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Generator Air tightness test
Generator Air tightness test pressure drop calculation
1 out of 1 members thought this post was helpful...

What is the pressure drop calculation for the loss in air pressure during Generator air tightness test and what is the allowable drop?

By Don Lowther on 7 November, 2015 - 4:27 pm
2 out of 2 members thought this post was helpful...

Refer to the OEM manual for your specific generator.

> What is the pressure drop calculation for the loss in air pressure during
> Generator air tightness test and what is the allowable drop?

The basic formula is:

L=238(V/H){[(P1+B1)/(273+T1)]-(P2+B2)/(273+T2)]}

Lh=3.38La

Where:

L = gas leakage
Lh = equivalent hydrogen leakage
La = gas leakage using air in the generator
H = duration of test in hours
V = volume of gas system in cubic feet
B1 & B2 = initial and final barametric pressure (inches of mercury)
P1 & P2 = initial and final generator gas pressure (inches of mercury)
T1 & T2 = initial and final generator gas temperature (degrees C)

The generator OEM manuals normally have the equations and further explanations.

What is allowable varies a bit. A reasonable value for a tight system with a system volume of 2500 cu ft is 350 cfd. However, higher leakages are acceptable under certain conditions. For example, a test at the end of an outage conducted as a very rough check with the unit not yet on turning gear will be substantially higher than the same unit once it is on gear with the seal oil system warm. But it can give a quick indication of gross problems when compared to similar data for similar units or past data for the same unit. This is one reason that a quick air test is often done on removing a unit from service. Obviously it is desirable to return a unit from an outage in better condition than when it was taken off for maintenance.

By I Nyoman Bagus Yudha Dharma on 4 August, 2016 - 12:19 pm
1 out of 1 members thought this post was helpful...

Dear sir,

your posting here is very help me so much, but i want to ask you for another question related with your formula above. I still confuse until now.

1) what is the different between "Barametric Pressure (B)" and "Gas Pressure (M)", How we can collect the data for B value ?

2) does this formula only can be used on GE generator ?

I'm very appreciate if you reply my question here..

thanks for advance

Hi,

Thanks, I followed the calculation and got a resultant as La=1154 Cu ft, is this per hour or per day? as we are dividing by 15, it may be per hour but the resultant looks too big.

Why to multiply by 3.38 for Lh from La?

Please guide.

Regards,
S Banerjee