Propane Tank Question

[rockhillmanor]

Is this true?

""Propane tanks have a safety valve that shuts if a gas line should break and allow full flow.""

[red31]

Type I QCC Connectors
EVACUATION COUPLING - 1-5/16” F. ACME X FULL FLOW
http://all-propane.com/Documents/aplpg_products.pdf

QCC ACME PURGING COUPLING
http://www.rutherfordequipment.com/pdfs/ConnectorsAdaptors.pdf

no outlet threads!

[magic43]

I had to replace my pigtail because the plastic nut failed (broke). I got a replacement from Tractor Supply (that I returned) that would shut off when I tried to light the stove. I now know why. It was black instead of green

The Black, Green, and Red explanation answered my question. Thank you Chris.

[Chris_Bryant]

I'm not sure you can get a full flow ACME pigtail- the ones I have are the older POL type. The POL type did have excess flow valves also, but they did not shut the flow down very much- they still allowed a pretty significant flow (in the tens of thousands of btus). The new ones do not always shut completely either, but the flow should be minimal.

[TenOC]

The key word is FULL FLOW. I had a squirrel (?) chew a hole in the rubber line from the tank to my TT -- before the regulator. The tank emptied very quickly.

[rockhillmanor]

Chris Bryant wrote:
The excess flow valve are sized so that just about nothing after the regulator will trip them. There are 3 capacities of ACME type, they are black, green and red. The black is low capacity, meant for grills. I believe their capacity is around 100,000 btu/hr. the green is standard RV, with a 200k but/ hr capacity, and the red is 400k/ hr.
They are meant as a last ditch, fail safe in case the line has been breached before the regulator. They usually will do nothing for a breach after the regulator.
The only reason people have problems with them is quickly opening the valve on an empty system allows a brief flow of over the capacity, they call it slugging.

Thank you.

[Chris_Bryant]

The excess flow valve are sized so that just about nothing after the regulator will trip them. There are 3 capacities of ACME type, they are black, green and red. The black is low capacity, meant for grills. I believe their capacity is around 100,000 btu/hr. the green is standard RV, with a 200k but/ hr capacity, and the red is 400k/ hr.
They are meant as a last ditch, fail safe in case the line has been breached before the regulator. They usually will do nothing for a breach after the regulator.
The only reason people have problems with them is quickly opening the valve on an empty system allows a brief flow of over the capacity, they call it slugging.

[rockhillmanor]

will shut off if there is a sudden increase in the flow, such as a broken line.

So theoretically a knob bumped open on the stove, not lit, 'should' cause the valve to shut off on propane tank. Right?
Seeing as that scenario would imitate a broken line and/or leak.

Or is the pressure of not lighted propane in an appliance in the RV the same as lighted propane so it doesn't recognize it as an increase of a leak/broken line??

The reason I asked the original question about a shut off on tanks.

[Chris_Bryant]

I hope you are not understanding what I am talking about, because everything I said is 100% accurate- let me try to make you understand..

parkmanaa wrote:
You are terribly wrong, Chris Bryant.
The "pigtail", when screwed into the OPD POL fitting, releases the check valve and allows normal flow of propane, but if you open it too quickly it will freeze the tiny orfice. You can open it very slowly and bring it to full flow, but again, as with a line failure, if it is a sudden burst of propane flow, it will freeze up.The "pigtail", or longer line, if you wish, has nothing to do with the safety features built into the OPD valves.

The check valve and the orifice in the valve are 2 different things, the check valve keeps LP from flowing if nothing is hooked to the valve- the ACME pigtails have low temp melting parts, so the pigtail will back out in a fire, shutting off the flow. We are not talking about that.
The orifice is just that- it does nothing to stop the flow, it simply limits it. If an orifice is freezing, the cylinder has been over filled, and is under liquid. It is not meant to shut anything off.


I just went out and hooked my full flow pigtail to my OPD equipped cylinder, and I got full, ~150 psi LP vapor for the 10 seconds I left it open- that's a lot of LP. Nothing stopped the flow or "froze". I can post a video if you wish.

I happen to own a propane dispensing station, and about the only time we screw a pigtail in the POL valve is to purge a new cylinder, and many times have opened the OPD valve too quickly and had the flow shut off immediately.

Yep- because the pigtail has the excess flow valve in it.

[Old-Biscuit]

There is a spring loaded shutoff vlave in the end of OPD service valve that will not allow propane flow unless a hose is attached that pushes the spring loaded shutoff valve open.

There is a ball check valve inside the ACME nut that moves closed when opening a OPD valve until downstream pressure builds up/equalizes and then the ball check valve moves back to center position allowing full flow.
If OPD opened to quickly the ball check valve will stay in closed position.
If a downstream leak should occur the ball check valve moves from center to closed position.



OPD Spring loaded Valve #24 (Pushed Open by #66 in ACME Nut)

ACME Ball Check Valve #86

[red31]

ACME excess flow does not shut completely if operating properly.

two safety features are built into the Acme nut itself. First, Acme nuts contain a thermal bushing, which will melt in a fire, and prevent the escape of gasses from the tank. When it melts, it allows the new OPD spring activated shut off valve, which will only allow the flow of gas if a fitting is attached, to pop out and completely shut the flow down. They also have an improved excess flow check valve,

Now to the new style excess flow check valve on the Acme nut that connects to the DOT cylinder's OPD valve. It is really a simple device. Inside the Acme nut, there is a ball bearing check valve that almost shuts off momentarily when full pressure is released by opening the cylinder valve. You should hear a click at that point. It doesn't shut down completely, as that would negate its ability to detect leaks and excess flow from a leak or major line break, and no gas could flow. It closes just enough to allow a bypass of gas that is very slight, about 10 cubic feet or less per hour (cf/hour) flow, as opposed to the max flow of 200 cf/hour. The bypass gas goes into the propane system, and if there are no leaks or broken pipes, it backs up and builds pressure in the gas lines in the RV. When it equalizes on both sides of the valve, the valve opens to allow full pressure up to about a max of 200 cf/hour at 100 psi. Then if you were standing there, you would hear a second click.

http://home.earthlink.net/~derekgore/rvroadiervfulltimingwhatisitreallylike/id44.html

[parkmanaa]

You are terribly wrong, Chris Bryant.
The "pigtail", when screwed into the OPD POL fitting, releases the check valve and allows normal flow of propane, but if you open it too quickly it will freeze the tiny orfice. You can open it very slowly and bring it to full flow, but again, as with a line failure, if it is a sudden burst of propane flow, it will freeze up.
The "pigtail", or longer line, if you wish, has nothing to do with the safety features built into the OPD valves.
I happen to own a propane dispensing station, and about the only time we screw a pigtail in the POL valve is to purge a new cylinder, and many times have opened the OPD valve too quickly and had the flow shut off immediately.

[Chris_Bryant]

parkmanaa wrote:
Any legal cylinder today, which requires a OPD (overfill prevention device)valve, will shut off if there is a sudden increase in the flow, such as a broken line. The propane passes thru a very small orfice that will immediately freeze closed if the normal flow amount is suddenly exceeded.
This feature is just part of the OPD valve safety features.

That's a bit misleading, the excess flow part is in the pigtail, not the valve. I have a full flow pigtail, and have no problem venting a cylinder at full blast through the OPD valve.

[parkmanaa]

Any legal cylinder today, which requires a OPD (overfill prevention device)valve, will shut off if there is a sudden increase in the flow, such as a broken line. The propane passes thru a very small orfice that will immediately freeze closed if the normal flow amount is suddenly exceeded.
This feature is just part of the OPD valve safety features.

[Chris_Bryant]

What Doug said- portable DOT cylinders do not have that built in to the tank, it is in the pigtail. The tank has a shutoff if nothing is attached, and shutoff while filling at 80% (the OPD part), but the excess flow valve is outside the cylinder.