Definition of water hammer pressure | Effects of water hammer

Definition of water hammer pressure

Water hammer pressure is defined as:

The sudden increase in pressure in the pipe lines due to reduction in velocity in a very short time is known as water hammer pressure.

1. This sudden rise in pressure is due to stoppage of flow.
2. It is also called as Hammer blow.
3. Terminology water hammer is perhaps misleading as this phenomenon can occur in any liquid.

Effects of water hammer pressure

It produces effects in the following ways:

1. It produces more pressure in pipes.
2. Produce shock waves.
3. It produces Hammering noise.
4. It causes damages to pipes.

 Types of pipes in which water hammer produces

There are two types of pipes in which water hammer can produce.

1. Elastic, frictionless pipe.
2. Rigid, frictionless pipe.

Types of Valve closure which produccs water hammer

There are following types of valve closure which produces water hammer.

1. Instantaneous valve closure.
2. Rapid valve closure.
3. Slow valve closure.

Instantaneous valve closure

If the time for closing the valve is assumed to zero, the valve closure is called as instantaneous.

Velocity of water hammer pressure wave is denoted by C. It is also called as celerity.

 Rapid valve closure

If time for closing the valve “tc” is more than zero but less than “tr=2L/C”, the valve closure is called as rapid valve closure.

The maximum pressure rise is still the same as for instantaneous valve closure.

Slow valve closure

If time for closing the valve “tc” is more than “tr=2L/C”, the valve closure is called as slow valve closure.

The maximum pressure rise is less as for instantaneous valve closure.