Pumps

CE NT RIFU GAL PU MP TER MS ABSOL UTE PR ESSUR E VACUUM SPEC IF IC GR AVIT Y PRES SUR E AND LIQUID HE IGH T RELATION SHIP S(H EA D) VAPOU R PRES SUR E SUC TION HEA D SUC TION LIF T TOT AL D YNA MIC HE AD

ABSO LU TE PRE SS URE Absolute Pressure is the sum of the available atmospheric pressure and the gage pressure in the pumping system Absolute Pressure(PSIA) = Gauge Pressure + Atmospheric Pressure

ATM OSP HERI C PRES SURE

VAC UUM The ful l or part ial el imi nation of Atmospheric Pressure Atmospheri c Pre ssu re on the Moon = 0 = Ful l V ac uum 1 Inch Hg Vacuum = 1. 13 Ft of Water

SP ECI FIC GRAVI TY The ratio of the weigh t of anythi ng to the wei ght of water. Exampl e Speci fic G ravi ty of HCl = Wei ght of H Cl ( /) Weight of Wate r = 10. 0 (/) 8. 34 = 1. 2

SPECI FIC GRA VIT Y

PRES SUR E AN D LIQ UID HEI GHT RELATI PON SH IPS (HEAD) 1 PSI = 2.31 Ft of Water Pressure, Liquid Height and Specific Gravity Relationship Gravity(SG) / 2.31 Pressure(PSI) = Head(FT) x Specific

VAPO UR PRES SUR E The pressure pushing agai nst atmospheric pressure on l iqui ds at el evated te mperat ures .

SUC TI ON HEA D A Suction Head exists when the liquid is taken from an open to atmosphere tank where the liquid level is above the centerline of the pump suction, commonly known as a Flooded Suction.

HEAD

FLOODED SUCTION HEAD

SUCTION LIFT A Suction Lift exists when the liquid is taken from an open to atmosphere tank where the liquid level is below the centerline of the pump suction

SUCTION LIFT

TOTAL DYNAMIC HEAD Total Dynamic Head (TDH) = Elevation(ft) + Friction(ft)

TOTAL DYNAMIC HEAD

Classification of pumps Reciprocating Single acting Double acting

Type of casing Volute

Closed

Triple cylinder Centrifugal

Diffuser ring

Type of impellor

Single cylinder Double cylinder

Vortex

Semi closed

Opened

Working head low

medium

high

Direction of flow Axial

Radial

mixed

Problems Pump does not deliver Pump deliver at reduced capacity Delivery performance reduced Pump delivers too much Delivery is interrupted Pumps runs in reverse direction Very noisy

Problems Unsteady running of the pump Pumping casing not leak proof Excessive leakage from stuffing box Fumes from stuffing box Mechanical Seal leaking Pump rotor blocked in stand still position Mechanical Seal leaking

Problems Pump is heating up and seizing Bearing temperature increase Motor will not start Motor is difficult to start Motor is running hot burning out

No delivery Incorrect layout of suction line (Formation of air pockets) Valve(s) in the suction and/or feed line not fully open. Screwed joints or flanges in the suction line not leak-proof. Ingress of air via leaking valves and fittings in the suction line (Stuffing box etc). Suction lift too great. Available NPSH too low (difference between pressure at suction branch and vapour pressure too low). Suction filter, foot valve clogged

No delivery 1. Delivery liquid too viscous. 2. Insufficient venting. 3. Speed too high (number of revolutions of driver

higher than nominal number of revolutions of pump). 4. Speed too low (number or revolutions of driver lower than nominal number of revolutions of pump). 5. Incorrect direction of rotation (electric motor, incorrectly connected, leads on the terminal board interchanged). 6. Impeller clogged.

No delivery Seating liquid tine/circulation line clogged Lantern Ring in the stuffing box is not positioned below the sealing liquid inlet. Sealing liquid omitted, Mechanical seal blocked; 0-ring-rotating seal ring or stationary seal ring damaged. Pump unsuitable for parallel operation. Type of pump unsuitable. Incorrect designing of pump for existing operating conditions.

Pump deliver at reduced capacity •

•

•

Speed too low (number or revolutions of driver lower than nominal number of revolutions of pump). Incorrect direction of rotation (electric motor, incorrectly connected, leads on the terminal board interchanged). Impeller clogged.

Pump deliver at reduced capacity 68. Pump unsuitable for parallel operation. 69. Type of pump unsuitable. 70. Incorrect designing of pump for existing operating conditions. 21. Impeller damaged. 74. Temperature of the liquid too high. _______

Reduced delivery performance Suction filter, foot valve clogged Suction does not reach down far enough into the delivery liquid Incorrect layout of suction line (Formation of air pockets) Screwed joints or flanges in the suction line not teak-proof. Ingress of air via leaking valves and fittings in the suction line (Stuffing box etc). Suction lift too great.

Reduced delivery performance Available NPSH too low (difference between pressure at suction branch and vapour pressure too low). 14.Delivery liquid containing too much gas and/or air. 15.Delivery liquid too viscous. 20. Impeller clogged. 21. Impeller damaged.

Reduced delivery performance 23. Separation of crystals from the delivery liquid (falling below the temperature limit/equilibrium temperature). 24. Seating liquid tine/circulation line clogged. 59. Unsuitable casing seal. 65. Contaminated delivery liquid, 69. Type of pump unsuitable. 74. Temperature of the liquid too high. _______

Pump delivers too much 17.Speed too high (number of revolutions of driver higher than nominal number of revolutions of pump). 68. Pump unsuitable for parallel operation. 69. Type of pump unsuitable. 70. Incorrect designing of pump for existing operating conditions.

Interrupted delivery 1. Suction filter, foot valve clogged. 3. Suction does not reach down far enough into the delivery liquid, 6. Shut-off valve in the feed line in unfavourable position. 7. Incorrect layout of suction line (Formation of air pockets) 8. Valve(s) in the suction and/or feed line not fully open. 11. Suction lift too great.

Interrupted delivery 12. Available NPSH too low (difference between pressure at suction branch and vapour pressure too low). 13. Cut-out level for starter too low (In automatic plants). 14. Delivery liquid containing too much gas and/or air. 15. Delivery liquid too viscous. 16. Insufficient venting.

Interrupted delivery 17. Speed too high (number of revolutions of driver higher than nominal number of revolutions of pump). 20. Impeller clogged. 23. Separation of crystals from the delivery liquid (falling below the temperature limit/equilibrium temperature). 24. Seating liquid tine/circulation line clogged.

Interrupted delivery 26. Lantern Ring in the stuffing box is not positioned below the sealing liquid inlet. 31. -Mechanical seal blocked; 0-ring-rotating seal ring or stationary seal ring damaged. 68. Pump unsuitable for parallel operation. 69. Type of pump unsuitable.

Interrupted delivery 70. Incorrect designing of pump for existing operating conditions. 74. Temperature of the liquid too high. _______

Pump runs in reverse direction 64. Non return valve gets stuck.

Pump noisy 1. Suction filter, foot valve clogged. 2. Nominal diameter of suction line too small. 6. Shut-off valve in the feed line in unfavourable position. 7. Incorrect layout of suction line (Formation of air pockets) 8. Valve(s) in the suction and/or feed line not fully open.

Pump noisy 11.Suction lift too great. 12.Available NPSH too low (difference between pressure at suction branch and vapour pressure too low). 14.Delivery liquid containing too much gas and/or air. 16.Insufficient venting. 20. Impeller clogged.

Pump noisy 21. Impeller damaged. 23. Separation of crystals from the delivery liquid (falling below the temperature limit/equilibrium temperature). 66. Delivery ftow too small. 67. Delivery flow too great. 68. Pump unsuitable for parallel operation. 69. Type of pump unsuitable.

Pump noisy 70. Incorrect designing of pump for existing operating conditions. 74. Temperature of the liquid too high. _______

Unsteady running of the pump 20. Impeller clogged. 21. Impeller damaged. 23. Separation of crystals from the delivery liquid (falling below the temperature limit/equilibrium temperature). 33. Bearing worn out.

Unsteady running of the pump 34. Insufficient lubrication of bearings (also in case of automatic lubrication). 36. Specified oil level not maintained . 67. Delivery flow too great. 70. Incorrect designing of pump for existing operating conditions. 38. Oil quality unsuitable. 39. Rolling contact bearings incorrectly fitted. 40. Axial stress on rolling contact bearings (no axial clearance for rotor)

Unsteady running of the pump 41. Bearings dirty. 42. Bearings rusty (corroded). 43. Axial thrust too great because of worn wearings, obstructed relief holes. 47. Alignment of coupling faulty or coupling loose. 48. Elastic element of coupling worn. 49. Foundation incorrectly performed.

Unsteady running of the pump 54. Pipe line under stress 55. Shaft runs untrue, 56. Shaft bent. 57. Rotor insufficiently balanced. 58. Rotor parts touching the casing. 63. Vibration of pipe work. 66. Delivery ftow too small.

Casing not leak proof 52 pump casing under stress 54. Pipe line under stress 59. Unsuitable casing seal. 60. Casing screws not light enough,

Leak from stuffing box 21. Impeller damaged. 25. Sealing liquid tine contaminated. 28. Packing incorrectly fitted. 29. Gland tightened too much/slanted. 30. Packing material not suitable for operating conditions. 32. Shaft sleeve/shaft worn in the region of the packing. 33. Bearing worn out.

Leak from stuffing box 55. Shaft runs untrue, 56. Shaft bent. 57. Rotor insufficiently balanced. 63. Vibration of pipe work. 66. Delivery flow too small. 67. Delivery flow too great. 70. Incorrect designing of pump for existing operating conditions.

Fumes from the stuffing box 23. Separation of crystals from the delivery liquid (falling below the temperature limit/equilibrium temperature). 24. Seating liquid tine/circulation line clogged. 25. Sealing liquid tine contaminated. 26. Lantern Ring in the stuffing box is not positioned below the sealing liquid inlet. 27. Sealing liquid omitted, 28. Packing incorrectly fitted. 29. Gland tightened too much/slanted.

32. Shaft sleeve/shaft worn in the region of the packing. 45. Insufficient cooling water supply. 46. Sediment in the cooling water chambers, 65. Contaminated delivery liquid,

Mechanical seal leak 21. Impeller damaged. 23. Separation of crystals from the delivery liquid (falling below the temperature limit/equilibrium temperature). 24. Seating liquid tine/circulation line clogged. 31. -Mechanical seal blocked; 0-ring-rotating seal ring or stationary seal ring damaged.

Mechanical seal leak 45. Insufficient cooling water supply. 46. Sediment in the cooling water chambers, 55. Shaft runs untrue, 57. Rotor insufficiently balanced. 65. Contaminated delivery liquid, 75. Spring of the mechanical seal damaged.

Pump rotor in stuck position 23. Separation of crystals from the delivery liquid (falling below the temperature limit/equilibrium temperature). 49. Foundation incorrectly performed. 50. Baseplate not rigid enough in the event of erection without foundation. 52. Pump casing under stress, 54. Pipe line under stress 58. Rotor parts touching the casing.

Pump is heating up and seizing 23. Separation of crystals from the delivery liquid (falling below the temperature limit/equilibrium temperature). 24. Seating liquid tine/circulation line clogged. 25. Sealing liquid tine contaminated. 26. Lantern Ring in the stuffing box is not positioned below the sealing liquid inlet. 27. Sealing liquid omitted,

Pump is heating up and seizing 28. Packing incorrectly fitted. 30. Packing material not suitable for operating conditions. 32. Shaft sleeve/shaft worn in the region of the packing. 43. Axial thrust too great because of worn wearings, obstructed relief holes.

Pump is heating up and seizing 45. Insufficient cooling water supply. 46. Sediment in the cooling water chambers, 49. Foundation incorrectly performed. 50. Baseplate not rigid enough in the event of erection without foundation. 54. Pipe line under stress 55. Shaft runs untrue,

Pump is heating up and seizing 56. Shaft bent. 57. Rotor insufficiently balanced. 58. Rotor parts touching the casing.

Bearing temperature increases 20. Impeller clogged. 21. Impeller damaged. 23. Separation of crystals from the delivery liquid (falling below the temperature limit/equilibrium temperature). 33. Bearing worn out. Insufficient lubrication

Bearing temperature increases Specified oil level not maintained 39. Rolling contact bearings incorrectly fitted. 40. Axial stress on rolling contact bearings (no axial clearance for rotor) 41. Bearings dirty. 42. Bearings rusty (corroded). 43. Axial thrust too great because of worn wearings, obstructed relief holes.

Bearing temperature increases 44. Radial shaft seal ring has not much tension (local heating-up of shaft) 45. Insufficient cooling water supply. 47. Alignment of coupling faulty or coupling loose. 48. Elastic element of coupling worn. 49. Foundation incorrectly performed. 50. Baseplate not rigid enough in the event of erection without foundation.

Bearing temperature increases 52. Pump casing under stress, 67. Delivery flow too great. 70. Incorrect designing of pump for existing operating conditions. 54. Pipe line under stress 55. Shaft runs untrue, 57. Rotor insufficiently balanced. 63. Vibration of pipe work. 66. Delivery ftow too small.

Motor will not start 15.Delivery liquid too viscous. 72. Short circuit-in the motor. 23. Separation of crystals from the delivery liquid (falling below the temperature limit/equilibrium temperature).

Motor difficult to start 15.Delivery liquid too viscous 17.Speed too high (number of revolutions of driver higher than nominal number of revolutions of pump). 23. Separation of crystals from the delivery liquid (falling below the temperature limit/equilibrium temperature).

Motor difficult to start 28. Packing incorrectly fitted. 29. Gland tightened too much/slanted. 49. Foundation incorrectly performed. 50. Baseplate not rigid enough in the event of erection without foundation. 54. Pipe line under stress

Motor difficult to start 58. Rotor parts touching the casing. 70. Incorrect designing of pump for existing operating conditions. 71. Voltage too low/power supply overloaded. 72. Short circuit-in the motor.

Motor running hot and burning out 15. Delivery liquid too viscous 17. Speed too high (number of revolutions of driver higher than nominal number of revolutions of pump). 23. Separation of crystals from the delivery liquid (falling below the temperature limit/equilibrium temperature). 28. Packing incorrectly fitted.

Motor running hot and burning out 29. Gland tightened too much/slanted. 43. Axial thrust too great because of worn wearings, obstructed relief holes. 58. Rotor parts touching the casing. 68. Pump unsuitable for parallel operation. 69. Type of pump unsuitable.

Motor running hot and burning out 70. Incorrect designing of pump for existing operating conditions. 71. Voltage too low/power supply overloaded. 72. Short circuit-in the motor. 73. Setting of circuit-breaker for motor handled too high.

Centrifugal Pump Operation

Centrifugal Pump Components The two main components of a centrifugal pump are the impeller and the volute. The impeller produces liquid velocity and the volute forces the liquid to discharge from the pump converting velocity to pressure. This is accomplished by offsetting the impeller in the volute and by maintaining a close clearance between the impeller and the volute at the cutwater. Please note the impeller rotation. A centrifugal pump impeller slings the liquid out of the volute. It does not cup the liquid.

PUMP OPERATION

CENTRIFUGAL PUMP TERMS Suction Cavitations Discharge Cavitations

Suction Cavitation

Suction Cavitation occurs when the pump suction is under a low pressure/high vacuum condition where the liquid turns into a vapor at the eye of the pump impeller. This vapor is carried over to the discharge side of the pump where it no longer sees vacuum and is compressed back into a liquid by the discharge pressure. This imploding action occurs violently and attacks the face of the impeller. An impeller that has been operating under a suction cavitation condition has large chunks of material removed from its face causing premature failure of the pump

SUCTION CAVITATION

Discharge Cavitation Discharge Cavitation occurs when the pump discharge is extremely high. It normally occurs in a pump that is running at less than 10% of its best efficiency point. The high discharge pressure causes the majority of the fluid to circulate inside the pump instead of being allowed to flow out the discharge.

•As the liquid flows around the impeller it must pass through the small clearance between the impeller and the pump cutwater at extremely high velocity. This velocity causes a vacuum to develop at the cutwater similar to what occurs in a venturi and turns the liquid into a vapor. A pump that has been operating under these conditions shows premature wear of the impeller vane tips and the pump cutwater. In addition due to the high pressure condition premature failure of the pump mechanical seal and bearings can be expected and under extreme conditions will break the impeller shaft.

DISCHARGE CAVITATION