Pumps are divided into 2 major categories: Dynamic and Positive Displacement (aka Displacement).
The two most common types of pumps used for pumping water are centrifugal pumps and positive displacement pumps.
Best Water Pumps for Domestic Use in India:
- Havells Hi-Flow MX2 Series 0.5 HP Centrifugal Water Pump.
- Havells Hi-Flow MX2 Series 0.5 HP Centrifugal Water Pump.
- Kirloskar 40S Mini Water Pump.
- Crompton 0.5HP SP Aquagold 50 Water Pump.
- Kirloskar KOSi-135 5 Star HP Openwell Submersible Pump.
Although, positive displacement pumps are generally more efficient than centrifugal pumps, the benefit of higher efficiency tends to be offset by increased maintenance costs. Since, worldwide, centrifugal pumps account for the majority of electricity used by pumps, the focus of this chapter is on centrifugal pump.
Difference between Pump and Motor The main difference between motor and pump is that a motor is a device that converts electricity to mechanical energy which results in motion, whereas a pump is a device that is used to transfer a fluid from one place to another.
Pump operating point or duty point is the intersection of pump characteristic and piping system characteristic. The pump will always operate where the system and pump curves intersect. At that point, there is a balance between what the system demands and what the pump can deliver.
It is clear that PDP are used when we need high outlet pressure and dynamic pumps are used when we need high discharge. Based on this, and many other issues, there are specific applications where reciprocating pumps can be used.
NPSH stands for Net Positive Suction Head and is a measure of the pressure experienced by a fluid on the suction side of a centrifugal pump.
Centrifugal pumps differ from rotary pumps in that they rely on kinetic energy rather than mechanical means to move liquid. Liquid is forced out of the pump by the energy it obtains from the rotating impeller.
Rotary pumps are commonly used for pumping high viscosity liquids such as oil including in handling lube oil and fuel oil in engine rooms. They are typically classified based on the type of rotating element they utilise.
What are the main applications for centrifugal pumps?
| Type of centrifugal pump | Application |
|---|
| Chopper/grinder pump | Waste water in industrial, chemical and food processing/ sewage |
| Circulator pump | Heating, ventilation and air conditioning |
| Multistage pump | High pressure applications |
| Cryogenic pump | Liquid natural gas, coolants |
Defining Rotary TypesSome of the common examples are: internal gear, screw pump, flexible or sliding vane, flexible impeller, circumferential pump, helical twisted roots, etc.
Priming is not required when pump is submerged (Submersible or Vertical Sump Pumps). Priming is not required when the pump is at a lower elevation than the supply and this ensures that pump suction will be completely filled with liquid at all times (known as “Flooded Suction Condition”). Self Priming Pumps.
Rotary vane pump working principleWhen the rotor turns the centrifugal force throws the vanes against the cylindrical wall and creates a chamber between the rotor and the cylinder. As the rotor continues to turn the chamber volume between the blades keep changing due to the rotor positioned eccentrically.
An impeller or impellor is a rotor used to increase the pressure and flow of a fluid. It is the opposite of a turbine, which extracts energy from, and reduces the pressure of, a flowing fluid.
The reciprocating pump provides a nearly constant flow rate over a wider range of pressure; the centrifugal pump gives uniform pressure over a range of flow, then it drops dramatically as the flow rate increases. On a reciprocating pump, fluid viscosity has little effect on the flow rate as the pressure increases.
Reciprocating Pump is a Positive Displacement type pump that works on the principle of movement of the piston in forwarding and backward directions whereas the Centrifugal pump uses the kinetic energy of the impeller to supply the liquid from one place to another place.
The main components of reciprocating pump are as follows:
- Suction Pipe.
- Suction Valve.
- Delivery Pipe.
- Delivery Valve.
- Cylinder.
- Piston and Piston Rod.
- Crank and Connecting Rod.
- Strainer.
Advantages of Centrifugal pump over Displacement (Reciprocating) pump
- Because of fewer parts centrifugal pump have less cost than reciprocating pump.
- Also because of fewer parts installation and maintenance are easier and cheaper as compared to reciprocating pump.
Pump Start-up Procedure
- Line up the pump valves.
- Ensure that the drain valve is closed.
- Open the suction valve.
- Open the vent valve to bleed off gases – when liquid comes from the vent valve – close it again.
- Open the gland-seal valve (if fitted).
- Commission the bearing and oil cooling systems (if fitted).
Reciprocating primer:These are reciprocating pumps which develop higher pressure by the direct action of the plunger on the fluid (liquid or gas) confined in a cylinder and forcing the fluid out from the discharge.
The biggest advantage of centrifugal pumps is their aforementioned simplicity. They don't require any valves, or many moving parts. This makes them easy to produce with many different materials. It also allows them to move at high speeds with minimal maintenance.
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.
A pump jack (also called nodding donkey, pumping unit, beam pump, or jack pump) is the above-ground drive for a reciprocating piston pump that is used to help extract the oil from the well. This arrangement is commonly used for onshore wells, which typically UKOG will be developing.
A hollow chamber with a simple valve opens and fills each time the rod descends, then closes and lifts it up to the surface. Once at the surface, any water and natural gas obtained are separated from the crude oil, then pumped into holding tanks until it can be moved to the refinery.
Beam pumping, also referred to as sucker rod pumping provides mechanical energy to lift oil from bottom-hole to surface. This pumping method is highly efficient, simple, and easy for the oil and gas people to operate on the field.
Pump jacks are a uniquely designed scaffold consisting of a platform supported by moveable brackets on vertical poles. The brackets are designed to be raised and lowered in a manner similar to an automobile jack.
About Oil DerricksThe classic oil derrick pump is known colloquially as a sucker rod pump, named for the plunger-like mechanics it uses to pump oil from underground wells up to the surface. It uses a series of gears and cranks to pump a polished rod up and down an oil well in a piston-like motion, albeit much slower.
The nodding donkey has a steel hammerhead hovering over the well, bobbing up and down to create suction in the hole, aided by a rotating counterweight. The method is effective on vertical wells that go straight down, but is less so when used on horizontal ones.
Its operational process can average up to 20 strokesper minute, and each stroke can produce volumesbetween 1 and 10 gallons.
Its operational process can average up to 20 strokes per minute, and each stroke can produce volumes between 1 and 10 gallons.
