Table of Contents
What happens when you dead head a positive displacement pump?
When a centrifugal pump is dead-heading, it can lead to explosions, due to the energy being put into the liquid in the pump. Hydraulic overpressure and possible chemical reactions in the pump can also be caused by the overexertion of pressure.
What happens when we close the valve in a discharge line while the pump is still working?
If the discharge valve is closed and there is no other flow path available to the pump, the impeller will churn the same volume of water as it rotates in the pump casing. If the pump is run in this condition for a significant amount of time, it will become damaged.
What happens if air is present in suction side?
The presence of an air pocket in the suction line is another example of a cause for pump troubles, which should never happen. Any high point in the suction line can become filled with air and interfere with proper operation of the pump.
What does it mean to dead head a pump?
A blockage on the discharge side of an operating pump which results in the flow reducing to zero and an increase in the discharge pressure. The energy input from the deadheaded pump increases the temperature and pressure of the fluid in the pump.
Why start a centrifugal pump with discharge valve closed?
A closed discharge valve at startup or shutdown also prevents backflow from any static discharge head. Pumps that require less shut-off power and torque than at normal flow conditions are usually started against a closed discharge valve.
Why positive displacement pump is called positive?
A positive displacement pump provides a constant flow at fixed speed, regardless of changes in pressure. The pump makes the fluid move by trapping a fixed amount and forcing the volume into the discharge pipe. Examples of positive displacement pumps are: diaphragm pumps.
What is meant by positive displacement pump?
A Positive Displacement pump (PD pump) is a mechanical device which displaces a known quantity of liquid for every revolution or cycle that the pump completes. The flow rate through a positive displacement pump is directly proportional to its speed and number of cycles over a given time.
Can a positive displacement pump operate against a closed valve?
A Positive Displacement Pump must never operate against closed valves on the discharge side of the pump – it has no shut-off head like Centrifugal Pumps.
What causes the potential energy of a positive displacement pump?
That is, the liquid is compressed mechanically, causing a direct rise in potential energy. Most positive displacement pumps are reciprocating pumps in which linear motion of a piston or plunger in a cylinder causes the displacement.
Where to measure the Rotary positive displacement of the pump?
Rotary Locations of measurement points for rotary positive-displacement pumps should be based on the same logic as in-line centrifugal pumps. The primary (X-axis) radial measurement should be taken in the plane opposite the discharge port. The secondary (Y-axis) radial should be at 90° to the primary and in the direction of the rotor’s rotation.
What happens if you turn off the discharge valve on a pump?
Shutting a discharge valve off on a pump causes the fluid remaining in the pump to get very hot and damages the housing, bushings, seals, etc. Hence, the focus of this article will be about proper pump installations in regards to pump suction conditions.
https://www.youtube.com/watch?v=gC-Oba1vXLA