Air conditioning gas

[GTSBoy]

You should also change any seals and hoses in an R12 system that are not compatible with R134a (whether you need to or not depends on the car). If you don't, that is one good reason for it to all leak out over a short period.

cheers

[slick]

Originally posted by GTSBoy
Propane and butane and so on are not corrosive to aluminium or it's alloys. That line in your posted up proerties regarding corrosion does not describe the the corrosive properties of hydrocarbons at all well. It was obviously written by someone who did not know what the corrosion in alloy would be like and wrote it to cover themselves.

The Australian standards for LPG are quite clear.

AS/NZS 1425:1999 - LP Gas fuel systems for vehicle engines
Section 2.5 METALS
Metals used in valves on the container shall be those specified in AS2473. Aluminium alloys may be used for other components except piping and pipe fitings. Metallic materials having a melting point lower than 500°C shall not be used in any aplication where failure may result in gas escape.

[Jim]

so you can have an alloy tank then? maybe not a good idea if corrosion is an issue?

[GTSBoy]

slick, there is no point in trotting out the standards if you do not know why the standard id written that way. The reason for not using aluminium in LPG pipework is not because of corrosion. it is purely because it does not stand up to fire the way that steel pipe does. Ally pipe gets soft really quick when heated and if there is much pressure inside it will go pop long before steel will.

Secoh is right. If corrosion was any issue at all then you would not be able to have alloy LPG tanks.

cheers

[Jim]

While i'm in this thread (prepare for some topic drifting) is there any issue with modifying an LPG tank to use as a petrol tank? I like the idea of a nice solid tank considering it's forward placement in the dub...

[hamish]

I'm just a bit puzzled why people are so concerned about 300odd grams of propane in an A/C system, yet they are happy to carry around up to 100 litres of petrol, which is being pumped continously between the engine bay & fuel tank at 40+psi, or have no problems with pumping said amount of fuel through an open filler neck every time they fill the car.

If you do a bit of a google search on HC refrigerants, you'll also find that there is a lot of reseach on the subject showing that the risks are extremely low, & have been grossly exaggerated. Even Greenpeace think that they are a good idea.

I've even seen material about the toxic effects of leaking 134a linking it to heart problems (can't confirm the accuracy of that), & my automotive textbooks carry warnings that R12 when it burns produces phosgene which is a toxic gas, & nobody had any real problems with that.

As GTSboy is pointing out, the risks are right down there with being struck by lightning (probably much lower).

[wildturkey]

Originally posted by Turbo4WD
For how long?

It seams that when air-con systems in older cars are re-conditioned they only last 1-3 years while the origonal system might have lasted say 5-15 years. I actualy know one person who recently sold their 85 magna that they had had since new and the air-con had neve needed servicing and worked great.

I do believe that car a/c systems that are not run on a regular basis are prone to leaking as the seals in the compressor and hose o-rings dry out and then leak. Another factor may also be the manufacturer of the system, some are better than others.

My old mans car never had a leak in the 8 years that he owned, then gives the car to my sister who likes to drive with the windows down and never uses the a/c and a leak pops up after 12 months. ?

My background is commercial a/c and i never did get involved with cars other than the od foreigner so i may not be entirely correct.

[GTSBoy]

Wildturkey, you are quite correct. Happens all the time.

[slick]

I am not arguing that HCs don't have good refrigeration characteristics, because they do.

I will get down off the fence and have a look on your side GTSBoy.
I will start with "Code of practice for the use of hydrocarbon refrigerants in motor vehicle air conditioners"

HYDROCARBON SAFETY
BRIEF OVERVIEW
1 Accreditation to CFC usage may be a prerequisite under the current relevant ozone depletion Acts in your State or Territory. It is your responsibility to be licensed where applicable.
2 Hydrocarbons are flammable - follow all safety and handling aspects as per Workplace Health and Safety regulations and other applicable Standards.
3 The vehicle Owner, Driver or Operator must be advised and informed about the conversion to and use of HC refrigerants.
Clearly visible system identification is compulsory under this Code:
* Date of last system service
* Refrigerant installed
* Date of replacement of filter drier
* Qualified technician/ company details
* Vehicle Registration or Identification Number [VIN]
* Prominently displayed red "Flammable Gas " diamond
* Warning that system is under pressure and tampering must not be considered.

4 HC refrigerant blends are to be charged as a liquid not a vapour.
5 Storage of Hydrocarbon refrigerants should conform to Australian Standard AS1596 and other relevant State codes.
6 Never overcharge A/C systems, as this will lead to reduced performance and possible over pressurisation. The HC refrigerant charge should never exceed 40% of the CFC or HFC charge by mass.
7 Use accurate weighing methods. Sight glasses are not considered an accurate form of measurement.
8 The installation, commissioning and service of equipment containing HC refrigerants must only be carried out by adequately trained and accredited persons familiar with the particular characteristics of HC refrigerants.

[slick]

Originally posted by GTSBoy
Wildturkey, you are quite correct. Happens all the time.

Ditto, we agree GTSBoy
Maybe there is a chance for us yet! Agree to disagree

[slick]

(J) SYSTEM SAFETY PROTECTION
UNDER NO CIRCUMSTANCES IS THE SYSTEM TO BE RECHARGED WITH REFRIGERANT UNLESS THE FOLLOWING CONTROLS HAVE BEEN FITTED:
1. A pressure/temperature relief device where fitted should be vented to the atmosphere and away from any ignition sources, high temperature or high voltage components. Either separate or combined HP/LP (High Pressure/Low Pressure) switches must be installed in all systems with the HP (High Pressure) switch having a lower set point than the pressure/temperature relief device.

2. A device or modification that will prevent the lower explosive limit (LEL) for the refrigerant gas (2% in air by volume for HC) within the passenger compartment of the vehicle from being reached in the event of a refrigerant leak. This requirement will be deemed to be met if :

a) in the case of a device, the device is manufactured for the specific purpose of ensuring that in the case of a refrigerant leakage 20 percent of the LEL within the passenger compartment of the vehicle could not be achieved. The device must come with adequate fitting instructions to enable the device to be correctly fitted to the motor vehicle air conditioning system, or

b) in the case of a modification, that the modification shall have been assessed (or tested) by a laboratory competent to conduct such assessing, as meeting the 20 per cent of the LEL requirement of this Section when used on the design of vehicle being recharged.

I can keep being a know it all day but it isn't going to win me any awards or make any friends. I could keep this up for a while but you aren't going to be persuaded and I am not going to change my mind. . But I have never read the code of practice pertaining to HCs and I thought the above is a nice point, I never knew that if there was a HC in a customers AC they had to be told and that there needs to be a red diamond and warnings of flammable gas contained in the system. And although I agree that the chances of a fire a small they are still there and I wouldn't risk my family or friends in a fire, obviously IAHRA feel the same way otherwise they would not ask for meetering devices to be placed in the cabins of cars to make sure that if there is a leak that it does not reach an ignitable level.

[GTSBoy]

Slick, I think we can agree to disagree on how safe it is.

But at the very least we should all consider hamish's last post and consider how much additional danger <1 kilo of propane makes to a car that may be carrying 50kg of petrol and perhaps another 30kg of LPG in it's tanks and fuel systems.

On top of that, I reiterate the problems with dragging out standards and parrotting them off. I could drag out clauses and subclauses of the Australian gas codes that would seem to make it impossible to do anything with a combustible gas anywhere under any circumstances. But when you read the whole code, and all the references and the other codes that apply you find out what is actually allowed. Sometimes, what is allowed actually coincides with what is smart, but not often.

cheers

[Jim]

FWIW as I recall the TV tabloid article was about existing flammable A/C refrigerant gas, and not LPG, so it seems now that I think about it, is that the use of LPG in the system is probably no more dangerous than keeping the current gas in there.

have to say though it's pretty funny to see the practical gingerbeer and the engineering lawyer dukeing it out :p

[slick]

Originally posted by GTSBoy
But at the very least we should all consider hamish's last post and consider how much additional danger <1 kilo of propane makes to a car that may be carrying 50kg of petrol and perhaps another 30kg of LPG in it's tanks and fuel systems.

Well the petrol tank is usually located under the car well away from the passanger compatrment. The fuel lines do not run through the foot well of the passangers, they run under the car to avoid as well as possible liquid or vapour from getting into the passanger compartment.

On the otherhand the evaporator has refrigerant running to it from the engine bay into the passanger compartment. When the airconditioning system is fully charged and operating the evaporator is flooded with liquid to make the system operate efficiently. This would mean that ~40-50% maybe more of the systems total charge is in the cabin when ever the system is operating. Although you would also probably know that being on the low side of the system the evaporator usually runs less than 40psi of pressure when operating. So the chance of letting much refrigernat into the car when it is being used is negligible. Although if there was a leak in your evaporator and you left the car parked in the sun the system pressures would skyrocket (>350psi). The perfect conditions for a leaking evaporator to leak oil and gas, into the cab.

So you some back to your car jump in and start it, light a cigarette whatever. Now what are the chances to you becoming a side of roast? Or at least having no eyebrows for the next few weeks?

Originally posted by GTSBoy
But when you read the whole code, and all the references and the other codes that apply you find out what is actually allowed. Sometimes, what is allowed actually coincides with what is smart, but not often.

Then with regard to the 30L of LPG in your dual fuel car you would be able to point me to the clauses that say the LPG cylinder needs to be in a sealed compartment. And that a boot is not a suitable compartment on its own? As there are difficulties with sealing, venttilation and the presence of electrical equipment located in the boots of most cars. Also that all pipes adn associated connectors will be sealed in a sub-compartment and vented to the atmosphere away from things like the exhaust.

[slick]

Originally posted by Secoh
FWIW as I recall the TV tabloid article was about existing flammable A/C refrigerant gas, and not LPG, so it seems now that I think about it, is that the use of LPG in the system is probably no more dangerous than keeping the current gas in there.

That TV tabloid article I think you will find is the one referneced here , one of our well paid government officials chasing some media attention on this same topic back in 1995. HCs and airconditioning.

Originally posted by Secoh
have to say though it's pretty funny to see the practical gingerbeer and the engineering lawyer dukeing it out

It is nice to know that I brought a smile to someones face. :p