Losing pressure through exhaust ?

Hi, I've recently bought a 2" Durham and north Yorkshire project and when I tried to pressurise it, air was leaking out of the exhaust? I tried moving the regulator and the valve lever. But still leaking, is there anything obvious I'm missing?

If you are pressure testing it then its usual to remove the regulator and fit a plate over the port to get a full seal. You should really be testing with water thats why its called a hydralic test, less dangerous if anything should fail.

J

Edited By JasonB on 26/10/2012 19:32:50

Ok I will try that when testing, thanks.

But is this going to be a problem when steaming? As it is a fair bit coming out. Could it be sorted by adjusting something?

Thanks

It may be that the valve has dropped away from the valve face and it may be stuck to the valve rod or buckle by a bit of dirt, dried oil, or rust. You mention air for your test - with steam, the valve may re-seat on its own if that is the only problem, where sometimes with air they will not. With the engine and boiler cold and everything at zero pressure, take off the steam chest cover and investigate. The valve must be free to move off and on to the valve port face on the cylinder by a few thou. A little oil or grease on the valve will help hold it to the face but will keep it lubed until you raise steam again, if there are no other faults visible.

The problem could also be caused by a broken valve buckle, broken valve rod , misadjusted valve, or a scored face on valve or port face, or a few other possible more horrendous gremlins. I hope it's nothing so serious, but a quick inspection with cover off will soon show what is going on.

JD

On the Durham and North Yorkshire engine, there is a drilling from the steam cavity under the cylinder block saddle which connects with the exhaust port, this passage has a plug to seal the passage off from the steam, if it leaks you have a direct way through to the exhaust port.

If all other advice you have had fails, then it could be the plug leaking which means you my have to take off the cylinder block to rectify.

Thank you very much for your help I shall investigate tonight.

As a home test its OK but you will need to get it done with a proper hydralic pump and accurate gauge for the cert.

Filling it 99% with water is better still

The problem with testing on air is that if there is a leak the air just hisses out gently but pressure is maintained, so in a noisy environment a leak could be easily missed. But with a hydraulic test when you have a leak, even a drip, the pressure drops off dramatically. Plus, the drip leaks a wet patch shows the location of the leak, whereas the air leak leaves no trace.

So a pressure test should always be done with 100% water.

ChrisH

And if a water-filled boiler fails it will do so with a whimper, rather than a bang, as incompressible water store much less energy than elastic air.

Neil