Hydro test
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johnp
- Full Steam Ahead
- Posts: 242
- Joined: Mon Nov 23, 2009 6:43 pm
- Boat Name: Cardinal Queen
- Location: Richmond Hill, Ontario, Canada
Hydro test
Trying to hydro test the boiler, there is no drips wet spots or anything. However it lost 50psi over 14hrs. Could it be seeping through a nylon ring on a ball valve? Last year when I tested it held pressure all day with every opening plugged.
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fredrosse
- Full Steam Ahead
- Posts: 1925
- Joined: Fri Nov 20, 2009 5:34 am
- Boat Name: Margaret S.
- Location: Phila PA USA
- Contact:
Re: Hydro test
There are several possibilities, none of them very consequential:
When the boiler is pumped up to test pressure, if there is an air pocket somewhere, the air is compressed to the test pressure. Over time this gas absorbs into the water, and reduces the test pressure even if there are no leaks.
When the boiler is pumped up to test pressure, the water temperature is some value. If there is a reduction in temperature, even a small reduction over time the water contracts slightly and reduces the test pressure even if there are no leaks.
As you mention, worn seals on valves, etc, can allow very small leakage to reduce test pressure over time. This tendency increases with the age of the steam plant, and is somewhat annoying. However the hydrostatic test is to prove the general integrity of the pressure parts, and minute leakages do not really matter.
When the boiler is pumped up to test pressure, if there is an air pocket somewhere, the air is compressed to the test pressure. Over time this gas absorbs into the water, and reduces the test pressure even if there are no leaks.
When the boiler is pumped up to test pressure, the water temperature is some value. If there is a reduction in temperature, even a small reduction over time the water contracts slightly and reduces the test pressure even if there are no leaks.
As you mention, worn seals on valves, etc, can allow very small leakage to reduce test pressure over time. This tendency increases with the age of the steam plant, and is somewhat annoying. However the hydrostatic test is to prove the general integrity of the pressure parts, and minute leakages do not really matter.