SCHROEDAHL AUTOMATIC RECIRCULATION SYSTEMS

Centrifugal Pump Minimum Flow Protection

A centrifugal pump can overheat and be damaged when flows are less then the minimum amount specified by the manufacture. The primary function of a pump protection system is to maintain a minimum flow thru the pump at low loads. This flow is allowed to pass thru the pump and diverted into a bypass line so that the process system will not be affected. This bypass flow is typically returned to the pump suction supply side of the system.

Two types of systems are commonly used to fulfill this function, a Conventional Feedback Control System or a Self-Contained Automatic Recirculation Valve.

The Conventional Feedback Control System

Key Components:

1. A check valve in the main pump discharge line to protect the pump from reverse flow.
2. A flow meter/sensor in the main discharge line to provide indication of the pump flow rate.
3. A flow controller or DCS input/output point to provide required bypass flow rate.
4. An electrically/pneumatically actuated bypass valve to maintain required bypass flow rate.
5. Valve automation equipment to convert bypass flow rate output signal to valve travel.
6. All wiring for the feedback control loop.

The Self-Contained Automatic Recirculation System

Key Components: (The Only Component)

1. SCHROEDAHL AUTOMATIC RECIRCULATION VALVE (ARV)

Check Valve: The ARV has an integral main-line check valve, witch not only prevents reverse flow but also provides pump discharge pulsation dampening throughout the entire flow range.

Bypass Valve: The bypass control device located in the ARV is actuated directly from the movement of the main disc. The bypass valve is designed to handle the entire pressure drop from the pump discharge to the suction inlet pressure without additional let down valves.

The SCHROEDAHL Advantage

The advantages of the Schroedahl ARV as compared to a Conventional Feedback Control System make it east see why it is becoming the system of choice.

• A single device in one housing replaces numerous components, resulting in a significant savings in the initial installed cost of the system.
• The ARV provides a single source responsibility for the performance of the pump protection system.
• The ARV provides long-term reliability with little or no maintenance.
• The ARV is factory set and its feed forward control requires no initial tuning and provides instant response from the bypass valve. Install it and go.
• The pump discharge pulsation-damping feature is not available with conventional non-return valves.

Note: Some applications may require a Schroedahl Anti-Flashing Device to be installed in the bypass line to protect the downstream piping.