In APU unit the filter are cleaned one by one in sequence.
My question is how the sequence is defined and how it works for frame 6 machine.

The timer cards is supplied by which companies.

I want to know the whole procedure from the instrumentation point of view.

May please suggest the whole procedure in detail.

Regards,

B K MEENA
Mail:brijendra81 [at] gmail.com

 

The Air Processing Unit just dries, cools and regulates the pressure the air which is extracted from the axial compressor discharge before it is used for pulsing of the filters during cleaning.

The cleaning cycle is initiated (automatically) by actuation of a differential-pressure switch measuring the pressure drop across the inlet air filters. Then, based on system settings (sometimes adjustable) on the controller the banks of filters are pulsed sequentially.

Sometimes the controller just pulses once through the banks of filters; some controllers continue pulsing until the d-p switch is de-actuated by a decrease in the pressure drop across the filters.

Some controllers can be manually pulsed from switches on the enclosure.

Some controllers can be set to pulse once by adjusting a timer. The timers can usually be set to start the pulsing once-per-day at a pre-set time. I have seen timers that can be adjusted for different days of the week.

The manufacturer of the controller (sometimes called a "sequencer" because it's really a very simple control system that just sequences through a number of pulses) designs their controllers (sequencers) differently, though similarly. I've seen controllers from Braden and from Farr, and some "home-made" controllers just using electromechanical relays and timer/counter mechanisms (they were crude but functional).

You should be able to find some information from the manufacturer about the programming/configuration of the controller in the Service Manuals provided with your turbine and auxiliaries.

 

The pulsing consists of energizing a solenoid for some period of time. Some controllers provide for an adjustable pulse length (meaning that the length the solenoid(s) are energized is adjustable); some do not.

Making the pulse length too long didn't seem to make cleaning more effective, in fact, sometimes it seemed to be exactly the opposite. So, it should be field-adjusted to suit the individual site needs, if necessary.