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The Reciprocating Pump Engineering Essay

A pump is a mechanised device which really helps to move liquids including fluids or gases. It is fundamentally a hydraulic machine which turns the mechanical energy to the hydraulic energy. The hydraulic energy is been within form of the pressure energy. There are many types of pumps such as positive displacement pumps, velocity pumps, Buoyancy pumps, Impulse pumps. The many different pumps are also been sub-classified in various other pumps. Positive Displacement pumps are one of the most frequently used pumps. They are sub-divided in to Reciprocating and Rotary pumps. Typical types of the Reciprocating pumps are Plunger pumps and Diaphragm Pumps. The "Plunger pump" is also called Piston Pumps. The Reciprocating Pumps are highly reliable pumps that happen to be even suited to the high heads at low flows. It really is a home priming kind of pump as it can draw the smooth from the level below the suction flange if the suction pipe is not evacuated. There should be a smooth stream required for achieving a good efficiency (Chinnuraj, 2009).

The complete system is dependant on the design of the pump. The head of cylinder is been installed with suction and discharge valves. The substance gets into the pump through the suction valve and is out threw the release valve. In suction stroke, suction valve opens when the plunger retracts. The liquid gets pushes out of the release valve in the front stroke. Reciprocating system has a pulsating discharge and it totally rely upon the acceleration of the pump which may be easily altered. The consumption of the smooth in the pump is always at a frequent volume. They are often used for slurry and sludge. There are many different designs from remaining pumps. The look containing single-acting motion discharges fluid from only 1 area of the piston. There is only one suction and release per revolution of the crank shaft. The other design is the double-acting piston design where the suction and the discharge occurs on the either aspect of the piston resulting in dual suction and double discharge per revolution of crack shaft.

Classification of PD Pump

Positive Displacement pump are been categorised as follows:

Positive Displacement Pump

Rotary Pump

Single Rotor

-Vane -Piston -Flexible -Member Screw

-Simplex -Duplex -Triplex -Multiplex

-Simplex -Duplex

Double Acting

Single Acting

Diaphragm

Piston Plunger

Reciprocating Pump

Simplex Multiplex

Multi Rotor

-Gear Lobe Circumferential Piston -Screw

(Gates, 2010)

Working Rule of Reciprocating Pump

The working process of the Reciprocating pump is very simple; it performs on the principle that a level of water would be displaced by solid equal to its volume. The mechanical energy is been converted into the pressure energy and takes place because of the suction of the liquid in to the cylinder where the piston is having a reciprocating movement (linear motion-threw and fore). This exerts the thrust on the liquid and hydraulic energy gets increased eventually. In single acting reciprocating pumps, a single piston moves forwards and backward in a closed down limited cylinder. The linear action of the piston in the cylinder is been distributed by joining piston to the crank with the help of a connecting pole. An electric electric motor is been used to provide motion to the crank and the rotary motion is been changed into the linear movement by the help of the attaching rod. The working basic principle is somewhat like the car engine's where the piston gets the same movements threw some similar kind of motions. In Reciprocating Pump, the suction valve allows the smooth to enter while the release valve tends to discharge it from the cylinder (Chinnuraj, 2009).

http://www. lcresources. com/resources/getstart/pump. gif

Fig 01: Working Principle of Reciprocating Pump (Getting Started in HPLC, 2001)

Types of Reciprocating Pumps

The Reciprocating Pumps are usually categorised the following:

Direct or Indirect acting

Simplex (solo) or duplex (two times)

Single acting or two times acting

High pressure or low pressure

The direct acting pumps are one of the most frequent kind of pump been used. It is been known in order in the particular design the pump fishing rod is a primary expansion of the piston rod in which the lower end is been immediately linked to the piston in the cylinder. Solo and Increase action pumps is as mentioned earlier. One action has a single suction and a single discharge per revolution and Increase action pump has two suctions and discharges per revolution.

Applications

Reciprocating Pumps have a very large contribution to the population with lots of uses. These are been used for no. of small and large applications including irrigation, chemical type movement, sewage activity, flood control and sea applications and even a lot more. Planning factors like size and kind of pump will depend on the utilization.

They are been used in various purposes such as:

High pressure jets: The goal of pumps used is producing a direct high jet pressure of the liquid. The inlet stream reaches a constant stream and pressure but the discharge at a high velocity and therefore results to high amount of pressure.

Chemical Injection: The Reciprocating Pumps are even used in the substance industry where they have to inject the substance in a certain movement or pressure. It is been used at high precise and accuracy

Irrigation: The pump is usually found in farms and gardens to spread water throughout similarly and automatically without the type of manual work.

Sewage movement: The pump are been used to go the slurry or sewage material in a very easy and automated way. The primary advantage is enough time constraint. It takes very less time as well as it's very cheap in comparison to other techniques.

Marine software: The vast amount of consumption has been the sea sector where they have to use water activity from one part to other via a pump. The pump is very easy and compact source of product which can be installed quickly and with no maintenance in future. In marine field pump is utilized for:

Lubricating petrol transfer

Fuel oil transfer

Auxiliary circulating and condensate.

Domestic uses: Reciprocating pump is even used as local purposes. In olden days it was very common to use a hand pump which was a kind of reciprocating pump with help which we can move the underground normal water for various purposes such as home consumption, irrigation, construction, small size industry and many more.

Discharge and Pressure Characteristics

The working basic principle and the attribute is been keenly seen earlier. It is been very easy to analyse the release and pressure constraints of reciprocating pumps. The discharge of the reciprocating pump is not standard and stable. The discharge characteristic depends on:

Head circulation of fluid

Fluid density

Speed of reciprocating piston

Pump size and design

The discharge is totally non-uniform and throttling. The pulsating property of the discharge fluid sometimes appears. This is because the piston steps at a high velocity striking the substance out wards and the striking of the piston is not a continuous action which can provide a uniform pressure shop. Despite of vital use, the reciprocating pump still encounter pulsating pressure which is been seen at the suction and discharge lines. This pulsating feature is consequence of the connection between unstable circulation of fluid and the vibrant characteristics of the liquid debris. Pressure pulsating in the suction brand can result in the cavitation, either in the brand itself or in the cylinder chamber. If cavitation is been experienced in the beginning of the piston stroke than the piston launching and the crank assembly can fail. Because of all of this factors it reduces the life of the pump and also influences the safe practices conditions (K A Border, 1997)

Pump Performance and Efficiency

The brain of flow against which the pump works is called total mind, H. The total head of the pump is the imparted to the water by the pump.

H = hd - hg

Therefore, the effective mind of an pump is indicated by the next equation:

H = -. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Equation 1 (Sorensen, 1969)

This design concept of the pump work similarly as that of the turbines. The vitality of supplied to the pump by the rotating shaft to go the piston inside the cylinder, in conditions of bhp:

Energy, e = =

The capacity of the pump is proportional to its displacement per product time, D. Presuming 100% of the hydraulic efficiency of the pump, the displacement of the pump is calculated. The displacement is the determined capacity of pump which is proportional to:

Cross-sectional part of piston, A

Length of the heart stroke, S

No. of cylinders, n

Pump quickness in rpm (gallons each and every minute)

D = (A - S - n - rpm) / 231

In case of double performing pumps, the cross sectional area is double to be taken in to account that the mix sectional area of piston rod (a) is subtracted.

In double acting pumps, D = ((2A - a) - S - n - rpm) / 231

The volumetric efficiency of the pump is expresses in terms of percentage. It is directly proportional to the proportion of the total discharge volume to piston displacement.

The percentage (r) is add up to (c + d)/d where:

D = quantity displaced by piston

C = Additional size between the discharge and suction valves.

So it is obviously seen that smaller the ratio, the volumetric efficiency is tend to be better. Mathematically it is portrayed as:

VE = 1 - (P - b - r ) - S

Where P is pressure

B is the liquid compressibility factor

R is level ratio

S is the slide. (Joe Evans, 2004)

Losses in Reciprocating Pump

There are various loss that happen to be been experienced in the pump such as:

Frictional losses

Head losses

Heat copy losses

The various losses occur because of the friction and the movement of the liquid. It will depend on the head stream of fluid, thickness of the liquid, piston velocity and the fluid suction capacity as well as discharge. There are lots of constraints been involved here, but it simply can be minimised but not 100% avoided.

Advantages

Easy in working

Inexpensive

Compact and Easy to install

Low maintenance

Works at high speed and at low power

Disadvantages

The major downside of the reciprocating pump is the fact it has a discontinuous discharge move which with changing pressure and therefore it adversely impacts the probable of the pump use. There are many techniques been used to minimise the pulsating feature but it still tend to create problems. There are a few complex ways used to minimise it by using detectors or throttle valves which keeps the release pressure even, but it can affect the overall circulation and creates a kind of friction to the entire release pressure.

Secondly, it has a disadvantage that it's prone to stream separation at the cheapest pressure point in the system. The design of the system is such that this problem would be there and cannot be solved. The various different tries and practical tests to minimise it could not work till the look is not thoroughly changed. Regardless of all this negatives it continues to be an extremely useful product and trusted.

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