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GT 6FA AFPCS Value
Why AFPCS value increasing during rain storm?

We are using 6FA machine with MARK V system.

AFPCS is DP between compressor inlet vs ambient pressure. AFPCS called inlet air total pressure transmitter.
Why AFPCS value silty increasing during raining?

1. What may be the reason for increasing of AFPCS value During raining.(Normal value showing during no rain)
Whether raining will affect the ambient pressure?

2. Need clarity about compressor air flow calculation (Formulas etc).

vijaycontrol,

>1. What may be the reason for increasing of AFPCS value
>During raining.(Normal value showing during no rain)
>Whether raining will affect the ambient pressure?

Have you checked the inlet air filters to see if they are wet? It's probably because the inlet air filters are getting wet, which usually increases the dp across the filters. Does the unit have rain hoods (which are designed to try to prevent rain from getting to the inlet filters--but don't always function properly, especially if the inlet filter house is not oriented on the site properly with respect to prevailing wind/rain directions)?

>2. Need clarity about compressor air flow calculation
>(Formulas etc).

Please refer to the block help for the air flow calculation block, and/or the Control Specification for the unit.

One last thing--the air flow calculation is really pretty crude, and is only meant to be used for comparing air flows when troubleshooting (presuming all the inputs are working correctly! which isn't always the case), or for determining when to perform an off-line water wash. The air flow calculation is not highly accurate, and was never designed to be. It is, however, useful for comparison purposes (one condition versus another--all things being equal (IGV angle; inlet filter dp; etc.), AND if the instrumentation/inputs to the calculation are working correctly.

Many times the sensors are not properly installed (the air flow sensor tubes are installed incorrectly; there are no low point drains in the sensing lines (tubing), or the low point drains are never drained), or the ambient pressure sensing lines are allowed to be plugged by insects or dirt, or the screens (usually sintered metal "filters") are never cleaned; etc. And, often times the ambient pressure sensors are not calibrated or scaled properly.

Hope this helps!