What can I keep in the gas locker? Possible daft question! (1 Viewer)

[Techno]

I thought most alarm external modules were sealed reed switches ? so no spark.

They are and insufficient electrical energy to do anything

Also it is not that easy to light hence piezo igniters

 

[Techno]

Now that I like.......Did you retro fit it?? Two, or all four??

http://www.motorhomefun.co.uk/forum/threads/i-love-my-e-p-jacks.108931/page-10

 

[eddie]

Sorry Eddie, it is not an incorrect statement. This is my specialist subject.

If you have an area, be it enclosed or open with a concentration of gas (between it's lower explosive limit and it's higher explosive limit) and there is a spark which contains enough electrical energy in that gaseous area then it will explode!

That is why houses are reduced to rubble by gas explosions, a gas concentration occurs then someone switches on a light or a timer clicks over.

A standard 12v DC supply, through a switch which changes state, will easily ignite gas. Of course it rarely happens, but it certainty could in the right (wrong) circumstances.

Our vacuum sealed magnetic reed switches are Normally Closed (N/C) to Negative. The Normally Closed alarm circuit is 0VDC IE you could smash the reed switch and rub the exposed ends of the switch on the metal of the gas locker and you will get no electrical spark whatsoever.

In essence the alarm ECU expects the Normally Closed circuit to be connected to the vehicle chassis at all times, opening the gas locker door makes the circuit "Open"

So the switching is carried out in a vacuum, enclosed in glass, encapsulated in a robust plastic housing with no voltage running through the circuit anyway

So no danger whatever, hence my first post

How do explain automatic gas solenoids that open and close the gas valves when gas alarms sound or vehicles are started?

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[Techno]

A little knowledge

 

[Techno]

with no voltage running through the circuit anyway

Exactly

 

[timetochill]

All electrical circuits that may be used or routed through hazardous areas i.e. Gas petroleum need to be connected through a zener type barrier and be intrinsically safe
Fact

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[Techno]

It is intrisically safe which is that it has insufficient energy to create or cause a spark as explained in better detail by Eddie

 

[eddie]

I am not even sure that "legally" a gas locker is a hazardous area. Having a "hazardous area" in a motor venicle would I should imagine open a huge can of worms with "Hazard" signage having to be displayed

However academic as at 0VDC a spark is impossible. If you were to measure the voltage between the gas system which has an Earth connection to the chassis and the 0VDC at the alarm switch there is no voltage

Our dedicated switching circuit N/C is completely diode protected

So I keep coming back to the fact that it is 100% safe It is as electrical as the metal box used to make the gas locker lol

 

[Sandancers]

It is intrisically safe which is that it has insufficient energy to create or cause a spark as explained in better detail by Eddie

It is ONLY intrinsically Safe when you have a certificate from an independent Test house, such as BASEEFA (in the old days) to say it is intrinsically safe. You cannot self declare something intrinsically safe.

If Eddie wanted to be totally sure the alarm cannot ignite gas then he would have to submit the circuit and any switches, enclosures to such a test house. Mind, that would cost an arm and a leg .

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[scotzsue]

When in europe I carry my warning triangles in the gas locker as it is on drivers side (nearside when driving on wrong side).This means I can get to them without getting killed.My garage door is the other-side.

Thanks for the reminder I moved ours there, they were previously stored in the gsrge, in a cupboard that you had to almost empty the garage to get at, don't ask, was not my idea.

 

[Techno]

Well it's a case of pedantry or realism and common sense
I'm quite satisfied my switches are not a hazard. By all means follow your own path

 

[Techno]

The gas locker is also open to the outside environment by virtue of the drop vents and a leak has more chance of being ignited by a discarded fag

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[eddie]

As we have no electrical current running through the vacuum sealed switch and the switching is monitored in the ECU under the dash there is no chance of a spark, which was why I challenged the original incorrect statement.

 

[Minxy]

They are and insufficient electrical energy to do anything

Also it is not that easy to light hence piezo igniters

You MIGHT want to rethink that last sentence Andy, it can ignite quite easily without any electrical or piezo induced spark!

See my post #25 ...

http://www.motorhomefun.co.uk/forum...-a-fire-extinguisher.60744/page-2#post-715424

The consensus by the experts etc seems to be in our case that static electricity in the camper ignited the gas!

 

[Techno]

I wonder how that was caused

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[Minxy]

I wonder how that was caused

Eh?

 

[Techno]

Nowt quite like going out with a bang

 

[Sandancers]

Wow, looks like this thread has touched a nerve with some people.

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[Robin McHood]

Hmm as things are going quietly in the engineering dept tonight so I guess I'll throw my hat into the ring as I do have hazardous area certification as part of my job. As we work alongside large gas platforms that are live and carrying millions of cubic metres of the stuff, the risks of gas explosion are at the forefront of our minds!.

The first thing you would have to establish as far as we are concerned is what the zoning of the locker is and this is dependent on the relative likelihood of gas being present in that area and the proximity of the area in question to any other area where there is a greater likelihood of gas occurring.
So its not just gas presence possibility, its also distance from source.
Depending on that you then have a number of strategy's to prevent an explosion occurring or preventing an explosion inside something from getting out to ignite any gas around it.

IS - Intrinsic safety where you effectively divert a fault current through a zener short circuit located outside the hazardous area is one method but there are multiple others.

I'm guessing here but as I have not seen a zoning notice displayed on any gas locker on any moho or caravan or trailer tent, that hazardous area rules do not apply. In which case the arguments about what type of protection is required in such lockers becomes moot.

All the sensible precautions referred to by multiple funsters above of keeping the area well ventilated and ensuring there is nothing in there that can gather gas are eminently sensible, as is making sure nothing can bang against anything else and cause a spark. If you really want a good energetic spark try rusty iron against aluminium alloy. That rusty old clubhammer and your aluminium ladder will do just fine....

@eddievanbitz 's decription of the circuitry is just such a precaution. For a start reed switches are tiny so its unlikely even if the vacuum failed that you could get enough gas in there to ignite. In hazardous equipment switches are designed to have limited internal volume for just this reason and in the past were sometimes sand or oil filled. It sounds as if the way Eddie's equipment is designed that the currents and voltages involved when the circuit opens are so tiny that the risk is equally low. I certainly hope so as I have a brand new Eddie system on my van with one of his switches in my gas locker...

(By the way voltage doesn't flow... current does)

Nope, follow @Minxy Girl et al's precautions, leave the alloy ladder and club hammer in the garage, make sure your vents are clear and your gas system regularly checked and you will never get near a concentration high enough to blow anything up unless you have a habit of disconnecting your cylinder and leaving the valve open... in which case you are likely to receive all that you deserve

 

[eddie]

Wow, looks like this thread has touched a nerve with some people.

incorrect assumptions tend to do that

 

[Robin McHood]

You MIGHT want to rethink that last sentence Andy, it can ignite quite easily without any electrical or piezo induced spark!

See my post #25 ...

http://www.motorhomefun.co.uk/forum...-a-fire-extinguisher.60744/page-2#post-715424

The consensus by the experts etc seems to be in our case that static electricity in the camper ignited the gas!

Beleive me there is a HUGE amount of energy in static electricity. One of the demonstrations on one of my courses was done using a nylon shirt (remember them) hence a ban offshore on such clothing materials..
The thing with gas though is you have to have enough but not too much so don't make it possible for it to accumulate and then it doesn't matter a hoot how many pairs of nylon jockstraps your nearest and dearest is wearing tonight, the flashing lights you see will probably be caused by something else entirely..

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[Sandancers]

incorrect assumptions tend to do that

Which incorrect assumption do you mean ?

 

[eddie]

Which incorrect assumption do you mean ?

That one

I am amazed that some vehicle alarm fitters actually put an electrical switch on the inside of the compartment door. If you had gas in there at the right concentration and you opened the door with the switch energised, then you'd be lucky not to cause an explosion.

I'm bored of explaining now that our dedicated Normally Close 0vdc cannot produce a spark

 

[Sandancers]

That one

I'm bored of explaining now that our dedicated Normally Close 0vdc cannot produce a spark

OK, the side of the nc switch that is connected to the chassis, 0v will never rise above that voltage. But tell me, when the door opens and the magnetic switch opens what happens to the voltage on the other side of the switch ? Does it stay at 0v, if so, how does the circuit know the door has opened as there has been no change of state on the line. Or perhaps THAT voltage rises to signal a change of state ?

I don't know your alarm circuitry, but the simplest way to have an alarm function is to have a wire feeding into a integrated circuit i/p line, with a pull up resistor in the range of 10k to 100k to 12v. When the wire is disconnected from ground the i/p voltage to the i/c rises, thus change of state, simples !! BUT not instrinsicaly safe unless tested and certified.

In reality the odds on an explosion being causes by your alarm circuits is vanishingly small, but when I get round to designing an fitting my alarm I won't be putting a switch in the gas locker. Just because I have seen what a gas explosion can do.

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[Techno]

I'd put more effort into making sure you don't have a leak and not worry about a bullet proof switch.
This DIY alarm won't have certification either unless you spend a lot of money so do you think the insurance company will accept it ?
Is there a CAT DIY ?

 

[Minxy]

Is there a CAT DIY ?

Don't need a CAT DIY, just a CAT TECHNO!

 

[Xabia]

Well I for one have 100% confidence in Eddie and his team and have no worries at all about my Strikeback alarm causing problems with the gas system. If there was a risk he would have taken steps to eliminate it.

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[Techno]

Don't need a CAT DIY, just a CAT TECHNO!

Thatcham approved pussy

 

[eddie]

OK, the side of the nc switch that is connected to the chassis, 0v will never rise above that voltage. But tell me, when the door opens and the magnetic switch opens what happens to the voltage on the other side of the switch ? Does it stay at 0v, if so, how does the circuit know the door has opened as there has been no change of state on the line. Or perhaps THAT voltage rises to signal a change of state ?

I don't know your alarm circuitry, but the simplest way to have an alarm function is to have a wire feeding into a integrated circuit i/p line, with a pull up resistor in the range of 10k to 100k to 12v. When the wire is disconnected from ground the i/p voltage to the i/c rises, thus change of state, simples !! BUT not instrinsicaly safe unless tested and certified.

In reality the odds on an explosion being causes by your alarm circuits is vanishingly small, but when I get round to designing an fitting my alarm I won't be putting a switch in the gas locker. Just because I have seen what a gas explosion can do.

I did, and I designed a system that cannot and will not produce a spark

Stop digging a hole OR provide a real life situation wher you can make a spark from a N/C negative switching circuit

IE put up or shut up

 

[wigster]

To go back to the ops original post , my grey waste pipe is stored in my gas locker in the original pipe clips put in by the manufacturer .

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