Operation:

• The valve operates based on the balance of forces acting upon it:
  • Downward Force: P1 × A, where P1 is the inlet pressure and A is the diaphragm area.
  • Upward Force: (P1−P2) × a+f, where P2​ is the outlet pressure, a is the valve area, and f is the spring force.

  At equilibrium:

  • P1×A = (P1−P2) × a+f
  • If P1​, A, and a are constant, P2 is directly proportional to the spring force f.
  • The discharge pressure P2​ can be adjusted by rotating the adjustment screw, which changes the spring force f.

  Hence, if supply pressure is kept constant, the discharge pressure can be reduced or increased by rotating the adjustment screw.

  Part (b)

  The air used in pneumatic control systems must be clean and dry to prevent damage to pneumatic components. Air from the starting air receivers undergoes the following treatment

  process:

  • The high-pressure air from the main air receiver is passed through a pressure-reducing valve, lowering the pressure to a range of 7–8 bar suitable for pneumatic systems.
  • The air is passed through a filter to remove oil and water carried over from the compressor. This step eliminates contaminants that could affect system performance.
  • The filtered air is sent through a dryer containing materials like silica gel or activated alumina to remove residual moisture. Dry air prevents corrosion and freezing in control lines.
  • Regular drainage of accumulated water, oil, and condensate is necessary to maintain the air quality and prevent blockages in the system.

  Now the air is clean & dry enough to be suitable for use in pneumatic control systems.