The Fairchild 4000ABP Pneumatic Precision Regulator is a no bleed design regulator that precisely controls a set pressure. With a control sensitivity of 1/2" water column, it allows use in precision applications.
The Fairchild 4000ABP Regulator uses the force balance principle to open the Relief Valve and vent system pressure when the set point is exceeded.
Upstream pressure is transmitted through the Aspirator Tube to the bottom of the Diaphragm Assembly. When you adjust the range screw for a specific set point, the Range Spring compresses and exerts a force on the top of the Diaphragm Assembly. As long as the pressure acting on the bottom of the Diaphragm Assembly produces a force less than the spring force acting on the top of the Diaphragm Assembly, the Relief Valve remains closed. When system pressure inreases, the force on the bottom of the Diaphragm Assembly increases until it reaches the set point. When system pressure increases beyond the set point, the assembly moved upward, lifting the Relief Valve from its seat and vents the downstream air.
If downstream pressure decreases below the set point, the assembly moves downward closing the Relief Valve.