LP powered stanby generators

[Bird]

<font color=blue>Never heard of this 10% loss rule</font color=blue>

Neither have I heard of it in those exact words, but I can't say I doubt it either. I only worked briefly on a job that required dispensing of LPG; still have my 1990 Operator's Manual for Safe Dispensing of Propane, but I also worked a couple of years doing gas leakage surveys, primarily for natural gas systems, but also some on LPG. I served two years on the board of directors for our local water company, and grew up with a father who owned a service station. I think you'll find that almost any liquid or gas operation "loses" a certain amount to leaks, evaporation, spills during transfer, etc. So I think most companies are quite satisfied if they only "lose" 10%, although once it's dispensed into your tank (propane bottle in this case) and everything (every seal, valve, connection, line, etc.) is in top condition and you don't ever open the valve or use any, then I might have doubts about you losing 10% a year, but Franz probably knows more than I do about the subject. The gas companies do keep those records and they're seldom heard of by other people. I know the company I worked for doing the leakage surveys said that any gas company that claims to lose less than 10% is either lying or keeping poor records./w3tcompact/icons/laugh.gif And the water company I was involved with would have been very happy to get our losses below 15% (which we never did)./w3tcompact/icons/frown.gif

 

[ebeacham]

I used to work for a small propane company years ago and I have never heard of the 10% loss rule. I am not saying that it does not exist but we had tanks on our lot left by Suburban propane that were over forty years old that were nearly full. Therefore I have my suspicions about the 10% rule.
Now, about the 5-10% loss in power for propane powered engines; that is simple. The BTU output for propane is @ 91,300 BTU's/gal. The BTU output for gasoline is 124,800 BTU's/gal Diesel= 138,700 BTU's/gal . A gas and a propane engine are exactly the same. Our propane truck was a 460 cubic inch gas motor that was converted over to propane. Even though there is less power, Propane has advantages. You need less oil changes due to the clean burning nature of propane. There is virtually no carbon build up either.
Addressing the generator questions.
Propane has a boiling pt of -44 degrees F. At lower temperatures you need more ullage space ( space in the tank for vaporization to occur. 20% in a propane tank. ie. a 1000 gallon tank should only be filled to 80% capacity this is where the overfill bleeder is set.) If your tank is buried you could go with a smaller tank. The most important thing to think about when setting up a high volume system is the distance between the tank and the genset. The further the distance the greater the pipe size needed to provide the fuel. You could use a 2 regulator system ( high pressure regulator at the tank, low pressure at the genset ) however I don't recommend this in extremly cold climates due to the possibility of the propane reverting to liquid in the high pressure line.
Check out this link for properties of fuels
<A target="_blank" HREF=http://www.afdc.doe.gov/pdfs/fueltable.pdf>http://www.afdc.doe.gov/pdfs/fueltable.pdf</A>

 

[WVBill]

I'm wondering if the 10% loss doesn't occur at the regulator (?). The experiences people have relayed about tanks staying full for long periods of time all seemed to be not hooked up to anything.
I know my propane system regulator has a vent and I've been told (by the propane company tech) that occasionally smelling propane from this vent is "normal". In fact, code requires the regulator to be at least 10' away from all windows and electrical devices for just this reason.
I don't know why the regulator would vent, but could this action account for an avberage 10% loss over time in an operating propane system?

 

[ebeacham]

I don't think that the vent should pass any propane, but they will on occasion due to moisture in the seal area freezing up or the internal spring failing. For this reason the regulator should always be installed with the vent pointing down and they should be replaced every ten years.

 

[kevinro]

<blockquote><font size=1>In reply to:</font><hr>

So I think most companies are quite satisfied if they only "lose" 10%, although once it's dispensed into your tank (propane bottle in this case) and everything (every seal, valve, connection, line, etc.)

<hr></blockquote>



For a cheap commodity which has no environmental impact, such as water, not being able to account for 10% of your product might be acceptable. Water districts usually have small leaks, and also people steal water from hydrants all the time. It would be difficult to get a 100% accounting, plus it probably isn't worth the effort since water is cheap.

Fuel, however, isn't cheap. Certainly, there is spillage and leakage. I have a very difficult time accepting that the industry would knowingly allow billions of dollars of their inventory to leak away each year due to bad storage technology. They would also be very concerned about potential environmental impacts. (Probably more about the potential liabilities if a law suit!) Conspiracy theories about gas companies letting it leak for profit aside, the gas companies store their inventory in the same technology that your house tank uses. A welded steel vessel.

Propane is just a hydrocarbon chain CH3CH2CH3 (C3H8 in a particular chain). Sometimes it is mixed with Butane (C4H10). They are both alkanes, which means they are unreactive. That means they are pretty stable, and store well. In relative terms, this is a fairly large molecule compared to other stored gasses (like oxygen, helium, nitrogen, hydrogen, carbon dioxide). I just don't see Propane being any more likely to leak out of a weld than these gasses.

As both a consumer and an investor in a propane company (I own Amerigas stock!), I would like to know if my money is leaking away!

Kevin

 

[Anonymous Poster]

Well guys, frankly I don't give a dam if you believe 10% tank losses or not. I spent the better part of 2 years searching out propane information during the Propane War with the L company, and I ain't giving away for free what cost me $$$$$ to learn.
I'll just give you a heads up, read all my posts on this subject, and the information you want is there. Comparing 40 year old tanks to new tanks isn't valid, the new tanks aren't equal in quality to the older ones. If your tank is made by Trinity, loss will be more than 10%. I had 2 100 gallon Trinitys sitting side by side, both "full" actually 80 gallons of liquid January of 2000, and in January of 2002, one read 50% and the other 70% by gague on the tank.
There are 2 types of tank gagues, flang mount & thread mount, and the flang mount gagues leak more. Most of them have been replaced.
Much of the current manufacture of Propane equipment is made in Mexico, and lacks manufacturing quality.
Underground tanks are of far heavier construction than above ground tanks.
BTW, just because you don't smell propane doesn't mean Propane isn't leaking. The odorant isn't added to propane till it leaves the terminal by many companys so people living near the storage facility won't complain about leaks.
Also bear in mind the wholesale cost of Propane is probably around 40 cents a gallon to Suburban, Burnwell, Agway, or any other retailer, so they really aren't too concerned about tank losses because they can easily factor the cost into your retail cost.

 

[ebeacham]

I'll buy that SOME tanks may leak. But as for a general rule that all propane tanks leak 10% I just can't buy it. If you look on trinity's website you will see that their 1000 wg underground tank is only 2 pounds heavier than than their 1000 wg aboveground tank, so I doubt that it is of sturdier construction. I just pulled out my old propane cylinder 20lb that no one will fill anymore due to having the wrong valve. Filled 2 years ago right before the 4th of July for a back up. Weighs 38.5 lbs on the money. Tare weight is 18.5 lbs that leaves 20 lbs for gas.

 

[WVBill]

By the way, I have a couple of old 20# propane tanks like that too (old, wrong valve, nobody will re-fill).

What is the correct way to get rid of them? There's no way my trash pickup is going to touch them and I really don't like having them just sitting around.

One option I had thought of is to drop them off in front of one of the box stores at the propane tank exchange cage, go inside but "forget" to buy an exchange...

 

[ebeacham]

Have you tried exchanging them? If you don't want to do that then I recommend making sure that they are totally empty then take them to your local propane supplier and see if he will take them.

 

[Anonymous Poster]

Most propane refill stations are taking the old non OPD cylinders free of charge. They are then going to the propane distributor who is selling them to outfits that change the valves and resell the cylinder to the swap a tank operators.