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Correct operation of the petrochemical process plant is achieved through the action of control loops. [1] These automatically maintain and control the pressure, temperature, liquid level and flowrate of fluid in vessels and piping. Control loops compare the measured value of a parameter on the plant, eg. pressure, with a pre-determined set point.
A control loop is the fundamental building block of control systems in general and industrial control systems in particular. It consists of the process sensor, the controller function, and the final control element (FCE) which controls the process necessary to automatically adjust the value of a measured process variable (PV) to equal the value of a desired set-point (SP).
Another loop may contain two passive chart recorders, a passive pressure transmitter, and a 24 V battery (the battery is the active device). Note that a 4-wire instrument has a power-supply input separate from the current loop. Panel mount displays and chart recorders are commonly termed "indicator devices" or "process monitors".
Instrument Uses Head Mirror with head band: to focus light into the cavity under inspection; mirror is concave and is used with a Chiron lamp to produce a parallel beam of light; doctor views through the hole (average diameter of mirror is 3 & 1/2" & that of hole is 1/4") Head mounted lights with head band: to focus light into the cavity under ...
Layers of protection analysis (LOPA) is a technique for evaluating the hazards, risks and layers of protection associated with a system, such as a chemical process plant. . In terms of complexity and rigour LOPA lies between qualitative techniques such as hazard and operability studies (HAZOP) and quantitative techniques such as fault trees and event trees.
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In general, a checklist is a quality management tool, an aid to completing a complex task correctly and completely. It is an aid to recall, provides a reminder of the correct sequence, and uses the operator's knowledge and skill efficiently to ensure that no critical steps are omitted, even when the operator is under stress or has degraded attention due to fatigue or other distractions, It ...
An SIS performs a safety instrumented function (SIF).The SIS is credited with a certain measure of reliability depending on its safety integrity level (SIL).The required SIL is determined from a quantitative process hazard analysis (PHA), such as a Layers of Protection Analysis (LOPA).