CONTROL AGENT

In process automatic-control work, material within a process system in which a variable (for example, concentration) is controlled.

In process automatic-control work, that quantity or condition of a controlled system that is directly measured or controlled.

Automatic safety switches incorporated into the boiler burner management system which will shut down the combustion process if an unsafe boiler condition exists.

Energy transformation process in which the resultant condition lacks the driving potential needed to reverse the process; the measure of this loss is expressed by the entropy increase of the system.

1. An instrument used to measure continuously or at intervals a condition that must be kept within prescribed limits, such as radioactivity at some point in a nuclear reactor, a variable quantity in an automatic process control system, the transmissions in a communication channel or bank, or the position of an aircraft in flight. 2. To use meters or special techniques to measure such a condition. 3. A person who watches a monitor.

The analysis of the behavior of the output variable of an automatic control system as the system changes from one steady-state condition to another in terms of such quantities as maximum overshoot, rise time, and response time.

A material-damaging process which occurs as a result of vaporous cavitation. 'Cavitation' refers to the occurrence or formation of gas- or vapor- filled pockets in flowing liquids due to the hydrodynamic generation of low pressure (below atmospheric pressure). This damage results from the hammering action when cavitation bubbles implode in the flow stream. Ultra- high pressures caused by the collapse of the vapor bubbles produce deformation, material failure and, finally, erosion of the surfaces.

The condition of a vessel with regards to materials, construction, equipment, crew and outfit which is considered safe for the trade in which it is employed

All material and energy present in and around an operating system, such as dust, air moisture, chemicals, and thermal energy.

Gas-free condition describes the full gas-freeing process carried out in order to achieve a safe atmosphere. It therefore includes two distinct operations: Inerting and Aeration. (Note: — In some gas trades the expression ‘Gas-free’ is used to denote a tank which is just Inerted. Some gas carrier operations can stop at this stage; for example prior to special dry dockings or cargo grade changes).