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ssullivan · 30-09-2007, 15:12

Quote:

Originally Posted by hellosailor

Sean-
"I can't see that I could shut it off with a solenoid, since it would create a spark (potentially)."
Look behind you. [g] AFAIK you don't turn the power ON to shut a gas solenoid, you turn the power OFF. So, there's no spark to shut the valve, it shuts when the power to it is cut off. I've seen those solenoids set up on timers, so you can turn them "on" before you start cooking, and then they will shut the gas off automatically in an hour whether you remember it or not.

I thought those lpg reefers had to run on gimbals, or be kept level, and that they were unsuitable for marine use because of that?

Don't worry, every year a couple of homes and businesses blow up from gas explosions in the US alone. And nother couple of gasoline stations--usually from the folks who stop there to buy and light cigarettes while they are fueling. Um.

This isn't helping calm my fears one bit! ha ha ha!

All of this stuff is installed in my new "land boat" (aka RV I built myself). Yes, the fridge has to be level. I didn't want to get too into the RV particulars because I was trying to keep it related to cruising and boats, which have the same type of lpg systems.

I think somewhere Wheels mentioned an LPG sniffer that was attached to a solenoid. Seems like a good way to go since it would shut off the gas on the first whiff of the stuff.

The fridge has been running for a day now, even though we're not moved off the boat and into the RV yet. (Testing it all out) We haul out on Tuesday never to live aboard our boat again...

But we are just going to put in extra effort and save up $$ for a new boat in about 5 years and will do it with a cruising kitty this time. (Go now doesn't work - unless you have the cash)

hellosailor · 30-09-2007, 16:10

"This isn't helping calm my fears one bit! ha ha ha!

"

Then forget about LPG blowing up, have you consider how hazardous DRIVING is? [g]

In some parts of South America guinea pig is considered a fresh roasted delicacy. No refrigeration required, individually portion packed. [g]

brian and clare · 30-09-2007, 17:15

A guy in the coromandel just blew up a catamaran this way. Was in the paper on friday. He was critical when I read it. Scary.

**Pblais** · 30-09-2007, 18:10

Quote:

Obviously, replacing the bad fitting isn't enough -- I'll have to do a thorough inspection of the system before I start using it again.

Being responsible has it's cost.

I lived a few blocks from a landlord that was repairing the natural gas system in a house. He finished the job and was walking out to his truck when he lit a cigar and suddenly forgot something in the house. He walked into the house and never walked out. The roof raised about 4 inches and came down in place slightly ajar. All windows were blown out totally. All walls on the exterior were slightly out of plumb. They had to tear the house down.

Your boat was saved because the propane locker was vented! Doing things right means you didn't explode. It's not pleasant finding such a leak but it could have been far worse. A total eval is deserved. We can't get new forum members as easy as we used to. We hope to keep (and you) them a long time.

coot · 30-09-2007, 20:19

Quote:

Originally Posted by ssullivan

He he... I should have known better than to suggest propane was scary. I know it's a passionate topic.

But the above snippet is important. Thanks for sharing that too. I was not sure what the safety factor was in having the remote electric solenoid shutoff.

Well, maybe it is scary, but the objective is to make it as non-scary as possible.

Quote:

My imagination was seeing an lpg leak INSIDE the cabin, filling it up with gas while I wasn't there. I have a Norcold refer/freezer that runs on lpg, meaning it has a flame on 24/7. If say, my stove were to leak lpg, it would fill up the room and once it hit the flame for the refer- BOOM!

Each appliance can have its own solenoid valve. Then you can shut off the stove without shutting off the refrigerator. You would leave the stove off most of the time, so it could only leak while you were using it.

Quote:

Originally Posted by hellosailor

AFAIK you don't turn the power ON to shut a gas solenoid, you turn the power OFF. So, there's no spark to shut the valve, it shuts when the power to it is cut off.

The spark is a property of the mechanical switch in the cabin. It occurs when you turn the switch on AND when you turn it off. That's why the gas company tells you not to turn anything off if you smell a leak.

**GordMay** · 01-10-2007, 01:39

Quote:

Originally Posted by coot

... The spark is a property of the mechanical switch in the cabin. It occurs when you turn the switch on AND when you turn it off. That's why the gas company tells you not to turn anything off if you smell a leak.

While DC switches can arc on both opening (off) and closing (on); low-energy circuits usually present greater arcing when opening. Accordingly, the greatest spark-hazzard occurs as you turn off the solenoid switch, closing off the gas supply.

Hopefully, your gas solenoid switch is mounted well above any likely pool of dangerous gas (*LPG is heavier than air, and collects at the bilge & sole level).

Switch contact arcing can be minimized with the addition of a "snubber" circuit (a 10 uF capacitor and 22-500 Ω resistor wired in series) in parallel with the contact.

ssullivan · 01-10-2007, 04:30

Quote:

Originally Posted by hellosailor

"This isn't helping calm my fears one bit! ha ha ha!

"

Then forget about LPG blowing up, have you consider how hazardous DRIVING is? [g]

In some parts of South America guinea pig is considered a fresh roasted delicacy. No refrigeration required, individually portion packed. [g]

Guinea pigs sound tasty... but what about that odd squirrel or skunk I find squished in the middle of the road? ha ha

When in Rome... (or driving around in an RV...)

You are right about driving. That does indeed make us a little nervous, coming from the safest place to live (the water). But... I'm weighing in at about 10,000lbs right now on a 14,000lb GVW vehicle. Unless it's another truck, or immovable object, I should be ok. Tiny weight numbers compared to boats though, huh?

Coot: Good ideas about the solenoids (or even a valve) upstream of each appliance. It would be good to have individual controls for LPG right next to each - even a manually turned valve. BUT... I also see a downside. That's 4 more flare fittings inside the vehicle (to install 2 valves or solenoids). I currently have only 2 flare fittings inside the vehicle - once connecting the gas line to the stove and one connecting the other gas line (they are "t"'ed outside the vehicle) to the refer. My main concern is a failure of a flare fitting rather than the appliance itself, since lpg valves on stoves are set to fail in a closed position and the refer has its own solenoid - computer controlled to shut of the lpg when it doesn't need it or senses a danger.

RonRicco · 01-10-2007, 04:50

For what it is worth, I have lpg stove and fridge, it is back up with a sniffer and solenoid.

In normal operation the solenoid is held open by electrical current, if the sniffer detects a leak (in theory it can detect at at levels much less than required for an explosion) it allows the solenoid to close.. Yes it is electrical, but it is removing electricity and it is also located at the tank, not inside the cabin where the leak would have to take place for the sniffer to detect it.

I feel comfortable with the system and sleep well at night.

Brian

hellosailor · 01-10-2007, 10:26

Gord-
For DC circuits, a similar "snubber" circuit uses a diode to discharge any spark and protect relay points. But those circuits (either kind) are designed to extend the relay/switch life, nothing more, AFAIK.

Here in the US, there are switches expressly rated "explosion proof" or "vapor safe" with a rating from our government Bureau of Mines (yes, that's a "BOM" stamp on the device) and only explosion safe switches are allowed in areas where explosive gasses may be present. The entire body of the device is supposed to be sealed, waterproof and vapor-proof, so even if it sparks internally, it can't set off an explosion.

I knew a fellow who cheaped out on a printing press, used a plain light switch for the power and used flamable thinner to clean it out at the end of the day. One day he flipped the switch...Oopsie, found out just how far extinguisher dust can carry. Next day the repairman comes in, and replaces the switch with another 79-cent light switch, instead of the expensive BOM-approved switch that would have prevented the fire. Hmmmmmm.......

**GordMay** · 01-10-2007, 11:52

Propane vapors (contained, but may be present), would be a Class I, Division 2, Group D hazardous location - which look something like these:
http://www.adalet.com/pdf/section_7c.pdf

Reed & Mercury switches can be “Intrinsically Safe” (they don’t spark), but I’ve never seen them configured (rocker/toggle) for this application.

hellosailor · 01-10-2007, 12:12

Gord, in the 70's mercury capsule light switches (wall mounted switches) were commonly sold in the US as "silent" switches, i.e. so you wouldn't wake someone with the "snap" of a switch.

I don't know if they are on the market here any more, with everyone trying to get mercury out of products and the environment.

**GordMay** · 01-10-2007, 13:06

Quote:

Originally Posted by hellosailor

Gord, in the 70's mercury capsule light switches (wall mounted switches) were commonly sold in the US as "silent" switches, i.e. so you wouldn't wake someone with the "snap" of a switch.

I don't know if they are on the market here any more, with everyone trying to get mercury out of products and the environment.

Could be (available) - I just don't know of any.

The "Explosion-Proof" switches enclosures* are wire in sealed (EYS*) GRS Conduit.
* http://www.hubbell-canada com/wiring/killark/PDF05/2SecF/F45-F49.pdf

* They use "standard" switches in cast/machined boxes.

By now, I hope most of us have concluded that the recommended procedure is to turn off (close) the MANUAL gas valve (at the tank).

ssullivan · 01-10-2007, 14:23

But the tank is a loooong way away from the connection at the stove. Running back to close the valve at the tank while hoping nothing sparks up the leaking lpg doesn't seem all too safe. This is the danger factor I see. They out to have a regulator that has its own built in shutoff at the tank and have that wired up to an lpg sniffer.

I nearly forgot to add this!

A house was leveled a few blocks from my current marina today. Cause? You guessed it... natural gas leak. Nobody was killed, luckily but you could feel the explosion from the marina. The dodgers flapped with the pressure wave. I'll say it again: YIKES!

Naturally, I ran out to see if my "land boat" was okay... ha ha ha! It wasn't my propane screw up.

forsailbyowner · 01-10-2007, 14:46

Ok I got the Seaward Princess two burner stove w/oven. The trident control panel, shutoff solenoid, regulator w/dual pigtails and dual guages. Fiberglass 10 lb propane tanks, all I need is to build a locker and run the line to the stove. Does the locker need an airtight lid? If so an overboard vent at top? What size does the drain have to be? The larger the better? Plan on building fiberglass locker that sits directly under hatch near stern. running vent to center of transom, looks like it will be a foot above waterline. Plan on having goodyear make a line, Is copper better way to go. Thanks in advance
steve aka forsailbyowner