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  2. Piping and instrumentation diagram - Wikipedia

    en.wikipedia.org/wiki/Piping_and_instrumentation...

    Valves and their types and identifications (e.g. isolation, shutoff, relief and safety valves, valve interlocks) Control inputs and outputs (sensors and final elements, interlocks) Miscellaneous - vents, drains, flanges, special fittings, sampling lines, reducers and swages; Interfaces for class changes; Computer control system

  3. Safety relay - Wikipedia

    en.wikipedia.org/wiki/Safety_relay

    Safety relays must always be designed in such a way that, if wired correctly, neither a fault in the device nor an external fault caused by the sensor or actuator will lead to the loss of the safety function. [8] A normal relay uses a wire coil and the mechanical movement of the metal contacts to switch the load on and off.

  4. Protective relay - Wikipedia

    en.wikipedia.org/wiki/Protective_relay

    Distance relays are actually double actuating quantity relays with one coil energized by voltage and other coil by current. The current element produces a positive or pick up torque while the voltage element produces a negative or reset torque. The relay operates only when the V/I ratio falls below a predetermined value (or set value). During a ...

  5. Relay - Wikipedia

    en.wikipedia.org/wiki/Relay

    The National Association of Relay Manufacturers and its successor, the Relay and Switch Industry Association define 23 distinct electrical contact forms found in relays and switches. [17] Of these, the following are commonly encountered: SPST-NO (Single-Pole Single-Throw, Normally-Open) relays have a single Form A or make contact. These have ...

  6. Control valve - Wikipedia

    en.wikipedia.org/wiki/Control_valve

    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.

  7. Relay logic - Wikipedia

    en.wikipedia.org/wiki/Relay_logic

    In many cases, it is possible to design a relay logic diagram directly from the narrative description of a control event sequence. In general, the following suggestions apply to designing a relay logic diagram: 1. Define the process to be controlled. 2. Draw a sketch of the operation process. Make sure all the components of the system are ...

  8. Flow control valve - Wikipedia

    en.wikipedia.org/wiki/Flow_control_valve

    Control valves are normally fitted with actuators and positioners. Pneumatically-actuated globe valves and diaphragm valves are widely used for control purposes in many industries, although quarter-turn types such as (modified) ball and butterfly valves are also used. Control valves can also work with hydraulic actuators (also known as ...

  9. Ladder logic - Wikipedia

    en.wikipedia.org/wiki/Ladder_logic

    Ladder logic was originally a written method to document the design and construction of relay racks as used in manufacturing and process control. [1] Each device in the relay rack would be represented by a symbol on the ladder diagram with connections between those devices shown.