Dos and Don’ts of Centrifugal Pumps

Centrifugal pump also known as the hydrodynamic pump which works on the principle of centrifugal force. These types of pumps are used at refinery off-sites, food industries, power stations, textile industries, rubber industries, and other process industries. Centrifugal pumps rely on kinetic energy rather than rotary pumps that use mechanical means to move liquid. Centrifugal pumps use kinetic energy to process.

Nov blog

Below-mentioned are some of the dos and don’ts while using centrifugal pumps for pressure testing. These will help you design and troubleshoot pump systems.

Dos and Don’ts:

Use Pressure Gauges:

While using centrifugal pumps, make sure your pump has a pressure gauge on the discharge side. It will help you diagnose pump system problems. Having a pressure gauge on the suction side also helps in signalling various problems.

Never run a pump at zero flow:

Do not let a centrifugal pump run at zero flow for a longer period of time. The pressure switch in the residential systems shuts the pump down when the pressure is high which means there is no flow. So, do not let the pump run at zero flow.

Problems of water hammer:

Be aware of the water hammer problems. This problem occurs particularly in large piping systems such as municipality water supply distribution systems. These systems have long gradually upwards and downward sloping pipes. The solution to this problem would be the pressure/vacuum reducing valves at the high and low points.

The pressure at a high point:

You need to calculate the level of pressure of the high point in your system. The pressure may be low enough for the fluid to create a vapor pocket which will decide the performance of the system. The pressure can be increased by installing a valve at some point past the high point. You can adjust the pressure at the high point by closing the valve.

Pump selection:

Based on the total head and flow rate, you should select your pump. The flow rate will depend on your requirements. The selection of the pump starts with acquiring detail knowledge of the system. If you are replacing the existing pump then, of course, there is no problem. But if you are replacing an existing pump with problems and looking for a pump for the new application then you need to know how the system works.

You should avoid pumping in reverse direction:

You should avoid running a pump in a different direction as it might prob=vide damage to the pump. If the pump is started while running backward then it will provide damage to the pump shafts. The simplest solution is to install a check valve on the discharge line to avoid such problems.

Avoid high points and pockets:

You should avoid pockets or high points where air can accumulate in the discharge piping. An ideal pipe run is when the piping slopes up from the pump to the outlet. This ensures that any air on the discharge side to be evacuated to the outlet.

Centrifugal pumps are an essential device for testing as compared to many pumps. The main mechanism of the centrifugal pump is to convert the centrifugal force to kinetic energy. So, while using this essential pump remember the above-mentioned dos and don’ts.

Five Important Variables for The Selection of Centrifugal Pump

Centrifugal pumps are one of the most widely used rotatory machines in the industry. Selection of the correct centrifugal pump for your required application is an important task. Often, customers are confused when it comes to selecting a right centrifugal pump.

Centrifugal Pump

Do you know the key criteria to consider while choosing a centrifugal pump? No! Find them below.

The top five factors to consider while choosing a right centrifugal pump:

1. Materials of Construction (MOC)

Since your pump is going to be in direct contact with the fluid, the construction material should be chosen accordingly. Otherwise, the fluid would harm and corrode the parts. And, soon your pump would be junk.

2. Flow rate

You should have clear data of flow rate (volume per unit time) needed. Once you know the flow rate, you can choose the right pump size depending on the viscosity of fluid. Other factors that affect flow rate are a static lift, friction losses and differential pressure in the line.

3. Net Positive Suction Head (NPSH)

NPSH is the difference between the fluid pressure at pump suction and fluid vapour pressure. It is denoted in terms of height of the liquid column. NPSHr, the required NPSH of a pump is specified by the manufacturer, while you have to calculate the available NPSHa. As a rule of thumb, the required NPSHr of a pump should always be lower than the available NPSHa of the system. Else, there would be an issue of cavitation.

4. fluid Properties And External Environment

External environment decides the metallurgy of your pump? Are you going to employ pump in minus temperature condition? Or is it going to be used in too hot surrounding? You would require cryogenic metallurgy for a low-temperature condition. Similarly, for hazardous condition ‘fire safe tested’ pumps are required.

Just as the external condition is important, the complete specifications of the fluid in line should be clear to you.

5. Important features of fluid to consider are:

  • Viscosity
  • Temperature
  • Density
  • Vapour pressure
  • Nature of fluid: Whether Abrasive or Non-abrasive? Or whether it is acidic, basic or neutral?

With all these points in mind, you can select right centrifugal pumps for any application without any confusions.