Pump - Firdaus Sabturani

Question 1

What is a pump?

Answer 1

Is an energy converter where it converts mechanical energy
supplied at the pump shaft into mechanical energy of the liquid
flowing into the pump

Question 2

Purpose of Pump

Answer 2

To enable the liquid to flow through a pipeline or rises to a higher level or pressure.

Question 3

Centrifugal Pump

Answer 3

– Widely used in process industry
– Most used to transfer huge amount of liquid
– Low operating cost

Question 4

Positive displacement Pump

Answer 4

– Small size
– More efficient than centrifugal pump
– Used for Chemical injection, dosing pump, etc

Question 5

Pump Fundamentals

Answer 5

• Fluid is led to the eye or center of the impeller and is set into rotation by the impeller vanes
• Fluid is thrown from the periphery of the impeller with considerable velocity and pressure through centrifugal
  force
• The casing, which surrounds the impeller, has a volute or diffuser shaped passage of increasing area
• The casing collects the fluid leaving the impeller and converts a portion of its velocity energy into additional
  pressure energy
• The casing passage leads to the discharge nozzle of the pump where connected piping discharges the fluid to its place of use

Question 6

Types of Positive Displacement Pump

Answer 6

• Reciprocating pump
• Rotary pump

Question 7

Reciprocating pump

Answer 7

– Capable of handling of liquids with a high viscosity.
– Capable of handling low flow / high differential head combinations.
– Suitable for dosing/metering applications, including hazardous

Question 8

Rotary pump

Answer 8

– Capable of handling of liquids with a high viscosity.
– Capable of handling low flow / high differential head combinations.
– Flow is almost independent of the discharge pressure.

Question 9

Pump Capacity

Answer 9

refers to a rate of flow typically expressed in either m3/hr, barrels per day, or Kg/hr

Question 10

The total developed head

Answer 10

equal to the discharge head minus the suction head, (TDH = hd–hs), and is typically expressed in either “Meter” or “Kg/cm2”.

Question 11

Affinity Law

Answer 11

– Flow changes DIRECTLY(linear) with RPM.
– Head changes as a SQUARE of RPM.
– Power is proportional to Flow times Head
-it changes as CUBE of RPM.

Question 12

Case for Net Positive Suction Head

Answer 12

– Inside a pump, if pressure gets low enough (below vapour pressure), liquid will boil. The lowest pressure zone is usually at the suction area.

Question 13

If too many bubbles

Answer 13

suction gets blocked by them, and no more pumping…That is where “pump losses its head”

Question 14

How to Prevent

NPSH Required

Answer 14

• Double suction impeller
• Enlarged eye impeller
• Lower speed
• Suction inducer

Question 15

How to Prevent

NPSH Available

Answer 15

• Raise suction liquid level ( hs)
• Increase suction pressure ( Ps)
• Booster pump
• Reduce suction friction ( hf)
• Cool liquid ( reduce Pv)

Question 16

Cavitation

Answer 16

the formation of bubbles or cavities in liquid, developed in areas of relatively low pressure around an impeller.

Question 17

what happen during

Cavitation

Answer 17

• As bubbles flow from low pressure to higher, they implode against metal surfaces. These micro-hammer-like impacts erode the material, creating cavities –thus “cavitation”
• The collapsing of these bubbles trigger intense shockwaves inside the pump, causing significant damage to the impeller and/or the pump housing.

Question 18

NPSHR

Answer 18

the suction capability of an impeller

Question 19

NPSHR determined by:

Answer 19

• Inlet Diameter
• Rotating Speed
• Inlet Blade Angle
• Suction Inlet Approach

Question 20

Typical low flow situation is normally encountered in the industry due to

Answer 20

• Malfunction of downstream control valve or check valve
• Inadvertent closure of block valve
• Improper line-up

Question 21

damage of the pump and its component due to
the following reasons:

Answer 21

• Re-circulation at impeller inlet & outlet
• Risk of hydraulic instability
• Increased risk of cavitation damage
• Increased radial & axial thrusts
• Increased vibration levels
• Reduced seal and bearing life
• Temperature rise within pump

Question 22

Minimum Flow Protection
For centrifugal pump

Answer 22

• Recycling
• Continuous recycle for small pumps

Question 23

Minimum Flow Protection For positive displacement pumps

Answer 23

• Speed variation
• Recycling
• Stroke variation

Question 24

Methods for regulating/control Pump Flow

Answer 24

• Discharge throttling
  – Reduce flow by throttling discharge valve
• By-Pass Control
  – Return excess flow back to suction tank
• Cyclic Control
  – Switch pump off & on to limit total flow
• Variable Speed
  – Reduce pump speed to reduce flow