In Our GE Frame 9E gas turbine self pulsating inlet air filters are there.

We are using the pulsation irrespective of the Filter DP. but I think for the best efficiency of the filter, there should be some optimum filter DP, above which the only the pulsation should be carried out for best efficiency of filter. Using pulsation at less DP will decrease the filter efficiency,thus quality of Air...

Am I right????

Can any one tell me how the efficiency of inlet air filter depend upon the inlet air filter DP?

And what should be the cut off limit of Filter DP for best air quality?

Regards,
BSJhala...

 

The differential pressure measured across inlet air filters is an indication of the cleanliness of the filters. A high dp means a dirty filter; a lower dp means a cleaner filter. Even new filters have some dp, they are, after all, a restriction in the air flow, albeit a slight restriction.

A dirty filter is going to restrict the amount of air that can be drawn into the axial compressor. This decreases the efficiency of the turbine; less air means less fuel can be burned. The harder the compressor has to work, since it's driven by the turbine, the less energy available for the generator.

A lot of sites pulse their inlet air filters on a cycle or schedule, and there is usually a timer which can be set just for this purpose. This is as opposed to pulsing the filters automatically when the differential pressure gets high.

The typical line of thought is that if the filters aren't pulsed until they get dirty, that it will be difficult to knock most of the dirt off with the pulsing, and depending on the configuration of the filters a lot of the dirt might just get sucked into adjacent filters, ones which were just pulsed clean.

The decision of when to pulse self-cleaning air filters is a site decision, made based on site conditions. Every turbine is located in a different environment, with different ambient conditions. Dust of all types ("natural", road dust, cement dust, wood dust, metal dust, etc.), humidity (fog, "natural" humidity or the lack thereof, steam vapors from nearby plants or cooling towers, etc.), as well as the type of filters in use all and their configuration contribute to the decision of whether to use the as-left differential pressure setting, to lower it, or to pulse on a regular periodic basis.

If the air pressure source for the pulsing is from compressor discharge extraction, then every time the pulsing system is used the efficiency of the compressor, and therefore the turbine, is decreased during the pulsing. Not by much, but any air extracted from the compressor decreases the efficiency of the turbine.

Many GE-design heavy duty gas turbines have "implosion" doors on the inlet filter assembly downstream of the filters. The purpose of these implosion doors is to open when the filter differential pressure get severely excessive in an effort to prevent rupturing the filters due to high differential pressure and ingesting all the dirt released from the ruptured filters as well as possibly some of the filter materials. Better to let some unfiltered air into the turbine while shutting it down (sometimes the actuation of these implosion doors initiates a turbine shutdown; if there is no automatic shutdown then the operators should be shutting the unit down manually!) than to suffer the effects of ruptured filters.