Steam Coil Air Heater (SCAH)

[GBurns]

Is there any way to quantify a leak based on lost pressure. A SCAH being pressure tested with air to 25 psig. Over a two hour period the pressure decays slowly to 5 psig. Is there criteria for how long pressure must be held to determine if there are no or no significant leaks leaks? I was not the one who did the test so I do not know if the rate of pressure drop was quick at first and then slowed and the internal pressure got lower.

 

[boilerdoc]

Hi GBurns,
what was the purpose of a pressure test with 25 psig? What I do normally is a leakage test with air slightly above atmospheric pressure ( 0.5 bar ) and check with soap water for leaks at weldings and flanges. The pressure test should be done as hydrotest with water in case of a steam coil with at least 1.3 x operating pressure. In case of leaks the pressure will drop within minutes and you should be able to detect the leaks by dripping water.
Hope this helps.

 

[GBurns]

The unit is currently on line. So the steam coil itself is not accessible. They are trying to determine condition prior a scheduled outage.

 

[quark]

The volume content of coil is constant at both pressures. Suppose if volume of the coil is V, total volume of compressed air in the coil is (25+14.7) x V.

Assume you expanded the gas to a pressure of 20 psig. Now the actual volume should be (20+14.7) x V. This comes out to be 14.4% (39.7/34.7) greater than volume at 25 psig. But as your coil volume remains constant, the leakage is 14.4%.

Though this method is not perfect it will give you some approximation and is generally used.

As far as pharmaceutical application is concerned, we don't bother if the leakage is less than or equal to
1.3 mBar/Minute.

 

[linux]

if you can access the unit use a mirror or cold peace of stainless steal it will mist up when in contact with the leak there for you will be able to visualy asses the leak and or mark it for repair at the outage hope this helps