building services..(22!7!13)

7/27/2019 Building Services..(22!7!13)

1/12

APPURTENANCES IN THE DISTRIBUTION SYSTEM

VALVES

FIRE HYDRANTS

WATER METERS

PUMPS


2/12

WATER METERS


3/12

Why are meters important?

Water meters are important to a utility for several

reasons:

1. They make it possible to charge customers in proportion to the amount of water theyuse.

2. They allow the system to demonstrate accountability.

3. They are fair for all customers because they record specific usage.

4. They encourage customers to conserve water (especially as compared to flat rates).

5. They allow a utility system to monitor the volume of finished water it puts out.

6. They aid in the detection of leaks and waterline breaks in the distribution system.


4/12

Meters are classified into two basic types:

VELOCITY and

POSITIVE DISPLACEMENT

Velocity meters:Such basically measure the horizontal velocity of water flowing through them.

This measured velocity when multiplied by the area of flow cross section , will give the

discharge through the meter.

Automatic arrangements are then made to record the integrated discharge.(or the volume of

flow) over the period of time.

Velocity meters can be successfully used for measuring high flows. They are therefore widely

used for measuring the supplies of industries and trades.These are not generally used for small

domestic supplies,although they are available in small sizes.Different types of velocity meters

are Rotary,Turbine and Venturi meters.


5/12

1.Rotary Metersconsists of radial vanes attached to a shaft and enclosed in a casing. When the water enters

and passes through the meter with a certain velocity,the radial vanes are rotated in clockwise direction,which

in turn will revolve the shaft.The no. of revolutions will depend on the velocity of the flow.The velocity of

flow and therefore the discharge is thus proportional to the speed of the shaft


6/12

2.Turbine meters is smilar to rotary meters,and consists of turbine wheel which is rotated by the moving

water.The no. of revolutions made by the turbine wheel will give the discharge as in rotary meters.

3.Ventur i metershave a section that has a smaller diameter than the pipe on the upstream side. Based on a

principle of hydraulics, as water flows through the pipe, its velocity is increased as it flows through a reduced

cross-sectional area. Difference in pressure before water enters the smaller diameter section and at the

smaller diameterthroat

is measured.The change in pressure is proportional to the square of velocity. Flow

rate can be determined by measuring the difference in pressure. Venturi meters are suitable for large pipelines

and do not require much maintenance


7/12

Positive or Displacement Meters:

1.Disc Meters have a round disc that is located inside a cylindrical chamber. The disc is mounted on a

spindle. The disk nutates, or wobbles, as it passes a known volume of liquid through the cylindrical chamber.

The rotating motion of the disk is then transmitted to the register that records the volume of water that went

through the meter.


8/12


9/12


10/12

DISPLACEMENT PUMPS:

These work on the principal of mechanically inducing vacuum in a chamber and thus sucking in

a certain amount of water which is then mechanically displaced and forced out of chamber.

Reciprocating pumps:

Simplest is the hand operated well pump. In such a

pump piston reciprocates in a closed vertical

cylinder.This is moved up and down by hand. On the

upstroke, a vacuum gets created in the cylinder,below

the piston,thereby opening the check valve V1 at the

base of the pump, thus withdrawing water into thespace below the piston.Simultaneously, the water

above the piston is forced out of the spout.On the

downstroke ,the check valve V1gets closed and the

piston valve V2 gets opened,thus permitting water to

enter the cylinder above the piston.On the next

upstroke ,the piston valve V2closes and the waterabove the piston comes out of the spout,a nd at the

same time ,the check valve V1 opens,permitting

water to enter the space above the piston.The cycle is

thus continued ,and continuous supply of water can

be obtained.


11/12

Rotary Pumps:

In rotary type of displacement pumps,the rotary motion is used in place of a reciprocating motion as in used

in reciprocating type of displacement pumps.The rotary motion is obtained by using two cams or two gears.

Which mesh together and rotate in opposite direction.The rotating elements fit the casing closely.The water

enters through the suction pipe and is trapped between the cams(or he teeth of the gears)and the casing.It

is then forced out through the discharge pipe,as the gears rotate.A definite quantity of water depending onthe size and shape of the gears is thus is raised with each revolution.


12/12

ROTODYNAMIC/VELOCITY PUMPS: these have wheels type rotating element called

impeller.The shape of the impeller may be such ,as to force the water outward in the direction at

right angles to its axis,(radial flow), or to give water an axial as well as radial velocity(mixed

flow) or to force the water in the axial direction alone (axial flow).

Radial flow and mixed flow machines are called centrifugal pumps, whereas the axial flow

machines are called axial flow pumps. Centrifugal pumps are the most common and widely used.

CENTRIFUGAL PUMPS

COMPONENTS

Centrifugal force is made use of in lifting

water . Electrical energy is converted to

potential or pressure energy of water.

building services..(22!7!13)

Documents