PYRTE Traction engine nearing comletion, but back to te beginning

[Ken Ratcliffe]

Hi All,
About a year ago now I asked for help with silver soldering a boiler as I was starting a PYRTE steam engine - my first attempt at a steam engine. Well, it is nearing completion, almost all done but I haven't tested if my boiler holds pressure. Why ? I didn't think I would get this far, so never really worried, it would make a good garden ornament, but now - I WANT TO SEE IT RUN - so, I was initially wanting to use a car tyre foot pump to check for leaks, but what seems simple - I am struggling......how can I connect a tyre pump to the back of my boiler - where I have 1/4" x 40 bushes - or any other suggestions.

 

[kwoodhands]

If I understand you correctly the bushing is 1/4 x 40 and you want to use a tire pump to check for leaks.
What is the thread on the pump hose end ? You need a coupling with 1/4 x 40 threads and the other end the pump thread.
mike

 

[Ken Ratcliffe]

Hi Mike - I am not sure what the thread on tyre pump is, but have a feeling it will be metric, so coupling will need to be imperial to metric with a non return valve...….not sure where (if) to get one

If I understand you correctly the bushing is 1/4 x 40 and you want to use a tire pump to check for leaks.
What is the thread on the pump hose end ? You need a coupling with 1/4 x 40 threads and the other end the pump thread.
mike

 

[kwoodhands]

.Ken, I see you are from Wales so metric threaded tire pump threads are likely.
This method I will describe I have not tried myself.
Get a plumbing lever valve with both ends tapped for pipe. Also need make one end of a brass plug tapped 1/8 x27 or 1/4 27 to go into the valve. The other end can be turned to a barb fitting and a couple of hose clamps will be needed.
The other end of the lever valve needs a brass plug too. This will be for the boiler 1/4 x 40 bushing.
Both plugs need a thru hole, 1/4" diameter or so should do.
These are standard plumbing taps readily available. You would have to cut the hose end and push the barb into the hose with a couple of small hose clamps. Save the cut off hose with the tire valve, you can re-install with a double barb after your test if needed.
I am reasonably sure that this will work even though I haven't tried it myself.
mike

 

[Ken Ratcliffe]

Yeah deepest darkest mid-Wales...….that all sounds doable and makes sense. I will give a go after trip to local plumbing supplies

 

[JCSteam]

Are you wanting to hydraulic the boiler, ie to twice working pressure to check for leaks, if so DO NOT use an air line.

If I'm right you Pyrte has a boiler feed pump, if you've made this you already have half the gear to test the boiler. You need to make sure it will hold pressure before attempting to put an air line to it.

Connect the pump between a tub of water, and pipe it to the boiler with a pressure gauge that reads a little over your x2 working pressure, I think working pressure is 60psi, and x2 test pressure would be 120psi, so a gauge that measures upto 160psi would be good. Get a gauge that is liquid filled. Fit it between the pump, and the connection to the boiler. Also fit between the pump and gauge an isolator tap. Then fill the boiler full of water, expelling any air!!! This is important! Then seal the boiler and pump until pressure reaches x2WP. Isolate the pump, and wait for half an hour. Check for leaks, it's also a good idea to work up to the x2 WP in 10 or 20PSI increments allowing the boilers copper to work harden.

Sorry if my message isn't clear but I'm at work and typing in a hurry.

Be safe the last thing you want is for the boiler to go bang filled with air, water cushions the blast if a boiler joint fails. So you get a weep instead of boom.

Regards
Jon

 

[JCSteam]

Ps, for testing the engine once hydraulic is done, the thread will be a 26TPI cycle thread, see Tracey tools for tap and die. Make an adaptor on your lathe, and keep to less than half the WP of the boiler.
Jon

 

[Ken Ratcliffe]

Thanks Jon,

Initially I was just wanting to see if the boiler is vaguely air tight - I am suspecting it won't be and there will be remedial work needed. If it holds any pressure at all from a pump, then I will be a) surprised, b) happy and c) looking at how to safely test it at the x2 pressure. I won't be going anywhere near air pressure to make it go bang

Ken

Are you wanting to hydraulic the boiler, ie to twice working pressure to check for leaks, if so DO NOT use an air line.

If I'm right you Pyrte has a boiler feed pump, if you've made this you already have half the gear to test the boiler. You need to make sure it will hold pressure before attempting to put an air line to it.

Connect the pump between a tub of water, and pipe it to the boiler with a pressure gauge that reads a little over your x2 working pressure, I think working pressure is 60psi, and x2 test pressure would be 120psi, so a gauge that measures upto 160psi would be good. Get a gauge that is liquid filled. Fit it between the pump, and the connection to the boiler. Also fit between the pump and gauge an isolator tap. Then fill the boiler full of water, expelling any air!!! This is important! Then seal the boiler and pump until pressure reaches x2WP. Isolate the pump, and wait for half an hour. Check for leaks, it's also a good idea to work up to the x2 WP in 10 or 20PSI increments allowing the boilers copper to work harden.

Sorry if my message isn't clear but I'm at work and typing in a hurry.

Be safe the last thing you want is for the boiler to go bang filled with air, water cushions the blast if a boiler joint fails. So you get a weep instead of boom.

Regards
Jon

 

[ddmckee54]

I know this has probably been gone over before many times before... But what would be wrong with filling the boiler under test with water and then using air to fully pressurize the system, especially if you were using a hand operated tire pump as Ken is intending to do? It would seem to me that the worst that could happen with a hand pump is you'd get wet. With the limited volume of compressed gas you'd have available, basically just the volume of the hose, it wouldn't take much of a leak to de-pressurize the system.

Don

 

[rklopp]

I know this has probably been gone over before many times before... But what would be wrong with filling the boiler under test with water and then using air to fully pressurize the system, especially if you were using a hand operated tire pump as Ken is intending to do? It would seem to me that the worst that could happen with a hand pump is you'd get wet. With the limited volume of compressed gas you'd have available, basically just the volume of the hose, it wouldn't take much of a leak to de-pressurize the system.

Don

We do hydro-tests in the lab this way up to a couple hundred PSIG. The important things are to make sure the test article is completely filled with water, use a small and long metal tube to connect to the air/gas supply, shield people from the test article, and stand back. If the air or gas (N2) supply is delivered via a long small tube, then the gas energy can be controlled if the test article breaks. This method does not apply at pressures beyond a couple hundred PSIG.

 

[ddmckee54]

rklopp:

Most of us will find small diameter pressure rated tubing in short supply in our shops. Using a small diameter orifice would accomplish the same thing for restricting the gas energy flow wouldn't it? Something like a gas jet for a burner, or the jet in a carburetor?

A couple hundred PSIG would cover the testing of most model pressure vessels. The way I figure it, I personally have no business building something that needs to be tested at anything over 120PSIG. I have WAY too much respect for compressed gasses.

Don

 

[JCSteam]

I know this has probably been gone over before many times before... But what would be wrong with filling the boiler under test with water and then using air to fully pressurize the system, especially if you were using a hand operated tire pump as Ken is intending to do?

Air will compress and it takes a lot of energy to compress it, the air stores this energy, if there is a failure that energy used to compress the air to 120psi is suddenly released. Water doesn't compress as well so takes less energy to compress it upto 120psi. This isn't to save your arm from pumping away, if the boiler fails with air there's more energy to be released to equalise to atmospheric pressure. If the boiler leaks with water you get a dribble or a small jet for a second or two and then the boiler is at atmospheric pressure again and thus safe. I do have a photo of a small toy boiler that had compressed air put into it which shows this quite well how the stored energy in air suddenly releasing can be quite catastrophic for the person testing it. Air does make for an exciting test if the boiler is not up to scratch.

As said before be safe and build a test rig that uses water as I've described above. Once you know the boiler is structurally sound, the engine can be tested on air upto half the working pressure of the boiler using an adaptor into one of the ME threads.

Jon

 

[fcheslop]

To make an adaptor why not simply go to a tyre shop and beg an old valve assy and silver solder it to a 1/4 x40 blanking plug
As mentioned do a hydro test first
A simple way immerse the boiler in water expel all air and fit the last blanking plug
Get a bucket of cold water
Gently heat the boiler and as the water expands you will see the pressure increasing on the gauge due to the water expanding. Take it slowly and in stages to the desired test pressure
If things start to go to fast simply dunk the boiler into the cold water. Not the way I would do it but Iv seen the technique in print on several builds

 

[Steamchick]

Schadenfreude valves on cars use 5/16 x 32 ME successfully for me.
K

 

[Steamchick]

SCHr-ad-er valves.... flippin' spell checker! Can't manage German proper nouns!
K

 

[William May]

Standard tire valve thread is 5/16"-32. I know because I made tire valve core tools for aircraft high pressure tires.

The difference between just "liquid" in a hydro-test, and "liquid and air", in a hydrotest, was vividly demonstrated for me when I was in training in a aircraft hydraulic service shop.
When disassembling the strut, the rod that forms the metering part of the strut is mounted in the bottom of the strut. It is a metering pin, but about 2 feet long. It has a varying taper over it's length, to control the rate at which the strut compresses and extends under heavy load. It is removed from the lower strut by removing a retaining bolt, and installing another bolt, but this one has a 1/8" hole in it, and a fitting for a hydraulic supply line. Hydraulic pressure is applied. When you get up to about 1000 psi, the metering pin pops out with a "plink". It moves about 1/4" total travel between being fully seated, and coming free for removal. They were careful to point out, that if there had been ANY air in the area under the head of the metering pin, when it came out, it would have blasted right through the opposite wall of the shop.
Hydraulic pressure is finite. If you relax the hydro-test containment vessel (ummm.......say..........by having a failure of any kind), pressure drops off linearly, meaning, INSTANTLY. Thus the little "plink" as the metering rod came loose.
Pneumatic pressure is constant and expanding, which means, if you have ANY air trapped in your hydro-test object, YOU HAVE A BOMB!
When hydro-testing, YOU.MUST BLEED ALL AIR OUT OF THE VESSEL BEFORE PRESSURE IS APPLIED.

 

[Peter Twissell]

Schadenfreude valves on cars use 5/16 x 32 ME successfully for me.
K

Unfortunate spell check error - implies you would be happy to see the test fail!

 

[Jasonb]

Why not make an adaptor as described on the PYRTE web site?

Also I've never seen a car foot pump with a threaded end, just pushes onto the valve thread.

 

[Iampappabear]

The old style bycicle pumps used a screw adaptor to screw onto the valve stem and probably still do, but I haven't checked one lately.

Colin

 

[reichpaul630]

would a vacuum leakdown test with an automotive vacuum tester be suitable for a small boiler?

paulr