DESIGN, INSTALLATION AND FABRICATION OF RECIPROCATING PUMP PDF

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DESIGN, INSTALLATION AND FABRICATION OF RECIPROCATING PUMP Downloaded from www.binodpandey.wordpress.com Preface This report is a job undertaken by the students mentioned previously for the project work integrated in the syllabus of bachelor in industrial engineering, 4th year, and 1st part. The use...

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DESIGN, INSTALLATION AND FABRICATION OF RECIPROCATING PUMP Gajjar Krupesh

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DESIGN, INSTALLATION AND FABRICATION OF RECIPROCATING PUMP Downloaded from www.binodpandey.wordpress.com

Preface This report is a job undertaken by the students mentioned previously for the project work integrated in the syllabus of bachelor in industrial engineering, 4th year, and 1st part. The use of various machines & devices has been employed since ages to assist human for various purposes. Simple machines have been age-long friends to human with complex ones being continuously derived from them. Energy can neither be created nor be destroyed but can be transformed from one form to another. This is the law of conservation of energy. Bernoulli's theorem states Energy cannot be created or destroyed. The sum of three types of energy (heads) at any point in a system is the same in any other point in the system assuming no frictional losses or the performance of extra work. Taking this as the source of inspiration, new innovative ideas, processes & machineries have been developed. One of such instance is the Reciprocating pump. The core of this report is a simple machine, reciprocating pump. A reciprocating positive displacement pump is one in which a plunger or piston displaces a given volume of fluid for each stroke. Water is the basic need of life. Our existence is in doubt in absence of water. Scarcity of it means life full of hardships & obstacles. It is a pitiful condition faced by many people in rural hilly areas, especially in country like ours. Though we boast of being the richest country in water resources, but ironically water supply is the growing & burning problem in Nepal. Owing to this problem, a need of some simple, effective & affordable solution for water supply in such areas can be reciprocating pump. It is a simple mechanical device built on easily available resources and based on simple technology. Though it is quite inefficient in terms of volume of water pumped owing to various losses & wastes, it still has a good prospect of serving in regards to continuous water supply. Its affordability, ease of construction & operation make it suitable for our focus areas where factors like poverty & lack of resources to support & sustain technology would set back the use of otherwise highly sophisticated modern devices. Another plus point for this simple device is that it runs on the kinetic energy of the water flow and no other source is required. Thus once installed, it can be used to supply water continuously, apart from minimum of maintenance. Overall it seems to be a very important device I context of Nepal & if properly employed in various parts, it can prove itself as a boon for many water starved areas of Nepal.

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Objectives The overall objective of the project is to demonstrate a functional reciprocating pump in a village of Tanahun District by the Industrial Engineering students so that students can learn the manufacturing and installation of the technology and rural people can help to disseminate the technology. Specific objectives are: a) To identify the potential site for reciprocating pump installations b) To design reciprocating pump per site and manufacture the same c) To construct a demonstration/testing facility consisting reciprocating pump d) To install the reciprocating pump e) To test the performance of reciprocating pump Other Objectives are: a) To facilitate the local people by providing water for various purposes. b) To socialize the technology. c) To apply the theoretical knowledge into practical application. d) To optimize the resources.

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Background Reciprocating pumps utilize the principle of a moving piston, plunger, or diaphragm to draw liquid into a cavity through an inlet valve and push it out through a discharge valve. These pumps have overall efficiency ranges from 50% for the small capacity pumps to 90% for the larger capacity sizes. They can handle a wide range of liquids, including those with extremely high viscosities, high temperatures, and high slurry concentrations due to the pump’s basic operating principle, i.e., the pump adds energy to the liquid by direct application of force, rather than by acceleration. There are numerous classes and categories of pumps due to the wide variation of processes and the distinct requirements of each application. Figure 1 illustrates the classes, categories, and types of pumps utilized in the world today. If the liquid can be handled by any of the three types within the common coverage area, the most economical order of selection would be the following: 1. Centrifugal 2. Rotary 3. Reciprocating However, the liquid may not be suitable for all three major pump types. Other considerations that may negate the selection of certain pumps and limit, choice include the following: - Self priming - Air -handling capabilities - Abrasion resistance - control requirements - Variation in flow - Viscosity - Density - Corrosion

DESIGN, INSTALLATION AND FABRICATION OF RECIPROCATING PUMP Downloaded from www.binodpandey.wordpress.com

DESIGN, INSTALLATION AND FABRICATION OF RECIPROCATING PUMP Downloaded from www.binodpandey.wordpress.com

Introduction Reciprocating pumps are those which cause the fluid to move using one or more oscillating pistons, plungers or membranes (diaphragms). To 'Reciprocate' means 'To Move Backwards and Forwards'. A 'RECIPROCATING' pump therefore, is one with a forward and backward operating action. The simplest reciprocating pump is the 'Bicycle Pump', which everyone at some time or other will have used to re-inflate their bike tyres. Reciprocating-type pumps require a system of suction and discharge valves to ensure that the fluid moves in a positive direction. Pumps in this category range from having "simplex" one cylinder, to in some cases "quad" four cylinders or more. Most reciprocating-type pumps are "duplex" (two) or "triplex" (three) cylinder. Furthermore, they can be either "single acting" independent suction and discharge strokes or "double acting" suction and discharge in both directions. The pumps can be powered by air, steam or through a belt drive from an engine or motor. This type of pump was used extensively in the early days of steam propulsion (19th century) as boiler feed water pumps. Reciprocating pumps are now typically used for pumping highly viscous fluids including concrete and heavy oils, and special applications demanding low flow rates against high resistance.

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Working Principle Reciprocating pump is a positive displacement pump, which causes a fluid to move by trapping a fixed amount of it then displacing that trapped volume into the discharge pipe. The fluid enters a pumping chamber via an inlet valve and is pushed out via a outlet valve by the action of the piston or diaphragm. They are either single acting; independent suction and discharge strokes or double acting; suction and discharge in both directions. During the suction stroke the piston moves left thus creating vacuum in the Cylinder. This vacuum causes the suction valve to open and water enters the Cylinder. During the delivery stroke the piston moves towards right. This increasing pressure in the cylinder causes the suction valve to close and delivery to open and water is forced in the delivery pipe. The air vessel is used to get uniform discharge.

Reciprocating pumps are self priming and are suitable for very high heads at low flows. They deliver reliable discharge flows and is often used for meteringduties because of constancy of flow rate. The flow rate is changed only by adjusting the rpm of the driver. These pumps deliver a highly pulsed flow. If a smooth flow is required then the discharge flow system has to include additional features such as accumulators. An automatic relief valve set at a safe pressure is used on the discharge side of all positive displacement pumps. The performance of a pump is characterized by its net head h, which is defined as the change in Bernoulli head between the suction side and the delivery side of the pump. h is expressed in equivalent column height of water.

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Reciprocating Pump Performance The following data will outline the main terms involved in determining the performance of a reciprocating pump. MAIN TERMS a) Brake Horsepower (BHP) • Brake horsepower is the actual power required at the pump input shaft in order to achieve the desired pressure and flow. It is defined as the following formula: BHP=(Q ¥ Pd)/(1714 ¥ Em) 102 Pumps Reference Guidewhere: BHP = brake horsepower Q = delivered capacity, (gpm US) Pd = developed pressure, (psi) Em = mechanical efficiency, (% as a decimal) b) Capacity (Q) • The capacity is the total volume of liquid delivered per unit of time. This liquid includes entrained gases and solids at specified conditions. c) Pressure (Pd) • The pressure used to determine brake horsepower is the differential developed pressure. Because the suction pressure is usually small relative to the discharge pressure, discharge pressure is used in lieu of differential pressure. d) Mechanical Efficiency (Em) • The mechanical efficiency of a power pump at full load pressure and speed is 90 to 95% depending on the size, speed, and construction. e) Displacement (D) • Displacement (gpm) is the calculated capacity of the pump with no slip losses. For singleacting plunger or piston pumps, it is defined as the following: Where: D = displacement, (gpm US) A = cross-sectional area of plunger or piston, (in2) M = number of plungers or pistons n = speed of pump, (rpm) s = stroke of pump, (in.) (half the linear distance the plunger or piston moves linearly in one revolution) f) Slip(s) • Slip is the capacity loss as a fraction or percentage of the suction capacity. It consists of stuffing box loss BL plus valve loss VL. However, stuffing box loss is usually considered

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negligible.

g) Valve Loss (VL) • Valve loss is the flow of liquid going back through the valve while it is closing and/or seated. This is a 2% to 10% loss depending on the valve design or condition. h) Speed (n) • Design speed of a power pump is usually between 300 to 800 rpm depending on the capacity, size, and horsepower. To maintain good packing life, speed is limited to a plunger velocity of 140 to 150 ft/minute. Pump speed is also limited by valve life and allowable suction conditions. i) Pulsations • The pulsating characteristics of the output of a power pump are extremely important in pump application. The magnitude of the discharge pulsation is mostly affected by the number of plungers or pistons on the crankshaft. j) Net Positive Suction Head Required (NPSHR) • The NPSHR is the head of clean clear liquid required at the suction centerline to ensure proper pump suction operating conditions. For any given plunger size, rotating speed, pumping capacity, and pressure, there is a specific value of NPSHR. A change in one or more of these variables changes the NPSHR. • It is a good practice to have the NPSHA (available) 3 to 5 psi greater than the NPSHR. This will prevent release of vapor and entrained gases into the suction system, which will cause cavitations damage in the internal passages. k) Net Positive Suction Head Available (NPSHA) • The NPSHA is the static head plus the atmospheric head minus lift loss, frictional loss, vapor pressure, velocity head, and acceleration loss in feet available at the suction center-line.

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Installation, Operation, and Troubleshooting of Pumps • The subsequent data will provide useful to personnel involved in the application or maintenance of pumps. The information is categorized into the following headings: I. Alignment of Shafts II. Water Hammer III. Troubleshooting Pump Problems I. ALIGNMENT OF SHAFTS Misalignment of the pump and driver shaft can be angular (shaft axes concentric but not parallel), parallel (shaft axes parallel but not concentric), or a combination of both a. COUPLINGS • Couplings provide a mechanically flexible connection for two shaft ends that are in line. • Couplings also provide limited shaft end float (for mechanical movement or thermal expansion) and within specified limits, angular and parallel misalignment of shafts. Couplings are not intended to compensate for major angularor parallel misalignment. • The allowable misalignment will vary with the type of coupling, and reference should be made to the manufacturer’s specifications enclosed with the coupling. Any improvement in alignment over the coupling-manufacturer’s minimum specification will increase pump, coupling, and prime mover life by reducing bearing loads and wear. • Flexible couplings in common use today are chain, gear,steel grid, and flex member. b. Angular Misalignment • To check angular misalignment - insert a feeler gauge between the coupling halves to check the gap; - check the gap between coupling halves at the same location on the coupling as for the original gap check. • To correct angular misalignment, adjust the amount of shims under the driver and/or adjust driver location in the horizontal plane. c. Parallel Misalignment • To check parallel misalignment, the dial indicator method is used - with the dial indicator attached to the pump or driver shaft, rotate both shafts simultaneously, and record dial indicator readings through one complete revolution; - correct the parallel misalignment by adjusting shims under the driver. • On certain large units, limited end float couplings are used. II.

WATER HAMMER Water hammer is an increase in pressure due to rapid changes in the velocity of a liquid flowing through a pipeline. This dynamic pressure change is the result of the transformation of the kinetic energy of the moving mass of liquid into pressure energy. When the velocity is changed by closing a valve or by some other means, the magnitude of the pressure produced is frequently

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much greater than the static pressure on the line, and may cause rupture or damage to the pump, piping, or fittings. This applies both to horizontal and vertical pump installations. The velocity of the pressure wave depends upon the ratio of the wall thickness to the inside pipe diameter, on the modulus of elasticity of the pipe material, and on the modulus of elasticity of the liquid. The head due to water hammer in excess of normal static head is a function of the destroyed velocity, the time of closure, and the velocity of pressure wave along the pipe. Water hammer may be controlled by regulating valve closure time, relief valves, surge chambers, and other means. III.

Troubleshooting Pump Problems i. Pump Fails to Deliver Required Capacity - speed incorrect, belts slipping - air leaking into pump - liquid cylinder valves, seats, piston packing, liner, rods or plungers worn - insufficient NPSHA - pump not filling - makeup in suction tank less than displacement of pump - capacity of booster pump less than displacement of power pump - vortex in supply tank - one or more cylinders not pumping - suction lift too great - broken valve springs - stuck foot valve - pump valve stuck open - clogged suction strainer - relief, bypass, pressure valves leaking - internal bypass in liquid cylinder ii. Suction and/or Discharge Piping Vibrates or Pounds - piping too small and/or too long - worn valves or seats - piping inadequately supported iii. Pump Vibrates or Pounds - gas in liquid - pump not filling - one or more cylinders not pumping - excessive pump speed - worn valves or seats - broken valve springs - loose piston or rod - unloader pump not in synchronism - loose or worn bearings - worn crossheads or guides

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- loose crosshead pin or crank pin; loose pull or side rods or connecting rod cap bolts - pump running backwards - water in power end crankcase - worn or noisy gear iv. Consistent Knock - worn or loose main bearing, crank pin bearing, wrist pin bushing, plunger, valve seat, low oil level - Note: High speed power pumps are not quiet. Checkonly when the sound is erratic. v. Packing Failure (Excessive) - improper installation - improper or inadequate lubrication - packing too tight - improper packing selection - scored plungers or rods - plunger or rod misalignment vi. Wear of Liquid End Parts - abrasive or corrosive action of the liquid - incorrect material vii. Liquid End Cylinder Failure - air entering suction system - incorrect material - flaws in casting or forging viii. Wear of Power End Parts (Excessive) - poor lubrication - overloading - liquid in power end ix. Excessive Heat in Power End (Above 180˚C) - pump operating backwards - insufficient oil in power end - excessive oil in power end - incorrect oil viscosity - overloading - tight main bearings - driver misaligned - belts too tight - discharge valve of a cylinder(s) stuck open - insufficient cooling - pump speed too low

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Methodology 1. Site visit and Selection: The site for the installation of safe drinking water system was selected in the village Daraingaun of Tanahun district. 2. Site Survey: The survey of site was done by measuring the head and flow rate and by interviewing the local people. 3.

Literature collection from various institutions and internet sites.

4. Design: The system design will be done by using various research paper and manuals 5.

Correction and suggestions from experts and supervisor.

DESIGN, INSTALLATION AND FABRICATION OF RECIPROCATING PUMP Downloaded from www.binodpandey.wordpress.com

Design and Cost Calculation

DESIGN, INSTALLATION AND FABRICATION OF RECIPROCATING PUMP Downloaded from www.binodpandey.wordpress.com

Design of components: SN

Components

Type

Specification

1

Turbine blades

Cast iron

12inch*6inch

Suction pipe

Garden pipe

1inch

3

Delivery tube

Garden pipe

0.5inch

4

Connecting rod

GI pipe

1inch of 6m length

5

Crank

GI pipe

0.5 inch of 6m length

6

Bearings

Cast iron

1 inch

7

Cylinder

Cast iron

8

Piston(washer)

Rubber

3.5 inch (diameter) 20 inch (length) 3.68inch(diameter)

9

Check valve) Check valve) Stand

2

10 11

valve(Suction Brass valve(Delivery Brass Cast iron

1 inch 0.5 inch 2.5inch (16 sq.feet)

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Calculation We assume, ...