Model 66BP is a stainless steel precision back pressure regulator for high performance applications with corrosive environments and/or high temperatures. The Model 66BP Stainless steel housing and internals, along with its fluorocarbon elastomers are compatible with a wide range of corrosive materials and difficult operating environments.

Operating Principles
When you adjust the Range Screw to a specific setpoint, the Range Spring exerts a downward force against the top of the Control Diaphragm. This downward force closes the Relief Valve. When the force from the system pressure that acts on the bottom of the Control diaphragm is less than the force that acts on the top of the Control Diaphragm, the Relief Valve remains closed. 

When the system pressure increases, the force that acts on the bottom of the Control Diaphragm increases until it reaches the setpoint. 

When the system pressure rises above the setpoint, the Diaphragm Assembly moves upward lifting the Relief Valve from its seat
and vents the excess pressure from the system. The relief valve closes as set point is reached.