Knowing more about the discharge head of a centrifugal pump

  26/08/2015

Knowing more about the discharge head of a centrifugal pump

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For any centrifugal pump, head is one of the key things and has close relationship with the pressure. Ok before you go any further, it is better that you have an idea about the head. Let’s put it simply, it means the height at which the pump is capable of taking the water in an upward direction. It is important that you are aware of the discharge head for the following reasons –

  • To make sure that the pump is packed with enough capacity.
  • In order to make an approximation of the stuffing box pressure where the discharge valve has got shut down along with the functioning of the pump.
  • For finding whether the pump is functioning at its BEP (best efficiency point). As and when the pump functions out of BEP, the shaft tends to deviate towards the radial side loading which give rise to various problems with bearings, couplings, mechanicals seals and packing.
  • In order to avoid cavitation issues if the head is considerably low.
  • It should be done in order to choose a right sized pump for new application.

If you really want to an insight about the head, make sure that you have grasped the following mentioned points –

  • Make a right calculation of the suction and discharge heads from losses in the piping. Make sure that you checked other associated hardware as well.
  • Discharge pressure gauge or the chart recorded that is installed towards the pump’s discharge end should be closely checked.

Well, it is easier said than done, there are still varied issues that can pose problems while deciding accurate head. The main reason behind is the chances in the discharge system. Following paragraphs will discuss how the designing and operation can end up influencing the discharge system.

Designing Issues -

  • There is a continuous change in the speed of the pump’s motor.
  • A mechanical seal has been installed, which has increased the speed of the motor. Hence, this has led to the variation in BEP (best efficiency point).
  • The smaller pump’s discharge check valve is closing by a bigger pump.
  • A pump of wrong size has been installed. This, most of the times, take place in new applications.
  • Check whether two or more pumps are running parallel.

Operational Issues -

  • There is a variation in the temperature of the product.
  • There has been a variation in the product’s viscosity.
  • A different product has been introduced via the piping. When we talk about pipeline applications, this is one of the common issues that comes across.
  • In order to save amperage, the discharge valve has been shut down.
  • The particular gravity of the product has undergone a change, thus it has bring up variation in the rpm of the motor.

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