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Glossary Term: CPQRA
(Guidelines for) Chemical Process Quantitative Risk Analysis
Glossary Term: CPT or PTC
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: Check valve
A flow control device that permits flow in one direction and prevents flow in the opposite direction
Glossary Term: CFSE/CFSP
Certified Functional Safety Expert/Professional Qualifications for safety engineers in either process applications, machine applications, hardware, or software that demonstrates competence in safety lifecycle activities. These qualifications are administered by the non-profit CFSE Governance managed by a global consortium of vendor, user, integrator and consultant companies.
Glossary Term: Cavitation
A two stage phenomenon of liquid flow. The first stage is the formation of voids or cavities within the liquid system; the second stage is the collapse or implosion of these cavities back into an all liquid state. Cavitation can cause excessive wear and damage to devices in regions where…
Glossary Term: Cause and effect diagram
One method commonly used to show the relationship between the sensor inputs to a safety function and the required outputs. Often used as part of a safety requirements specification. The method’s strengths are a low level of effort and clear visual representation while its weaknesses are a rigid format (some…
Glossary Term: Capacitance
The ability of a capacitor to store a charge. The greater the capacitance, the greater the charge that can be stored. Also applied to tanks in process fluid flow systems.
Glossary Term: Calibration curve
A plot of indicated value versus true value used to adjust instrument readings for inherent error; a calibration curve is usually determined for each calibrated instrument in a standard procedure and its validity confirmed or a new calibration curve determined by periodically repeating the procedure.
Glossary Term: Butterfly valve
A valve consisting of a disc inside a valve body which operates by rotating about an axis in the plane of the disc to shut off or regulate flow.
Glossary Term: Bus
A group of wires or conductors, considered as a single entity, which interconnects part of a system.
Glossary Term: Burn-in
Device operation, usually under accelerated environmental conditions that simulate life in the devices’ intended application, used to detect early-life (infant mortality) failures. Such testing helps to ensure that constant failure rate assumptions for equipment are valid and do not lead to accidents during plant start up.
Glossary Term: BPCS
See Basic Process Control System.
Glossary Term: BMS
Burner management system. The control system designed to improve combustion safety and assist the operator in starting and stopping the burners. It also should prevent mis-operation and damage to the fuel preparation and burning equipment. The BMS can include: interlock system, fuel trip system, master fuel trip system, master fuel…
Glossary Term: BLEVE
Boiling liquid expanding vapor explosion. A specific type of fireball that can occur as the result of the situation where a vessel containing a pressurized liquid comes in direct contact with external flame. As the liquid inside the vessel absorbs the heat of the external fire, the liquid begins to…
Glossary Term: β-factor
Beta factor, indicating common cause susceptibility. The fraction of total failure rate that is attributed to a single cause in common with other units in the group. A common cause failure will result in all units with the group failing simultaneously.
Glossary Term: Batch process
A process that manufactures a fixed quantity of material by subjecting measured quantities of raw materials to a time sequential order of processing actions using one or more pieces of equipment. Typically used for small volume production of high value materials.
Glossary Term: Basic process control system
System which responds to input signals from the process, associated equipment, and/or an operator and generates output signals causing the process and its associated equipment to operate in the desired way. The BPCS can not perform any safety instrumented functions rated with a safety integrity level of 1 or better…
Glossary Term: Availability
The probability that a device is operating successfully at a given moment in time. This is a measure of the “uptime” and is defined in units of percent. For most tested and repaired safety system components, the availability varies as a saw tooth with time as governed by the proof…
Glossary Term: Auto-tuning
Controller feature that calculates proportional, integral and derivative (PID) output settings based on calculations using measured process dynamics and combining those with the parameters of a PID controller. Calculations may be based on transient responses, frequency responses or parametric models.
Glossary Term: Asynchronous communication
Circuitry or operation without common clock or timing signals. Often called start/stop transmission; a way of transmitting data in which each character is preceded by a start bit and followed by a stop bit.
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