Building Services and
Entrepreneurship Development
• Lecture details :-
Plumbing – Types of Valves in Plumbing Pipe System
• Date:-
07 – 01 - 2022
Presented by :
Mr. Soham Mukherjee (Lecturer)
S.N. BOSE GOVERNMENT POLYTECHNIC
Plumbing
(Types of Valves in Plumbing Pipe System)
E-CONTENTS:-
Sl. Slide
Description
No. No.
1. Introduction to Valves 3-6
2. Types of Valves – Sluice Valve 7-8
3. Types of Valves – Scour Valve 9
4. Types of Valves – Pressure Relief Valve 10 - 11
5. Types of Valves – Reflux Valve 12 - 13
6. Types of Valves – Air Relief Valve 14 - 15
7. Types of Valves – Stop Valve & Bib Tap 16 - 18
Valves :-
❖ A valve is a device that regulates, directs or controls the flow of a
fluid by opening, closing or partially obstructing various
passageways.
❖ Purpose of Valves :-
a) To stop and start fluid flow in pipe.
b) To vary the amount of fluid flow in pipe.
c) To control the direction of fluid flow in pipes.
d) To regulate downstream system or process pressure.
e) To relieve component or piping over pressure.
Valves & Terminal Fittings:-
❖ Types of Valves & Its Purpose :-
Valves are installed throughout water systems in treatment plants,
pumping stations, and pipe networks, as well as at storage reservoirs.
Their purpose is to control the magnitude or direction of water flow.
To regulate flow, all valves have a movable part that extends into the
pipeline for opening or closing the interior passage.
The main types of valves are
a) Sluice Valves,
b) gate valves,
c) stop-cock,
d) bib-tap,
e) shut-off valve,
f) Scour valves,
g) Pressure relief valves,
h) Reflux valve or check valve (non return valve),
i) Air Valve or Air-relief valves,
j) Flush & mixing valves.
Valves & Terminal Fittings:-
❖ Types of Valves & Its Purpose :-
➢ Valves are also commonly classified by operating purpose (for
example, shutoff and altitude) and function (by-pass and flow
control) without regard to the kind of device used.
➢ The means of operating the movable element of a valve are by
screw, gears, or water pressure.
➢ Screw stems are common in gate, globe, and needle valves and can
be opened or closed by a manually operated hand-wheel or by a
powered operator.
➢ In some designs, the screw stem rises as the shutoff element
closes, and in others the element rides up the screw inside the
body of the valve as the stem turns, the latter non-rising stem
being more common.
Valves & Terminal Fittings:-
➢ In large valves, where water pressure prevents use of a screw, a
gear train can be employed to allow the shutoff element to be
moved slowly by applying a minimum of torque to the stem.
➢ The gear system may be operated manually or by electric,
hydraulic, or pneumatic power operators.
➢ The kinds of valves that may be equipped with a geared operator
include butterfly, gate, globe, and ball.
➢ Water pressure can open or close some kinds of valves by direct
pressure on the movable element.
➢ The simplest is a hinged swing gate that opens under water
pressure and closes under the influence of gravity or back
pressure.
➢ Another example is the automatic globe valve with a body design
that controls movement of the shutoff element by system water
pressure.
Sluice or Gate Valves :-
These valves (also called gate valves or stop-valves or shut-off
valves) are provided to control the flow of water in the distribution
network system at street corners, where pipelines intersect.
They are generally located along the pipe line at intervals of about 3
to 5 kilometers, so as to divide the pipe line into different sections.
The entire distribution system is divided into blocks by providing
these valves at appropriate places.
They are also provided in straight pipe lengths at 150 – 250 m
intervals.
These valves should be provided at small intervals in order to cause
minimum dislocation of the service, if a portion of the pipeline is to
be shut-off. the flow of water can be controlled by raising or
lowering the handle or wheel.
Sluice or Gate Valves :-
The valve is made of cast iron with brass, bronze or stainless steel
mountings. The ends of the valve are properly jointed on both sides
of the pipe lengths, by suitable standard joints.
The valve consists of a wedge shaped circular disc fitted closely in a
recess against the opening in the valve. This is connected to a
wheel by means of a threaded spindle. The valve can be raised or
lowered by rotating the wheel from the top either manually or
mechanically.
Double disc parallel seat cast iron valves are most commonly
used in the distribution mains.
Scour Valve:-
The scour valves (also known as blow-off or washout valves) are
ordinary sluice valves which are provided at all dead ends in the
distribution system and at all depressions (lowest points) in the
pipeline.
These are opened (operated by hand) occasionally to remove silt or
dirt by allowing the water to run out until it is clear.
Pressure Relief Valve :-
Pressure relief valves are also known as automatic cutoff valves or
safety valves.
They are located at those points where pressure is likely to be
maximum.
When the line pressure increases above the preset value, the valve
operates automatically and thus protects it against the possible
danger of bursting due to excessive pressure.
Pressure Relief Valve :-
A pressure-relief valve consists of a spring loaded disc. The load on
the disc can be adjusted by releasing or compressing the spring
with the help of a handle. The valve is fitted on an opening provided
at the top of the pipeline.
As long as the pressure in the pipe is less than the design value the
disc is held tightly fitting against the opening and the valve remains
closed.
When the pressure in the pipe exceeds the design value, the disc is
forced to be lifted up and certain amount of water is allowed to flow
out from the pipe to waste, thereby pressure in the pipe is reduced.
With the reduction in pressure in the pipe the disc is forced back to
fit against the opening and the valve is again closed.
Reflux Valve:-
Reflux valve (also called check valve or non-return valve) is a
semiautomatic device that allow flow in one direction only and
automatically close in case the flow is reversed.
It consists of a flat disc or door within the pipe line, pivoted so that
it is forced open when flow of water is in one direction, and forced
shut against a gunmetal seating when flow tries to be in the reverse
direction.
It will be observed that the seating is normally arranged slightly out
of perpendicular. This enables the disc to close automatically by
gravity when there is no flow, with the valve fixed in a horizontal
pipe.
Reflux Valve:-
They are placed in water pipes which obtain water directly from
the pump.
When the pump is stopped, the water in the pipe line does not rush
back and damage the pump.
They are also used at the foot of the rising main along the slope to
prevent back-running of water, in case the pipe bursts in the lower
reaches.
They are provided at regular intervals in long force mains to
prevent back pressure on the engine and the rising main, at the
foot of the rising leg of an inverted syphon and in mains just
beyond the pumps.
When water flows to the left, the valve swings upwards around a
pivot and water is allowed to pass through. When water, however,
flows in the opposite direction, the valve closes and does not allow
backflow.
Air Valve or Air Relief Valve:-
The water flowing through the pipe lines always contain some air.
Sometimes air gets accumulated at high points in a long pipeline
when the supply is restored and the pipe is refilled after repairs,
and may interfere with the flow.
The accumulated air obstructs the free flow of water and the pipe
may get air locked.
Air relief valves (also known as float valve) are, therefore,
required to be provided at all summits, along the water pipe, to
provide an exit for such accumulated air. An air valve consists of a
cast iron chamber (circular or rectangular), float, lever and poppet
valve.
Air Valve or Air Relief Valve:-
The chamber is connected to the pipeline at its top through a short
pipe length. In the normal condition, the chamber is full of water
entering from the pipeline.
The float, therefore touches the roof of the chamber and the poppet
valve is held in closed position. When air from the pipeline enters
the chamber, it starts accumulating at the top of the chamber.
With more and more air accumulating in the chamber air pressure
is built up due to which the water level in the chamber gets
depressed, consequently the float is brought down and the valve is
opened.
The accumulated air is thus allowed to escape through the valve.
When air escapes, water rises again in the chamber and the float is
raised which results in the closing of the valve so that water does
not escape through it.
Air valves are also required to discharge air when a main is being
filled and to admit air when it is being emptied. The admission of
air on emptying the main is of great importance on large steel
mains, which may flatten if the pressure falls below that of the
atmosphere.
Bib-Taps & Stop Valves:-
A Stop Cock is a screw down type of sluice valve which is used in
smaller sized pipes in service connections for stopping or opening
the supply.
They are generally provided at the water entrance of each
building and also within the building. When provided just prior
to the water meter in each house connection, they should be
enclosed in a proper cast iron box having a hinged cover.
The body of the valve is so cast that the water passes through an
orifice when the valve stem is raised. When the valve is closed, it
rests against the seat, and thereby closing the orifice. They are
extensively used in pipes up to 50 mm sizes.
Bib-Taps & Stop Valves:-
Water taps are the types of valves provided at the end of service
pipes for withdrawing water at the consumers’ houses. Several
varieties of water taps are available, and the most common of them
is a “Bib-Tap”.
By rotating the handle of the bib cock, the orifice opening, through
which the water passes, can be increased or decreased, thereby
controlling the outflow through the spout.
They are available to be fitted in different pipe sizes from 10 to 50
mm dia.
Bib-Taps & Stop Valves:-
The bib cocks may also be of the push type which opens from a
slight push given vertically upward, and closes down automatically
due to self-weight when the push is removed.
Such valves are used in public taps in order to avoid wastage of
water from handle type bib cocks, which may be left open by the
irresponsible people.
The bib cocks should be water-tight and should not leak, as it may
lead to considerable wastage of water.
The rubber or leather washers used in them may get damaged and
lead to leakage, and hence should be replaced as and when needed.
