What happens when too little flow is allowed through a pump?

Pump Surging If a pump does not have adequate flow, it can build up discharge pressure. When this pressure reaches a certain level, the pump cannot overcome it and the fluid starts to reverse flow. The reverse momentum causes the pump speed to slow down and the impeller slips backward, building pressure again.

What are the implications of the minimum flow required by a pump?

Operating pumps at below minimum flow can result in the following consequences: Pitted/worn impeller vanes. Overheated casing/bearings. Excessive noise or vibration.

What will happen when pressure at any point inside a centrifugal pump goes below the vapor pressure corresponding to the temperature of the liquid?

Consider the first limitation: high flow. The centrifugal pump stops pumping when liquid turns to vapor. This happens when the pressure somewhere inside the pump drops below liquid vapor pressure. It will boil at room temperature, if the absolute pressure is less than approximately 0.4 psia.

What is minimum safe flow of pump?

MCSF is an acronym that stands for Minimum Continuous Stable Flow. It is the minimum flow that must be maintained through a pump to avoid excessive recirculation at the impeller inlet. When a pump is operating at BEP flow through the impeller is very stable and uniform.

Can low flow damage a pump?

When a pump is run at a very low flow rate, the majority of the power input is converted to thermal energy, causing a rapid temperature rise. If the temperature rise continues, the liquid within the pump can vaporize and cause thermal expansion of the internal parts.

What is low flow cavitation?

In the case of suction cavitation, low-pressure or high-vacuum conditions “starve” the pump of incoming liquid, resulting in low flow. Discharge cavitation happens when a pump’s discharge pressure is inordinately high — In other words, the pump is running at less than 10 percent of its best efficiency point (BEP).

What happens if pressure drops below vapor pressure?

If the pressure is below the vapor pressure, it will flash to vapor—not because of a temperature change, but because of a pressure change.

What happens when pressure falls below vapor pressure?

Suction pressure falling below vapor pressure causes bubble formation [3]. Cavitation in pumps is known as the formation of vapor bubbles due to pressure drop and collapsing these bubbles. In some conditions, it has been observed that the formation of bubbles occurs at the pressure side of centrifugal pump blades.

How do you calculate minimum pump flow?

If you need to operate a centrifugal pump back on the curve, the minimum suggested point is at 10\% of BEP (Best Efficiency Point). For example, a 620 pump with a full impeller has a BEP of 44\% at 24 GPM. Therefore, the minimum flow should be limited to 10\% of 24 or 2.4 GPM.