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Sullair compressor doesn't keep up load demand

Discussion in 'Other Construction/Demolition Equipment' started by JCho, Sep 30, 2022.

  1. JCho

    JCho New Member

    Joined:
    Sep 30, 2022
    Messages:
    1
    Location:
    Canada
    Hello I have a Sullair 750 diesel driven compressor.
    Please refer the attached photo and drawings
    When I put the compressor under load, I cannot quickly compensate the load demand.
    I made sure that the inlet air valve on the compressor is working fine. I noticed that when the compressor is at the start mode, the 60 psi control air from the back pressure regulator (according to the drawing) is sent to the back of the inlet valve pushing the valve so that it is closed, when the compressor is at the run mode, the 60psi goes to the front of the inlet valve pushing the plate and the control air from low pressure regulator ~40psi (i assume, No gauge) is sent to the back of the air inlet valve causing the valve to open. The problem is that when it is under high load, the low pressure regulator should decrease the control air pressure going behind the air inlet valve so that it can open up the valve more and compensate the load amount, but it doesn't. The low pressure air regulator maintains the 40 psi regardless the load amount. This results in bad load keep up. Do you have any idea how i can solve this problem? compressor drawing component description.JPG compressor drawing.JPG Compressor pic.JPG Inlet valve drawing.JPG

    Thank you
     
  2. OFF

    OFF Senior Member

    Joined:
    Sep 30, 2009
    Messages:
    950
    Occupation:
    HD Mechanic
    Location:
    Alberta, Canada
    Have you ever replaced the oil separator filter?

    Does the engine speed up when you open an air line?
     
  3. OFF

    OFF Senior Member

    Joined:
    Sep 30, 2009
    Messages:
    950
    Occupation:
    HD Mechanic
    Location:
    Alberta, Canada
    How many hours are on this beast?