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Glossary Term: CHAZOP
Control Hazard and Operability Study (CHAZOP) is a procedure for carrying the safety and reliability analysis of existing or planned Control and Computer systems. The technique is similar to, and has been adopted from the Hazard and Operability analysis (HAZOP) procedure that is widely used and is very successful for…
Glossary Term: Automotive Safety Integrity Level (ASIL)
Automotive Safety Integrity Level (ASIL) is a risk classification scheme defined by the ISO 26262 - Functional Safety for Road Vehicles standard. This is an adaptation of the Safety Integrity Level used in IEC 61508 for the automotive industry. This classification helps defining the safety requirements necessary to be in…
Glossary Term: ISO 13949
Method for the assessment of the degree of pigment dispersion in polyolefin pipes, fittings and compounds.
Glossary Term: ISO 26262
ISO 26262 is a Functional Safety standard, titled “Road vehicles – Functional safety”. Functional safety features form an integral part of each product development phase, ranging from the specification, to design, implementation, integration, verification, validation, and production release. The standard ISO 26262 is an adaptation of the Functional Safety standard…
Glossary Term: Functional Safety Management Plan (FSM)
The Safety Plan or Functional Safety Management (FSM) Plan is a key document in any IEC 61508 / ISO 26262 development project. It specifies how functional safety will be ensured throughout the entire development project and in production. The Safety Plan must identify the various roles and responsibilities as they…
Glossary Term: Zone
The international method of specifying the probability that a location is made hazardous by the presence, or potential presence, of flammable concentrations of gases and vapors. NOTE: Zone classification has not yet been defined for dust. Zone 0: Classification of a location in which an explosive concentration of a flammable…
Glossary Term: Zero shift
A change in the output in response to a zero input over a specified period of time and at room conditions.. NOTE: This error is characterized by a parallel displacement of the entire calibration curve [S37. 1]. 2. A shift in the instrument calibrated span evidenced by a change in…
Glossary Term: Windup
Saturation of the integral mode of a controller developing during times when control cannot be achieved, which causes the controlled variable to overshoot its set point when the obstacle to control is removed.
Glossary Term: Wearout
The point where a piece of equipment has accumulated enough stress and weakened to the point where its failure rate increases significantly. Note that since essentially all safety systems assume a constant failure rate, theye must be replaced before they reach this wearout point.
Glossary Term: Vortex flow meter
A device that measures flow by sensing the movement of vortices in a pipe or conduit. The instrument usually is constructed with a partial barrier (vortex shedder) inserted perpendicular to the flow to allow formation of vortices, and sensor(s) to detect the passing vortices. The vortices are shed from one…
Glossary Term: Verification
Activity of demonstrating for each phase of the safety lifecycle by analysis and/or tests that, for the specific inputs, the deliverables meet the objectives and requirements set for the specific phase.
Glossary Term: Venturi meter
A type of flow meter that measures flow rate by determining the pressure drop through a venturi constriction. A venturi is a constriction in a pipe, tube or flume consisting of a tapered inlet, a short straight constricted throat and a gradually tapered outlet; fluid velocity is greater and pressure…
Glossary Term: Vapor pressure
1. The pressure of a vapor corresponding to a given temperature where the liquid and vapor are in equilibrium. Vapor pressure increases with temperature. 2. The pressure (for a given temperature) at which a liquid is in equilibrium with its vapor. As a liquid is heated, its vapor pressure will…
Glossary Term: Valve flow coefficient
(Cv) The number of US gallons (3.785 liters) per minute of 60°F (15.6°C) water that will flow through a valve with a one pound per square inch (6.89 kPa) pressure drop.
Glossary Term: Valve bonnet
An assembly including the part through which a valve plug stem moves and a means for sealing against leakage along the stem. It usually provides a means for mounting the actuator. Sealing against leakage may be accomplished by packing or a bellows. A bonnet assembly may include a packing lubricator…
Glossary Term: Valve body assembly
An assembly of a body, bonnet assembly, bottom flange and trim elements. The trim includes a valve plug which opens, shuts or partially obstructs one or more ports.
Glossary Term: Valve body
The part of the valve which is the main pressure boundary relative to the ambient. The body also provides the pipe connecting ends, the fluid flow passageway, and may support the seating surfaces and the valve closure member.
Glossary Term: Validation
the activity of demonstrating that the safety instrumented function(s) and safety instrumented system〈s〉 under consideration after installation meets in all respects the safety requirements specification.
Glossary Term: V orifice
“V”-shaped flow control orifice which allows a characterized flow control as the gate moves in relation to the fixed Vee opening.
Glossary Term: V Model
The basic project execution model that starts with high level design and goes down to detailed design followed by testing of the detailed design and then testing of the higher level design elements.
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