Solution for pump protection
Modern industrial equipment process request centrifugal
pump are basically work under condition of variable flow. An automatic recirculation valve (ARC valve) is a multifunctional valve whose primary purpose is to ensure that a pre-determined minimum flow is assured through a centrifugal pump at all times. This is important as centrifugal pumps
suffer from overheating and cavitation and can be permanently damaged if they run dry.
Through many years of research and development, continuous innovation and practice, shanghai datian valve Co. research ZD series Automatic recirculation control Valve, to prevent overheating, serious noise, unstable and erosion damage of centrifugal pump under low load operation. As long as the flow rate of the pump valve
below a certain value, the bypass backflow mouth will automatically open to ensure necessary minimum flow of pump.
Fire protection system
Traditional power plant
Centrifugal pumps require protection
If you use centrifugal pumps for any liquid-boiler feed water, condensate, or process fluids, a significant investment has been made in the pump, driver and related controls. Minimum flow protection is vital upon
pump start up and low demand conditions. If reliable protection does not exist, the following unfavorable effects can interfere with the performance and reliable operation of the pump. The liquid’s temperature will rise due to friction and hydraulic losses within the pump. Figure 2a illustrates the temperature rise in relationship to the H-Q curve. The curve indicates that at or near the best efficiency point, the temperature rise is minimal and not significant to the pump operation.
The process flow removes the generated heat from the pump. The temperature increases as the flow through the pump is reduced. Frictional and hydraulic losses generate heat, while the quantity of fluid to which this heat is transmitted is reduced. The rise in
temperature results in the formation of vapor. The elevated temperature / vapor pressure of the liquid results in problems ranging from damaged seals and bearings to complete failure of the rotating elements. Internal recirculation within the pump, often termed incipient
recirculation, can cause a form of cavitation leading to impeller damage. Internal recirculation is illustrated in Figures 2b and 2c.
High specific speed pumps have power curves which rise as the flow reduces. If adequate flow is not maintained, motor overload will result.
Three protection ways for pump
Continuous circulat ing system
Minimum requirement of continuous circulating system pump is unrelated with the discharge of Process flow changes system. After setting of minimum flow, through orifice plate directly backflow to storage tank. Although continuous minimum flow circulation can protect pump very good, but pump must provide greater power output to ensure system process flow plus recycle flow, which causing additional energy waste.
Control circulat ing system
Control circulatory system is assembly by the check valve, flow gauge, minimum flow control valve, control circulation system, control circulation system can provide minimum flow protection, when process flow is greater than minimum flow of pump, loop closed, no extra energy loss. But system is complex, control components, purchase, installation, maintenance cost is higher.
Automat ic recirculat ion control valve
Automatic recirculation valve set check valve, flow perception, bypass control valve, multi-stage step-down in one, do not need power, control system and wiring, essential safety. Taking up small space, reducing the possibility of high-speed fluid to
malfunction to minimum, with lower Installation and maintenance cost, It is the priority pump protection way of modern industrial process.
Zd series automatic recirculation control valve
ZDT Model Automatic recirculation control valve
Simple structure, low cost, long life, suitable for Low pressure Working conditions.
Cast valve body, material: carbon steel or stainless steel etc.
Big flow of bypass, maximum flow is 60% of main flow, KV value can be adjusted.
Bypass maximum operating pressure differential up to 4 MPa.
Pressure CL150# – 400#, size1″ – 16″.
ZDL Model Automatic recirculation control valve
Multi-orifice cage bypass, low noise, suitable for middle and low pressure conditions.
Forged steel body, material: carbon steel or Stainless steel etc.
Non-return valve function is standard, Maximum pressure differential up to 6 MPa.
With venturi port main flow check valve structure, be applicable for complicated working conditions.
Pressure CLASS150# – 600#, size1″ – 20″.
Manual bypass operation is optional.
ZDM Model Automatic recirculation control valve
Multistage decompression to preventing cavitation, reducing velocity, suitable for high pressure conditions.
Forged valve body, material: carbon steel or Stainless etc.
Non-return valve function is standard, Maximum pressure differential up to 30 MPa.
Pressure CLASS150# – 2500#, size1″ – 20″.
Manual bypass operation is achieveable.