Pump inlet and outlet pipelines

1. Requirements for the piping of the pump's suction and discharge pipelines 1) Shut-off valves must be installed at both the pump's inlet and outlet. Generally, gate valves and butterfly valves can be used for large pipe diameters, and ball valves can be used for small pipe diameters; 2) Adjustable brackets should be installed at the pump's inlet and outlet pipes. Vibrating pipes should be equipped with vibration-damping brackets to properly adjust the pipe position and reduce the additional force on the pump nozzle caused by installation errors; 3) When the pipe connecting the pump and the equipment is short and the two are not on the same foundation, the connecting pipe should have a certain degree of flexibility, or a metal hose should be added to compensate for the uneven settlement of the foundation; 4) The diameter of the suction and discharge pipes should not be smaller than the inlet and outlet diameters of the pump; 5) The pump's suction pipe should meet the required net positive suction pressure head ( NPSHa), the pipeline should be as short as possible and with fewer bends; 6) The length of the straight pipe section before the centrifugal pump inlet should not be less than 3D of the inlet diameter; 7) For double-suction pumps, in order to avoid cavitation of the centrifugal pump caused by uneven two-way suction, the double suction pipes should be arranged symmetrically to ensure uniform flow distribution on both sides; 8) In order to prevent material backflow when the centrifugal pump is not started, a check valve should be installed at its outlet, and it should be installed close to the pump outlet for maintenance after cutting off; 9) A safety valve should be installed between the outlet pipe and the outlet cut-off valve of the reciprocating pump; 10) A pressure gauge should be installed at the outlet of the pump; a filter should be installed at the pump suction port. Generally, a Y-shaped filter is used for pipes not larger than 2″, and a T-shaped filter is used for pipes larger than 2″.

2. Auxiliary pipeline settings of the pump

1) Balance pipeline: When the medium is prone to gasification at the pump inlet, a balance pipe that can return to the gas phase space of the upstream equipment on the suction side can be set between the pump inlet nozzle and the pump inlet cut-off valve to reflux the generated gas and avoid cavitation of the pump. A cut-off valve should be set on the balance pipe.

2) Minimum return pipe: To prevent the centrifugal pump from operating at a flow rate lower than the minimum flow rate of the pump, a minimum return pipe should be set to allow part of the fluid to return from the pump discharge port to the container at the pump suction port to ensure the pump flow rate.

3) Warm pump pipe: When the temperature of the material transported by the centrifugal pump exceeds 200℃, a warm pump pipe should be set to allow a small amount of material to be led from the discharge pipe of the operating pump to the outlet of the standby pump, and then flow through the standby pump and return to the pump inlet, so that the standby pump is in a hot standby state for easy startup.

4) Anti-freeze pipe: For pumps with condensable media at room temperature, a DN20 25 antifreeze pipe should be set, and the setting method is the same as the warm pump pipe.

3. Typical pump piping examples

3.1 Side-inlet type precautions: (1) The eccentric reducer at the pump inlet should be flat on the top to prevent the formation of air pockets and gas accumulation causing pump cavitation. (2) The pump inlet bracket should be a guide adjustable bracket to prevent excessive stress on the pump due to installation errors. (3) Pay attention to the core pulling space of the pump inlet filter. If the vertical core pulling space is insufficient, you can choose to install it at a 45# angle downward or use an angle filter.

3.2 Notes on top-in type: (1) A vent valve is installed near the pump inlet pipe for exhaust when it is just started. (2) Bracket 1 should be close to the pump inlet and should be set as a guide adjustable bracket.

3.3 Notes on top-out type: (1) This type of setting is mostly used for large-diameter pipelines and can reduce the valve operating height. (2) This is the most common setting type for warm pumps, anti-condensation, and minimum flow pipelines. (3) Pipe rack 1 is easy to be axially limited, and pipe rack 2 is easy to be guided, which can reduce the stress at the pump inlet.