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Example of a single industrial control loop; showing continuously modulated control of process flow. Piping and instrumentation diagram of pump with storage tank. Symbols according to EN ISO 10628 and EN 62424. A more complex example of a P&ID. A piping and instrumentation diagram (P&ID) is defined as follows:
In all cases, a control loop diagram is a very convenient and useful way of representing the control function and its interaction with plant. In practice at a process control level, control loops are normally abbreviated using standard symbols in a Piping and instrumentation diagram , which shows all elements of the process measurement and ...
Diagram of a flow control instrumentation loop. The throughput of a petrochemical plant is measured and controlled by flow instrumentation. Flow measuring devices devices (FE) include vortex, positive displacement (PD), [12] differential pressure (DP), [13] coriolis, ultrasonic, [14] and rotameters. Compressor control
Some large systems may have several hundreds or thousands of control loops. In complex processes the loops are interactive, so that the operation of one loop may affect the operation of another. The system diagram for representing control loops is a Piping and instrumentation diagram.
A major application of current loops is the industry de facto standard 4–20 mA current loop for process control applications, where they are extensively used to carry signals from process instrumentation to proportional–integral–derivative (PID) controllers, supervisory control and data acquisition (SCADA) systems, and programmable logic ...
A block diagram of a PID controller in a feedback loop. r ( t ) is the desired process variable (PV) or setpoint (SP), and y ( t ) is the measured PV. The distinguishing feature of the PID controller is the ability to use the three control terms of proportional, integral and derivative influence on the controller output to apply accurate and ...
Example of a continuous flow control loop. Signalling is by industry standard 4–20 mA current loops, and a "smart" valve positioner ensures the control valve operates correctly. The processor nodes and operator graphical displays are connected over proprietary or industry standard networks, and network reliability is increased by dual ...
The diagram shows leakage current from an appliance such as an electric motor A flowing through the building's ground system G to the neutral wire at the utility ground bonding point at the service panel. The ground loop between components C1 and C2 creates a second parallel path for the current. [8]