Pressure test

[johnp]

Can I hydro test against the valves?

[Lopez Mike]

Need more information.

If you mean the various shut off and isolation valves, Yes. They should be shut during the test.

If you mean safety valve(s), no as they should be removed and replaced with plugs or caps for the test.

If you mean check valves, it shouldn't be an issue as there should be an isolation valve (closed for the test) between the boiler and the check valve.

If you mean the engine's slide or piston valve, no as the engine will run on water if you feed it pressurized water.

Sorry if these sound dumb but I'm not sure which valves you mean.

Mike

[johnp]

Thanks Mike, sorry to be so vague, I meant the shut off ball valves. I was just thinking about weepage after an hour or so.

[Lopez Mike]

On my boiler I have a mixture of traditional steam valves and ball valves. I have had no problem with leakage in any of them when they are in the off position. And I have pumped things up to 225 and gone off to answer the phone and forgotten them for hours.

As you have probably found out, the fresh water that gets put in the boiler tends to absorb any bits of air trapped here and there so you will find that there is an initial pressure drop of a few pounds. Then it should stabilize.

I have had some valve stem weeping from both types but a small tweak with a wrench seems to stop them from dripping.

Mike

[SailorHarry]

Adding to what Mike said, testing your stop valves is a useful part of doing a hydrotest. Important valves like the main steam stop, feed water stop, blow down valves, etc. should be included in the test. If there's an unexplained pressure loss start taking things apart to see which valve is leaking. This will let you know what needs work before it gets bad.

If you never test this stuff, one day you might have a feed water pipe connection burst and discover that your isolation valve and check valve don't hold only when the boiler starts to empty into the bilge...

[Lopez Mike]

I concur completely.

It's not just your pressure vessel that needs testing, though it has by far the biggest potential for catastrophe! A fee water isolation valve can be leaking for a long time and you might not know it as the check valve has been taking the load. I fool around with cold water at pressure in the system (low pressure at first!) and see what weeps and spurts at first. Open up swinging check valves and such. No point in getting scalded or squirted hard.

Mike