American Propane Tank Air Release Value

[chuckr]

does any one have an idea on how to open the air release value on the American propane tanks without what appears to be a special tool
we have in the past gotten our tanks filled using gravity feed but now in Romania they use a lot of pressure and will not sell us just the gas in a bottle to return the bottle later - I have to buy bottle and all

we have all the adaptors and got to a filling station only to be stymied by the air release value - one tank is a 5 star fitting and the fiberglass one is like a head of a screw with only 2 sides and indented so I can not get anything around it -

any thoughts would be appreciated

[DotDun]

I thought it was just a flat blade screwdriver....

[a64pilot]

I thought those were over pressure relief valves ?
As a kid I drove forklifts and we bulk filled our own tanks, opened the release valve and let the gas escape until liquid came out, then closed the valve, but I did not think regular bottles had those release valves on them?

[DotDun]

The liquid can't go in unless the gas comes out....

[chuckr]

ok - I think I know the problem after a bit of internet research - we hooked the tank up to their system to fill and they have them all over the city as cars run on lpg - so when they started to pump it cut off as filled - so need to get air out - so opened bleed value and tried and some gas escaped - they cut it off -
problem is we are trying to transfer under high pressure and it is all gas - if we could use low pressure and cool the receiving tank it would turn to liquid and we could open bleed value and let air out - right now just want to get to Turkey where they know how to do this - maybe in Bulgaria but I doubt it - I could get another tank but they are way to large to store
I could get another tank and transfer but marina may not be too happy with that - need a gas dealer as in Romania all gas is at a public downtown station and they will not allow a transfer -
so a problem

[a64pilot]

You sure you are not trying to put in CNG? Sure sounds like it.
I think CNG would blow a propane tank up right away, and its been years bit I think they ran cars off of CNG when I was in Europe and not propane?

[a64pilot]

Originally Posted by DotDun

The liquid can't go in unless the gas comes out....

It can if, liquid is being pumped in at a pressure higher than what it takes to liquefy the gas, but if your trying to transfer from one tank to another either the receiving tank has to be cold, or you have to let the vapor escape, to fill the fork lift tanks, we let the pressure escape

On edit some tanks have a vapor return valve where the vapor is returned during filling, but I think this is required only on very hot days on bigger household tanks that sit out in the sun?

[HopCar]

When you say very high pressure how high are you talking about? Propane turns to liquid at less than 200 psi.
As A64 pointed out, it sounds like you're playing with CNG which stays a gas at very high pressures and needs tanks like scuba tanks to contain it.

[Cheechako]

It's a flat blade screwdriver.

[TacomaSailor]

Why are you doing anything with the valve?

I've never been to a LPG or CNG fill facility that allowed the customer to operate the equipment.

[foufou]

As Cheechaco said it's a flat blade screw driver. I just had mine filled 4 days ago and always watch. Propane is pressurized to about 250 psi, cng to about 3600psi! No room for error here!

[Cadence]

I would have to agree with Hopcar. They may be supplying CNG.

[Rorzech]

That's not true ! The pressure of any vessel containing propane is determined by the temperature of it's contents. Connect any two vessels containing Propane and the warmer contents will always freely flow into the vessel with the cooler temperature. No if's and's or but's about it.

[Rorzech]

A sure way to open the relief valve is to ram 25 lbs of liquid propane into a 20 lb tank and leave it out in the hot sun for an hour or two. It won't be long before you see liquid propane squirting out of that relief valve just like it's supposed to all on its own. That's why they usually have people with licenses operating tank filling depots.

[Djarraluda]

To clarify the gas type:
CNG - essentially methane, used for converting a Diesel engine to gas. Lower calorific value than propane etc.
LPG - some sort of mixture between propane and butane is for converted petrol engines. It varies depending on the field it comes from and thus the country. Poms have a choice of Red (propane) or Blue (butane) or is that green - Blue is the Camping Gaz which is a different proportion.
So country by country, it will vary