In fields such as industrial production, municipal construction, and water conservancy projects, centrifugal pumps play an indispensable role. To ensure that centrifugal pumps always maintain an efficient and stable working state, reasonable pipeline design is of vital importance. So, when designing the pipelines for centrifugal pumps, what aspects should we pay special attention to? Below, Zoomlian Pump Industry will introduce some relevant knowledge in detail for everyone.
I. Design of Suction Pipeline
Pipe diameter and length: The suction pipe diameter should be appropriately larger than the inlet pipe diameter of the centrifugal pump to reduce the fluid flow velocity, lower the suction resistance, and prevent cavitation. At the same time, the suction pipe should be as short and straight as possible, minimizing unnecessary elbows and valves to shorten the fluid flow path and reduce frictional resistance. For instance, in some industrial applications with high requirements for flow and pressure, the suction pipe diameter can be 1-2 sizes larger than the pump inlet pipe diameter. A reasonable pipe diameter selection and a short and straight pipe design can effectively enhance the pump's suction performance and reduce the risk of cavitation.
The slope of the horizontal layout: The horizontal suction pipe should have a certain slope (generally 0.005 - 0.01), and the slope should be towards the inlet of the centrifugal pump to facilitate the removal of air in the pipe and prevent the formation of air pockets. If the installation position of the pump is higher than the suction liquid level, the slope should be more strictly controlled to ensure that the liquid can flow smoothly into the pump. In the analysis of actual engineering cases, it was found that the suction pipes that do not meet the slope requirements are prone to cause cavitation, affecting the normal operation of the pump.
Avoid negative pressure: Determine the installation height of the pump reasonably to ensure that there is still sufficient positive pressure head at the pump inlet when the liquid level is at its lowest, preventing vaporization of the liquid and cavitation. Make precise calculations based on parameters such as the pump's net positive suction head (NPSH) and resistance losses in the suction pipeline.
II. Design of Discharge Pipelines
Pipe diameter selection: The diameter of the discharge pipe should be reasonably selected based on the flow rate and head of the centrifugal pump as well as the requirements of the system to ensure a moderate flow velocity of the fluid within the pipe (generally controlled at 2-3 m/s), avoiding excessive pressure loss due to high flow velocity or sedimentation of impurities within the pipe due to low flow velocity. Relevant fluid mechanics research indicates that an appropriate pipe diameter can effectively reduce energy loss in the pipeline and enhance the system's transportation efficiency.
Support and Fixation: As the centrifugal pump generates vibration during operation, the discharge pipeline must be firmly supported and fixed to prevent damage to the pump and connected components caused by pipeline vibration. For long-distance pipelines, fixed supports and guide supports should be set at certain intervals to ensure the stability of the pipeline.
Valve settings: Appropriate valves, such as check valves and globe valves, should be installed on the discharge pipe. Check valves prevent backflow of liquids, safeguarding the pump and system safety; globe valves are used to regulate flow and pressure. The installation position of the valves should be convenient for operation and maintenance, and the thermal expansion and contraction of the pipes should be taken into account. In the actual design of industrial piping systems, reasonable valve settings can effectively ensure the safe and stable operation of the system.
III. Pipe Connections
The use of concentric reducers: When connecting the inlet and outlet of a centrifugal pump to the pipeline, concentric reducers (for the suction pipe) and eccentric reducers (for the discharge pipe) should be used to ensure a smooth transition at the interface between the pipe and the pump, reducing fluid impact and resistance. When installing eccentric reducers, the flat side should face upwards to prevent the formation of air pockets.
Sealing and gaskets: When connecting pipes, ensure a good seal by using appropriate gaskets and sealing materials to prevent leakage. For pipes carrying high-temperature, high-pressure or corrosive media, pay more attention to the sealing performance and select gaskets that are resistant to temperature, pressure and corrosion.
IV. Other Matters to Note
Installation of pressure gauges and thermometers: Pressure gauges and thermometers should be installed on the inlet and outlet pipelines of the centrifugal pump to monitor the operating parameters of the pump in real time and detect abnormal conditions promptly. The installation positions of the pressure gauges and thermometers should be selected at locations where the fluid flow is stable to ensure accurate and reliable measurement data.
Buffer tank and safety valve settings: For systems with high requirements for flow and pressure fluctuations, a buffer tank can be installed on the discharge pipeline to buffer pressure fluctuations and stabilize flow. At the same time, to prevent system overpressure, a safety valve should be installed and ensure that the safety valve's discharge port is unobstructed.
Pipeline cleaning and maintenance: When designing pipelines, it is necessary to take into account the convenience of cleaning and maintenance, and set up necessary cleaning ports and inspection ports. For pipelines transporting media that are prone to scaling or contain impurities, filters should also be installed to prevent impurities from entering the pump and damaging the components of the centrifugal pump.
The design of centrifugal pump pipelines requires comprehensive consideration from aspects such as suction pipelines, discharge pipelines, connection methods, and other related factors, adhering to relevant design norms and standards to ensure the safety, stability, and efficient operation of the system. It is hoped that the above content can be helpful to everyone in the design of centrifugal pump pipelines.