Pumps and Pumping system&Class test: 01

Building Services 1

Reference:

Plumbing Practicesby-Syed Azizul Haq, PEng

Week 03: Class 5 and 6

Introduction:

Pump is a mechanical device used for conveying fluid form one position to another by applying some form of energy.

Pumps are primarily of three types. 01. Centrifugal pump. 02. Positive reciprocating pump and 03. Rotary pump

The most common type of pump used in plumbing system is Centrifugal pump

Centrifugal PumpThe two main components of a centrifugal pump are the impeller and the volute.

Volute is the casing in which the impeller of pump is housed.

Impeller is a circular element within the volute in which curved vanes are made attached with a circular disc called shroud

VaneShroud

The impeller produces liquid velocity and The volute forces the liquid to discharge from the pump converting velocity to pressure. This is accomplished by offsetting the impeller in the volute and by maintaining a close clearance between the impeller and the volute at the cut-water.

Centrifugal Pump ApplicationsCentrifugal pumps are used in buildings for following purposes.

1. Water supply

2. Drainage

3. Pressure boosting.

4. Hot water circulation.

Characteristics of a Centrifugal Pump is dependent upon following parameters. 01. Capacity

02. Head 03. Power 04. Efficiency 05. Speed etc. Capacity:

The capacity of pump is the rate of flow of liquid through the impeller. The actual flow rate achieved is directly dependent on the Total Dynamic Head

it must work against.

The flow capacity of a centrifugal pump also depends on three (3) other factors:

Pump Design Impeller Diameter Pump Speed

Pump characteristics

Head:

Energy contained in a fluid per unit weight is termed as Head of Energy or simply “Head’ denoted by H. It is the energy needed to flow water from one position to other

Pump characteristics

Head is the sum of potential, kinetic and pressure head.

Potential head (hp) = Potential energy per unit weight = = hm.g.h m.g

Kinetic head (hv) = Kinetic energy per unit weight = =½.m.v2 m.g

v2 2g

Where m = Mass (pound), g = Acceleration due to gravity (32.2 ft.sq/sec),h = Vertical height from a datum (foot), v = Velocity of fluid flow (ft./sec)V = volume of fluid (cft), =Specific weight of fluid, p = Pressure (psi)

=Pressure head (hp) = Pressure energy per unit weight = =p.V m.g

p.m.g/ץ m.g ץ

p

ץ

Head = h + ± v2 2g ץ

p

Head of Pump

The total head of a pump

= Suction head + Delivery head + Friction loss

UG reservoir

OH tank

G.F

Roof

Suc

tion

Hea

dD

eliv

ery

Hea

d

Tota

l Sta

tic H

ead

Head is the energy needed to flow water from one position to other. It is expressed in Feet of water.

Total (Dynamic) Head H = Suction head + Delivery head + Friction head loss

Head H (in ft) = Potential head + kinetic head + Pressure head

Capacity Q is the rate of flow (in gpm) through pump

Output power = Q H/ 3960

Input power is the Brake Horse power (BHP) needed to drive a pump

Efficiency of pump is the ratio of Output to input power

Q x H Brake Horse Power (BHP) = x 100 3960 x Efficiency

Power of Centrifugal Pump

Capacity, gpm

Tota

l Hea

d, ft

Brea

k Ho

rse

Powe

r

Effic

ienc

y,%

Total HeadEff

icienc

y

Break Horse Power

Performance Characteristics of Centrifugal Pump

Speed of Pump Characteristics of centrifugal pump varies with the speed according to following relationships.

Q1

Q2 N1

N201. Capacity

=

(N2)2

(N1)2

H2

H1

02. Head =

P2

P1

(N2)3

(N1)303. Power =

N1= Rotating speed of one pump

N2= Rotating speed of another pump

Q1= Capacity at speed N1

Q2= capacity at speed N2

H1= Total head at speed N1

H2= Total head at speed N2

P1= Power at speed N1

P2= Power at speed N2

Generally a centrifugal pump is driven by constant speed motor. Pump can also be driven by variable speed motor.

2. Variable speed drive: This type of drive is recommended for following conditions.

    i. Large fluctuation of pressure in water supply system.

     ii. High pressure boosting is needed.

     iii. Large variation of water demand.

      iv. Power required more than 40 hp.

Various Centrifugal PumpsBooster Pump: Booster pump is used to increase the pressure in a water supply system where pressure is insufficient and variable. Two types of booster pump drivers are available to adjust the flow and pressure in the water supply system

1. Constant Speed Drive: Suitable for following conditions.

i. Water demand is more or less constant

ii. Low to medium range of pressure to be boosted

iii. Low cost is the major factor

iv. When fluctuation of pressure is less than about 20 psi.

Sewage and Sump Pump: The sewage or sump pump is used to make empty the sumps where sewage or liquid wastes are temporarily stored. Pumps should operate under positive head on suction.

1. Solid handling pump :Sewage containing large particles (maximum 80% of outlet size), abrasive and viscous wastes, fibrous and soft solids in suspension, sludge and pulpy materials etc. are pumped. Pumps are available 8 to 80 m. head having flow range 5 to 200 lps. Two hand holes shall be provided.

2. Non-Clog pump: Sewage containing muddy, viscous liquid having solids in suspension are pumped. S-type semi-open impeller is used. For both dry and wet pit application this pump is available. Wet pit design pumps have head range 2 to 45 m and flow range 4 to 150 lps. Column pipe is limited to 8 m.

Various Centrifugal Pumps

3. Submersible sewage pump: Both pump and motor remains submerged into the sewage. Pump casing is made radially split type with integral cast suction and delivery nozzle. The impeller is designed non-clog, wide channel, with two vanes. Double mechanical seals with oil lubrication are provided in between motor and pump.

Submersible Pump: In submersible pump the driving motor remains submerged in the liquid to be pumped below the pumping assembly. Motor and pump is assembled in a single unit. The electric motor remains protected by a waterproofed housing. Bearings are usually lubricated by water or water –oil emulsion whose leakage is protected by mechanical seal. Power to the motor is fed by waterproof cable clipped to the side of rising main

Advantages of Submersible pump:01. Exceptional quietness02. No priming is required.03. No pump house is required.04. Quick and easy installation.

Various Centrifugal Pumps

Disadvantages of Submersible pump:01. Less efficiency. 02. Maintenance is troublesome.

Circulation Pump: For circulating water in a piping system a circulation pump is used. Circulation pumps are mostly installed on pipe of the system.

For circulation of cold water in air conditioning system and for circulation of hot water in hot water supply system circulation pump is used for circulation of water in the piping system.

Special features of circulation pump:01. Shall operate quietly02. Operates at low speed.03. Motor and pump is connected by very flexible coupling.04. Motor mountings are cushioned properly.

Various Centrifugal Pumps

Pump Installation

VWLP

GATE VALVE

CHECK VALVE

FLEXIBLE CONNECTION

U.G. TANK WALL

PIPE SLEEVE

AdjustablePUMP BASE

STRAINER

45090

0

By the tank side

12D

Following important factors shall be considered for pump installation

Location: Pump shall be located nearer to the source, where it is accessible and sufficient light to inspect condition of packing and bearings.

Foundation: Foundation shall be rugged enough to afford permanent rigid support to the base area of the bed plate and to absorb all stress and strains. Concrete foundation is most satisfactory. Foundation bolts shall be correctly positioned according to drawing supplied.

Grouting: 20 to 50 mm thick grouting (1:2 cement sand ratio) shall be poured under bed plate to provide solid bearing. Grouting shall be allowed to set for at least 48 hours.

Pump InstallationLeveling: Pump and motor shall be accurately aligned to minimize vibration and load on pump. Alignment is checked by checking the faces of the coupling halves of pump and motor for parallelism with the help of Feeler gauge, and straightness of sides and leveling of tops by straightedge.

Suction pipe requirements: Suction pipe shall be as short and direct as possible. Suction pipe larger than the suction inlet of pump shall be connected with pump inlet by an eccentric reducer and flexible connector. Pipe shall be slightly graded downward and if needed bending can be done 12 times the diameter apart. Strainer having opening area 3 times the pipe x-sectional area shall be installed at end. All joints shall be tested for air tightness.

Delivery pipe requirements: delivery pipe shall have minimum bends. Delivery pipe shall also be fitted with pump outlet by a flexible connector. A gate valve and a check valve (when the riser pipe is more than 10 meter) shall be installed near the pump.

Pump RoomPump room shall be sufficiently spaced to accommodate the required number of pumps along with its piping and other accessories. In addition to that sufficient working space is also needed for easy operation and maintenance works. Minimum 1.2 meter clearance should be provided near foundation or between foundations as working space.

Pump room shall be sufficiently ventilated and illuminated. Sufficient and proper drainage system shall be provided for waste or leakage water.

For pumps over 40 hp, sufficient overhead arrangements for lifting and lowering the pump shall be provided.

Pump room shall be constructed where there is no danger of flooding and should be away from occupancies of low sound tolerance.

Number and Horse power

1-10

2-10

1-25

2-25

1-40

2-40

1-100

2-100

2-100 Fire pump

SpaceSq.m

Horizontal shaft 6 8 9 14 13 20 25 40 90Vertical shaft 6 8 7 12 10 14 12 16 -

Space requirement for electric driven pumping rooms

Class Test: 01

01. Draw and show different parts of Cast Iron pipe. 2

Results of Assignment: 01 and Class test: 01 On 4th Week

Time 30 min. Marks-10

02. Name in full various type of plastic pipes.

For what purpose CPVC pipe is used. 4

03. For what purposes pipe fittings are used.

Name the fittings used for branching. 4

3rd Week, 20.09.08,