Search
Glossary Term: Receptor
The object or persons on the receiving end of the harm in an unwanted event. Common receptors include personnel, plant equipment, plant production, the environment, and the general public.
Glossary Term: Ratio controller
1. A controller that maintains a predetermined ratio between two or more variables. 2. Maintains the magnitude of a controlled variable at a fixed ratio to another variable.
Glossary Term: Rated capacity
The manufacturers stated capacity rating for mechanical equipment, for instance, the maximum continuous capacity in pounds of steam per hour for which a boiler is designed.
Glossary Term: Random failure
A failure occurring at a random time, which results from one or more degradation mechanisms. Random failures can be effectively predicted with statistics and are the basis for the probability of failure on demand based calculations requirements for safety integrity level. See systematic failure.
Glossary Term: Quick-opening valve
Control valve with trim characteristic designed to produce large flow capacity with small amount of valve opening.
Glossary Term: Pyrometer
Any of a broad class of temperature measuring instruments or devices. Some typical pyrometers include thermocouples, radiation pyrometers, resistance pyrometers and thermistors, but usually not thermometers. It is a temperature transducer that measures temperatures by the EM radiation emitted by an object, which is a function of the temperature.
Glossary Term: Purging
1. The addition of air or inert gas (such as nitrogen) into the enclosure around the electrical equipment at sufficient flow to remove any hazardous vapors present and sufficient pressure to prevent their re entry. 2. Elimination of an undesirable gas or material from an enclosure by means of displacing…
Glossary Term: PTI or TI
Proof Test Interval - The time interval between servicing of the equipment.
Glossary Term: PTC or CPT
Proof Test Coverage – The percentage failures that are detected during the servicing of equipment. In general it is assumed that when a proof test is performed any errors in the system are detected and corrected (100% proof test coverage).
Glossary Term: PSM
Process safety management. Part of the US requirement under the Occupational Safety and Health Administration (OSHA) guidelines for managing risk when dealing with large quantities of certain materials. The regulation (29 CFR 1910.119) was published in 1992 to help prevent or minimize the consequences of catastrophic releases of toxic, reactive,…
Glossary Term: Proportional control
A control mode in which there is a continual linear relationship between the deviation computer in the controller, the signal of the controller, and the position of the final control element.
Glossary Term: Proven in use
Basis for use of a component or system as part of a safety integrity level (SIL) rated safety instrumented system 〈SIS〉 that has not been designed in accordance with IEC 61508. It requires sufficient product operational hours, revision history, fault reporting systems, and field failure data to determine if the…
Glossary Term: Proof test
Testing of safety system components to detect any failures not detected by automatic on-line diagnostics i.e. dangerous failures, diagnostic failures, parametric failures followed by repair of those failures to an equivalent as- new state. Proof testing is a vital part of the safety lifecycle and is critical to ensuring that…
Glossary Term: Pressure relief device
A mechanism that vents fluid from an internally pressurized system to counteract system overpressure; the mechanism may release all pressure and shut the system down (as does a rupture disc) or it may merely reduce the pressure in a controlled manner to return the system to a safe operating pressure…
Glossary Term: Pressure, maximum working
The maximum total pressure permissible in a device under any circumstances during operation, at a specified temperature. It is the highest pressure to which it will be subjected in the process. It is a designed safe limit for regular use. NOTE: MWP can be arrived at by two methods: a)…
Glossary Term: Pressure, design
The pressure used in the design of a vessel or device for the purpose of determining the minimum permissible thickness or physical characteristics of the parts for a given maximum working pressure (MWP) at a given temperature.
Glossary Term: Predictive control
1. A type of automatic control in which the current state of a process is evaluated in terms of a model of the process and controller actions modified to anticipate and avoid undesired excursions. 2. Self tuning. 3. Artificial intelligence.
Glossary Term: PLC
Programmable Logic Controller. These computers replace relay logic and often have PID (proportional integral and derivative) controllers built into them. PLCs are very fast at processing discrete signals (like a switch condition). They can be designed for either regular or SIL rated applications.
Glossary Term: Positioner
A position controller, which is mechanically connected to a moving part of a final control element or its actuator, and automatically adjusts its output pressure to the actuator in order to maintain a desired position that bears a predetermined relationship to the input signal. The positioner can be used to…
Glossary Term: Plug valve
1. A valve with a closing element that may be cylindrical, conical or a spherical segment in shape that is opened or closed with rotary motion. 2. A type of shutoff valve consisting of a tapered rod with a lateral hole through it. As the rod is rotated 90° about…
Page 111 of 146 pages. ‹ First < 109 110 111 112 113 > Last ›