crews."

Have you ever had a gas leak on a yacht and if so, how did you deal with it? Was it caused by someone making a mistake, or by someone who 'couldn't be bothered'?

Never had a problem. As I've said many times, LPG on a boat is safe as long as you're basically sensible and careful.

 

[capnsensible]

The established procedures for clearing the small amount of gas that may get into the bilge from routine cooker operation works then. So not really a huge amount of pumping for a tiny amount of gas.

If you have had a known gas leak and use a manual bilge pump as part of the standard operating procedure to ventilate the bilge then clearly effort will need to be applied. A huge amount of pumping for a lot of gas. When a leak has been discovered.

I acknowledge your admission that you have never sailed on a service yacht which gives suitable weight to your opinions of how they are managed. B Z.

 

[jdc]

The 'LPG is heavier than air so must accumulate in the bilges' theory is, in my opinion, something of a myth. The density of propane (a lot of us use propane) is identical to carbon dioxide (both have molecular weight 44). It may sink on release, but that's only when the release is a sudden escape of a significant quantity as the act of vaporisation cools the escaping gas. But a slow leak will be at equilibrium temperature with the environment and so 'it'll the sink to the bilges' notion is dubious and I doubt that any experiments have ever been done.

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!

 

[johnalison]

The 'LPG is heavier than air so must accumulate in the bilges' theory is, in my opinion, something of a myth. The density of propane (a lot of us use propane) is identical to carbon dioxide (both have molecular weight 44). It may sink on release, but that's only when the release is a sudden escape of a significant quantity as the act of vaporisation cools the escaping gas. But a slow leak will be at equilibrium temperature with the environment and so 'it'll the sink to the bilges' notion is dubious and I doubt that any experiments have ever been done.

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!

I don’t know whether your theory is right, but I don’t know of anyone who died as a result of pumping the bilges........

 

[JumbleDuck]

A lot of people don't seem to be aware of the principle reason why a gas leak is more dangerous in a vessel: gas is heavier than air, and will accumulate in the bilge, with no way of dispersing.

It's amazing how many people think that because gas is heavier than air, it will accumulate in the bilge, with no way of dispersing. After all, this wasn't caused by LPG:

This post has been brought to you by the word "diffusion".

 

[pvb]

I acknowledge your admission that you have never sailed on a service yacht which gives suitable weight to your opinions of how they are managed. B Z.

They were managed very badly, according to the MAIB report into the Trenchard explosion. My opinion seems to agree with the MAIB findings.

 

[JumbleDuck]

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.

Agreed. The only really significant effect of density in the atmosphere is that both hydrogen and helium can escape, which is why we can't distill either of them from air.

If propane/butane really did head straight for the bilges and stay there there would be very little danger. Th eproblem is that they diffuse into the air and, under the right circumstances, form an explosive mixture.

 

[jdc]

Agreed. The only really significant effect of density in the atmosphere is that both hydrogen and helium can escape, which is why we can't distill either of them from air...

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.

 

[capnsensible]

Why do the manufacturers of gas detectors require that the sensors are placed low in bilges?

 

[capnsensible]

They were managed very badly, according to the MAIB report into the Trenchard explosion. My opinion seems to agree with the MAIB findings.

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.

Again, from that one incident, a great deal has been learned in order to make sailing safer. I'm very unsure about your problem with that. Much the same with other incidents that have resulted in investigations and fatalities. Clipper, for example. The faux outrage is difficult for me to understand.

 

[TernVI]

It's amazing how many people think that because gas is heavier than air, it will accumulate in the bilge, with no way of dispersing. After all, this wasn't caused by LPG:

This post has been brought to you by the word "diffusion".

Indeed.
The thing about gases, is that they behave as gases, not liquids. Funny that.

 

[jdc]

Why do the manufacturers of gas detectors require that the sensors are placed low in bilges?

It's entirely in their interest to go with the flow of people's thinking, even if that thinking is dubious, and it does no harm. And it is quite sensible to detect gas elsewhere than your nose. So put your gas detector where you will not be makes a sort-of sense.

Besides, they are probably only repeating advice which their grandfathers before them gave, and, for all I know the BS standard insisted on them printing on the manual. I've no particular axe to grind but suspect that there are many pieces of received wisdom which, while we continue to follow them, no longer apply, if they ever did (eggs are bad for your cholesterol, oh no they aren't, oh yes they are... )

 

[TernVI]

The 'LPG is heavier than air so must accumulate in the bilges' theory is, in my opinion, something of a myth. The density of propane (a lot of us use propane) is identical to carbon dioxide (both have molecular weight 44). It may sink on release, but that's only when the release is a sudden escape of a significant quantity as the act of vaporisation cools the escaping gas. But a slow leak will be at equilibrium temperature with the environment and so 'it'll the sink to the bilges' notion is dubious and I doubt that any experiments have ever been done.

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!

Indeed, a lot of people should lie on the floor to see if they get some oxygen to their brains, as it's heavier than the nitrogen.

 

[TernVI]

The established procedures for clearing the small amount of gas that may get into the bilge from routine cooker operation works then. So not really a huge amount of pumping for a tiny amount of gas.

If you have had a known gas leak and use a manual bilge pump as part of the standard operating procedure to ventilate the bilge then clearly effort will need to be applied. A huge amount of pumping for a lot of gas. When a leak has been discovered.

I acknowledge your admission that you have never sailed on a service yacht which gives suitable weight to your opinions of how they are managed. B Z.

Using a manual bilge pump to shift gas from a bilge is usually a complete waste of time.
Those pumps are really crap at priming with air.
The flap valves only really seal with water.
Anyone who's sailed a wooden boat or open boat and had to pump water will tell you that bilge pumps often don't prime when dry.
It's mostly just a make-work activity to keep the lower orders busy in sail training.

I've worked with the services, with safety related equipment. Their culture is to hide anything that they've broken and to do stuff by numbers to avoid taking responsibility. Then to close ranks when found out.

 

[pvb]

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.

The MAIB report, which you said you'd read many times, also highlighted the basic safety failures of other Joint Services boats, and recommended that "This points to a need for the gas installations on all of JSASTC’s fleet to be inspected carefully for compliance with requirements and best practice."

I'm not in any way attacking service sailing. You mentioned the Lord Trenchard incident in post 20, I didn't. However, as you'd mentioned it, I felt it was only fair to point out that the Lord Trenchard explosion was the result of incompetence and carelessness.

Again, from that one incident, a great deal has been learned in order to make sailing safer. I'm very unsure about your problem with that.

I don't have a "problem with that".

 

[zoidberg]

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....

 

[pvb]

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 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.

But was he aware that the gas bottle locker wasn't gas-tight, as it should have been? Safety systems and procedures are all very well on paper, but if the boat is badly built they won't work, as was sadly the case.

 

[capnsensible]

It's entirely in their interest to go with the flow of people's thinking, even if that thinking is dubious, and it does no harm. And it is quite sensible to detect gas elsewhere than your nose. So put your gas detector where you will not be makes a sort-of sense.

Besides, they are probably only repeating advice which their grandfathers before them gave, and, for all I know the BS standard insisted on them printing on the manual. I've no particular axe to grind but suspect that there are many pieces of received wisdom which, while we continue to follow them, no longer apply, if they ever did (eggs are bad for your cholesterol, oh no they aren't, oh yes they are... )

No, actually, they aren't. They are designers and manufacturers of safety equipment. Who actually know what they are talking about.

 

[capnsensible]

The MAIB report, which you said you'd read many times, also highlighted the basic safety failures of other Joint Services boats, and recommended that "This points to a need for the gas installations on all of JSASTC’s fleet to be inspected carefully for compliance with requirements and best practice."

I'm not in any way attacking service sailing. You mentioned the Lord Trenchard incident in post 20, I didn't. However, as you'd mentioned it, I felt it was only fair to point out that the Lord Trenchard explosion was the result of incompetence and carelessness.



I don't have a "problem with that".

Read that post and you will see my reference to people who should have known better.,