WATER HAMMER

(Hydraulic Transient / Surge)

Surge

Electricity/ Magnetic FluxFluid – GasesFluid - Water

Surge -Water

Open ChannelSea - TsunamiPipes – Water Hammer

WATER HAMMER IS CAUSED BY CHANGES IN STEADY STATE (FLOW) CONDITION.

Closure of Valves.Pump Start / Stop.Pipe BurstLoad acceptance/rejection (Turbine)

Water Hammer caused by Sudden Pump Stops

Q0

1

Q0

Pressure drop(Down Surge)

Q=0

2

Q0

Pressure drop(Down Surge)

Q=0

3

Q0

Pressure drop(Down Surge)

Q=0

Q=0Pressure drop(Down Surge)

4

Q=0

Pressure drop(Down Surge)

Q=0

Q=0Pressure drop(Down Surge)

5

Q

Q=0

Q=0Pressure recover

6

Q

Pressure increaseUp Surge

Q=0

7

Q

Pressure increaseUp Surge

Q=0

8

Q

Pressure increaseUp Surge

Q=0

9

Q

Pressure increaseUp Surge

Q=0

Q=0

10

Q=0

Pressure increaseUp Surge

Q=0

11

Q

Pressure recover

Q=0

12

Q

Pressure Recover

Q=0

13

Effect of Water Hammer(Surge Pressures)High Up Surge PressuresLow Down Surge Pressures

METHODS FOR CONTROLLING WATER HAMMERPipe MaterialPump InertiaSurge VesselAir ValvesOpen Surge TankSurge Valve

P2*V2

1

P1V1n =K

PIPE MATERIAL

P2*V2

2

P1V1n =K

P2*V2

3

P1V1n =K

P2*V2

4

P1V1n =K

PUMP INERTIA

Reservoir

NRV closed in 1 second12

Pump

Gr2 = 3.5kg-m2

Speed =1450

3

SURGE VESSEL

bypass

Suction tank

NRV

12

Pump

Gr2 = 3.5kg-m2

Speed =1450

3

AIR VALVES

Reservoir

Pump Gr2 = 5kg-m2

Speed =1485

Vacuum Relief and Air Release Valves

12

Pump

Gr2 = 3.5kg-m2

Speed =1450

3

OPEN SURGE TANK

non-return valve

Raw WaterPump

Aerator

3m x 3m x 2m deepOpen surge tank

12

Pump

Gr2 = 3.5kg-m2

Speed =1450

3

SURGE CONTROL VALVE

Reservoir

Pump Gr2 = 5kg-m2

Speed =1485

Pressure relief valve (set to open at 100m pressure)

123