Introduction:

Instrumentation gives the several indications used to operate a nuclear facility. Within a few cases, operators record these indications for use in day-to-day operation of the facility. The data recorded helps the operator evaluate the current condition of the system and take actions if the conditions are not as expected.

Requiring the operator to take all of the needed corrective actions is impractical, or many times impossible, especially if a large number of indications have to be monitored. By this purpose, most systems are controlled automatically at one they are operating under normal conditions. Automatic controls greatly decrease the burden on the operator and create his or her job manageable.

Process variables needs control in a system involve, but are not limited to, flow, level, temperature, and pressure.A few systems do not need all of their procedure variables to be controlled. Suppose of a central heating system. A basic heating system operates on temperature and disregards the other atmospheric parameters of the house.A thermostat monitors the temperature of the house. While the temperature drops to the value chosen through the occupants of the house, the system activates to increase the temperature of the house. While the temperature reaches the desired value and the system turns off.

Automatic control systems neither exchange nor relieve the operator of the responsibility for managing the facility. An operation of the control systems is periodically checked for verify proper operation. The operator must be able to take over and control the process manually if a control system fails.In most cases, understanding how the control system works aids the operator in determining if the system is operating properly and that actions are needs to manage the system in a safe condition.