Gas cookers and Gas storage

[Firefly]

gas ffd

all new domestic gas appliances have to have flame failure devices fitted and have for quite a few years now. I was under the impression that only the cheapest camping ones don't. Even some of the ones where you clip a can into the side have them andf I know there is a move to ban the sale of the ones that don't. Are you quite sure that the one you have bought hasnt?

This is such a simple and unobtrusive safety device I am amazed at the aggresive rejection of it from some posters on this site - you don't even know it is there, it doesnt affect the operation of the cooker, but it might save the loss of your boat or even your life. I guess the problem is that no-one ever knows that it has done that.

The amount of gas requitred to create a dirty great bang is actually very small. Best avoided.

 

[VicS]

The amount of gas requitred to create a dirty great bang is actually very small. Best avoided.

I asked before got got no answer.

How much gas would have to leak into the cabin of a small boat to create an dangerous situation and how long would that take from a typical gas burner on full.

and no as I said earlier I could not find a cooker with FFDs that would fit the space. Originally designed to take a small camping cooker or the marine version of it ( which did not have FFDs either) So only another small camping stove will fit.

Not really happy with what I have .. Don't think is is particularly well made, not like the original British made one and would have preferred one with FFDs .

As also said I'm going to look at a gas alarm ... that will detect leaks from all sources not just an extinguished burner.

 

[Pye_End]

There is no logical argument for anyone not buying into the latest safety device of any kind, anywhere. All boats should have liferaft; PLB (to be carried at all times); lifejackets (to be worn at all times); alcohol stoves not gas appliances; CO detector; smkoke detector; gas detector etc. etc. I am sure you get the gist. And yet we don't go for every safety option.

Now instead of making every one of these compulsory (this was Norman's argument - FFD should be a must have not just desirable), each boat owner has to make their own judgement of what they use on their boat. Upgrading existing equipment based on the lastest technology is a balancing act given the risks involved, together with the costs / priorities. It may be that this year you can afford a new cooker or a PLB - but which one?

Make safety the top priority - don't own a boat - don't drive to it - stay at home (and don't do DIY).

 

[prv]

all new domestic gas appliances have to have flame failure devices fitted and have for quite a few years now.

Cite?

My gas cooker bought two years ago doesn't have one; neither did most on sale at the time.

I subscribe to a newsgroup in which domestic gas topics are regularly discussed by knowledgeable amateurs and a handful of professional fitters. The requirement for FFDs in blocks of flats was talked about when it came in; noone has ever mentioned such a requirement in other domestic buildings.

Pete

 

[Bodach na mara]

Regarding domestic gas hobs, I found lots last year that had no FFDs. The ones that had were labeled as "suitable for installation in flats." As I said before, I used to see reports of houses blown up every year by gas explosions, so gas is dangerous in houses as well as boats.

For a view of the effects of a gas explosion, have a look at this short film. http://www.youtube.com/watch?v=obOWAGRY_IY

The wife of my boss at the time was sitting in a car on the roof car cark when it went up. She was lucky and escaped without a scratch.

By the way, whatever happened to the original poster?

 

[VicS]

you may remember that I posted that someone turned off the main switch for moment which shut the fail safe solenoid, and then filled up the boat with gas when the electrics were switched on again moments later - no-one new that the power had been off

That sort of situation really requires to be engineered so that the gas valve does not automatically re-energise when the power is restored. If it shuts then it should require a deliberate act by someone to restore the gas supply.

Nearly had a school laboratory wired up like that some years ago. Short power interruption. All the Bunsen burners warming one lab before classes start go out but then gas restored when power restored. Stay on in adjacent room because that has a manual shut off system.

Potentially half way through morning assembly ... school hall in same building packed literally shoulder to shoulder .. a bit of gas gets wafted from one room to the adjacent one or the technicians room and BANG

Imagine what the reaction would have been to 700 Grammar school boys being blown up during school assembly.

"Oh I'm sure that couldn't happen" was the response until I suggested we ought to test it to see if I was right or not!

 

[Ubergeekian]

I would have thought that every conciencious boat owner would be well aware of the danger of escaped gas accumulating in the bottom of the boat. If you are unaware of this danger, I recommend that you do some very basic research on the subject.

I am sure he is. I am also sure he is intelligent enough not to rely on one device to assure his safety. Just how reliable do you think FFDs are? How do you know?

I find your complacency regarding your use of gas, astounding. (e.g. "no source of ignition").

You'd love my cooker. The Camping Gaz 904 cylinder is screwed to the bottom - it's what makes the gimbals work.

 

[VicS]

The Camping Gaz 904 cylinder is screwed to the bottom

At least the number of potential leaking joints , out of date hoses out of date regulator etc are reduced to the minimum. Its what was fitted in many boats at one time.

the bottle gets in way of the grill though

but you dont have to go outside to the gas bottle locker to change the bottle.

904 bottles difficult to find though ?? I have one as my spare bottle but the locker ... theres a surprise I have a gas bottle locker .. takes a 907.

 

[Ubergeekian]

At least the number of potential leaking joints , out of date hoses out of date regulator etc are reduced to the minimum. Its what was fitted in many boats at one time.

Indeed - I think all small Westerlies had 'em. It also has the advantage that if you need a BSS survey you can take the whole thing out in about ten seconds, stick it in the boot of your car and say, innocently, "Gas system? What gas system?"

 

[tabernacleman]

domestic hob

have you looked for a hob made for the domestic market, fitted with a FFD, or is there a problem fitting a domestic unit into a boat, corrosion etc? I know a lot come with interchangable jets for those households not on mains gas.

 

[ghostlymoron]

Congratulations VicS

I wish to congratulate VicS for his tenacious defense of his position. On a small boat it is often impractical or impossible to comply with all safety recommendations but with safe practices the danger can be minimised. I'm sure he is fastidious in operating his gas system and this is a sensible approach to minimising risk rather than relying too much on a 'safety device' which can lead to complacency. The problem comes when you forget your safe procedure.
I was interested in the question of how much gas is required to cause an explosion and how long it would take to produce the required volume. There are several factors involved: volume of boat, LEL, and dispersion for example which makes the calculation complicated. I'll try to come up with an answer.

 

[VicS]

I was interested in the question of how much gas is required to cause an explosion and how long it would take to produce the required volume. There are several factors involved: volume of boat, LEL, and dispersion for example which makes the calculation complicated. I'll try to come up with an answer.

You dont for one moment think I have not already done that do you? I did that first before embarking on any of the above debates.
As you say rate of dispersion is the unknown factor. It'll be mixed with the cabin air fairly quickly on a windy day ... but when its not windy.... the flame wont have blown out in the first place!

It'll be interesting to know if you get anywhere near the figure I got; 38 minutes to get 2 cu metres of air up to the LEL. Its not a figure I'd put any trust in of course but I thought it would put some sort or perspective on it.

Thanks for the support.

 

[ghostlymoron]

As you say rate of dispersion is the unknown factor. It'll be mixed with the cabin air fairly quickly on a windy day ... but when its not windy.... the flame wont have blown out in the first place!

Touchez !

 

[pratkins]

Placement of Gas Bottle(s)

You will see what has worked well for me on Peter Robyn at the stern on deck one gas container and provision for a second. At the moment I have a container of fuel for my wood burning heater. Inside the cabin there is an extra turn-off valve with a large sign,"Turn off the Gas Bottle".

 

[willpatten]

I personally prefer (& use) pressurised parafin & yet I am qualified to install and test gas on boats. (yes VicS, an 'unsafe registered engineer'

FFDs, bubble testers, solenoids, detectors etc. are there to minimise risk of an explosion - for very good reason.

However, as VicS points out, many boats operate without conforming to current day standards, hopefully by taking responsible action when in use.

So, the question is one of choice....or it was until the insurers and BSS came to pass.

My concern is the potential to over legislate what is a recreational pastime & assumes we are all irresponsible. It should be a question of choice, made by balancing risk and use, a choice which is being reduced by insurers.

IMHO, Gas on boats is not an ideal fuel and so not one I have chosen. Even the standards raise questions in my mind. For example, flex hose V. Copper. i.e. given the environment, issue over number of joins etc, would it be better to use flex over rigid copper?

The points I am trying to make is that:

1. Just because it is BSS approved does not mean we are relinquished of responsibility
2. If it is not BSS approved, we have to be very mindfull of the dangers & still have resposibility
3. Gas is not the only fuel we can use onboard - and in fact there are other, 'safer' alternatives
4. If we are not careful, we will end up being legislated against what should be a free, enjoyable, traditional pastime.
5. However, If in any doubt, whatsoever, get it checked/get advice, so you can go sailing with peace of mind.

Welcome to discuss.

 

[mikemonty]

And the BIG danger here is that despite being fail safe, if you turn OFF the electrics whilst cooking (without FFD) by mistake, and then turn them on again, then you will be flooding the boat with gas. This happened on my last boat, so I think there is an arguement to wire this direct to the battery, so that you cannot accidently cut the supply.

Actually what you describe suggests that you should have wired the solenoid through a holding relay,not just an in-line switch, so that a power failure would open circuit the solenoid until you pressed the button to energise the solenoid again. A low-tech failsafe.

Anyone thinking of using a solenoid should consider this.

For once I agree with Vic - do what you can to minimise risk but don't slavishly employ all available tech just because it's there - there is nothing wrong with a non-FFD unit as long as you understand the limitations. Just dont walk away from it for extended periods.

 

[saltylegs]

If I could have found one to fit the space I would probably have bought it .... But I couldn't ... hence another camping stove.[/QUOTE]

vics
I'm not sure of the space you have but there is a 2 burner and grill available from www.gasproducts.co.uk (its not on their web site yet but is in their 2010 catalogue)
It's called a Tasman 2500 £203 or as a 2 burner without grill £114 + vat I think.
both have stainless steel top and sides and full FFD protection width 450mm and depth 370mm.

As to how long a hob burner will take to produce a lower explosive level per cubic meter (not allowing for drafts etc)

1 hob burner is approx 1.65 KW / hr this is 0.0636 m3/hr or 0.00106 m3/min

LEL for butane is 1.8% in air so 0.018 m3 of butane is the LEL / m3 of air

so without drafts etc. LEL for 1 cubic metre would be achieved 17 mins.

 

[VicS]

Thanks for trying. That's the camping version of the Plastimo Neptune 2500
Too deep back to front !

I don't think it was available this time last year but the Neptune was the one I was hoping to fit. I can't actually see what the difference between them is.

Both made, I think, by the same firm that made my old one

I think the difference in price between those and the one I bought will pay for a gas detector.

You have come up with about the same figure that I did to reach an explosive mixture. I though it would be interesting to try to quantify it. I know its not something one would want to put to the test though.

 

[Pye_End]

That's quite a long time for gas to be escaping for. The mark I nose picks it up in seconds (so long as it is in the area).

Any idea how sensitive a nose is in relation to explosive levels?

 

[VicS]

Any idea how sensitive a nose is in relation to explosive levels?

Very... very I should think.

Some heavy Googling ought to be able to turn up some figure for typical threshold of smell, but peoples sense of smell varies enormously and can be affected by colds etc even lost altogether. My mother totally lost her sense of smell, and taste for years. We had to make get rid of all gas appliances and go electric instead.

Ethyl mercaptan is the main stenching agent. Its threshold of smell is 1ppb. 50ppm is added to the butane

A little bit of simple arithmetic will give you the butane concentration that will be equivalent to. Compare that with 1.8% for the LEL