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Pump FAQs

Pump FAQs

A centrifugal pump is a pump with an impeller that rotates to increase the pressure of a fluid. They are often used in piping systems. It appeared as early as 1475.

Centrifugal pumps work by spinning water with propellers inside a housing or casing. During the spinning, pressure builds outwards. The pressure propels the water through the desired path.

It basically works by the conversion of the rotational kinetic energy, typically from an electric motor or turbine, to an increased static fluid pressure.

Centrifugal pump is typically used in plumbing to propel liquids in the pipes. The pump utilizes a spinning bit that raises the pipe pressure to move the liquid. Such pumps can be used in homes and buildings to increase the plumbing systems efficiency, as well as in outdoor pools, ponds and other decorative water features.

The centrifugal pump has to be filled with fluid before it can start to move fluid. It means filling the pump with liquid to get it to pump because the pump will not fill itself with liquid from being dry (it wont self-prime). They cannot suck fluid in by creating a vacuum in the pump chamber like some other types of pumps.

Centrifugal pumps are used for virtually all straight pumping applications of low viscosity fluids like water without complications, such as liquids containing hard solids. These pumps can be single stage, or they can be stages stacked in a series-flow arrangement to deliver high output pressures. Centrifugal pumps are simple in concept and construction and deliver the highest flow performance at moderate pressures. Centrifugal pumps are available in all machinable materialsincluding all metals, plastics, and ceramics.

A centrifugal pump takes up little floor space relative to say a plunger pump and weighs comparatively little so minimal structural reinforcement is required for the load bearing floor space. It has a low initial cost as well as low maintenance cost since all motion is rotary and there are no sensitive parts such as the valves in a plunger pump. No air vessels or alleviators are required. It can be keyed directly to a power source as it generally has high working speeds and hence needs no stepping. A centrifugal pump has the ability to handle muddy,dirty and corrosive liquids it can pump water at temperatures of up to 400 and circulate oil at high temperatures providing it reaches the pump at high pressure ie. a full pressure system. There is little if any vibration and the discharge of liquid is continuous and without shock and the flow can be controlled from full flow to no flow without shutting the pump down or damaging the pump or pipes providing suitable switching gear has been installed.

A centrifugal pump is not too complicated. It has a rotating impeller in a chamber and a motor to turn the impeller. Centrifugal pumps come in two forms horizontal pumps, with horizontal impeller shafts and vertical impellers, and vertical pumps, with an opposite orientation, like a sump pump. You can often notice problems with a centrifugal pump by the sound the pump makes or a change in the pumps rate of discharge or suction. There are five problems that are directly observable when the pump is in operation and three problems that can be ascertained from the pumps maintenance files.

You may mean a "close-coupled pump" in which case, that is a pump which is mounted directly on the same shaft as the driving motor: i.e. there is no base plate or coupling to join the two shafts, drive and driven, and the pump hangs off the motor frame. A centrifugal pump is a type of pump where the liquid is forced to travel by an impeller which is inside a close-fitting chamber or "volute" - it is probably the most common industrial and domestic pump type.

A centrifugal pump cannot pump air, therefore cannot self prime, like a positive displacement pump.

Ecognizing erosion and corrosion in a centrifugal pump can be done by one of three mediums depending upon the area affected. It can be done visually, by microscopic examination or with the use of inspection tools such as dyes and magnetic particles. Some of the most apparent signs of a problem include loss of pressure and efficiency, low fluid flow rate and an increase in operational costs. Any of these indicators warrant further investigation.

Cavitation is caused when vapour pressure in the fluid in higher equal to the surrounding pressure.In the case of centrifugal pump, when the hydraulic pressure (due to height) in the fluid falls below the vapour pressure of the fluid itself, cavitations will occur.

If you are pumping from a tank you have to lower the pump in relation to the height of the water in the tank. The more feet of water above the center of the pump, the greater your net positive suction head. If that is not possible you have to have a pump to increase the pressure of the water coming into the eye of the pump impeller.

We know that the ship's engine room contains several different types of pumps including centrifugal pumps. We have also seen how a planned maintenance schedule is carried out on board ships for the purpose of maintaining the equipment in perfect health. In this article we will take a look at the procedure to disassemble, inspect and reassemble a centrifugal pump. The following steps describe the entire process in  chronological order.

- Switch off the supply from the control room and isolate breaker with masking tape and place a safety board (Men at work).

- Switch off  the supply from the local panel and isolate by masking tape, place a safety board on the panel (Men at work).

- Close suction and discharge valves and lash them with rope.

- Drain the suction pipe and ensure water is not coming, then loosen or crack open the joints and ensure that the pump is safe for opening .

- Fix chain block and ensure its cable length and strength are satisfactory.

- Mark on coupling and casings and then remove the coupling bolts.