PUMPS

PRESENTED BY :

Rizwan Ali 2014-UET-KIT-Mech-11

Fahad Rafiq2014-UET-KIT-Mech-21

D.R AQ Khan Instetute Mianwali

Subject Code : 351

Name Of Subject : Fluid Flow Process

Name of Unit : Pumps

Topic : Reciprocating pumps

Defination

• Water pumps are devices designed to convert mechanical energy to hydraulic energy.

• They are used to move water from lower points to higher points with a required discharge and pressure head.

• This chapter will deal with the basic hydraulic concepts of water pumps.

Pump ClassificationPumps

Positive Displacement Dynamic

Rotary Reciprocating Centrifugal Axial

Singlerotor

Multiplerotor Diaphragm Piston, Plunger

Pump Classification

• Turbo-hydraulic (kinetic) pumpsCentrifugal pumps (radial-flow pumps)Propeller pumps (axial-flow pumps)Jet pumps (mixed-flow pumps)• Positive-displacement pumps Screw pumpsReciprocating pumps

Positive Displacement PumpPositive Displacement pumps apply pressure directly to the

liquid by a reciprocating piston, or by rotating members.Uses: 1.can handle shear sensitive liquid.2.Use for high pressure application.3.Use for variable viscosity applications.Types:Reciprocating pumpRotary pump

Positive Displacement Characteristic

Actual Theoretical

Flow Q m3/h

Total HeadH m

Reciprocating Pumps

• 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.

Working Of Reciprocating pumps.• In the reciprocating pump a piston sucks the

fluid into a cylinder then pushes it up causing the water to rise.

vlc-record-2016-12-01-18h20m35s-Reciprocating pump working animation HD.mp4-.mp4

Type & Construction features of reciprocating Pump:--

1. Position - Vertical - Horizontal 2. Purpose - Metering Pump - Power Pump 3. Piston or Plunger acting : Single acting, Double

acting 4. Number of Plunger in One Casing : Single, Duplex,

Triplex, Multiplex 5. Liquid End Type : Direct exposed, Diaphragm 6. Plunger direction : Forward, Backward. Reduction

Reciprocating PumpIn Reciprocating pumps, the chamber is a stationary cylinder that contains a

piston or plunger.Types: Piston Pump Plunger Pump Diaphragm Pump Single acting Double acting Simple hand operated Power operated Single acting Double acting

Piston PumpUSE=1.transmission of fluids or gases under pressure.

2.Power consumption is low.

3.Ensure maximum safety.

Piston Pump (double acting)

B C

A

D

Plunger pump

1.Have high efficiency.

2.Capable of developing very high pressures.

3.Low and easy maintenance

Plunger pump (single acting)

Diaphragm Pump1.flexible diaphragm is used(rubber, thermo-plastic, metal).

2. Can be used to make artificial hearts.

3. Can handle highly viscous liquids.

4.Can handle toxic or corrosive liquids.

5. 97% efficient.

Diaphragm Pump (single acting)

Rotary PumpIn Rotary pumps, the chamber moves from inlet to discharge

and back to the inlet. A wide variety of rotary pumps are available like

gear pumps, lobe pumps, screw pumps, cam pumps, vane pumps.

Most popular: gear pumps Relatively constant output

Types-Single RotorMultiple Rotor

Gear Pump

Drive Gear

Inlet Cam

Driven Gear

Delivery

Screw Pump

Elastomer Stator Universal Coupling

Single Screw Rotor

Lobe Pump

• Single acting reciprocating pump In the single acting reciprocating pump, a piston moves inside a cylinder with the help of a piston rod operated by a wheel through a connecting rod. There is one suction pipe and one delivery pipe in the cylinder. When the piston moves outwards, a vacuum is created, the suction valve opens, and the delivery pipe is closed. The water enters through the delivery pipe. When the piston moves downwards, it forces the water in one cylinder outward through the delivery pipe. Water is accordingly lifted up and delivered for use. Flow is not continuous.

• Double acting reciprocating pump • In the double acting reciprocating pump, two

suction and two delivery valves are provided in the same cylinder enabling continuous flow.

Components of Reciprocating Pump:--

• Main components of reciprocating pump : - • 1.Reduction gear - Coupling - Casing and

crankcase – • 2.Crankshaft - Connecting Rod – 3.Spacer rod

- Plunger – • 4.Packing - Check valves – • 5.Bearings for crankshaft and connecting rod

Main component of 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 single-acting 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 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.

General advantages of reciprocating pumps are:

•Ability to pump water that contains sand

•Adaptable to low-capacity water supplies where high lifts are required above the pump.

•Can operate with a variety of head pressures

•Can be installed in very small diameter wells

Head: The term head is used to measure the kinetic energy created by the pump.

.Different Types of Pump Head• Total Static Head - Total head when the pump is not running • Total Dynamic Head (Total System Head) - Total head when

the pump is running • Static Suction Head - Head on the suction side, with pump

off, if the head is higher than the pump impeller • Static Suction Lift - Head on the suction side, with pump off,

if the head is lower than the pump impeller • Static Discharge Head - Head on discharge side of pump with

the pump off • Dynamic Suction Head/Lift - Head on suction side of pump

with pump on • Dynamic Discharge Head - Head on discharge side of pump

with pump on

Pump Head

Suction Head

Pumps do not SUCK.

It is not possible to PULL a fluid

A pump simply lowers the pressure at its inlet and the fluid is pushed in

Net Positive Suction HeadThe pump has a NPSH requirement in order to

prevent cavitation damage occurring and causing severe damage.

The NPSH increases with flow due to pump internal losses - friction, impeller losses etc.

Net Positive Suction HeadThe requirement is that:

NPSHNPSHA Otherwise (if NPSHA < NPSHpump), the pressure at the pump inlet will drop to that of the vapor pressure of the fluid being moved and the fluid will boil.

The resulting gas bubbles will collapse inside the pump as the pressure rises again. These implosions occur at the impeller and can lead to pump damage and decreased efficiency.

Cavitation

Any question?

The end