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In a hydraulic circuit, net positive suction head (NPSH) may refer to one of two quantities in the analysis of cavitation: The Available NPSH (NPSH A): a measure of how close the fluid at a given point is to flashing, and so to cavitation. Technically it is the absolute pressure head minus the vapour pressure of the liquid.
The fluid will cavitate in the suction of the pump if the Thoma number is smaller than the critical cavitation parameter or the critical Thoma number defined as = Where is the net positive suction head required to prevent cavitation. It is a parameter found experimentally for each pump model.
From an initial design point of view, engineers often use a quantity termed the specific speed to identify the most suitable pump type for a particular combination of flow rate and head. Net Positive Suction Head (NPSH) is crucial for pump performance. It has two key aspects: 1) NPSHr (Required): The Head required for the pump to operate ...
NPSH(R) – net-positive suction head (required) NPT – Non-Productive Time (used during drilling or well intervention operations mainly, malfunction of equipment or the lack of personnel competencies that result in loss of time, which is costly) NPV – net present value; NRB – not required back; NRPs – non-rotating protectors
Cavitation—the net positive suction head of the system is too low for the selected pump; Wear of the impeller—can be worsened by suspended solids or cavitation; Corrosion inside the pump caused by the fluid properties; Overheating due to low flow; Leakage along rotating shaft.
Discharge Head, is the net head obtained at the outlet of a pump. For a centrifugal pump, the discharge pressure depends on the suction or inlet pressure as well, along with the fluid’s density. Thus, for the same flow rate of the fluid, we may have different values of discharge pressure depending on the inlet pressure.
NPSH represents the head (pressure and gravity head) of liquid in the suction line of the pump that will overcome the friction along the suction line. NPSHR is the amount of liquid pressure required at the intake port of a pre-designed and manufactured pump. This is known as NPSHR (Net Positive Suction Head Required).
Additionally, careful design is required of the pumping system so it can pull in and deliver cleaning solution at temperatures that approach boiling in the parts washer. All centrifugal pumps require a net positive suction head (NPSHr) in order to be able to pump solution. As the temperature of the solution approaches the NPSHr, the pump stops ...