# gas tank relief valve



## placitassteam (Jan 2, 2008)

Sunday I was helping a friend with his new K27 and ran into something I had never seen before; a pressure relief valve on the gas tank. Like most Accucraft relief valves it leaks. Has anyone else seen this? I suggested just plugging it as I see no necessity to have one. Any thoughts?


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## HMeinhold (Jan 2, 2008)

I agree. What happens, if the valve blows off while the loco is running? Fireball? The gas tank should be designed for the highest possible gas pressure anyway.


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## John 842 (Oct 1, 2015)

Yes, but what happens if the tank did blow - an even bigger and much more destructive fireball?. All possibilities should be risk assessed, no matter how unlikely. What if the tank *or it's associated pipework and fittings* had been damaged it some point in their history? - what effect do contaminants in the gas have on the materials of the gas system over time? - what are the properties of that mysterious liquid I've found lurking in the bottom of some tanks?

Now that gas tanks tend to come with their own test certificates, perhaps the answer is to periodically update these certificates in the same way that boiler certs are - maybe with a longer periods between re-tests.

One thing that is slowing a more widespread adoption of this practice, is that clubs and boiler testers need to upgrade the pressure capability their test gear.


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## Chris Scott (Jan 2, 2008)

Unless you live in th UK where law requires periodic testing/retesting (if you go to a steamup gas tank and boiler have to be tested and pass before you steam it in public - that's mentioned regularly on forum, etc., by UK G1MRA folks). There is no reason to retest the tank except I suppose if you buy an old/used loco that looks like some took really really lousy care of it, or if it will just make you feel better. The U.K. folks are often lamenting what a pita and unnecessary repeated testing is. In this they generally think we across the pond are much more rational, aka properly less regulated. 

Plug the bushing permanently, silver solder. Hydro pressure test it to 300 psi same as Accucraft. If it passes great. Maybe make a record of it or a brass plate glued to the tank. Test the integrity of every other section and part of the gas feed. If the tank doesn't pass cut it in half or sledgehammer it (hazardous disposal safety practice) and give to a metals recycler - or throw it in the trash, whatever. Make or buy another. Pretty simple. 

Pressure relief valve on a properly built and tested butane gas tank is unnecessary, dumb and dangerous. IMHO


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## TonyW (Jul 5, 2009)

Chris Scott said:


> Unless you live in th UK where law requires periodic testing/retesting (if you go to a steamup gas tank and boiler have to be tested and pass before you steam it in public - that's mentioned regularly on forum, etc., by UK G1MRA folks). There is no reason to retest the tank except I suppose if you buy an old/used loco that looks like some took really really lousy care of it, or if it will just make you feel better. The U.K. folks are often lamenting what a pita and unnecessary repeated testing is. In this they generally think we across the pond are much more rational, aka properly less regulated.


I am not a member of G1MRA so I cannot comment on Gauge 1 operations but anybody in the UK can buy a commercially-made 16mm/foot scale or similar model steam loco and do what they like with it on their own premises at their own risk. There is no need for any kind of periodic testing. Regulation only comes in to effect if a person chooses to join an organisation that enforces regulation, and even then it may not be mandatory.

Running in public is a different matter and the specific requirements of the event organiser would have to be met, whatever they may be.

UK-based members of the Association of 16mm Narrow Gauge Modellers have insurance cover included as part of their membership, subject to a few conditions. These can be read here: http://www.16mm.org.uk/newsite/insurance/default.html

Note the use of words such as "*should*" and "*recommended*" rather than "*must*" and "*required*". In reference to this post: "*Currently there are no laid down rules for the testing of gas tanks*".

To meet the Association's insurance requirements only a boiler tester appointed by the 16mm Association can test a boiler or gas tank. Test certificates issued by anybody else are only for the owner's peace of mind.


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## John 842 (Oct 1, 2015)

Chris Scott said:


> ............... Hydro pressure test it to 300 psi same as Accucraft.......


300 psi sounds far too low - my Accucraft tanks come with certification to 600 psi - and my Roundhouse ones are certified to 34.0 bar (493psi) 




> Pressure relief valve on a properly built and tested butane gas tank is unnecessary, dumb and dangerous. * IMHO*


I'm glad you added that ....


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## Naptowneng (Jun 14, 2010)

An observation, I own an Aster Climax circa 1988, and it comes with a pressure relief valve fitted to the butane tank. No problems have been observed with the valve. Should the owner choose to keep the valve, perhaps a replacement Aster valve could be used? I have no knowledge of the thread type, just a thought.

Jerry


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## Kovacjr (Jan 2, 2008)

Just put in a M10 plug. I think it was M10. 

My Aster Climax had one and it failed when I filled the tank one time. No fire happened, lasted a few seconds till empty. Ive since plugged that after it happened.


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## Chris Scott (Jan 2, 2008)

Chris Scott said:


> Unless you live in th UK where law requires periodic testing/retesting* (if you go to a steamup gas tank and boiler have to be tested and pass before you steam it in public - that's mentioned regularly on forum, etc., by UK G1MRA folks).* There is no reason to retest the tank except I suppose if you buy an old/used loco that looks like some took really really lousy care of it, or if it will just make you feel better. The U.K. folks are often lamenting what a pita and unnecessary repeated testing is. In this they generally think we across the pond are much more rational, aka properly less regulated.





TonyW said:


> I am not a member of G1MRA so I cannot comment on Gauge 1 operations but anybody in the UK can buy a commercially-made 16mm/foot scale or similar model steam loco and do what they like with it on their own premises at their own risk. There is no need for any kind of periodic testing. Regulation only comes in to effect if a person chooses to join an organisation that enforces regulation, and even then it may not be mandatory.
> 
> *Running in public is a different matter and the specific requirements of the event organiser would have to be met, whatever they may be.*
> 
> ...


I think we agree on the "public" part. You are quite correct, insurance covers a great deal of these issues. However all the testing and insurance details are the result of compliance with the UK governing laws / regulations for pressure vessels; their application, testing and certification.

The offical G1MRA Website does not require membership to view most of the website. This might be a little tangled but if you check out the various G1MRA _Standards, Documents & Guidance_ documents they will, I think, answer all your questions and issues. 

This "blue" section is the header from "blue" item listed below.
_THE GAUGE ONE MODEL RAILWAY ASSOCIATION 

PRESSURE VESSEL TEST PROCEDURE 

Issue No. 3 — 5th July 2008 

INTRODUCTION 

This document sets out the procedure to be adopted when pressure vessels (boilers and fuel tanks) used in Gauge One live steam locomotives are tested for safety. All locomotives operated at exhibitions and events organised or sponsored by the Gauge One Model Railway Association (or one of its local regional groups) must be tested to this procedure and a certificate of conformance issued. 

Locomotives tested to earlier versions of this procedure continue to meet the Gauge One Model Railway Association’s safety requirements. However, upon re-test all locomotives MUST be tested to this revised procedure and a new certificate issued. _

The link below takes you to the G1MRA websit: the webpage with links to all the documents in the 3 sections. In the various docs they cover the cross validity of testing and cedrtification / certificats between G1MRA and 16mm Assoc. As well as testing by a member of either organization of another members equipment; and a nonrecognition buddy testing (you test mine I'll test yours.)


http://www.g1mra.com/resources-links/standard-guidance/
Standards, Documents & Guidance
G1MRA publishes standards, boiler documents, guidance and various books including construction guides (click here for the Books page)

Standards
G1MRA Standards Sheet 1 – Track & Wheels
G1MRA Standards Sheet 2 – General Dimensions
ScaleOne32 Standards
Suggested Track spacing for non-British stock
Boiler Documents

Boiler Examiners Personal Record of Hydraulic Tests
_Boiler Test Procs revised 2008_
Boiler Testing and Documentation
New Boiler Certificate

Guidance

Steam loco fault diagnosis

Note that neither G1MRA, nor the authors, retain liability for guidance


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## TonyW (Jul 5, 2009)

Very interesting, thank you. Thank goodness I'm not a member of G1MRA!

I don't have any questions or issues.


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## Chris Scott (Jan 2, 2008)

Quote:
Originally Posted by Chris Scott View Post
............... Hydro pressure test it to 300 psi same as Accucraft.......
300 psi sounds far too low - my Accucraft tanks come with certification to 600 psi - and my Roundhouse ones are certified to 34.0 bar (493psi) 



John 842 said:


> 300 psi sounds far too low - my Accucraft tanks come with certification to 600 psi - and my Roundhouse ones are certified to 34.0 bar (493psi)
> 
> *Your right, Accucraft Gas Tank test certificate; 600 psi.*[/COLOR
> Quote:
> ...




I think the fact that no equipment and parts supplier for our steamers (disclaimer: as far as I'm aware) offer a gas tank with a pressure relief valve. Some year ago a couple of suppliers, Stuarts, etc., did offer gas tanks that had a spare bushing. Maybe it was for a pressure relief valve or (though unlikely) it could have been for a second gas regulator valve to support liquid gas feed. In any event they are no longer to be found - unless you know of a supplier for either. It could be wild speculation but I think they did away with either or both because their presence caused more trouble than they were worth or function they might have provided. Not to mention the inquires they prompted, "what is this for?", or "why is it there?", "how..."

I do have a couple of gas tanks, bought some time ago before they became extinct, that have the spare bushing intended for a project(?) to convert to liquid feed. And two other gas tanks custom built for me with the second valve for liquid feed. I'm fascinated by liquid gas feed - no more warming water bath. Admittedly a bit of an esoteric topic I picked up from G1MRA exposure.

So, I think it reasonable to conclude suppliers share my view of the gas tank pressure relief valve.


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## Chris Scott (Jan 2, 2008)

TonyW said:


> Very interesting, thank you. Thank goodness I'm not a member of G1MRA!
> 
> I don't have any questions or issues.


Pretty incredible source of information, technical and non-technical, perspectives and the quite colorful writing.


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## Tomahawk & Western RR (Sep 22, 2015)

i find it funny that none of my cars, locos, live steam locos, roadbed, tunnels, and trackwork would pass their standards!


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## TonyW (Jul 5, 2009)

Tomahawk & Western RR said:


> i find it funny that none of my cars, locos, live steam locos, roadbed, tunnels, and trackwork would pass their standards!


I'm not sure mine would either!

The old adage applies: If you don't like the club rules don't join the club.


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## HMeinhold (Jan 2, 2008)

John 842 said:


> Yes, but what happens if the tank did blow - an even bigger and much more destructive fireball?. All possibilities should be risk assessed, no matter how unlikely. ...


Contrary to steam boilers the highest pressure of a gas tank is predictable. If designed and tested for this pressure, there is no need for a relief valve. At least my big propane tank for silver soldering does not have such a valve.


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## John 842 (Oct 1, 2015)

Chris Scott said:


> ........ a pressure relief valve on a properly built and tested butane gas tank is unnecessary, dumb and dangerous. IMHO





John 842 said:


> I'm glad you added that ....





Chris Scott said:


> ........... So, I think it reasonable to conclude suppliers share my view of the gas tank pressure relief valve.


Well I'll conceed that they may think it unnecessary - but "dumb and dangerous"? - I would imagine that goes far beyond what they really think. The debate is too wide for that to be the case. 

All IMHO of course ....


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## John 842 (Oct 1, 2015)

HMeinhold said:


> Contrary to steam boilers the highest pressure of a gas tank is predictable. If designed and tested for this pressure, there is no need for a relief valve. At least *my big propane tank for silver soldering does not have such a valve.*


Then you are at risk of invalidating your household insurance and your supplier is at risk of supplying illegal cylinders. 

I hope your insurance agent doesn't read this forum .... 

http://www.propane101.com/safetyreliefvalve.htm


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## Tomahawk & Western RR (Sep 22, 2015)

this is jake, from state farm. we have read forum, and we have declared that you are violating propane storage rules and regulations. you insurance will no longer cover any damage caused by propane use and storage in exactly 5 minutes and 31 seconds you will be taken to jail for your actions.

OK OK now back to why there are releif valves on gas tanks. i know most accucraft boilers and tanks have a little tag indicating they successfully passed all tests. mine has no tag on the boiler OR gas tank. what does this mean?


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## John 842 (Oct 1, 2015)

Ha ha - that is too funny - I think we may have invented a new catch phrase for the forum - whenever we spot some dodgy, illegal or otherwise doubtful practice we can just say ..... "I hope Jake doesn't see that" ....


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## Tomahawk & Western RR (Sep 22, 2015)

good idea! i think by now i would be in BIG trouble with him










i never realized ow much forums can wonder. from live steam loco gas tank to g1mra standards to illegal propane tanks to jake from state farm.

does anybody know what PSI butane is stored at?


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## John 842 (Oct 1, 2015)

I've been googling the pressure in a cylinder of n-butane caught in a typical house fire, which can reach as high as 1400 deg F - but had no luck - anybody?


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## HMeinhold (Jan 2, 2008)

This discussion is getting almost ridiculous. My 20lb propane tank is a certified type sold and refilled by all big home improvement stores. I cannot detect any pressure relief valve on this tank. And in case of a house fire the butane in the tank of my little steamers is my least concern. By the way: Do you drain the tank of your car, before you pull into your garage ?


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## John 842 (Oct 1, 2015)

If your propane tank is a legitimate one and it was sold by a legitimate store, then what *is* "almost ridiculous" is to say - as you did in your post #15 - that your tank "does not have such a valve"

And if you'd read the link I put in my post #17, you might have realised that your tank almost certainly has an *internal* relief device.


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## placitassteam (Jan 2, 2008)

Thanks for all the comments. My friend bought his K27 used but it appears to have been barely run, if at all. The tank appears to be the original from Accucraft but of all the Accucraft locos that I have seen it is the only one with a relief valve on the tank. I think my friend is going to call Cliff about it. In its present form it certainly is not usable.


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## HMeinhold (Jan 2, 2008)

OK,
I have to apologize and eat crow. The relief valve on these propane tanks is opposite to the outlet.


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## John 842 (Oct 1, 2015)

No need for apologies - it's all just part of lively debate.

I found out my tank had a relief valve in a rather unusual way. I was living on my boat in Fort Lauderdale at the time and I'd left a spare cylinder of gas for the cooker in the back of the station wagon. It had been sitting under the Florida sun with all the windows closed untill mid-afternoon or so when I went to retrieve it. As I approached the car I thought - what vandal has sprayed all my windows white?

What had happened of course was the relief valve on the cylinder had blown and I was looking at the consequent vapor release ....


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## John 842 (Oct 1, 2015)

Chris - all I can say is read through the thread again and take particular note of .....

- post #15 where we are talking about a 'big propane tank for silver soldering' 

- post #22 when you will see we are talking about a 20 lb capacity tank 

- post #25 where we finally establish that the tank in post #15 does in fact have a relief valve.

All the tanks that fall into this category are required by law to have pressure relief devices.

I simply don't know how to explain it more clearly than the link in my post #17

*EDIT* - Ah ha! - I see you've wisely deleted your post Chris ....


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## xo18thfa (Jan 2, 2008)

200 PSI is an adequate test pressure for a fuel tank. 70% Butane 30% Propane mix reaches a vapor pressure of 93 PSI at 110 degrees F. It's a common practice to test to twice operating pressure. 200 PSI is fine. The highest pressure I ever saw on one of mine was 65 PSI. When running they rarely get over 40 PSI

http://www.engineeringtoolbox.com/propane-butane-mix-d_1043.html


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## John 842 (Oct 1, 2015)

xo18thfa said:


> *200 PSI is an adequate test pressure for a fuel tank.* 70% Butane 30% Propane mix reaches a vapor pressure of 93 PSI at 110 degrees F. It's a common practice to test to twice operating pressure. 200 PSI is fine. The highest pressure I ever saw on one of mine was 65 PSI. When running they rarely get over 40 PSI
> 
> http://www.engineeringtoolbox.com/propane-butane-mix-d_1043.html



The official highest recorded air temperature is 56.7 C (*134 F*) measured at El Azizia Libya. 

The vapour pressure of propane at 50 C is 20 bar (290 psi)

Propane tank relief valves are normally set at between 250 and 312 psig

I disagree with Accucraft on a number of issues - but testing their gas tanks to 600 psi is not one of them .... 

EDIT .... Don't forget that in any risk-assessment you should allow for people putting various propane mixes in their model tanks, even when they say "Butane only".


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