What happens when the discharge valve is closed on a centrifugal pump?

What happens when the discharge valve is closed on a centrifugal pump?

If the discharge valve is closed and the pump has no alternative flow channel, the impeller will churn the same volume of water as it revolves in the pump casing. This raises the temperature of the liquid in the pump casing (due to friction) to the point where it flashes to vapor. This is called "steam popping" and should be avoided.

The heat generated by this process can be quite high. If the steam pops, then the pump needs cooling. Otherwise, it will fail prematurely due to overheating.

What happens if the discharge valve of a reciprocating pump is closed?

Closing the discharge valve raises the pressure but has no effect on the flow. Reciprocating pumps are substantially slower than centrifugal pumps. The packing and sealing life of the machine might be jeopardized by raising the pace. However, closing the discharge valve can have two beneficial effects: first, it will reduce the noise produced by the pump; second, it will reduce the power consumption of the pump.

Why is it necessary for any displacement pump to be fitted with a relief valve on the discharge side?

As the cavity on the suction side expands, liquid flows into the pump, and liquid flows out of the discharge as the cavity contracts. Given each cycle of operation, the volume remains constant. As a result, a relief or safety valve on the pump's discharge side is absolutely essential. The purpose of the valve is two-fold: first, it prevents damage to the pump by preventing its casing from being overpressured; second, it prevents destruction of surrounding structure such as house walls by preventing the pump from sucking in too much water.

The type of relief valve required depends on how much pressure the pump will be expected to withstand. If the pump is intended to lift water from a well, then an automatic well pump shutoff (AWPS) valve is needed. These valves are designed to close automatically when the cavity gets low enough to prevent damage to the pump. They do this by using air pressure inside the valve to open the discharge port, which allows water to drain back down the well.

If the pump is intended to lift water from a tank, then a float-operated valve is required. These valves operate based on fluid level. When water reaches a certain height, the valve opens automatically. They differ from AWPS valves in that they don't use air but rather float sensors to open the discharge port.

If the pump is intended to lift water from a river or other body of water, then a gate valve is required.

Why is the centrifugal pump called a high-discharge pump?

A centrifugal pump is an example of a kinetic device. As a result, the revolving impeller imparts kinetic energy to the liquid entering the pump. The impeller's centrifugal force accelerates the liquid at high speeds, imparting mechanical (rotational) energy to the liquid. As a result, the liquid is discharged at a rapid rate. Because the speed of the impeller is so high, the pump is also referred to as a high-speed pump.

The discharge from a centrifugal pump can be as high as 90% of its capacity. This is much higher than the typical 50% efficiency of other pumps and allows the centrifugal pump to operate more efficiently. In addition, the high speed of the impeller causes less friction between the fluid and the pump housing, which further increases the pump's efficiency.

Because of these advantages, centrifugal pumps are used in many applications where it is necessary to transfer large amounts of fluid at a fast rate, such as in industrial water supplies, boiler feeders, and air compressors. Centrifugal pumps are also used in recreational vehicles to provide fresh water for drinking and vehicle cooling.

Some disadvantages of centrifugal pumps are that they require lubrication parts that affect maintenance cost, they cannot pump abrasive fluids, and they cannot handle fluids at very low temperatures.

Other types of pumps are available for different applications.

What is pump churning?

Churning happens in centrifugal pumps when the pump's outlet (discharge) is blocked, forcing the impeller to merely churn or "mix" the same water within the pump body. As a result, the internal temperature of the pump begins to rise, potentially leading to the pump's catastrophic failure. Modern centrifugal pumps are designed to avoid this problem by using valves known as "choke tubes" that open during pumping operations to allow water to escape from inside the pump casing back into the source pool. This prevents excessive heating of the fluid being pumped.

In older centrifugal pumps, there was no way to prevent the discharge from blocking. In these cases, it was necessary to have someone regularly check the pump for signs of blockage, such as an increased noise level or lack of movement of the handle when turning it on and off. If the blockage is not cleared, the pump will continue to heat up until it fails.

The use of choke tubes in modern centrifugal pumps reduces the risk of pump churning significantly because the operator is able to shut off the supply of water to any one zone of a multi-zone installation via its own control valve. If a malfunction does occur, it will usually be detected by a reduction in water pressure before the pump reaches an unsafe operating temperature. The operator can then turn off the power source (electricity, gas, etc.) to the pump or move it away from the main line if it is an installed system component.

About Article Author

Mary Miranda

Mary Miranda loves to find old treasures and turn them into something new and useful. She has an eye for detail, which helps her see the beauty in even the most worn-out pieces of furniture ornaments


GrowTown.org is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.

Related posts