3.18.5.2Piping
•Use piping with a diameter equal to or greater than the connection ports of the pump and with the shortest possible lengths.
•The pipe diameter has to be calculated in function of the liquid parameters and the installation parameters. If necessary use larger diameters to limit pressure losses.
•If the fluid to be pumped is viscous, pressure losses in the suction and discharge lines may increase considerably. Other piping components like valves, elbows, strainers, filters and foot valve also cause pressure losses.
•Diameters, length of piping and other components should be selected in such a way that the pump will operate without causing mechanical damage to the pump/pump unit, taking into account the minimum required inlet pressure, the maximum allowable working pressure and the installed motor power and torque.
•Check the tightness of the pipes after connection.
Suction piping
•Liquids should enter the pump from a level higher than the pump level, the inclining pipe should rise upwards towards the pump without any air pockets.
•A too small diameter or a too long suction pipe, a too small or blocked strainer will increase pressure losses so that the NPSHa (NPSH available) becomes smaller than the NPSH (NPSH required).
Cavitation will occur, causing noise and vibrations. Mechanical damage to pump and pump unit may occur.
•When a suction strainer or filter is installed pressure losses in the suction line must be checked constantly. Also check if the inlet pressure at the suction flange of the pump is still sufficiently high.
Self-priming operation
At the start sufficient liquid must be available in the pump filling up the internal clearance volume and the dead spaces, allowing the pump to build up a pressure difference.
Therefore, for pumping low viscosity fluids, a foot valve with the same or larger diameter than the suction pipe must be installed or the pump can be installed without
Note! A foot valve is not recommended when pumping high viscous liquids.
•To remove air and gases from suction line and pump, counter pressure at the discharge side must be reduced. In case of
•Another possibility in case of long lines or when a
•The bypass should be lead back to the supply tank – not to the suction port.
3.18.5.3Isolating valves
To allow proper maintenance it is necessary to be able to isolate the pump. Isolation can be done by installing valves in suction and discharge lines.
•These valves must have a cylindrical passage of the same diameter of the piping (full bore). (Gate or ball valves are preferable).
•When operating the pump, the valves must be opened completely. The output must never be regulated by means of closing valves in suction or discharge pipes. It must be regulated by changing shaft speed or by
Discharge
Suction
Piping
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