PPT CONSISTS OF VARIOUS PUMPS USED IN A SHIP, DIFFERENT PACKING MATERIALS

1. PUMPS
OBJECTIVE: Understand the construction and operating principles of
commonly used pumps.
PUMP is device which adds to the energy of a liquid or gas causing an increase
in its pressure and perhaps a movement of the fluid. There are many forms of
energy, but when pumps are being considered, use can be made of the energy
equation as follows.
A simple pumping system consists of a suction branch, a pump & a discharge
branch.

2. Names of Pumps used on board
• Main Lube oil pump
• Jacket cooling pump
• Piston cooling pump
• Main Seawater Pump
• Ballast Pump
• Fire & GS pump
• Ejector pump

3. • M.E. FO Booster pump
• Auxiliary Cooling water pump
• A/C Cooling water pump
• Bilge pump
• FO Transfer pump
• Heleshaw pump

4. • DO Transfer pump
• Hydrophor pumps
• Sludge pump
• Boiler water circulating pump
• Boiler feed water pump
• FWG Ejector pump
• FWG Condensate pump

7. Pump
characteristics
Pump only adds to the energy of the fluid in the system. Energy
required to bring the fluid to the pump is an external one and in most
practical conditions is provided by the atmospheric pressure. .Reference to
the figure, even though liquid on suction side is below the pump center
line, still liquid will rise up to the pump center because of external
atmospheric pressure acting on surface of liquid; & no pressure acting on
other side (i.e. at pump center).

8. Portable Positive Displacement pump (variable speed)
Coupling
guard
Pump
Motor
Suction Discharge Gearbox
pipe pipe

9. Marine pumps fall into two broad classes:
2.Displacement (self priming)
3.Dynamic
Displacement:
Liquid or gas is displaced from suction to the discharge by the
mechanical variation of the volume of a chamber or chambers. All
displacement pumps are self-priming pumps. These
pumps include Reciprocating pump, Gear pump, and Screw
pump.
Dynamic (Centrifugal pumps, Axial pumps) :
These dynamic pumps are basically radial flow or axial flow
type.
Centrifugal pump: Flow through the pump is induced by the
centrifugal force imparted to the liquid by the rotation of an impeller
or impellers. These pumps are not self-priming pumps and must be
primed by gravity supply or by priming equipment external or
internal with the pump.

10. Heart (Pump)

11. PISTON PUMP

12. RECIPROCATING-PISTON PUMP (self priming)
(Single Acting piston Pump)

13. Reciprocating motion of bucket
(piston) is obtained through a
connecting rod and crank
mechanism from an electric
motor drive or directly from a
steam reciprocating engine. On
downward stroke suction valve
lifts up against spring and
discharge valve remains shut and
upward travel discharge valve
against spring opens and suction
valve remains shut.
If the level of liquid to be pumped is below the pump center line, the initial
strokes of bucket will draw out air (gas, in case liquid is volatile) from the
suction pipe into discharge pipe, creating a low pressure (vacuum) in the
suction line. Liquid now rises into suction pipeline under atmospheric
pressure, (If the liquid is say water it will theoretically rise up to 10.3 meter and
hence pump can theoretically handle a suction lift of 10.3 meter; However in
real practice the pump can handle only upto 6 meter of suction head) once
liquid gets into the chamber, it will get discharged under pressure through the
discharge valve into discharge line. Pumping will continue in subsequent

14. RECIPROCATING-PISTON PUMP (self priming)
(Double Acting piston Pump)
Relief valve

15. Double acting piston pump

16. Double acting piston pump

17. Double Acting piston Pump
To get discharge of even flow
we utilize bottom water
chamber also by not keeping
it open to atmosphere;
instead using this chamber
along with one more set of
suction and delivery valve in
similar way as explained for
top chamber. It is therefore
Relief called a double acting pump;
valve which means that liquid is
discharged from both top and
bottom side of the bucket.
A relief valve is always fitted between the pump suction and discharge
chambers as shown in the figure, to protect the pump, should it be
operated with closed discharge valve. Otherwise damage may occur to
the pump being a positive displacement pump. Further, an air vessel is
provided, whose function is to reduce the pressure fluctuations, which
result from up an down strokes of piston (bucket). This is illustrated in
the above diagram.

18. Effect of providing air vessel at the discharge of a double acting
Without Air vessel With Air vessel

19. Advantages of Reciprocating
Pump
1. Ability to handle large portion of air, vapour or gas which enable
them to deal with volatile or hot liquids. Hence, these pumps are
used as cargo stripping pump for oil, chemical or gas tanker.
Also used as boiler feed water pump.
2. As these pumps are self-priming and can handle high suction
lifts, they can be used effectively as priming pumps, engine
room bilge pumps, cargo hold bilge pumps or cargo stripper
pumps.
Disadvantages of Reciprocating Pump
1. Construction is complicated due to presence of suction
valve, discharge valve, air vessels and relief valve. All positive
displacement pumps need a relief valve to prevent excess built
up of pressure under closure of delivery lines.

20. To start an electrically driven Reciprocating
Pump, proceed as follows.
1. Check lubrication.
2. Open water-end valves, suction & discharge. Never start
the pump with stop valves shut.
3. Open air vent cock: intermittent liquid discharge or air
indicates the pump is not primed.
4. Observe suction & discharge pressure gauges for
operating conditions of the pump.

21. Indications on Suc. & Disch. Pressure Gauges
while the reciprocating pump is in operation.
• For Suction Pressure Gauge:
• A) If pressure is approximately 76 cmHg vacuum – there is probably a
blockage in the suction line, eg; choked filters, causing a vacuum in the
system.
B) If pressure is zero – system is air-locked, eg; holed pipes, strainer cover
joints leaking etc.
C) If pressure is between 10 – 40cmHg - pump is operating normally with
liquid below pump level (eg; E.R. bilge wells). If pressure is positive
pump is also operating normally, with liquid above pump level
(eg; sea water suction).

22. Indications on Suc. & Disc. Pressure Gauges while the
reciprocating pump is in operation.
For Discharge Pressure Gauge:
1. If Pressure gauge shows immediate rise to max of scale or very high
there is blockage in the discharge line, eg; discharge valve not
opened. Relief valve would have lifted.
2. If pressure gauge pointer is fluctuating widely – air vessel or
chamber has little or no air.
3. If Pressure is zero – there is no discharge.
4. If Pressure is between 1.0 to 3.0 bar – pump is operating normally,
liquid should issue from the vent cock.

23. GEAR PUMP
This is a rotary displacement or rotary positive displacement pump. Two toothed
wheels, shown, mesh together and are a close fit in casing.. Initially the air or gas is
trapped between each pair of two consecutive teeth and same is dragged along the
casing from suction to discharge side till no more air is left on the suction side. Liquid
from the tank will thus rise up into suction line under atmospheric pressure.
Subsequently this liquid will now be trapped between each pair of two consecutive
teeth and dragged along the casing into discharge side and pumping of liquid will
commence. The working principle just explained is what makes the pump a self-
priming pump. Further if the liquid level on suction side is at a higher level, the liquid
will flow into suction side on its own at first instant itself.
Usually the pump is electric motor driven through a chain or wheel drive. Control
of flow rate is achieved by a by-pass valve or by controlling speed of prime-mover.
A number of such pumps in series can be used to develop high pressure. Such
pumps are efficient (i.e very little losses) and smooth running.
These pumps are used for duties as a lube oil pump, boiler fuel oil pump, fuel oil
transfer pump, main engine driven lube oil pump. As a main Engine driven lube oil
pump it will have a set of suction and discharge valve to gave same side discharge
at all times irrespective of ahead or astern movement of the main engine.

24. GEAR PUMP OR GEAR WHEEL PUMP

25. Gear Pump Discharge
Suction

27. Gear Pump (3 lobe)

29. SCREW PUMP OR SCREW DISPLACEMENT PUMP
Two screws are driven in phase by timing gear. (Unlike gear pump where
one gear drives the other). This ensures that correct clearance is
maintained at all times between the screws, thereby preventing over
heating and possible seizure. Pumping is effected by the two
intermeshing screws rotating within a pump casing. Each screw shaft has
a right and a left-had screw, see figure
When the screws rotate, their close relation to each other creates
pockets in the helices; these pockets move axially and have the same
effect as a piston moving constantly in one direction.
The pump initially draws in air or gas (from volatile liquids) if liquid
level is below pump center, creates vacuum; liquid rises up under
atmosphere pressure filling pump casing.
Displacement or pumping takes place when the screws are further
rotated and liquid is drawn into the screws at the outer ends and pumped
inwards to discharge into the pump outlet.
Relief valve prevents built up of excessive pressure due to
obstruction on discharge line and thus protects the casing against
possible damage.

30. Helical Rotor, Eccentric Screw Pumps(single screw)

31. Double Screw Pump

32. Construction
and working
of screw
pump

34. Advantages of screw pumps
Since pumps are self-priming and able to pump liquid and
vapour without loss of suction they are particular useful when
draining tanks of high vapour pressure liquids (Chemical /
liquefied gases).
Pumps are well suited for tank draining and where fluid supply
in intermittent, such as may occur in lubricating oil supply to
engines, with the vessel rolling and pitching.
They are suitable for operation at high rotational speed (3500
rpm; 1000 Lts /Min.) and can thus be driven by electric motor.
Can handle high viscosity (4000 centistokes) fluid. Pumps are
quiet, smooth running and reliable.

37. CENTRIFUGAL PUMPS
Ships use centrifugal pumps for fire and flushing systems.
Internal-combustion engines use centrifugal pumps to circulate
cooling water. There are many types of centrifugal pumps,
but all operate on the same principle

38. The centrifugal pump uses the throwing force of a rapidly
revolving IMPELLER. The rotating impeller creates an empty
space at the center hole (eye). The pressure at this point is
less than atmospheric pressure (because of the mechanically
displaced liquid). This causes atmospheric pres-sure to act on
the surface of the liquid being pumped, forcing it into the
pump casing and through the hole in the center of the
impeller. It is then discharged from the outer rim of the
impeller.

39. By the time the liquid reaches the outer rim of the impeller,
it has acquired considerable velocity (kinetic energy). The
flow of liquid then slows down as it moves through a volute
or series of diffusing passages. As the velocity of the liquid
decreases, its pressure increases; and thus its kinetic energy
is transformed into potential energy.

40. DYNAMIC PUMPS - CENTRIFUGAL PUMP

42. CONSTRUCTION AND WORKING:
The pump consists of rotating impeller within a stationary casing. The impeller
construction has two discs joined at in between surface by a set of internal
curved vanes. Impeller has an eye (opening) at the center and is mounted on
shaft, which is driven by an electric motor, steam engine through crank
mechanism or turbine, or other prime mover.
Opening in the sides of the impeller near the shaft, called eye,
communicates with the suction branch as shown in figure
Assume there is a certain amount of fluid at the eye of the rotating impeller.
The fluid will flow radially outwards (because of centrifugal action) along the
curved vanes in the impeller, increasing its linear velocity.

43. When the pump impeller rotates the fluid leaves the impeller. The high velocity fluid
is collected in specially shaped casing (volute casing), where some of the
kinetic energy of the fluid is converted into pressure energy. Fluid under
pressure now leaves the impeller producing a drop in pressure behind it at the
eye of the impeller. This causes fluid from the suction pipe to flow into pump
under atmospheric pressure. However, if initially there is not liquid at the eye,
there will be no pumping action as explained.
Centrifugal pump therefore is not a self-priming pump. In such case, where
normally at start of the pump the level of the liquid is below the eye of the
centrifugal pump, we have to prime the pump.

44. Centrifugal pumps
Horizontal pump Discharge
Suction
Discharge
Vertical pump
Impeller

45. Impeller

49. Prime the pump: Use an air pump initially to draw out air from the suction
branch & thus make liquid rise to the eye under atmospheric pressure.
Eg: Emergency fire pump. Bilge and ballast pump.
BILGE AND BALLAST PUMP
In absence of liquid, air (sometimes also vapour) will be present at the eye,
and owing to its light density air could be thrown out under centrifugal force
only if rpm of the impeller is very high (Turbo charger blower).

50. Automatic arrangement for pumping out bilges, using a centrifugal pump is shown
above, where the air (vane) pump will get engaged automatically and draw out any
air at the start or during running. Once air is drawn out it will get disengaged
automatically.

51. In case of pumping out engine room bilges using a centrifugal pump – we
can prime the pump by initially drawing in water from outside sea, level of
which is higher. Once water runs into the eye of rotating impeller, the suction
branch of pump can be switched over from sea to engine room bilge’s and
pumping out of bilge’s can now commence.

52. Similar (previous) method can be used when stripping a cargo tank. Initial
liquid can be drawn from an oil tank, level of which is higher than the pump.

53. Performance Characteristic Curves of a Centrifugal Pump
From above it is clear
I. That if the pump discharge head is lesser the flow rate of liquid is
higher and therefore pumping of liquid is faster.
Pump if run at normal duty flow rate by maintaining normal duty discharge
head the liquid will be pumped utilizing least possible rate of energy by the
pump (at this point of the pump is maximum).

54. NPSH
This stand for net Positive Suction Head. If the pressure exerted by atmospheric
air ( or any other atmosphere which is surrounding the liquid on suction side) is
H0 and is more than the three losses mentioned below :
Loss of head because of friction in the suction line H1.
+
Loss of head because of volatility of liquid H2.
+
Loss of head in raising the liquid to the pump suction H3.
Only then will the liquid rise up to the pump. However the liquid can be
discharged effectively and without cavitations of the pump only if this “left over
head” called available NPSH is greater than the required NPSH provided by the
pump manufacturer.

55. CAVITATION
This process of the formation and subsequent collapse of vapor bubbles in a
pump is called cavitation.Cavitation causes
2. Degrades the performance of a pump - fluctuating flow rate and
discharge pr.
3. Destructive to pumps internal components. When a pump cavitates,
vapor bubbles form in the low-pressure region directly behind the
rotating impeller vanes. These vapor bubbles then move toward the
oncoming impeller vane, where they collapse and cause a physical shock
to the leading edge of the impeller vane. This physical shock creates
small pits on the leading edge of the impeller vane. Each individual pit is
microscopic in size, but the cumulative effect of millions of these pits
formed over a period of hours or days can literally destroy a pump
impeller.
3. Excessive pump vibration. Vibration could damage pump bearings, wearing
rings, and seals. Noise is one of the indications that a centrifugal pump is
cavitating.
A cavitating pump can sound like a can of marbles being shaken. Other
indications that can be observed from a remote operating station are
fluctuating discharge pressure, flow rate, and pump motor current.

57. VAPOUR PRESSURE
 VAPOUR PRESSURE OF A LIQUID IS THE ABSOLUTE
PRESSURE AT WHICH THE FLUID VAPOURISES OR
CONVERTS INTO GAS AT A SPECIFIC TEMPERATURE.
 IT IS EXPRESSED IN ILBS / SQUARE INCH, (KG/CM2).
 THE VAPOUR PRESSURE OF A LIQUID INCREASES WITH
ITS TEMPERATURE.

58. CAVITATION
 IT IS THE FORMATION OF AND SUBSEQUENT COLLAPSE OR
IMPLOSION OF VAPOUR BUBBLES IN THE PUMP.
 IT OCCURS BECAUSE THE ABSOLUTE PRESSURE ON THE
LIQUID FALLS BELOW THE LIQUIDS VAPOUR PRESSURE.
 WHEN THE VAPOUR BUBBLES COLLAPSE WITH ENOUGH
FREQUENCY, IT SOUNDS LIKE MARBLES AND ROCKS ARE
MOVING THROUGH THE PUMP.
 IF VAPOUR BUBBLES COLLAPSE WITH ENOUGH ENERGY,
THEY CAN REMOVE METAL FROM INTERNAL CASING WALL
AND LEAVE INDENT MARKS APPEARING LIKE BLOWS
FROM A LARGE BALL PEIN HAMMER.

59. Reasons for cavitation
 REDUCTION OF PRESSURE AT THE SUCTION
NOZZLE.
 INCREASE IN TEMPERATURE OF THE LIQUID.
 INCREASE IN VELOCITY OR FLOW.
 REDUCTION OF THE FLOW, DUE TO CHANGE
IN VISCOSITY OF THE LIQUID.

60. EFFECTS OF CAVITATION
 PITTING MARKS ON THE IMPELLOR BLADES
AND ON THE INTERNAL VOLUTE CASING WALL
OF THE PUMP.
.
 PREMATURE BEARING FAILURE.
 SHAFT BREAKAGE & OTHER FATIGUE
FAILURES IN THE PUMP
 PREMATURE MECHANICAL FAILURE.

62. Cavitation damage to propeller

63. Impeller
• A scroll type inducer may be fitted to the
inlet which improves the efficiency of unit
and allows the pump to operate with low
suction pressures.

64. Wear Rings
• For efficient operation it is important to
ensure that leakage from the high to low
pressure side is kept to a minimum. This is
achieved by the use of wearing rings.
Traditionally these are fitted to the casing,to
increase the longevity of the impeller wear
ring tyres may be fitted.

65. Wear Rings
• The clearance given for wear rings is often
a source of contention especially when
dealing with on-ship made rings. A
clearance of 1/1000 of the diameter of the
bore is often quoted although this may be
very difficult to achieve in practice.

66. Types of Centrifugal Pumps
There are many different types of centrifugal pumps, but the
two you are most likely to encounter onboard ship are the
volute pump and the diffuser pump.

67. VOLUTE PUMP
In the volute pump, shown in figure 13-6, the impeller
discharges into a volute (a gradually widening spiral chan-
nel in the pump casing). As the liquid passes through the
volute and into the discharge noz-zle, a great part of its
kinetic energy (velocity head) is converted into potential
energy (pressure head)

69. DIFFUSER PUMP
In the diffuser pump, shown in figure 13-7, the liquid
leaving the impeller is first slowed down by the stationary
dif-fuser vanes that surround the impeller. The liquid is
forced through gradually widening passages in the diffuser
ring and into the volute (casing). Since both the diffuser
vanes and the volute reduce the velocity of the liquid,
there is an almost complete conversion of kinetic energy to
potential energy.

71. AXIAL FLOW PUMP or STRAIGHT FLOW or PROPELLER PUMP
Axial flow pump is one in
which a screw propeller is
used to create an increase
in pressure by causing an
axial acceleration of liquid.
The velocity increase is then
converted into pressure by
suitably shaped outlet
passage and guide vanes.
Pump works similar to an
idea of a propeller working
in a closed duct.
When conditions like large
capacity and relatively low
discharge head of upto 12 m
have to be met, a horizontal
or vertically arranged axial
pump is most suitable.
These pumps are used as sw circulating pumps for main condenser,
which flow rate has to be large and discharge head to be low (as
pumping is from sea to sea). Also used for the duties of heeling and
trimming of ships. This is again because the pump is of reversible flow

72. PUMP MAINTENANCE INTERVAL
• MONTHLY: Check the temp. not exceeding >160*F.
• QUARTERLY: Drain bearing oil, wash out & refill.
• SEMI ANNUALLY: Check shaft packing for leakage, clearencr
not to exceed 0.003”/inch on the wear ring.
• DISADVANTAGE IN OVERHAULING:
• Cost is high.
• Unavailable for emergency.
• Faulty assembly.
• Uneconomical.
• REASONS FOR PUMP INSPECTION
• 1. Fall of performance.
• 2. Excessive noise.
• 3. Driver is overloaded.
• 4. Excessive vibration.
• This rule does not hold good for corrosion or errosion. 85% of the
troubles are due to suction side of the pump.

73. Diaphragm pump

74. Double Acting Diaphragm
pump(Weldon)

75. WELDON PUMP
• 1. Blow out the air supply line to remove any water or dirt before it
• is attached to the pump.
2. Pour a small amount of clean luboil into the air inlet.
3. Fill lub oil in reservoir.
4. Exhaust pipe to see that its outlet is above the air supply box.
VITAL SPARES FOR THE CENTRIFUGAL PUMP.
1. One set of shaft bearings.
2. One set of shaft seal.
3. One set of wearing ring.
4. Suitable Packing or Mechanical seal.
FREEZING.
Drain a pump when it is to be left idle in an area in which freezing
temperature are likely.

76. Multistage Centrifugal pump

77. Duplex pump

78. Axial piston pump

80. Radial piston pump

81. DUTCH PUMP

82. VANE PUMP

83. Rotary VANE Pump

85. 1) Piston Block
2) Cylinder Drum
3) Piston Shaft
4) Five degree angled
control surface
5) End Plate
6 & 7) Ports
8) Drive Shaft
9) Piston Head
1) Piston Block
2) Cylinder Drum
3) Piston Shaft
4) Five degree angled
control surface
5) End Plate
6 & 7) Ports
8) Drive Shaft
9) Piston Head

88. Centrifugal Pumps
Shaft: Any wear which is observed on the sleeve in way of
packing area to be monitored and unevenness
removed. Packing accordingly used for the changed
dia. However, cause Impeller clearance: To be
checked for excessive side clearance between
impeller and wear ring.
If so, rings to be replaced. Casing and impeller also to be
examined for thinning/wear, corrective action as
necessary to be taken.
for the wear could be wrong type of packing and if so,
proper type to be used.
Temporary repair can be done on shafts without sleeves,
or sleeves can be renewed when they are fitted.

89. Bushes and Bearings: Bush clearance to be checked and
changed, if found excessive. Similarly, bearings to
be changed, if worn excessively.
Stuffing boxes: The packing are to be kept in good
condition and their condition regularly checked and
renewed if required, when leakages are found
greater, even on even tightening.
Hydraulic Balance: Wherever balance devices are fitted,
these need to be checked.

90. Axial Thrust
• The pressures generated by a centrifugal pump
exert forces on both its stationary and rotating
parts.
• Axial hydraulic thrust is the sum of unbalanced
forces acting on the impeller in the axial direction.
• Impeller design balances some of the forces, but
some other means have to adopted to counter
balance others.

91. Axial Thrust
• Single Suction Impeller
showing the acting
forces.
• A suitable large capacity
thrust bearing can take
up the axial thrust in
single stage pumps.
• Larger pumps needs to
be balanced within.

92. Actual Pressure Distribution on front and back shrouds of
single suction impeller with shaft thro the impeller eye

93. Effect of pump out vanes in a single-suction
impeller to reduce axial thrust.

95. Axial Thrust
• Double Suction Impeller
showing the forces acting.
• Theoretically a double-
suction impeller is in
hydraulic balance.
• Limiting factors: suction
passages to both suction
sides may not provide equal
flow.
• Non symmetrical waterway
construction.

100. The Liquid ring air pump consists of a bladed circular rotor
shrouded on the underside, rotating in an oval casing. Sealing
water is drawn into the whirlpool casing through a make up supply
pipe.
The water follows the periphery of the casing due to the centrifugal
force imparted to it by the rotor and the ‘water ring’ , revolving
eccentric to the blade recedes from and reapproaches the rotor
boss twice in one revolution, thus producing in effect a series of
reciprocating water pistons between the blades

101. • The inner edge of the water ring forms
the boundary of two eccentric cores
round the rotor boss, while the blades
run full of water. A and B in fig.
• Assuming the space between each
blade to be cylinder, then in one-half
revolution the water is thrown from F
to G and back again to F, constituting
one suction and one discharge stroke
and this occurs twice in one revolution

102. • It will be understood therefore, that if
shaped suction and discharge ports are
provided in way of the path of the eccentric
cores formed by the rotating water, air will
be drawn through the suction ports and
expelled through the discharge ports, as
each blade passes the ports.
• Such ports are arranged in the stationery
rotor plate fitted in the cover above the
rotor.

103. • In each revolution,therefore, the water
recedes from the rotor boss,drawing air
through the suction ports in the rotor plate
into the eccentric core of the water
ring,from where it is forced through the
discharge ports in the rotor plate after the
points of maximum throw-out as ‘G’ have
been passed and the water reapproaches
the rotor boss.
• A continous supply of sealing water is
circulated from the reservoir to the
whirlpool casing and is discharged with the
air back to the reservoir.(The air passes to
atmosphere through the overflow pipe.)

104. • This circulation ensures that a full ‘Water
Ring’ is maintained and the cooling coil
incorporated in the reservoir limits the
temp. rise of the sealing water during
long periods of operation. The supply for
the cooling coil can be taken from any
convenient seawater connection. About
0.152 lits/sec is required at a pressure
not exceeding 2 bar
• The reservoir has a cooling coil through
which passes seawater and this cools the
fresh water which gets heated due to the
churning action of the air pump impeller.

112. Advantages of a Central Priming System
1. Lower initial cost or reduced capital cost.
2. Saving in total power since each pump does not have
its own exhauster or priming unit operating all
the while the pump is operating.
3. easier or simpler maintenance.
4. Automatic-takes care of any minor leaks that may be
present in the suction side of a centrifugal pump.
5. Very effective.
6. Easy to operate.

115. – Centrifugal pumps may be started
against a shut or partially shut
discharge valve.
– This is especially true for larger pumps
where the shutting of the discharge
reduces starting and running load.
– It should be noted that the partially
shutting of the suction valve on both
types of pumps leads to damaging
cavitation.

116. • Without careful design an axial force is created by
the action of the impeller.
• This is due to the low pressure acting on the suction
eye whilst the rest of the impeller is subjected to
discharge pressure.
• One solution is shown above where radial blades are
cast into the back (stuffing box side) of the impeller.

117. • These blades are commonly called pump-out
vanes, and are meant to increase the centrifugal
force of the fluid trapped behind the impeller.
• This causes the fluid to be "thrown" outwards,
reducing the pressure behind the impeller for the
same reason that the impeller causes a reduction
of pressure at the suction eye.

118. • Another method which may be found in
conjunction with the pump-out vanes are the
balancing holes.
• These are holes drilled near the center of the
impeller, connecting the space in the back of the
impeller with the suction eye.
• This reliefs the pressure behind the impeller by
allowing the high pressure fluid trapped there to
flow to the low pressure region at the suction eye.
• In order for this to be effective, there must be a
tight clearance between the impeller and the casing
to reduce the flow of fluid into the back of the
impeller.

119. • Alternately dual back to back impellers may be
fitted in common with a double casing
• Materials suitable for general service
• Shaft Stainless steel
• Impeller - Aluminum bronze
• Casing - Bronze or cast iron
• Wear ring - Aluminum bronze or brass

120. Alignment of couplings
Flexible couplings will absorb small deviating in the relative
positions of the shaft ends to be connected, however, a careful
and accurate alignment will prolong the life of the coupling
flexibles. When aligning the coupling halves the parallel and
angular accuracy should be as great as possible. Alignment
must be carried out in two axial planes at right angles (see
sketch).

122. A perfect alignment can be achieved by means of a
straight-edge (axial parallelism) and a feeler gauge
(squareness) or by means of an indicator, as shown in
figures above. The coupling clearance must be within
2-6 mm according to the size of the coupling.

123. Before starting any pump, you should
check these basic items.
Check direction of rotation (marked with an arrow).
Check that there is liquid in the pump (might have been
emptied by standstill).
Check that the pump is able to turn by hand.
Check that the pump has been lubricated with grease.
Check the pump for noises and vibrations immediately
after starting.
Check priming pump (if any).

124. Starting of the pump:
When the preceding preparations and installations have been
completed the pump can be started. Centrifugal pumps must be
provided with a bypass if it is operated for long periods with
closed valve on the discharge side as, otherwise, a too strong
heating and expansion of the pump medium will occur. When
starting positive pumps (e.g. piston pumps, gear pumps and
others), the valve on the discharge side must be open as,
otherwise, the pump may burst, in spite of the fact that a
bypass valve to the suction side is incorporated in these
pumps.

125. Pumps with mechanical shaft seal must be protected against
impurities and dry running. Supply of liquid or oil to the
mechanical shaft seal is imperative. Please note that clogged
filters will cause considerable friction losses, which may
decisively affect the suction capacity and output of the pump.

126. Check also that the pump shaft can be turned by hand. Check
also when starting the pump that the direction of rotation is
correct (usually shown with an arrow on the pump), and open
slowly the valve on the discharge side of the pump. At
normal discharge head the pump should run smoothly without
abnormal noises and vibrations after about one minute of
operation.

127. It is an absolute requirement that pumps are not operating
unnecessarily long without liquid, normally max. 5 min.
During the first hours of operation bearings, packings and
mechanical shaft (seal(s) should be checked for heating and
leakage. Normal bearing temperature is 40-75'C. Max.
temperature for normal ball and roller bearings is up to 105'C.

128. PUMP TROUBLE SHOOTING
• Pump and motor cannot be actuated:
1. Impeller or shaft blocked.
2. Motor fault.

129. B. Motor running but no pumping effect:
1. Motor rotation is not transmitted through
coupling.
2. Discharge valve closed.
3. Non-return valve or other valves are closed.
4. Suction line closed or filter clogged.
5. Air in pump casing.
6. Suction line leaking.
7. Shaft seal leaking.
8. Bottom valve defective.
9. Suction lift too high.
10. Priming pump defective.

130. C. Insufficient capacity:
1. Wrong direction of rotation.
2. Number of revolutions too low.
3. Counter-pressure too high.
4. Suction line or impeller partly clogged.
5. Air in pump casing.
6. Air in pumping medium.
7. Suction lift too high (inlet pressure too low).
8. Capitation.
9. Suction line leaking.
10. Shaft seal leaking.
11. Pump worn out.

131. D. Pump pressure too high:
1. Number of revolutions too high.
2. Impeller oversized.
3. Too many pressure stages.
4. Specific gravity of pumping medium too high.
5. Viscosity of pumping medium too low.
6. Inlet pressure too high.
7. Manometer defective.

132. E. Capacity too large:
1. Number of revolutions too high.
2. Impeller diameter too big.
3. Counter-pressure too low.

133. F. Discharge head too low:
1. Number of revolutions too low.
2. Impeller diameter too small.
3. Too few pressure stages.
4. Specific gravity of pumping medium too low.
5. Viscosity of pumping medium too high.
6. Manometer defective.

134. G. Power consumption too large:
1. Motor too small.
2. Motor fault.
3. Capacity too large.
4. Counter-pressure too low.
5. Stuffing-box tightened too much.
6. Shaft ends out of alignment.
7. Electricity supply incorrect (voltage, amperage,
frequency).

135. H. Pump output decreases or stops:
1. Suction line leaking.
2. Shaft seal leaking.
3. Increasing suction lift.
4. Filter clogged.
5. Cavitation.

136. • Irregular running:
1. Bearings defective.
2. Motor fault.

137. K. Increasing noise level:
1. Beginning cavitations.
2. Air in pumping medium.
3. Capacity too large.
4. Clamping to base loosened.
5. Base bolts loosened.
6. Influences from pipe connections or base.

138. L. Leaks:
1. Cracks in pump casing.
2. Faulty assembly of pump.
3. Pipe connections leaking.
4. Shaft seal leaking (in case of soft stuffing-box packing
minor leaks are necessary).

139. M. Bearing temperature too high:
1. Faulty lubrication or wrong lubricant.
2. Deficient pump alignment.
3. Influences from pipe line.
4. Coupling distance wrong.
5. Shaft bent.
6. Foreign bodies or impurities in bearings

140. N. Pump wears out quickly:
1. Wrong materials in relation to pumping medium.
2. Cavitations.
3. Stuffing-box tightened too much.
4. Shaft bent.
5. Deficient alignment.
6. Influences through pipe line.

141. O. Stark vibrations:
1. Foreign bodies in pump.
2. Motor out of balance.
3. Other influences.

142. Starting of a Cargo Oil Pump
1. Fire the boiler & maintain max. Pressure.
2. Keep the drain valves in the steam pipe lines to Cargo Oil Pump Turbine open
and the drain valves in the Turbines also kept open .
3. Check Lub Oil level is normal in the turbine and run the priming Lub Oil pump to
the turbine on auto mode.
4 Open steam at the boiler, crack open only & open warming up steam line to
turbine and gland packing steam line.
5 Drain all the condensate from the pipe lines and the Turbine.
6 Now , when steam starts coming out, shut all the drain valves , which were kept
open.
7. Keep the turbine in Preheat condition for 30 minutes.
8. Start vacuum pump to the condenser & rotate the pump shaft few turns.
9. When duty officer requests for COP, open steam valve at the boiler to full open
position slowly.
10. Open, turbine steam outlet valve to full open & crack open turbine steam inlet
valve.
11. Pump shaft starts to revolve, keep around 100 – 200 RPM for 10 minutes in order
to warm up the steam turbine parts. Check for any abnormalities.
12. Finally open steam inlet valve slowly to full open condition & maintain the boiler
pressure.
13. Check for few minutes whether all the parameters are okey.Then leave the
place.

143. Stopping of a Cargo Oil Pump
When duty officer informs to stop the COP, shut the steam
inlet valve to turbine slowly & the steam outlet valve
shut full.
At the Boiler ,steam valve to turbine shut.
Keep all the drains open, after 30 minutes, stop the
Priming LO pump & the vacuum pump.

144. Bilge oil seperator
•

146. Hydropher System

147. e.r. Bilge system
•

148. JOINTING & PACKING MATERIALS
AND ITS USE
MEDIUM PACKING MATERIAL JOINTING MATERIAL
COLD WATER TALLOW PACKING OF NATURAL OR
HEMP, FLAX COTTON OR SYNTHETIC RUBBER
RAYON WITH OR WITHOUT
LINEN LINING.
HOT WATER GRAPHITED ASBESTOS, NATURAL OR
ASBESTOS WITH MICA SYBTHETIC RUBBER
(S.S.SHAFT) WITH OR WITHOUT
LINEN ASBESTOS FOR
TEMP. 100*C
LO & FO NYLON, TEFLON BONDED CORK, OIL
PAPER & FIBRE,
ASBESTOS FOR TEMP.
100*C
STEAM SAME AS FOR HOT ASBESTOS WITH METAL
WATER LINING OR WIRE MESH
FOR SUPERHEATED
148
STEAM.

149. 1 1. Seating ring 2.
Seating(stationary)
3.Seating(rotating) 6) Bellows
7) Spring
4.Steel ring
8) Driving ring
5. Spring retainer 9) Spring
retainer.
While the stationary seating(2) can be of bronze or stainless steel, the
rotating seat(3) can be of carbon, bronze or stainless steel, possibly
with a monel or stellite surface.
It is important that cooling/lubricating liquid is led to mechanical
seals from the lowest point on the pressure side of the pump, to ensure
that some liquid reaches them, even when priming. They must not run
in an air pocket and care must be taken to prevent ingress of foreign
matter. Most mechanical seals incorporate a carbon face.

150. Oil Seal

151. MECHANICAL SEALS
The design of mechanical seals may differ in various physical aspects, but
all are fundamentally the same in principle. The sealing surfaces are located in
a plane perpendicular to the shaft and usually consists of two highly polished
surfaces running adjacently, one surface being in contact with the shaft and the
other to the stationary portion of the pump. The polished and lapped surfaces
which are of dissimilar materials are held in continual contact by a spring,
forming a fluid-tight seal between the rotating and stationary members with very
small frictional losses.
A mechanical seal is similar to a bearing in that it involves a close running
clearance with a liquid film between the faces of two dissimilar materials. The
lubrication and cooling provided by this film cuts down wear as does a proper
choice of the seal face materials.

152. JOINTING
( Gaskets)
The jointing used between assembled machined parts in the form of thin sheets.
There are innumerable jointing manufactured on an asbestos base. These usually
consists of approximately 60 to 90% long – threaded asbestos mixed with a
binding agent comprised of India rubber or synthetic resin and mineral filling
material. Such sheet jointing can be used up to approximately 500*C and upto 100
bar. A special asbestos-type jointing has been developed for refrigerating plants.
The asbestos jointing can be reinforced with brass or steel wire mesh or with
perforated metal plate. These jointing can be used at very high temperature and
pressure and especially for pipeline systems for superheated steam or as joining in
diesel engine exhaust systems.

153. PACKINGS, JOINTING AND SEALS.
PACKING
To create tightness or sealing between machine parts, a plastic material normally termed
“packing” is often used.
The various types of packing or sealing can be divided into two Main groups:
1. Sealing between reciprocating/rotating parts (dynamic)
2. Sealing between static parts.
Objective:-
1.To prevent fluid, eg. water, lubricating oil, fuel oil, etc., from escaping from a system.
2.To prevent gases and vapours from escaping from a system.
3. To prevent undesirable entry of gases, fluids and dirt into a system.
For a sealing material to function satisfactorily it must fulfill certain requirements,
which differ widely depending on the type of system in which the seal is to be used.
Eg. – a packing material, which is well suited to one system, may be completely
unusable in another.
The three most important requirements that a packing or seal must fulfill are :
1. It must be made of correct material.
2. It must be suitably dimensioned.