Initial fill of new Propane tank fact or fiction on purge needed

Have you considered the explosive potential of mixing propane with the air (oxygen) contained within the tank? Once the tank has been purged, it should be free of oxygen, which is the chief reason for purging them originally. You dodged a bullet if you didn't have other tanks purged.

Harold

Tis SOP! Will prevent problems down the road. You have to get all the air/oxygen & moisture out, you just want propane vapor/gas. But sounds like $25 is a bit much! How much ya paying per gallon for the propane? The last time I did this, it was like $5 more for the purge.

Lane

So, what is considered a "safe and acceptable" standard purging routine for propane containers?

Does it involve evacuating the cylinder to some negative pressure (without imploding it of course) and then backfilling it with propane?

Or is it some number of cycles of squirting in some amount of propane and letting the air/propane mixture vent out of the container?

Jeff

Assuming the tank is built to take significantly more than 2 atm of positive pressure, could you possibly implode it even if it had a perfect vacuum inside?

Googled this up at several locations...:

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Have your LP-gas container purged. It only takes a few minutes and your LP-gas dealer is equipped to perform this service (see NPGA bulletin 133-a).

To purge a container, the following steps should be taken:

1. Purging of containers should be performed in an approved area (see NFPA #58)

1. Determine if the container pressure is zero. Should the container contain only air pressure, the air may be vented directly to the atmosphere through the service valve.

2. If free water is present in the container, it should be drained.

1. Pressurize the container to approximately 15 PSIG with LP-gas vapor. Never purge with liquid LP-gas; to do so will cause the moisture vapor to chill and remain in the container.

2. Fully open the container service valve and vent safely to the atmosphere.

1. Repeat the fourth and fifth steps for a total of five purgings.

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Jeff

And exactly how is doing this making the tank safer than if it were filled without purging?

As soon as the tank goes from zero pressure to 15psi the first time, the contents are no longer an explosion hazard. So why pressurize and vent?

Is it simply to remove air because the air may contain moisture?

Dave

Well I can buy the reasoning behind it, but at 25 a whack is out of line. I'll carry it to the dealer that I usually use to get my fills. These others were on my way home and I stopped by to see about getting it filled. The others I called on the phone, as my regular dealer is closed today after 12 noon. He has been in business for 49 years now, so he should know what the story is and how to handle it.

I pay $7.35 for a 20# refill from this fellow. But if there is propane in the tank he will weigh it and only charge you for what he puts in it, unlike the others that you pay a flat fee regardless of how much may be left in it. Thats one reason I was going to get it filled at the other places as my dealer is further away and these were on my way and the tank was empty anyhow. I sure don;t know how folks pay those high prices at places like Lowes and wally world for 20# refills.

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expressed are those of my wifes, I had no input whatsoever. Remove "nospam" from email addy.

What a rip off. Far as I knew we purged new tanks for free.

Tanks are purges to prevent odorant fade.

Here are a couple of links for the how and why:

Not mentioned there but something I recall from the past was a recommendation to put a few ounces (in a 20# tank) of either methanol or isopropyl alcohol in the tank and slosh it around and pour it out prior to purging. That will dilute and absorb any moisture present and result in the bulk of the moisture being removed prior to and during the purging process.

I think the bottom line on purging is to reduce the potential for explosions.

I don't think it is a rip off, but maybe it is not done as often as it should be for the smaller bottles.

I remember reading about "wet propane"which contains moisture acquired during its travels to the end user.This was on a gas industry webpage.Keeping it dry poses a special handling procedure.

Weight it? Flat fee? I've never had either of these done. Every place I've had propane tanks filled had a meter on the filling hose and measured what went in.

Lane

Hum, never heard of that reason, I always heard it was to get oxygen/air and moisture out.

Lane

And that's the exact reason OPD valves were mandated.

I dunno for sure, but probably not.

Though if you think about it, a fire hose can hold a lot of positive pressure but will easily collapse under vacuum. It's probably a matter of the physical properties of the tank material, and it's shape, isn't it?

I only mentioned it to show I'd thought of the possibility, so some smart ass who knew for sure thst it would collapse didn't seize the opportunity to jump all over me about it. (G)

Jeff

Of course, the possibility of ending up with an air/propane mixture in the explosive range is infinitesimally small if you do put above some minimum amount of propane in. But it can't be guaranteed to be so for every idiotic thing some moron might decide to try, so the reg writers play it safe with that CYA procedure.

I refuse to get sucked into this one again dammit!

Couldn't hurt. IIRC water can diminish or remove the odorant which is added to propane so people can smell leaking gas.

Happy Holidays,

Jeff

By LAW a tank without an overfill protection device MUST be filled by weight. It may only be filled to 80% of it's capacity. Now the fuel may be metered, and charged by the standard litre - but MOST places filling BarBQ and recreational tanks charge a flat rate for refills - it's up to $11 Canadian most places here now, and a lot charge more than that. Minimum 3 times what you pay for motor fuel propane. Ripoff. And the purge on a new tank is MANDATORY. Not optional.

After the last propane thread I'm not hot on jumping into this one.

It takes very little ethyl mercaptan to make the stink. The ratio is roughly 1:40,000 (1 pound to 10,000 gallons). Ethyl oxidizes easily. When Ethyl oxidizes it looses her stink. Air and moisture both contain oxygen.

You are correct, tanks are purged to remove air and moisture so Ethyl keeps her stink. Rust is also a known problem as it contains O2 and can't be removed by purging. Odorant fade can also be caused by absorption or adsorption.

Not much can be done about absorption on the walls of a bare steel tank. Just use the tank often enough to have it refilled soon after it's initial filling. Eventually the tank will become seasoned and will have absorbed all of Ethyl it can.

Adsorption is what produces Ethyl in the bottom of an older tank.

Then there's fading of gas as it passes through the ground/ concrete. That's why it's important to do a leak down test.

This article touches on these subjects:

I don't recall hearing any concerns of explosion during purging in any safety meetings. Even if one stopped putting propane in a tank on it's first purge how the hell would you get a flame/ ignition source inside the tank to light it off?

Even if the tank were filled without purging because, once again, how would you get a flame inside the tank? Plus it would be a little too rich of mix to light off.

In both these instances you would have to work awful damned hard to hurt yourself.

If that's the case, then why do we use gasoline tanks full of air? Shouldn't they be purged, too?

TOO LATE! (You just were sucked into it ;-) )