Valves, notch, weir, types of instruments, Piping and Instruments

1. Valves, notch, weir, types of
instruments, Piping and
Instruments
Dr Sourav Poddar
Department of Chemical Engineering
National Institute of Technology
Warangal, Telangana

7. CHECK VALVES
 Prevent reversal of flow
 Open with forward flow and close against reverse flow
 Types of check valves
– Lift check valves
– Swing check valves
– Tilting-disk check valve

18. Control
Valves
-
Flow
Characteristics

22. Pressure
Drop
Across
Control
Valves

24. VALVES Configuration of Piping Associated with a Control Valve

28. PRESSURE RELIEF VALVES
Direct-loaded Relief Valves

29. Safety Valves

30. PRESSURE RELIEF VALVES

31. Safety-Relief Valves

45. The sheet of water flowing through a notch or over a weir is known as nappe or vein. The bottom edge of the
notch or the top of a weir over which water flows is known as sill or crest. The height above the bottom of the
tank or channel is known as crest height.

68. Types of notches

69. Types of weir on basis of shape

71. 1. Calculate the flow velocity of water at the opening of an orifice if the orifice is located 4 m below the water
surface in a tank.
2. Calculate the coefficient of velocity Cv if the actual velocity of jet is 5.1 m/s. Orifice is located 2m below the water
surface in a tank.
3. Determine discharge through a internal mouthpiece (running free) if there are a y mouth piece is 0.09 m2. The
distance between the centre of mouthpiece and free water surface is 2.5 m.

73. 4. Determine discharge through a internal mouthpiece (running free) if the are a of mouthpiece is 0.15 m2. The
distance between the centre of mouthpiece and free water surface is 3.0 m.
5. Determine flow rate through a rectangular hutch if L = 0.20 m and H = 0.15 m. Take value of cd = 0.645
6. Determine flow rate through a triangular hutch if H = 0.20 m and θ = 60o . Take value of cd = 0.85.
7. Determine flow rate through a rectangular weir if L = 0.30 m and H = 0.25 m. Take value of cd = 0.95

76. 1)Indicating:
Indicating instruments are those which indicate the instantaneous value of the electrical quantity being measured,
at the time at which it is being measured. Their indications are given by pointers moving over calibrated
dials(scale), e.g. ammeters, voltmeters and wattmeters.
2)Recording:
Recording instruments are those which give a continuous record of variations of the electrical quantity over a
selected period of time. The moving system of the instrument carries an inked pen which rests tightly on a graph
chart. E.g. recording voltmeters used in supply station.
3)Integrating:
Integrating instruments are those which measure and register the total quantity of electricity (in ampere-hour) or the
total amount of electrical energy(in watt-hours or kilowatt-hours) supplied to a circuit over a period of time, e.g.
ampere-hour meters, energy meters.

77. ESSENTIALS OF INDICATING INSTRUMENTS
Deflecting Torque(Td):
It is the torque which deflects the pointer on a calibrated scale according to the electrical quantity passing through
the instrument. The deflecting torque causes the moving system and hence the pointer attached to it to move from
zero position to indicate on a graduated scale the value of electrical quantity being measured.
Controlling Torque(Tc):
It is the torque which controls the movement of the pointer on a particular scale according to the quantity of
electricity passing through it. If deflecting torque were acting alone, the pointer would continue to move indefinitely
and would swing over to the maximum deflected position irrespective of the magnitude of current (or voltage or
power) to be measured.

79. Thus, controlling torque in a gravity control system is proportional to the sine of the angle of deflection.
The degree of control is adjusted by screwing the weight up or down on the carrying system.

80. Eddy-current damping uses a conducting material which moves in a magnetic field so as to cut through the
lines of force, thus setting up eddy currents. Force always exists between the eddy current and magnetic field
which is always opposite to the direction of motion. This is most efficient type of damping and is largely used
in permanent magnet moving coil instruments.

89. Working:
When current to be measured or current proportional to the voltage to be
measured flows through the coil, a magnetic field is set up by the coil. This
magnetic field magnetizes the two vanes in the same direction i.e. similar
polarities are developed at the same ends of the vanes. Since the adjacent
edges of the vanes are of the same polarity, the two vanes repel each
other. As the fixed vane cannot move, the movable vane deflects and
causes the pointer to move from zero position. The pointer will come to
rest at a position where deflecting torque is equal to controlling torque
provided by the spring. If the current in the coil is reversed, the direction
of deflection remains unchanged. It is because reversal of the field of the
coil reverses the magnetization of both iron vanes so that they repel each
other regardless which way current flows through the coil. For this reason,
such instruments can be used for both d.c. and a.c. applications.

101. As a Voltmeter: To use the instrument as a voltmeter, the coils are wound with high resistance wire and
fixed and moving coils are connected in series with a high resistance.

109. Fig. 2: Typical PTFE Gasket

110. Fig. 3: Cam Profile Composite gasket

124. Fig. 10: Typical Gasket in piping flanged Joint

132. Color-Coded Chart for the type of gasket identification
Spiral wound gaskets with stainless steel core and PTFE or graphite as the filler material is the most widely used gasket
for process industries. For inspection and identification purposes, ASME B16.20 provides a Color Coding Chart as
shown in Fig. 11 below:

149. Thank You