BLEVE

BLEVE

Definition(s)

BLEVE

Boiling liquid expanding vapor explosion.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards

BAM

BAM

Definition(s)

BAM

Bundesanstalt fur Materialforschung und -prufung (Federal Institute of Material Research and Testing).

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards

Ventilation-controlled Fire

Ventilation-controlled Fire

Definition(s)

Ventilation-controlled Fire

Fire that is in shortage of air such that the available air—the ventilation—controls the heat release rate.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Orifice Seal

Orifice Seal

Definition(s)

Orifice Seal

Dry vapor seal based on a flow restriction that minimizes the required purge gas needed to protect against air infiltration into the flare burner exit.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Vapor Depressuring System

Vapor Depressuring System

Definition(s)

Vapor Depressuring System

Protective arrangement of valves and piping intended to provide for rapid reduction of pressure in equipment by releasing vapors.
  • NOTE: The actuation of the system can be automatic or manual.
Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Superimposed Backpressure

Superimposed Backpressure

Definition(s)

Superimposed Backpressure

Static pressure that exists at the outlet of a pressure-relief device at the time the device is required to operate.
  • NOTE: It is the result of pressure in the discharge system coming from other sources and can be constant or variable.
Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Storage Vessel

Storage Vessel

Definition(s)

Storage Vessel

Fixed tank or vessel that is not part of the processing unit in petrochemical facilities, refineries, gas plants, oil and gas production facilities, and other facilities.
  • NOTE: 1 See process tank (3.1.61).
  • NOTE: 2 These tanks or vessels are often located in tank farms.
Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Storage Tank

Storage Tank

Definition(s)

Storage Tank

Fixed tank or vessel that is not part of the processing unit in petrochemical facilities, refineries, gas plants, oil and gas production facilities, and other facilities.
  • NOTE: 1 See process tank (3.1.61).
  • NOTE:  2 These tanks or vessels are often located in tank farms.
Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Stoichiometric Air/Fuel Ratio

Stoichiometric Air/Fuel Ratio

Definition(s)

Stoichiometric Air/Fuel Ratio

Chemically correct ratio of air to fuel capable of perfect combustion with no unused fuel or air.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
HIPS

HIPS

Definition(s)

HIPS

High-integrity protection system. Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards

HIPS

System composed of sensors, logic solvers, and final control elements for the purpose of taking the process to a safe state when predetermined conditions are met.
  • NOTE: Other terms commonly used for a SIS include emergency shutdown system (ESD, ESS), safety shutdown system (SSD), and safety interlock system (see E.3.3.1).
Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
SIS

SIS

Definition(s)

SIS

Safety instrumented system. Source:  DNVGL-RP-G108, Cyber security in the oil and gas industry based on IEC 62443, DNV GL, September 2017. Global Standards Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards Source: ANSI/ISA–99.00.01–2007, Security for Industrial Automation and Control Systems, Part 1: Terminology, Concepts, and Models, 29 October 2007. National Standard

SIS

System composed of sensors, logic solvers, and final control elements for the purpose of taking the process to a safe state when predetermined conditions are met.
  • NOTE: Other terms commonly used for a SIS include emergency shutdown system (ESD, ESS), safety shutdown system (SSD), and safety interlock system (see E.3.3.1).
Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Required Relief Rate

Required Relief Rate

Definition(s)

Required Relief Rate

Estimated flow rate that needs to be relieved to prevent the equipment pressure from exceeding the specified design value.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Relief Gas

Relief Gas

Definition(s)

Relief Gas

All gases and vapors sent to the flare tip, not including entrained air, and consisting of the sum of organic material, nitrogen, and any other gases added to the vent gas collection system, natural gas added as supplemental fuel, nitrogen added as purge gas, natural gas flowing to the flare pilots, and steam added at the flare tip.
  • NOTE: Other terms used for relief gas include flared gas, vent gas, waste gas, and waste vapor.
Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Process Tank

Process Tank

Definition(s)

Process Tank

Tank or vessel used for an integrated operation in petrochemical facilities, refineries, gas plants, oil and gas production facilities, and other facilities.
  • NOTE: 1 See storage tank (3.1.79).
  • NOTE: 2 A process tank or vessel used for an integrated operation can involve, but is not limited to, preparation, separation, reaction, surge control, blending, purification, change in state, energy content, or composition of a material.
Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Pilot-operated Pressure-relief valve

Pilot-operated Pressure-relief valve

Definition(s)

Pilot-operated Pressure-relief valve

Pressure-relief valve in which the major relieving device or main valve is combined with and controlled by a self-actuated auxiliary pressure-relief valve (pilot). Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Open Fire

Open Fire

Definition(s)

Open Fire

Fire for which the surroundings do not contribute to preheating the ventilation air or reradiation.
  • NOTE: More heat will be lost to the surroundings as compared with confined fires.
Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Noncondensable Gas

Noncondensable Gas

Definition(s)

Noncondensable Gas

Gas or vapor that remains in the gaseous state at a given temperature and pressure.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Molecular Mass

Molecular Mass

Definition(s)

Molecular Mass

The SI term “relative molecular mass” is used rather than “molecular weight” in this standard.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Water Seal

Water Seal

Definition(s)

Water Seal

Device that directs the flow of relief gases through a liquid (normally water) on the path to the flare burner, used to protect the flare header from air infiltration or flashback, to divert flow, or to create backpressure for the flare header.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Liquid Seal

Liquid Seal

Definition(s)

Liquid Seal

Device that directs the flow of relief gases through a liquid (normally water) on the path to the flare burner, used to protect the flare header from air infiltration or flashback, to divert flow, or to create backpressure for the flare header.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Flare Burner

Flare Burner

Definition(s)

Flare Burner

Part of the flare where fuel and air are mixed at the velocities, turbulence, and concentration required to establish and maintain proper ignition and stable combustion.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Flare Tip

Flare Tip

Definition(s)

Flare Tip

Part of the flare where fuel and air are mixed at the velocities, turbulence, and concentration required to establish and maintain proper ignition and stable combustion.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Confined Fire

Confined Fire

Definition(s)

Confined Fire

Fire inside a building or a compact process module where the walls and/or surrounding equipment can reradiate and preheat the combustion air, causing higher heat fluxes than an unconfined (i.e. open) fire.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Combustion Efficiency

Combustion Efficiency

Definition(s)

Combustion Efficiency

The percentage of the total fuel stream entering the flare that is oxidized to form only the products of complete combustion and heat.

NOTE: For example, in the case of hydrocarbons, these products are carbon dioxide, water, and heat.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
CDTP

CDTP

Definition(s)

CDTP

Cold differential test pressure.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards

CDTP

Inlet static pressure at which a pressure-relief valve is adjusted to open on the test stand.
  • NOTE: The CDTP includes corrections for the service conditions of backpressure or temperature or both.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards

Choke Valve

Choke Valve

Definition(s)

Choke Valve

Valve commonly used to control flow in oil and gas production applications.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Burn-pit

Burn-pit

Definition(s)

Burn-pit

Open excavation, normally equipped with a horizontal flare burner that can handle liquid as well as vapor hydrocarbons. Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Flame Velocity

Flame Velocity

Definition(s)

Flame Velocity

Speed at which a flame front travels into an unburned combustible mixture.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Burning Velocity

Burning Velocity

Definition(s)

Burning Velocity

Speed at which a flame front travels into an unburned combustible mixture.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Built-up Backpressure

Built-up Backpressure

Definition(s)

Built-up Backpressure

Increase in pressure at the outlet of a pressure-relief device that develops as a result of flow after the pressure-relief device opens.

Source:API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards