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Functions of a Pump

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Title: Functions of a Pump


1
Functions of a Pump
  • Transfer fluid between two points.
  • Produce required flow rate.
  • Produce required pressure.

2
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3
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4
Pump - Facts
  • Pump changes both velocity and pressure of the
    fluid.
  • Pump only adds to the system energy.
  • Power supplied to the pump is to transfer fluid
    at specified flow rate and pressure by overcoming
    resistance in the pump and the system.
  • A pump does not create pressure, it only provides
    flow. Pressure is just an indication of the
    amount of resistance to the flow.

5
Pumps and Viscosity of Fluid Handled.

  • Viscosity of the fluid pumped must be within the
    range specified in the pump design.
  • Reciprocating Displacement pumps can handle any
    required viscosity.
  • Rotary Positive Displacement Pumps ( Common- Gear
    and Screw ) are used for intermediate range of
    viscosities.
  • Centrifugal Pumps are used for Medium to Low
    range of viscosities.
  • Onboard ships, permission should be obtained
    before any fluids are moved, which might affect
    the stability of the ship.

6
Centrifugal Pump
(Rotodynamic)
  • Centrifugal pump distinguished from Positive
    displacement pump ------
  • Requirement of relative velocity between
  • the fluid and the impeller.
  • Shaped casing or diverging nozzle converts
  • kinetic energy into pressure energy.
  • Liquid in the impeller and casing essential
  • for pump operation.

7
Centrifugal Pump.
8
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9
Centrifugal Pump- Theory
  • The energy changes occur in a centrifugal pump by
    virtue of two main parts of the pump.
  • The Impeller The rotating part that converts
    driver energy into kinetic energy.
  • The volute or Diffuser The stationary part that
    converts the kinetic energy into pressure energy.
  • The process liquid enters the suction nozzle and
    then into the eye of the impeller. Impeller spins
    the liquid sitting in the cavities between the
    vanes, outwards and provides centrifugal
    acceleration. As liquid leaves the eye of the
    impeller, a low pressure area is created, causing
    more liquid to flow towards the inlet. Because
    the impeller blades are curved, the fluid is
    pushed in a tangential and radial direction by
    the centrifugal forces.

10
Centrifugal Pump- Theory
  • The process liquid enters the suction nozzle and
    then into the eye of the impeller. Impeller spins
    the liquid sitting in the cavities between the
    vanes, outwards and provides centrifugal
    acceleration. As liquid leaves the eye of the
    impeller, a low pressure area is created, causing
    more liquid to flow towards the inlet. Because
    the impeller blades are curved, the fluid is
    pushed in a tangential and radial direction by
    the centrifugal forces.

11
Centrifugal Pump - Theory
The amount of energy given to the liquid is
proportional to the velocity at the edge or vane
tip of the impeller. The faster the impeller
revolves or bigger the impeller is, then higher
will be the velocity of the liquid at the vane
tip and greater the energy imparted to the
liquid.
12
Centrifugal Pump Theory.
The kinetic energy of a liquid coming out of an
impeller is harnessed by creating a resistance to
the flow. The first resistance is created by
pump volute casing, which catches the liquid
and slows it down. In the discharge nozzle, the
liquid further decelerates and its velocity is
converted to pressure.
13
Centrifugal Pump - Head
The pressure at any point in a liquid can be
thought of as being caused by a vertical column
of the liquid due to its weight. The height of
this column is called the static head and is
expressed in terms of meters of liquid. Head is a
measurement of height of a liquid column that a
pump could create from kinetic energy imparted to
the liquid. Imagine a pipe shooting a jet of
water straight up into the air, the height the
water goes up would be the head.
14
Centrifugal Pump - Vapour Pressure
Vapor pressure is the pressure at which a liquid
and its vapor co-exist in equilibrium, at a given
temperature. Vaporization begins when the vapor
pressure of the liquid at the operating
temperature equals the external system pressure,
which in an open system always equal to the
atmospheric pressure. Any decrease in external
pressure or rise in operating temperature can
induce vaporization and the pump stops pumping.
15
Centrifugal Pump Velocity Head
Velocity Head refers to the energy of a liquid as
a result of its motion at some velocity, V . It
is the equivalent head in meters through which
the water would have to fall to acquire the same
velocity or the head necessary to accelerate the
water. Velocity head is insignificant in most
high head systems, but it can be large in low
head systems.
16
Factors Affecting Suction Lift
  • Temperature and volatility of the fluid
  • Pressure exerted on the free side of the
    liquid.
  • Friction Losses at entrances, bends and pipes
    in the suction system.

17
Priming of Centrifugal Pump.
  • Priming is the process of removing Air/Vapour and
    filling the suction piping, impeller and pump
    casing with the fluid.
  • METHODS OF PRIMING
  • Liquid ring air-pump.
  • Ejector.
  • Reciprocating Pump. Obsolete.

18
Impeller of Centrifugal Pump
19
Types of Impellers, With Respect to Flow.
  • Radial flow.
  • Axial flow.
  • Mixed flow.

20
For low flows and high pressures, the action of
the impeller is largely radial. For higher flows
and lower discharge pressures, the direction of
the flow within the pump is more nearly parallel
to the axis of the shaft, and the pump is said to
have an axial flow. The impeller in this case
acts as a propeller. The transition from one set
of flow conditions to the other is gradual, and
for intermediate conditions, the device is called
a mixed-flow pump. Conical designs also featured
in the transition from radial to axial flow
conditions. Specific Speed Range     Pump Type
Below 5,000                      Radial Flow
Pumps 4,000 - 10,000                 Mixed Flow
Pumps 9,000 - 15,000                       Axial
Flow Pumps
21
Types of Impellers With Respect to Construction.
  • Open (with partial shrouds for strength. - - For
    abrasive liquids with suspended solids.
  • Semi-Open - - For viscous liquids.
  • Enclosed - - For clear liquids.

22
Impellers
23
Open, Semi-open and enclosed Impellers
24
Open, Semi-open, Enclosed
25
Single and Double Entry Impellers
26
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27
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28
Types of Centrifugal Pumps With Respect to the
Construction of the Casing.
  • Volute
  • Diffuser
  • Regenerative

29
Volute Casing
  • It is like a curved funnel increasing in area to
    the discharge port, which converts velocity
    energy into pressure energy. Also it helps to
    balance the hydraulic pressure on the shaft of
    the pump- occurs at the recommended capacity.
    Running at lower capacity can put lateral stress
    on pump shaft, increase wear-and-tear on the
    seals, bearings and on the shaft itself.

30
Centrifugal Pump
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33
Double Volute Pump
34
Diffuser or Circular Casing
  • It has stationary diffusion vanes, surrounding
    the impeller periphery that convert velocity
    energy into pressure energy.
  • Conventionally the diffusers are applied to
    multistage pumps.

35
Diffuser Casing
36
Regenerative(turbine Pump)
  • The impeller , which has very tight axial
    clearance and uses pump channel rings. Liquid
    entering the channel from the inlet is picked up
    immediately by the vanes on both sides of the
    impeller and pumped through the channel by
    shearing action. The process is repeated over and
    over with each pass imparting more energy until
    the liquid is discharged.

37
Turbine Pump
38
Turbine Pump
39
Axially/Radially Split Casing
40
Gland Packing- Stuffing Box
41
Stuffing Box
42
Impeller, wear rings
43
Centrifugal Pump
44
Horizontal Two-stage C Pump
45
Two-Stage Vertical C Pump
46
Cavitation
47
Centrifugal Pump Operational
Summary
  • THREE INDICATIONS IF A PUMP IS CAVITATING
  • Noise.
  • Fluctuating discharge pressure and flow.
  • Fluctuating pump motor current.

48
Steps to Stop cavitation of a Pump
  • Increase pressure at the suction of the pump.
  • Reduce the temperature of the liquid being
    pumped.
  • Reduce head losses in the suction piping.
  • Reduce the flow rate through the pump.
  • Reduce the speed of the pump impeller.

49
Effects of cavitation.
  • Degraded pump performance.
  • Metal gets corroded seen as small pittings.
  • Audiable rattling or crackling sounds which
    can reach a pitch of dangerous vibrations.
  • Damage to pump impeller, bearings, wear rings
    and seals.

50
Pump Operation - Facts
  • To avoid pump cavitaion, NPSH available must be
    greater than NPSH required.
  • NPSH available is the difference between the
    pump suction pressure and the saturation pressure
    of the liquid being pumped.
  • Cavitation is the process of the formation and
    subsequent collapse of vapor bubbles in a pump.
  • Gas binding of a centrifugal pump is a condition
    where the pump casing is filled with gases or
    vapors to the point where the impeller is no
    longer able to contact enough fluid to function
    correctly.

51
Pump Operation - Facts
  • Shut off head is the maximum head that can be
    developed by a centrifugal pump operating at a
    set speed.
  • Pump run out is the maximum flow that can be
    developed by a centrifugal pump without damaging
    the pump.
  • The greater the head against which a pump
    operates, the lower the flow rate through the
    pump.
  • Centrifugal pumps are protected from run-out by
    placing orifice or throttle valve immediately
    downstream of the pump discharge and through
    proper piping system design.
  • The centrifugal pump can be protected from
    dead-heading by providing a recirculation from
    the pump discharge back to the supply source of
    the pump.

52
Centrifugal Pump Operation - Facts
  • Discharge Pressure Minimum throughput when
    head is maximum.
  • Power Minimum power consumed when no flow and
    the discharge head is at the highest.
  • Losses 1) Shock and eddy losses caused by
    impeller blade thickness and other mechanical
    considerations. 2)
    Frictional losses due to fluid contact with the
    pump casing etc.
  • 3) Inlet and Impact losses.

53
Characteristics of Variable Speed Centrifugal
Pump.
  • Head varies as the square of the speed.
  • Capacity varies directly as the speed.
  • Power varies as cube of the speed.

54
Characteristics of Constant Speed Centrifugal Pump
  • Head varies as square of the diameter.
  • Capacity varies as the diameter.
  • Power varies as the cube of the diameter.

55
Problems in Centrifugal Pump Operation
Problem     Possible Causes   No Liquid
Delivered     - Pump not primed     -
Insufficient available NPSH     - Suction line
strainer clogged     - End of suction line not
in water     - System total head higher than
pump total head at zero capacity.
56
Problems- Centrifugal Pumps
Pump Delivers Less Than Rated Capacity     - Air
leak in suction line or pump seal     -
Insufficient available NPSH     - Suction line
strainer partially clogged or of insufficient
area     - System total head higher than
calculated     - Partially clogged impeller
    - Impeller rotates in wrong direction     -
Suction or discharge valves partially closed
    - Impeller speed too low     - Impeller
installed in reverse direction.
57
Problems- Centrifugal Pumps
Loss of Prime While Pump is Operating     -
Water level falls below the suction line intake
    - Air leak develops in pump or seal     -
Air leak develops in suction line     - Water
vaporizes in suction line.  
58
Problems- Centrifugal Pumps
Pump Delivers Less Than Rated Capacity     - Air
leak in suction line or pump seal     -
Insufficient available NPSH     - Suction line
strainer partially clogged or of insufficient
area     - System total head higher than
calculated     - Partially clogged impeller
    - Impeller rotates in wrong direction     -
Suction or discharge valves partially closed
    - Impeller speed too low     - Impeller
installed in reverse direction.
59
Problems- Centrifugal Pumps
Loss of Prime While Pump is Operating
   - Water level falls below the suction line
intake     - Air leak develops in pump or seal
    - Air leak develops in suction line     -
Water vaporizes in suction line.
60
Problems- Centrifugal Pumps
Pump Takes Too Much Power     - Impeller speed
too high     - Shaft packing too light     -
Misalignment     - Impeller touching casing
    - System total head too low causing the pump
to deliver too much liquid     - Impeller
rotates     - Impeller installed in wrong
direction.
61
Problems- Centrifugal Pumps
Pump is Noisy     - Cavitation     -
Misalignment     - Foreign material inside pump
    - Bent shaft     - Impeller touching
casing.
62
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63
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64
Coupling
65
Coupling Alignment
66
Alignment
67
Alignment
68
Alignment
69
Centrifugal P/P, Ohauling
Basic Types of Parts- Rotating Parts
Impeller, Shaft, wearing rings, shaft sleeves,
bearings, Mechanical seal etc Stationary Parts
Casing, bearing housing, suction and discharge
flanges, packing, leak-off tubing, base plate etc
70
Cent P/P, Ohauling- Impeller
  • Inspect eyes, vanes, shrouds,wearing rings,
    passages, hubs and other parts.
  • Corrosion, Cavitation, and Erosion are generally
    accompanied by a wasting away of the impeller and
    vane surfaces. Where attack is severe, the
    thinned sections may have holes through them or
    may warp and deflect.
  • Badly worn or corroded impellers may vibrate
    excessively. Balancing is required. Check on a
    lathe. Metal to be removed on heavier side. If
    required take a cut on the shroud, deepest at the
    rim.
  • Compare with a spare Impeller.

71
Cent P/P, Ohauling- shaft
  • Check for bent shaft out of square, dirty or
    burred impeller end of the shaft or spacer
    sleeve.
  • Check Lock nut washer is burred or the faces
    of it and other parts are not parallel.
  • Check for bent shaft by means of a dial gauge,
    swinging between lathe or other centers.
  • Tap and check impeller shaft key to see it is
    tight. Twist of shaft under load, Expansion or
    corrosion will progressively loosen the
    impeller..

72
CentP/P Ohauling- wear ring
  • Wear rings are installed in the casing or
    impeller or both. It will run as bearings while
    lubricated by the fluid being pumped. Check the
    clearances to make sure it is within limits. If
    not replace the wear rings.
  • Wear rings are usually made out of non-galling
    materials. EXBronze with dissimilar bronze.
  • Make sure that the wear rings are fitted
    correctly.

73
CentP/P- Ohauling- Bearings
  • Ball bearings etc. Keep all rolling-contact
    bearings clean at all times. Use clean tools and
    clean surroundings. Use clean solvents and
    flushing oils. Clean inside of housing before
    replacing the bearings. Install new bearings as
    removed from their package, without washing. To
    remove a bearing, press or pull only on the rings
    which is tight press pull straight.
  • Sleeve/Bush bearings Check clearances, if over
    the limit value, replace the same.

74
CentP/P,Ohauling-Mechanical seal.
  • Normally only faces require repair.
  • If stationary face is slightly scored, lap it on
    a lapping plate. If dirt or scale is imbedded,
    take a cut in lathe, to remove material to below
    the imbedded element.
  • Remove spring assembly for cleaning and
    inspection.
  • For replacement, choose the correct type.
  • Good Practice To rotate pumps equipped with
    mechanical seals, once a day, when stopped.

75
CentP/P, Ohauling, Shaft Sleeve, Gland Packings.
  • Check for worn shaft and shaft sleeve. Machine
    it and use it if groove/wear is not deep.
    Otherwise replace the sleeve. Check and replace
    the sealing ring of the sleeve.
  • Remove and replace all gland packings with
    correct type and size packings. Clean the housing
    thoroughly before inserting the packings.
  • Do not over-tight the gland. Check by rotating
    the shaft by hand.

76
Centp/p,Ohauling, Stationary Parts
  • Casing- Examine for corrosion or erosion. May
    be repaired by welding, brazing and machining or
    metal spraying depending on the material.
  • Gaskets- To be renewed with correct thickness
    and type. Surface of gasket seating has to be
    clean. Do not use oil, grease or varnish. Use
    proper tightening sequence for casing bolts and
    studs.
  • Bedplate and Foundation- Keep clean, Check for
    irregularity, keep drain lines clear. Check
    foundation bolts for tightness.
  • Piping- Check for leaks, damaged insulation,
    water hammer, defective valves, improper
    alignment etc.

77
Axial Pump
78
Axial Pump
  • Under low head ( 2.5 to 6.2 m), High throughput
    (2800- 9500 m3/hr )- conditions required by main
    condensers in steam ships.
  • Pump is reversible.
  • Pump will idle and offer little resistance when
    flow is induced through it by external means.
  • Ideal for condenser circulating duties in steam
    ships and for heeling and trimming duties.

79
Axial Flow Pump
  • A screw propeller by causing and axial
    acceleration of liquid within its blades, create
    a pressure increase.
  • Incidental rotation imparted to the liquid is
    converted to axial movement by suitably shaped
    outlet guide vanes.
  • Throttling of the discharge valve causes a rise
    in pressure and power. With discharge valve
    closed and zero discharge, the head will be three
    times and power doubled. Causes water hammer.

80
Axial Flow Pump
81
Mixed Flow Pump
82
Positive Displacement Pumps.
  • Liquid or gas displaced from suction to
    discharge by mechanical variation of the volume
    of a chamber or chambers.

83
Types of Positive Displacement Pumps.
  • RECIPROCATING Plunger or Piston mechanically
    reciprocated.
  • ROTARY Liquid forced through the pump cylinder
    or casing by means of screws or gears etc.

84
Necessity of Relief Valve in Positive
Displacement Pumps.
  • Positive Displacement Pumps will produce
    increasing pressure until rupture or drive
    failure.
  • Hazardous material discharge from Relief Valve
    must be contained within the pumping system.

85
Types of Positive displacement Pumps.
  • Reciprocating piston pump.
  • Gear type rotary pump.
  • Lobe type rotary pump.
  • Screw type rotary pump.
  • Moving vane type pump.
  • Diaphragm pump.
  • Flexible vane pump.

86
Types of P D Pumps
87
Piston Pump
88
Piston Pump
89
Reciprocating Piston Pump
90
Plunger Pump
91
Various Check V/Vs
92
Axial Piston Pump
93
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94
Axial Piston Pump
95
Swash Plate Pump
96
Axial Piston Pump
97
Wobble Pump
98
Radial Piston Pump
99
Radial Piston Pump
100
Lobe Pump
101
Lobe Pump
102
Lobe Pump
  • Two or more rotors cut with two, three or more
    lobes on each rotor.
  • Rotors are synchronized for positive rotation by
    external gears.
  • Liquid delivered in a small number of large
    quantities. Hence flow is not as constant as from
    gear pumps.

103
Lobe Pump- Type 2
  • Inner and outer elements rotate in a renewable
    liner fitted in the pump body.
  • The inner rotor is eccentric to the outer and is
    fitted to a shaft located by bearings in the pump
    covers.
  • Pump types are defined by the number of lobes
    and recesses Three-Four, Seven-Eight, etc.
  • Normal Max Pr 21 bar, Cap 400 t/hr
  • Three-Four typesSlow speeds, high viscosity
    fluids
  • Seven-Eight typesHigher speeds and lower
    viscosity fluids.


104
Gear Pump
105
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106
Gear Pump
107
Gear Pump
Internal Gear Pump
108
Crescent Internal Gear Pump
109
Crescent Internal Gear Pump
110

Gear Pumps.
  • Classified by the type of gears used- Spur,
    Helical, Herringbone etc
  • Commonly used on board for handling small
    quantities of Fuel oil, Lub oil etc
  • Shafts running on bushes or bearings, usually
    lubricated by oil being pumped.
  • Gear backlash,0.2-0.5mm (amount by which a tooth
    space exceeds the thickness of the engaging)- If
    no backlash, trapped oil between two teeth
    impedes gear rotation, Loss in power, additional
    load on bearings, spreading of gears and heating
    of the liquid.

111
Gears
112
Reciprocating Pump
113
Diaphragm Pump
114
Diaphragm Pump
115
Vane Pump
116
Slide Vane Pump
117
Vane Pump
118
Flexible Impeller Pump(flexible Vane Pump)
119
Flexible Impeller Pump
  • Self priming, can be mounted above or below the
    source of the fluid.
  • Simple construction- Inexpensive.
  • Gentle pumping action effectively handles
    thin, viscous and particle-laden fluids.
  • Typical applications- Low rate, low pressure,
    high viscosity uses. Temperature range- 0 to 90
    oC.
  • Impeller- Flexible synthetic rubber
  • Housing- Stainless Steel

120
Lobe Pump
121
Single Screw Pump
122
Single Screw Pump (Eccentric Helical Rotor Pump,
Snake P/P)
  • Used for smooth flow, low capacity applications.
  • During rotation, rotor (stainless steel)
    tightens against the stator (natural or synthetic
    rubber) with double internal screw threads and
    enclosed fluid is displaced axially.
  • All cross sections of rotor are circular.
  • Center-line of pump moves radially during
    rotation, hence driven through universal joint.

123
Double Screw Pump
  • Mounted horizontally or vertically.
  • Each screw shaft has a right and left hand screw
    which ensures hydraulic balance.
  • Metal contact avoided by timing gears.
  • Liquid drawn and pumped inwards to the discharge
    located at rotor mid-length.
  • Discharge is without pulsations.
  • For non-corrosive liquids of reasonable
    lubricity, usually internal bearings are used.

124
Double Screw Pump
  • For corrosive liquid with lack of lubricity
    and/or high, very high viscosity outside
    bearings which can be independantly lubricated
    are used.
  • Pumps with inside bearings are shorter and
    lighted and have only one shaft seal against four
    in the other case.
  • Shaft seal is usually at the suction end of the
    pump ( low pressure or vacuum ).
  • Usually mechanical seals are cooled and
    lubricated by the pumped liquid.

125
Triple Screw Pump
126
Triple Screw Pumps
127
Triple Screw Pump.
  • Center screw is driven, outer screws are idle.
    Outer screws are driven by fluid pressure and act
    as seals.
  • When screws rotate, their close relation to
    each other creates pockets in the helices these
    pockets move axially.
  • These pumps work well at high pressure and with
    high viscosity fluids.

128
Triple Screw Pump
129
Triple Screw Pump
130
Triple Screw Pump
131
Triple Screw Pump
132
Screw Pumps
  • High helix angle screws are used for relatively
    high speed on small pumps.
  • Lower helix angle screws are used on large pumps.

133
Screw Pumps Are Used---
  • For pumping high viscosity liquids such as oils
    and some liquid cargoes.
  • For draining tanks of high vapor pressure
    liquids, since self priming and being able to
    pump liquid and vapor without loss of suction.
  • For operation at high rotational speeds, since
    it can be easily matched with standard motors.

134
Circumferential Piston Pump
135
Positive Displacement Pumps
  • Often used for small capacities and when needed
    to avoid churning. Also used for high viscosity
    liquids.
  • Can control flow by regulating speed.
  • Used often for high or very high pressure. Also
    as metering pumps.
  • Will produce any head that is impressed on them.

136
Direct Acting Reciprocating pump classed as
  • Horizontal or Vertical ( H or V )
  • Single or Duplex ( S or D )
  • Single or Double Acting ( SA or DA )

137
Positive Displacement Pumps- Characteristics.
  • Output is almost directly proportional to the
    speed.
  • Output marginally reduced at increased pressure.
    (Slip)
  • Will develop discharge pressure equal to the
    resistance to be overcome.
  • Self priming.
  • Will accept high suction lifts.
  • Can handle large amounts of entrained gases or
    vapors.
  • Construction is complicated.

138
Rotary Displacement Pumps.
  • Rely on fine clearances between moving parts for
    their efficient operation.
  • Contact between elements in some screw pumps etc
    is made unnecessary by gear drives.
  • When used for lubricating oil and hydraulic
    systems, these pumps benefit from sealing effect
    and lubrication between parts.

139
RDP Pumped Volume.
  • Volumetric efficiency should be 100, but as the
    differential pressure increases, the leakage will
    increase. Slip less - if the pumped liquid is
    more viscous.
  • Slip - function of clearance, viscosity and
    differential pressure, hence constant
    irrespective of speed.
  • Slip or Leakage cause erosion and increase of
    clearance (more if liquid contains abrasives)

140
RDP Pressure, Limited by
  • Torque available from the motor.
  • Strength of the parts.
  • Amount of slip and leakage.
  • Consideration of overall efficiency.

141
RDP Acceleration Losses.
  • These are the greatest losses (Acceleration is a
    function of distance moved and speed.
  • In gear pump, depth and form of tooth influence
    this.
  • In screw pump, pitch of the screw influence
    this.

142
Air Operated Diaphragm Pump
143
Globe Valve
144
Piping
  • Piping systems are used to convey fluids. The
    term piping generally refers to the pipe,
    valves, fittings, flanges, and other components.
  • Fittings Everything in a system except pipes.
  • Pipe and tubing No definite rule for
    distinguishing between pipe and tubing. One
    difference is wall thickness typically, pipe has
    heavier walls. Pipe generally conveys fluid flow
    from one location to another, whereas tubing may
    direct static pressure for control or
    measurement. The term tubing also applies to the
    cylindrical elements that separate fluids in
    boilers and other heat exchangers.

145
Piping
  • Materials joined in a piping system must be
    similar, to avoid galvanic corrosion (where
    different metals connected and mutually in
    contact with seawater the metal which comes
    later in the galvanic series may corrode acts
    like a sacrificial anode).
  • Example of galvanic series Zinc, Aluminium,
    Carbon Steels, Cast Iron, Lead-Tin alloy, Lead,
    Brass, Copper, Bronze, Gunmetal, Copper-Nickel
    Iron, Monel Metal etc.
  • Pipe and fitting strength is affected by
    temperature as well as pressure, and both must be
    considered in the selection of materials and wall
    thickness. As temperature increases, material
    strength decreases. Higher pressure results in
    higher stresses on components.

146
Piping
  • Pipe is sized by nominal pipe size (NPS).
  • The nominal pipe size is based on nominal inside
    diameter for sizes up to 300 mm. Since the pipe
    is joined using standard size fittings, the
    outside diameter must be the same regardless of
    wall thickness. Consequently, pipe wall thickness
    is achieved by adjusting the inside diameter.
  • For larger pipe sizes (350mm and more), the
    nominal pipe size is based on the outside
    diameter.
  • Seamed pipe is formed by rolling a flat plate
    into a cylindrical shape and then welding along
    the longitudinal seam.
  • Seamless pipe is formed by a drawing process
    where red-hot metal is drawn over a piercing
    mandrel, forming the tubular shape directly.

147
Piping
  • Pipe threads differ from machine threads in that
    they are cut on a taper i.e., the thread diameter
    is smaller at the end of the pipe and
    progressively larger along the pipe length. As a
    result of the taper, when the pipe is screwed
    into a fitting, the threads force and increasing
    interference that assists in sealing against
    leakage. Compounds are applied to the external
    threads to any imperfections. Teflon tape or
    teflon-bearing pipe dope used on lower
    temperature connections and lubricants bearing
    copper or silver metal flakes are used in higher
    pressure, higher temperature joints. These
    compounds also prevent galling of the threads and
    seizing, thereby facilitating future disassembly
    for maintenance or repair.

148
Piping
  • Flanges consist of flat-faced disks that are
    bolted together, with a compliant gasket material
    installed between them. For high-pressure piping,
    it is standard practice to use raised-face
    flanges, where the flange face in the area within
    the bolt holes is raised to increase compression
    of the gasket in the sealing area. It should be
    noted that in any installation using cast-iron
    valves, raised face should not be used on the
    flanges. Using flat faces with cast iron avoids
    high bending stresses on the cast-iron flange.
  • Welded joints are used for general purpose
    piping and are required for high-pressure,
    high-temperature piping systems. Two types -
    socket-welded fittings and butt-welded fittings
    are used. Largerbore pipe systems are made up
    using butt-welded fittings.

149
Piping
Steel Subject to galvanic action and
rusting. Mild steel pipes for seawater are
protected by being galvanized or rubber
lined. Mild steel ERW or hot rolled pipes are
galvanized by hot-dipping. Seamless mild steel
pipes- used for (less than 460oc) steam, high
pressure air, feed discharges and all fuel oil
pressure piping. For greater than 460oc
applications steel requires additions of alloying
materials like Molybdenum and Chromium.
150
Piping
Cast Iron Poor corrosion resistance in
seawater, especially vulnerable to
graphitization. Weakness of Grey Cast Iron In
tension, and under shock loading. It is brittle
in nature. Hence limits applications to low
pressure requirements. Advantage Ease of
casting. Spheroidal Graphite Cast Iron ( S G Iron
) and Meehanite High strength versions,
suitable for use in shipside valves. S G Iron
also used for high pressure service and steam
below 460oc.
151
Piping
  • Copper pipes Suitable for moderate temperature
    and pressure.
  • Stainless Steel Widely used for cargo pipes of
    chemical tankers carrying very corrosive cargoes.
  • Non-ferrous alloys Brass is an alloy of copper
    and zinc. Bronze is an alloy of copper and tin.
    In both the cases there may be additions of other
    metals. Aluminium brass is also widely used. All
    these are resistant to seawater corrosion.
    Non-ferrous alloys are protected from corrosion
    by deposition of iron ions, if iron or steel
    fittings are used. Iron ion protection can also
    be supplied from sacrificial or driven iron
    anodes by dosing with ferrous sulphate.
  • Brasses in presence of seawater undergo
    dezincification. Remedy- Addition of arsenic
    (0.04) or other metals.
  • Some brasses prone to corrosion-stress cracking.

152
Piping
  • Erosion Result of abrasives, high water speed,
    entrained air, turbulence, cavitation. Turbulence
    and cavitation often caused by protuberances,
    high bends, abrupt change of pipe cross-sectional
    area, incorrectly cut jointing, weld deposits.
  • Temperature Above 450oc cause
    recrystallization creep in iron and steel. Low
    temperature (-162oc) as in liqified natural gas
    cause brittle failure. Varying temperatures cause
    stresses due to expansion and contraction.
  • Pipe fittings Cast iron gunmetal fittings
    are used for small sizes and moderate pressure.
    Cast or fusion welded (fabricated) mild steel or
    S G iron are used for high pressure and
    temperature and fuel oil under pressure. 0.5
    molybdenum steel used for temp greater than
    460oc- Molybdenum inhibits recrystallisation and
    therefore the resulting creep.

153
Pipe Installations
  • Vibration is the frequent cause of eventual pipe
    failure. Supports and clips (must permit free
    expansion and contraction) are used to prevent
    this. It is essential that pipe systems and heavy
    valve chests are seperately supported and
    stayed. Flanged connection to the pumps to be the
    last to be coupled after faces are correctly
    aligned.
  • Expansion arrangements to accommodate changes
    in length due to change in temperature (to
    prevent undue stress or distortion). Methods
    Anchored sleeve with stuffing box gland, right
    angle bend or loop, stainless steel bellows or
    expansion joint.
  • Water-tight bulkhead- Pipes carried thorough
    water-tight bulkheads, use special fittings to
    avoid impairment of their integrity.
  • Drains For steam pipes to avoid water-hammer

154
Expansion bellows
155
Expansion joints, bellows
  • Max and Min temperature to be considered when
    choosing bellows.
  • while installing do not over-compress or
    over-extend.
  • Usually the material is stainless steel upto
    500oc.
  • Normally bellows have internal sleeves to give
    smooth flow. Fit the bellows in correct
    direction.
  • Bellows will absorb movement or vibration in
    several planes, eliminating maintenance reduce
    friction and heat losses.

156
Globe Valve
157
Globe Valve
158
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159
Globe Valve
  • Bulbous body, valve seat, screw down plug or
    disc arranged at right angles to the axis of the
    pipe.
  • Sometimes both seat and disc faces are stellited
    or seat may be renewable and screwed into the
    valve chest or given a light interference fit and
    secured by grub screw. Seating may be flat or
    mitered (common). Spindle or stem may have a vee
    or square thread. Leakage along spindle arrested
    by stuffing box.
  • If there is any change in direction angle valve
    is used.

160
Stop check valve
161
Gate Valve
162
Gate Valve, Non rising
163
Gate Valve, Rising stem
164
Lift Check Valve
165
Swing Check Valve
166
Swing Check Valves
167
Check valve
168
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169
Ball Valve
170
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171
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172
Butterfly Valve
173
Pressure Reducing Valve
174
Valve Maintenance
175
Steam Trap

176
Flash Steam
177
Thermo Steam Traps
178
Thermostatic Steam Traps
179
Balanced Steam Traps
180
Bimetallic Steam Trap
181
Bimetallic Steam Trap
182
Steam Trap (Mechanical- Float)
183
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184
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185
Inverted Bucket Steam Trap
186
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187
Thermostatic Steam Traps
188
Thermodynamic Steam Traps
189
Thermodynamic Steam Traps
190
Strainers
191
Filter Elements
192
Baskets and Filter Bags
193
Filter Candles
194
Coupling
195
Gaskets
196
GASKETS
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