Gas tank testing
- Thread starter hornbeam
- Start date
Pleased to hear it regarding beds group test kit. There is no set routine to do so however. The gauge I have here is years old and it is just as cheap (so I have been told) to exchange for a new one as to calibrate the old.dunnyrail said:
As to the gas tank I think I could recognise say a Roundhouse tank in good condition. One of unknown provenance is a different matter. I have an Archangel tank here with which I am distinctly unimpressed. Thin gauge brass with the filler valve SOLDERED in instead of being screwed into a boss. In fact the gauge is so thin that the very act of filling it has depressed the top of the tank.
New Haven Neil 2
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A memory has flickered into being of testing gauges at sea, with a deadweight tester. Took ages sometimes, the locking screw for the lever that sets the amplification used to vibrate loose (30,000 bhp diesels!) so it was trial and error to get them set correctly.
Back on topic, I'm with Tag on a visual inspection being worth a lot - after all, we don't pressure test full size boilers every year, although as Bob says, the model engineering guide tells us 4 years for copper boilers and 2 for steel I think.
As for the old presumably original? Archangel tank - eek!
Back on topic, I'm with Tag on a visual inspection being worth a lot - after all, we don't pressure test full size boilers every year, although as Bob says, the model engineering guide tells us 4 years for copper boilers and 2 for steel I think.
As for the old presumably original? Archangel tank - eek!
New Haven Neil 2
Registered
Oh, safety valves - not only do they need to lift, but also pass an accumulation test - which means pressure not to rise to more than 110% with the boiler being fired at full capacity (eg blower on/gas full up, no feed water entering). I have seen quite a few boilers fail this over the years. One major strop was on a (full size) boiler the inspector had only passed for operation at reduced pressure - the safeties were incapable of passing sufficient steam at the lower pressure to pass the accumulation test. Oops.
On full sized boilers the accumulation test is a PIA, so bloomin noisy!
On full sized boilers the accumulation test is a PIA, so bloomin noisy!
bobg
Registered
tagorton said:
The problem with pressure gauges is the system by which they work (Bourdon tube). The mechanism can be very delicate and just dropping the gauge can change the cailbration. However re-calibration is not that difficult, all that is required is a means of raising the pressure and another gauge of known standard.
Start by removing the front bezel and glass of the gauge to be adjusted (usually two small screws). Then very carefully remove the needle. It is held on a tapered spigot, and though there is a proper tool for this, two small screwdivers pushed evenly under the edge of the boss can be used to prise the needle free. Using the good gauge apply a known pressure to the gauge, somewhere in it's mid range, and refit the needle at the correct reading and push it back onto it's taper to lock it. A bit watch-makery, but well within the bounds of the average modeller.
Ideally a gauge used for testing should aways have a range that covers the required pressure in the middle third of that range as that is the most accurate part of the scale.
Hi Guys
One way out of any gas tank testing is use the complete butane pressure pak can (used in folding picnic stoves) in the following wagon, when empty, just throw it away. This came about when a friend built a Beyer Garratt on 2 billies and a tich type boiler I think. He had problems with low gas pressure (gas tank freezing) in a small tank in the following wagon, the idea of using the whole can solved all his problems. If can freezing was a problem, a warm wet face washer cloth laid on the can, fixed things. The "tank car" wagon did not hold water. The gas can attachment and control device was converted from a cheap picnic stove. I have not seen this idea used in Magazine articles.
Regards
Steve Malone
One way out of any gas tank testing is use the complete butane pressure pak can (used in folding picnic stoves) in the following wagon, when empty, just throw it away. This came about when a friend built a Beyer Garratt on 2 billies and a tich type boiler I think. He had problems with low gas pressure (gas tank freezing) in a small tank in the following wagon, the idea of using the whole can solved all his problems. If can freezing was a problem, a warm wet face washer cloth laid on the can, fixed things. The "tank car" wagon did not hold water. The gas can attachment and control device was converted from a cheap picnic stove. I have not seen this idea used in Magazine articles.
Regards
Steve Malone
Wow I never realised gas tanks got to these kind of pressures! I'll post some pics of the tank when it arrives but to be honest may use a accucraft tank I have. I borght the tank with some other bits so even if I never use it I'll get my moneys worth. The thread has been very interesting reading thank you all.
But surely Steve, unless you built your own (in which case you would have the ability to test the results), a commercial gas tank comes ready tested. One also needs the warmth from the boiler to ensure that the pressure stays high enough to keep the fire going. Of course one could always switch completely to coal firingstevem said:
No problems with gas tanks there!Tag, comments like that do not help my pocket. The top of the wish list at the mo is a gauge 3 live steam pannier tank but the GRS kit is known as a pig to build. I'm about to build my first gauge 3 engine using an edrig boiler and smoke box and a regner lumberjack cylinder unit and years. Going to get a mate to draw the frames, footplate and a few other bits up in CAD for a few beers. Then will get these lazercut. Still on the lookout for an edrig gas tank. Ive already thought of getting an edrig type power plant and convert to coal and I'm trying to resist as it is! 
hornbeam said:Tag, comments like that do not help my pocket. The top of the wish list at the mo is a gauge 3 live steam pannier tank but the GRS kit is known as a pig to build. I'm about to build my first gauge 3 engine using an edrig boiler and smoke box and a regner lumberjack cylinder unit and years. Going to get a mate to draw the frames, footplate and a few other bits up in CAD for a few beers. Then will get these lazercut. Still on the lookout for an edrig gas tank. Ive already thought of getting an edrig type power plant and convert to coal and I'm trying to resist as it is!
Sorry about that ? but then a Pannier would be quite difficult to coal... I am about to demolish my coal fired Ragleth for a few cosmetic and operating improvements. Day in workshop tomorrow ? GREAT!!
Coal firing could be considered safer. One way to test gas tanks is to fill the tank with gas and drop it in hot water. I like the idea of square gas tanks, It would be obvious if the tank was exposed to higher pressures, it would turn into a round shape as a warning. I am told the main difference between hand grenade and a fire cracker is the container, if you build gas tanks and boilers like a bomb they will act like one, if you build them with common sense they just fizzle if there is a problem. Hence the plastic gas tanks on the supermarket lighters. When I joined the hobby I did not believe that Butane is called a "safe" gas, but after 10 years I believe it. For homemade gas tanks, 300psi is a good test.
Regards
Steve
Regards
Steve