control valve

What is an automatic recirculating valve and where is it used?

The automatic recirculating valve is a type of control valve for the protection of centrifugal pumps. So this valve can be considered as a pump protection device, this valve would protect the pump by assuring minimum flow through the pump at all times. The major feature of this valve is that it has a modular design and they are capable of automatic bypass operation. These valves have non-return function and self-cleaning bore. These valves are used to protect the centrifugal pumps it can automatically protect the centrifugal pumps especially hot water pumps from damages that could occur through partial evaporation of the pump content during a low load operation. So when the main flow falls below a predetermined rate the valve would open its bypass in the required manner to maintain the minimum flow rate of the pump.

What are the features and characteristics of an automatic recirculating valve?

These valves are suitable for high-pressure conditions and they are small in size so there won’t be any trouble related to installation. It can reduce velocity and also can prevent cavitation multistage decompression bypass. This valve can prevent the reverse flow and are capable to detect the low flow.

How does an automatic recirculation valve operates?

During the low load conditions, the combined bypass and the check valve would protect the centrifugal pump. So if the load of the pump is reduced below its preset flow rate then the disc of the valve would move towards its seat and the bypass bush would open. So because of this, there is a flow path and the minimum flow of the pump can be maintained.

How to install an automatic recirculation valve?

The automatic recirculation valve must be installed near the pump discharge. The bypass flow would be returned to a de-aerator or during certain times it could be transferred to the pump. It must be installed at the pump outlet. The distance from the outlet of the pump and the inlet shouldn’t be more than one and a half meter, in order to prevent liquid pulsing which would cause a low-frequency water attack. We must avoid installing this valve vertically and try to install it horizontally. If there is any change in temperature. Pressure, main flow, and the required minimum flow would affect the operation of the valve so this must be considered while installing the valve.

Operational check

If the valve is installed properly then the combined main and the bypass flow should be equal to or above that of the specified minimum flow of the pump. If there is a change in the operational characteristics than the original specifications then field adjustment should be done.

What are the advantages of automatic recirculating valve?

  • It has a combination of both check and bypass features
  • Controlled flow
  • There is no need for external actuation
  • Proprietary CV calculation system
  • Three-phase slurry and high-pressure variants are available
  • It would prevent reverse flow
  • Bypass flow pressure reduction and backpressure regulation of the bypass flow
  • Less maintenance is needed
  • Compact in size

What are the applications of automatic recirculating valve?

  • It is used in boiler feed-water
  • Condensate
  • Turbine cooling
  • Injection
  • It is used in process systems
  • It is used in steam turbines
  • Demineralized water
  • Hydrocarbons

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