PRODUCT INFORMATION

748 – Pump Circulation, Pressure Sustaining Control Valve AS5081

The Model 748 Pump Circulation and Pressure Sustaining Control Valve adds the advanced “active check valve” logic to standard pump systems. It is a hydraulically operated, diaphragm actuated control valve that opens or shuts off in response to electric signals (during the pump starting and stopping processes) while sustaining discharge pressure.

By progressively circulating pump flow, it enables a standard mechanical check valve to respond gradually during the pump starting and stopping processes, preventing pipeline surges.

Model 748 isolates system from the effects of pump starts and stops for:

• Solitary single speed pumps
• Battery of single speed pumps (add & switch)
• Battery of variable speed pumps (add)
• Applicable to existing systems
• Controlled pipeline fill-up

FEATURES & BENEFITS

• Line pressure driven
  • Independent operation
  • No motor required
  • Long term drip tight sealing
• Off-line (circulation) installation
  
  • Replaces in-line "active check valve"
  • Reduces system energy consumption
  • Low capital investment
  • Short valve operating time
  • Applicable to existing systemsSolenoid controlled
  • Low cost wiring
  • Wide ranges of pressures and voltages
• Check feature (spring loaded type)
  
  • Replaces line sized check valve
  • Fail-safe mechanical closure
• In-line serviceable - Easy maintenance
• Double chamber
  • Non-slam opening and closing characteristics
  • Protected diaphragm
  • Full powered opening and closing

Major Additional Features

• Relief override - 748 - 3Q
• Electronic control - 748 - 18
• Pump circulation and flow control valve - 749 - U
• Deep well pump electric control valve - 745

TECHNICAL DATA

The Model 748 Pump Circulation and Pressure Sustaining Control Valve, installed off-line, enhances standard pump systems with advanced "active check valve" logic. It is particularly suited to:

• Large diameter systems where line sized automatic control valves are not available or very expensive.
• Existing systems with mechanical check valves
• System designs where mechanical check valves are preferred

During the pump starting and stopping processes the Model 748 circulates zero to 100% of pump discharge to suction, while sustaining discharge pressure slightly below system static pressure. It prevents pipeline surges by enabling a standard mechanical check valve to respond gradually:

• When the pump starts, it gradually closes, increasing to check valve upstream pressure
• Prior to pump stop, it gradually opens, reducing that pressure

Complete process control is accomplished by a dedicated controller that coordinates all system components.

The controller consists of three timers (TD1, TD2 & TD3) used for timing the process and for the control.

LITERATURE

748 – Pump Circulation, Pressure Sustaining Control Valve Brochure