How high? Safe to Pressure Test steam?


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Old 02-09-09, 10:59 AM
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How high? Safe to Pressure Test steam?

I want to crank up the pressure a little on a single pipe system to help track down any steam pressure leaks (at the fixtures, valve packing, rad fins, etc.)

A Heat-Timer tech said that 5-6# probably won't hurt the vents. What about other components...Site gauge, valve packing, Pressuretrol...?

I'm pretty sure there are various leaks, the system will drop pressure from the moment the pressure cut off engages. This causes the boiler to continually cycle, every minute or so, until the thermostat is satisfied. (Obviously by my concern) This continues to happen after all the rads are up to temp and the vents have closed. So I need to find the leaks

The system should hold normal operating pressure for a while after cut-off, shouldn't it? (I'm running it 0.5-1.5#)
<O
How high of a pressure is safe, or advisable, to take the system up to for testing (8-10#?) and, is this even a good idea? Will the additional pressure just force more leaks?
 
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Old 02-09-09, 02:09 PM
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You should not have to go above 5 psi to look for a leak. use a mirror or flashlight around vents and valves. If there are return lines under the floor they may also be leaking.
 
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Old 02-10-09, 08:40 AM
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Five PSI shouldn't hurt most components, although there are a few air vent types that may be near their limit. You may indeed have leaks, but the condition you describe can be attributed to other factors.


1) Your boiler may be oversized making more steam that the pipes/radiators can condense. The pressure (above the boiler) will rapidly rise and trip the pressuretrol. As soon as that pressure is relieved the boiler kicks back on. This is called short cycling. You should measure your radiators, calculate their EDR and compare that to the "net" rating (Sq. Ft. Steam) of the boiler. These values should be close


2) The system will not hold steam pressure unless all the radiators are hot all the way across. Steam travels from the valve, across the top of the radiator to the far end, while also moving down to the lower half of the tubes. The air vent will often get hot and close before the bottom section of several of the tubes reach "steam" temperature. As long as there is metal cold enough to condense steam, you won't build pressure even if the air vent is hot and closed. Actually, the steam will condense causing a vacuum and suck up any steam elsewhere in the system. This is normal operation.
 
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Old 02-10-09, 12:53 PM
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PS,

here's a link to a sizing guide for radiators

Radiator Sizing Guide
 
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Old 02-10-09, 12:56 PM
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Thanx

Thanks guys:

I'm gonna crank it up and search for excaping vapors...I'll let you know what I find. It will probably be a few days, especially if I find alot of em.
 
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Old 02-12-09, 11:18 AM
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What I found..

...was alot of leaks.

at 3-1/2# everything hissed (like a brood of vipers.) Mostly leaking at the unions connecting the rads/valves. Also had a few packing nuts on the valves which went nuts and needed re-packed.

I'm sanding the mating surfaces of the unions and applying Hercules Brush-on Blue Block to both surfaces. Does anyone have experience with this product, or have a suggestion for another one that will be a good 'gasket'?
 
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Old 02-12-09, 03:29 PM
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A pair of 18 or 24 inch pipe wrenches might not be a bad suggestion! Don't go crazy with the blue block, you wanna keep that out of the system if possible, any oils in it will create a need to 'skim' the boiler if they get into the water. Use sparingly!

Seriously though, you probably won't get by with 6 or 12 inch wrenches when you tighten them.
 
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Old 02-12-09, 03:59 PM
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lack of muscles?

I have a pair of 24's...also have a 3' cheater bar.

Thanks for the advice on going minimal with the goop.
 
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Old 02-12-09, 05:51 PM
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Also remember another thing affecting pressure is un-insulated main piping.
 
 

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