Fisher 4660 Pneumatic High-Low Pressure Pilot
The Fisher 4660 pneumatic high-low pressure pilot activates safety shutdown systems for flowlines, production vessels, and compressors. This pilot is available with either single or dual set point capability, using switch points to maintain full output pressure when the process pressure is within the set point range. If the process pressure is outside this range, the pilot switches from full output pressure to zero output pressure. The primary switching mechanism in this pilot is a block-and-bleed relay assembly. This construction can be used in both block-and-bleed and bleed-only systems.