What is shut off head of the pump?

The Maximum pressure developed by a Pump when the delivery valve is FULLY CLOSED, and NO-DISCHARGE of the fluid is produced.

iits head of pump at zero flow

"Shut-off " head is a condition,when a centrifugal pump runs with discharge valve closed. -When a serviced pump is to be tested for its performance , we are running pump with different discharge condition to ensure that the pump is capable of performing as designed.

It is the head developed by the pump when the delivery valve is in ‘close'. For low specific speed pumps, normally it is the 'Y' intercept of the head Vs capacity curve.

However for high specific speed pumps, like large axial flow pumps, it is extrapolated from the above curve, as running the pump at shut off condition will damage the system components. For this reason, these pumps are started with delivery valve in open by atleast 10–15%. Otherwise the the prime mover will not provide the high starting torque and power required, leading to equipment failures.

Whereas for the low specific speed pumps, the manuals prescribe starting the pump at shut off condition and then loading the pump with immediate gradual opening of the delivery valve.

This ultimately depends on a number of factors. The most important one would be what type of pump is at work. There are a myriad to choose from: centrifugal, peristaltic, worm, axial, diaphragm, reciprocating, and so on. In some cases, you will simply cause the pump to speed up or slow down and make more noise, but otherwise nothing significant happens. In other types of pumps - as in positive displacement pumps - shutting off the outlet, or dead-heading, a pump will cause damage - sometimes catastrophic - unless the pump has some sort of pressure relief system

when pump dlivery side is zero head 

Shut head is the maximum pressure which pump can develope at zero flow.

it means highest head with 0 flow

It is determined by the impeller diameter and shaft rpm.

Shut-off or Zero flow rate head

Definition: The maximum head that a pump can produce at zero flow.

Constrains for parallel operation: According to API 610, 11th Ed.: If parallel operation is specified, the head rise from rated point to shutoff shall be at least 10 %.

Importance for FAT / SAT

According to API 610, 11th Ed.:The performance test shall be conducted as well as the test data including head, flow rate, power and vibration at a minimum of five points.

 the SHUTOFF HEAD POINT is one of these five points but no vibration  data required.

If discharge valve been closed accidentally, temperature of Pump and water will become more and more, also pressure of water will hncrease

icreasing temperature of pump will damage it but may be the pressure of water can swen the valve heart to open it by force and in this case we will lose the valve but it will save the pump