Instrumentation, & Process Drawings

Instrumentation

the set of devices used to measure,
control, or indicate flow, temperature, level, pressure, and
analytical data

Process variable

a measurement of the chemical or physical properties of a process stream, generally relating to operating parameters or product specifications

Process variables controlled by instrumentation

Pressure, Temperature, Level, Flow, Analytical values

Control Loop

A series of instruments that work together to monitor and control a process variable

Flow Rate

A quantity of a fluid that moves past a specific point within a given amount of time

Alarm

A device that provides visual and/or audible cues of conditions outside the normal operating range

Analytical Variable

A measurement of the chemical or physical properties of a substance

Control Valve

The final component of a control loop that receives its signal from the controller

Controller

The component of a control loop that receives information from the transmitter in the form of a pneumatic or electric signal

Hydraulic Instruments

Devices that use pressurized fluid as the power source

Indicator

An instrument that shows the current condition of a process variable

Actuator

An electrical, pneumatic, or hydraulic device that manipulates a control device

Distributed Control System

A computer-based system consisting of a series of controllers used to monitor and control a process

Valve Positioner

A device that ensures a valve is positioned properly in reference to the signal received from the controller

Transducer

The control loop component that converts one instrumentation signal type to another type

Transmitter

The control loop component that receives a signal from the sensor, measures that signal, and sends it forward to the controller or indicator

Local

related to instrumentation in close physical proximity to the process

Sensor

the control loop component that is in direct contact with the process variable to be measured

Steps of a Control Loop

Step 1. a sensor in direct contact with the process sends out a signal to the measuring device

Step 2. the process variable is measured and the measurement is converted into a proportional pneumatic or electric signal

Step 3. the set point is compared to the current input signal from the transmitter

Step 4. the controller produces an output signal for the final control element

Step 5. as the error is corrected, the process variable returns to math the set point

Analog

continuously variable representation of a process variable

Fiber optic

a system that uses light frequency signals

Digital

uses the binary numbers to represent continuous values

Error

difference between the set point and the current process variable value

Network

common component of a DCS system used to connect systems

Supervisory computers

common component of a DCS system issued to monitor production​ targets

Cascade control (remote setpoint)

controller gets setpoint form other control loops

SUPV

controller gets its setpoints from multivariable predictive controller

Application Block

main part of a drawing that contains symbols and defines elements

Title Block

a section of a drawing that contains information such as drawing title, drawing number, revision number, sheet number, and approval signature

Plot plan diagram

created before the plant exists and isnot regularly used by process​ technicians

Schematics

used by process technicians to visualize how current flows between two or more​ circuits