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Posted by Apache -=CW=- on January 16, 2009, 9:26 pm
How large of a system are we looking at? A pint of water in a system that
is two pints in size will no doubt have a different reaction to the
contamination vs
a system that's 50 million pints in volume. Moisture is moisture yes, but
you can't make a procedure that is all encompassing as ever job has it's own
uniqueness.
However, if I were to suspect contamination were present I'd first try and
determine how it entered the system rather than treat the symptom. After
that,
I'd remove the moisture, and then evacuate the system with a micron gauge
connected, breaking the vacume at various stages with a dry compressed gas,
such as nitrogen or perhaps with
a trace amount of refrigerent to help scavenge the moisture, until I
achieved a deep vacume that would hold. There's no time limit either, I've
had systems take a few weeks to remove
the water/moisture to a point where I was confident enough to walk away from
the job knowing that the system was perfectly free from contamination.
You're not telling us your operating pressures (normal) so I can't comment
on your pressure test. Again... a 30 pound test on a system that runs at 300
pounds
would be kind of useless don't you think? But I use a 1.5 times the normal
operating pressure for my tests, and then it's done for 24 hours. Any drop
in pressure
is absolutely unacceptable.
A New York State Journeyman :)
> With new installations we would ordinarily start the pre-commissioning
> tests with a strength pressure test, perhaps for 30 mins, followed by
> a 24hr tightness. Then there is a 24hr vacuum finished off with a 30
> minute vacuum rise test for moisture.
> Is this similar to your procedures?
> Assuming the piping system inadvertently took on say a pint of water
> with out you knowing. What would you expect to see on the Torr gauge
> after a 24 hr vacuum.
> I have done a few calculations and have recently made a discovery
> which I'd like to share but first I ask the above to set a benchmark
> against which to discover what is common practice and what might
> become new practice.
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> tests with a strength pressure test, perhaps for 30 mins, followed by
> a 24hr tightness. Then there is a 24hr vacuum finished off with a 30
> minute vacuum rise test for moisture.
> Is this similar to your procedures?
> Assuming the piping system inadvertently took on say a pint of water
> with out you knowing. What would you expect to see on the Torr gauge
> after a 24 hr vacuum.
> I have done a few calculations and have recently made a discovery
> which I'd like to share but first I ask the above to set a benchmark
> against which to discover what is common practice and what might
> become new practice.