Search results
Results from the WOW.Com Content Network
A level control valve or altitude control valve is a type of valve that automatically responds to changes in the height of a liquid in some storage system. A common example is the set of ballcocks in a flush toilet, where each stage of the flush cycle is actuated by the emptying or filling of the tank.
A more complex example of a P&ID. A piping and instrumentation diagram (P&ID) is defined as follows: A diagram which shows the interconnection of process equipment and the instrumentation used to control the process. In the process industry, a standard set of symbols is used to prepare drawings of processes.
Valves are actuated by an electric motor, hydraulic fluid or air. For air-operated control valves, electrical signals from the control system are converted to an air pressure for the valve actuator in a current/pneumatic I/P converter. Upon loss of pneumatic or hydraulic pressure valves may fail to an open (FO) or fail to a closed (FC) position.
A control valve is a valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a controller. [1] This enables the direct control of flow rate and the consequential control of process quantities such as pressure, temperature, and liquid level.
The accompanying diagram is a general model which shows functional manufacturing levels in a large process using processor and computer-based control. Referring to the diagram: Level 0 contains the field devices such as flow and temperature sensors (process value readings - PV), and final control elements (FCE), such as control valves; Level 1 ...
The control system performance can be improved by combining the feedback (or closed-loop) control of a PID controller with feed-forward (or open-loop) control. Knowledge about the system (such as the desired acceleration and inertia) can be fed forward and combined with the PID output to improve the overall system performance.
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
Controllers like Level Control or Flow Control; Isolation and shutoff valves; Maintenance vents and drains; Relief and safety valves; Flanges; Process flow diagrams of multiple process units within a large industrial plant will usually contain less detail and may be called block flow diagrams or schematic flow diagrams.