ANNEX IRON MINE
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This information is a combination of Web Site research, Testing different POL (propane out let) fittings with flow measuring equipment, and interviews with various people in the propane service and sales in my area.
If this is not the Information you are looking for check out these sites, They are Commercial sites that also offer very good explanations of Propane , and Propane Products. i highly recommend these two sites.
The OPD valve has been blamed for many problems relating to propane appliance malfunctions. I have mistakenly done this on numerous occasions.
Keep in mind if a cylinder is mounted in a tilted position as seen on recreational vehicles the only way of safely filling these systems is using an 80% valve. Do not assume an attendant at a fill station will understand this. The attendant could overfill your system thinking it will shut off when filled! monitor what is being done! It could be your vacation going up in smoke! or worse
Pressure Relief Valve. Prevents the contents of the cylinder from exceeding 250psig. And is unchanged from the old style valves.
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I alluded to the cylinder outlet fitting and the main shut off valve being the cause of most problem with propane devices. This chapter will explain the differences in P.O.L. fittings and what we should expect of them.
In the above chapter there was discussion on a function called "Excess Flow".
We didnít go to far into it as this is more commonly a function of the POL fitting(s).
What is excess flow,
Any marked increase in the normal flow of a liquid or gas can be termed Excess, and is usually the result of a malfunction or failure of a delivery component. An example of a malfunction could be a free flow regulator.
An example of a component failure could be a broken hose or fitting.
When something like that happens an excess (much more) flow of vapor would be discharged into the surrounding air, thereby setting up a very unsafe condition.
PLO fitting have been available for a long time that would sense this increase flow, and immediately shut down the discharge of Gas Vapor.
Some of the early fitting set up this way would have to be manually reset after being activated, after the malfunction was corrected. The ones we see today are automatically reset by the use of a very small orifice in the valve witch is an integral part of the fitting.
A valve like this is also used in the Hydraulic industry and is called a "Velocity Fuse".
We will find Excess Flow fitting on most new Grills and Stoves that are used in recreation. They will be sized to meet this application. One for a small propane barbecue grill might be rated for 70,000btu, and that would mean enough vapor to accomplish this could leak and the device most likely wouldnít know the difference, But if the appliance (Grill) is using most of this establish flow, and a leak occurred causing flow in excess of what would be consumed at 70,000btu there would be an imbalance in the sensor and the valve would close. The excess flow valve would stay closed until the appliance valve(s) are closed and enough time has elapsed for the vapor passing through the small orifice in the excess valve bring the pressure up to match the pressure on the cylinder side of the excess flow valve, or the malfunction corrected.
So if we have a setup like this,
1. Cylinder, 2. Excess flow P.O.L. fitting, 3. Regulator, 4. Delivery hose, 5. Appliance. We may never have a problem unless the pressure regulators free flowís. This is a rare event, that could be caused by a fire or icing of the regulator, or its vent, but may not sense a failed delivery hose. The excess flow valve would have to be very closely matched to sense a leak downstream of a regulator, as a regulator is in its design a flow control devise on its own.
This is the setup that will cause us the most problem when we donít understand what is happening.
1. Cylinder, 2. Excess flow POL fitting, 3. Delivery Hose (this was #4 in other setup), 4. Regulator 5. Appliance.
With this arrangement, the hose and regulator are in a different orientation and the length of the hose and the speed of opening the cylinder valve would dictate how problematic this could be.
I use this arrangement on 2 different appliances, 1st is a Weber IQ portable Gas grill where I have a 20 lbs cylinder adapted, instead of using disposable cylinders (1lbs size), The 2nd is a Mr. Heater portable "Buddy" heater that I use in my fish house and I also have this adapted to a 20 lbs cylinder in favor of the 1 lbs throw away. Both of these adapters were purchased as per the manufacture recommendations.
This problem has such a simple solution that its almost nauseating, but if one isnít aware of what is happening it could be terribly frustrating.
When the cylinder valve is opened, gas vapor is delivered through the excess flow valve, but because the delivery hose is empty, and depending on its length, an imbalance occurs each time this arrangement is assembled. Now if we were to just leave this device alone for a minuet, (unless there was a leak and this could just be a burner valve opened ever so slightly), the automatic reset function of the excess flow valve would reopen the valve. But what happens is when we donít understand the mechanics of this we turn on our tank, and then open the burner valve and try and light the burner. By doing this we prevent the auto reset from functioning.
This can be remedied by simply waiting a short time after turning on the cylinder with the burner valve(s) in the off position until the delivery hose is charged by the orifice to match the cylinder side. And if your hearing is good one can easily hear the click of the excess flow valve upon closing and again upon opening.
Or, one could very slowly, open the cylinder valve. This is something that you will have to experiment with on your system and isnít the best way to overcome this problem. The reason being, when you connect everything together, then make sure the burner valve(s) are off, and then open the cylinder valve we then know that it will take up to 1 minuet to reset the excess flow valve, and if this then doesnít happen we most likely have a leak.
But,(donít we love ifís and butís)(and if they were mintís and nutís we could have a party). (In loving remembrance of Joseph Roots, RIP Joe)
BUT, if we elect to open our cylinder valve very slowly, thereby filling the delivery hose and as long as the leak wasnít in excess of our excess flow valve, we could then light our burner with a relatively large gas vapor leak.
Remember, the excess flow valve isnít all that smart. It can only see an imbalance of pressure on each side of it to activate. It doesnít know why that is happening. That is our job.
The excess flow valve (velocity fuse) is a good thing to have in your system, but we need to understand how it works. We will see more problems with the excess flow POL fittings when temps are high and tanks(cylinders are full, and valves are turned on too fast. We may get away with faster valve turning in cold seasons where it will cause trouble in the hot seasons.
I have purchases 2 of these OEM conversion kits for the 2 above described appliance and I truly did not understand what they did, nor could I find any information on the internet to explain what they are and how they work in the way we do things in our day to day life.
I hope this will be of benefit to anyone who reads it, and if you are like me, you also may feel a tad foolish because its such an easy problem to over come.
Also keep in mind that every time we change the cylinder we must check for leaks. This is usually done with a soapy water solution like bubble soap. There are products available with a ethylene glycol base for cold weather use, or the high price electronic units the gas company might use. Just don't use a bic!
I will again remind everyone again that I am not an engineer, and this information was determined by un-scientific methods. Proceed with utmost caution at your own risk.
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