The AR Valve

An essential component

Despite its long and cumbersome name, the Automatic Recirculation Valve (AR Valve) is an inconspicuous element in the centrifugal pump circuit. The AR Valve’s main purpose is to ensure that a pre-determined minimum flow through a centrifugal pump is guaranteed at all times. This is important because centrifugal pumps operating below the minimum flow suffer from overheating, vibrations and cavitation and can be permanently damaged and even completely destroyed if they run dry.

Like a fuse in a power circuit – the AR Valve is essential for the safety of a plant.

The metal components for a valve are milled with high precision by Schroeder Valves

Engineers plan the construction of the AR valves in a digital work process

A metal worker programs the CNC milling machine

Safety

Most centrifugal pumps operate with a constant speed along a fixed curve. The pumps are integrated into plants with variable discharge flows. The variable flows lead to operating ranges where process-related flowrates are below the required pump-specific minimum flow. These low flow conditions can cause severe incidents and downtime. The AR Valve ensures that the entire pump flowrate is greater than the required minimum flow-rate at all times. Thus, the pump is always protected from low flow conditions.

Operating principle

AR Valves are mounted on the discharge branch of the pump or in the discharge line right after the pump. The bypass branch of the valve is connected to the bypass line. The valve is solely flow-controlled. In start-up conditions with closed main line, the valve will allow the minimum flow through the bypass. As the discharge line is open, the valve will modulate flow between the process and the bypass branch. As soon as the process demand exceeds the minimum flow, the bypass will fully close and all flow through the valve is sent to process. If the actual process flowrate falls below the required minimum flow, the valve automatically opens the bypass and the determined flowrate recirculates through the bypass line to a tank or vessel.