Average Failure Rate

Average Failure Rate

Definition(s)

Average Failure Rate

3.1.19 λ (t1t2 ), λ (T) average value of the time-dependent failure rate over a given time interval afr Source: ISO/TR 12489:2013(E) Reliability modelling and calculation of safety systems. Global Standards
Steady State Availability Asymptotic Availability

Steady State Availability Asymptotic Availability

Definition(s)

Steady State Availability Asymptotic Availability

3.1.17 steady state availability Source: ISO/TR 12489:2013(E) Reliability modelling and calculation of safety systems. Global Standards
Average Probability of Failure on Demand

Average Probability of Failure on Demand

Definition(s)

Average Probability of Failure on Demand PFDavg

3.1.16 average unavailability as per 3.1.12 in the functional safety standard terminology (e.g. IEC 61508[2]) Note 1 to entry: “Failure on demand” means here “failure likely to be observed when a demand occurs”. PFDavg encompasses both the failure occurred before the demand and the failure occurring due to the demand itself. Then this term needs not to be mixed up with the probability of a failure due to a demand (see 3.2.13). Source: ISO/TR 12489:2013(E) Reliability modelling and calculation of safety systems. Global Standards
Probability of Failure on Demand

Probability of Failure on Demand

Definition(s)

Probability of Failure on Demand PFD

3.1.15 unavailability as per 3.1.12 in the functional safety standard terminology (e.g. IEC 61508[2]) Note 1 to entry: “Failure on demand” means here “failure likely to be observed when a demand occurs”. This encompasses both the failure occurred before the demand and the failure occurring due to the demand itself. Then this term needs not to be mixed up with the probability of a failure due to a demand (see 3.2.13). Source: ISO/TR 12489:2013(E) Reliability modelling and calculation of safety systems. Global Standards
Average Unavailability

Average Unavailability

Definition(s)

Average Unavailability

3.1.14 average unavailability average unavailability2

Source: ISO/TR 12489:2013(E) Reliability modelling and calculation of safety systems. Global Standards
Average Availability

Average Availability

Definition(s)

A(t1,t2)

Average Availability

3.1.13 〈measure〉 average value of the availability A(t) over a given interval [t ,t ] 1 2. average availability Source: ISO/TR 12489:2013(E) Reliability modelling and calculation of safety systems. Global Standards
Unavailability

Unavailability

Definition(s)

Unavailability

3.1.12 instantaneous unavailability point unavailability U(t) 〈measure〉 probability for an item not to be in a state to perform as required at a given instant Note 1 to entry: The unavailability is the complementary of the availability: U(t)=1− A(t ) Note 2 to entry: The unavailability is called “Probability of Failure on Demand” (PFD) by the standards related to the functional safety of safety related/instrumented systems (e.g. IEC 61508[2]). Note 3 to entry: Note 3 to entry: When dealing with safety U(t) is generally small compared to 1 and this property is used to develop approximated formulae (see Clause 7). Source: ISO/TR 12489:2013(E) Reliability modelling and calculation of safety systems. Global Standards
Instantaneous Availability

Instantaneous Availability

Definition(s)

Instantaneous Availability

3.1.11 point availability A(t) probability for an item to be in a state to perform as required at a given instant Note 1 to entry: In this Technical Report the word “availability” used alone stands for “instantaneous availability”. Note 2 to entry: This is a time-dependent parameter. Note 3 to entry: No matter if the item has failed before the given instant if it has been repaired before. Note 4 to entry: For non-repairable items, Availability and Reliability are identical. Note 5 to entry: When dealing with safety, A(t) is generally close to 1 and this property is used to develop approximated formulae (see Clause 7). Source: ISO/TR 12489:2013(E) Reliability modelling and calculation of safety systems. Global Standards
Failure Probability Density

Failure Probability Density

Definition(s)

Failure Probability Density 3.1.10

f(t) 〈measure〉 probability for an item to fail between t and t+dt   failure probability density Source: ISO/TR 12489:2013(E) Reliability modelling and calculation of safety systems. Global Standards
Unreliability

Unreliability

Definition(s)

Unreliability 3.1.9

F(t) 〈measure〉 probability for an item to fail to perform a required function under given conditions over a given time interval [0, t] Note 1 to entry: F(t) is also the probability that the time of the first failure tf is lower than t: F(t)= P(t _ t) f . This is in relationship with the occurrence of the first failure. Note 2 to entry: F(t) is the cdf (cumulative distribution function) of the time to the first failure tf of the item. It ranges from 0 to 1 when t goes from 0 to infinity. Note 3 to entry: The unreliability is the complementary of the reliability: F(t)=1−R(t) Note 4 to entry: When dealing with safety, F(t) is generally small compared to 1 and this property is used to develop approximated formulae (see Clause 7). Note 5 to entry: Unreliability is better to communicate than MTTF. Source: ISO/TR 12489:2013(E) Reliability modelling and calculation of safety systems. Global Standards
Safety Function

Safety Function

Definition(s)

Safety Function

Functions that are related to overload protection i.e. break-away system (see [6.7]), automatic/manual protection systems (see [6.8] and [6.9]), protection against movements outside operational limitations - i.e. limit switches, physical stops (see [6.10.2]), protections against dangerous gangway movements i.e. emergency stop function (see [6.10.3]). Source: Offshore Gangways, DNVGL-ST-0358, DNV GL, September 2017. Global Standards

Safety Function

3.1.6

function which is intended to achieve or maintain a safe state, in respect of a specific hazardous event Note 1 to entry: This term deviates from the definition in IEC 61508–4 to reflect differences in process sector terminology. Source: ISO/TR 12489:2013(E). Global Standards
Dangerous State

Dangerous State

Definition(s)

Dangerous State

state of the process when safety is not achieved Note 1 to entry: A dangerous state is the result of the occurrence of a critical dangerous failure (3.2.4, Figure B.1).   fb1 Source: ISO/TR 12489:2013(E). Global Standards
Safe State

Safe State

Definition(s)

Safe State

state of the process when safety is achieved Note 1 to entry: Some states are safer than others (see Figures B.1, B.2 and B.3) and in going from a potentially hazardous condition to the final safe state, or in going from the nominal safe condition to a potentially hazardous condition, the process may have to go through a number of intermediate safe-states. Note 2 to entry: For some situations, a safe state exists only so long as the process is continuously controlled. Such continuous control may be for a short or an indefinite period of time. Note 3 to entry: A state which is safe with regard to a given safety function may increase the probability of hazardous event with regard to another given safety function. In this case, the maximum allowable spurious trip rate (see 10.3) for the first function should consider the potential increased risk associated with the other function.   fb1   Figure B.2 — Example of the classes of states for a 2oo3 system  
Figure B.3 — Synthesis of states and failures taxonomy for one continuous mode safety systems
 
Source: ISO/TR 12489:2013(E). Global Standards    
Safety Integrity

Safety Integrity

Definition(s)

Safety Integrity

ability of a safety instrumented system to perform the required safety instrumented functions as and when required Note 1 to entry: This definition is equivalent to the dependability of the SIS (Safety Instrumented System) with regard to the required safety instrumented function. Dependability, being often understood as an economical rather a safety concept, has not been used to avoid confusion. Note 2 to entry: The term “integrity” is used to point out that a SIS aims to protect the integrity of the operators as well as of the process and its related equipment from hazardous events. Source: ISO/TR 12489:2013(E), Global Standards  

Safety Integrity

The attribute of an information system when it performs its intended function in an unimpaired manner, free from deliberate or inadvertent unauthorized manipulation of the system. From: CNSSI 4009. Source: NICCS™ Portal Cybersecurity Lexicon, National Initiative for Cybersecurity Careers and Studies (https://niccs.us-cert.gov/glossary) as of 11 November 2015, Global Standards
Dependability

Dependability

Definition(s)

Dependability

ability to perform as and when required Note 1 to entry: Dependability is mainly business oriented. Note 2 to entry: IEC/TC 56 which is the international “dependability” technical committee deals with reliability, availability, maintainability and maintenance support. More than 80 dependability standards have been published by the IEC/TC56. In particular, it is in charge of the international vocabulary related to those topics (IEV 191[14]) and also of the methods used in the reliability field (e.g. FMEA, HAZOP, reliability block diagrams, fault trees, Markovian approach, event tree, Petri nets). Note 3 to entry: The production availability is an extension, for production systems, of the classical dependability measures. This term is defined in the ISO 20815[16] standard which deals with production assurance and relates to systems and operations associated with drilling, processing and transport of petroleum, petrochemical and natural gas. The relationship between production-assurance terms can be found in Figure G.1 of ISO 20815[16]. Figure G.1 — PDS CCF model [SOURCE: IEC 60050 −191]. Source: ISO/TR 12489:2013(E), Global Standards
WLCPF

WLCPF

Definition(s)

WLCPF

Well Life Cycle Practices Forum. Source: Oil & Gas UK, Guidelines on subsea BOP systems, Issue 1, July 2012, Global Standards
Well Intervention Operation

Well Intervention Operation

Definition(s)

Well Intervention Operation

Well intervention operation is well servicing operations conducted within a completed wellbore.

Source: Norwegian Oil and Gas Association, Guideline No. 135, Recommended Guidelines for Classification and categorization of well control incidents and well integrity incidents, Rev. 4, 27 June 2017, National or Regional Standards

Well Intervention Operation

An operation in which a well is re-entered for a purpose other than to continue drilling or to maintain or repair it. Regulation 2, DCR. Source: Oil & Gas UK, Guidelines on subsea BOP systems, Issue 1, July 2012, Global Standards
Well-examiner

Well-examiner

Definition(s)

Well-examiner

In this document “well-examiner”  covers any individual team, department or company providing well examination services as described by Regulation 18, DCR. Source: Oil & Gas UK, Guidelines on subsea BOP systems, Issue 1, July 2012, Global Standards
UPR

UPR

Definition(s)

UPR

upper pipe ram Source: Oil & Gas UK, Guidelines on subsea BOP systems, Issue 1, July 2012, Global Standards
UBO

UBO

Definition(s)

UBO

under-balanced operation. Source: Oil & Gas UK, Guidelines on subsea BOP systems, Issue 1, July 2012, Global Standards
Pressure Containment Barrier

Pressure Containment Barrier

Definition(s)

Pressure Containment Barrier

The well is defined in terms of its pressure containment boundary. Any equipment that is vital to controlling the pressure within the well is therefore covered. This would include downhole pressure-containing equipment and the pressure-containing equipment on top of the well such as blowout preventers or Christmas trees, but excludes well control equipment downstream that can be isolated from the well by valves. Examples of where the well ends are:
  • above the top blowout preventer (BOP) in the BOP stack and outside the choke and kill valves;
  • downstream of the swab and production win valves of a Christmas tree;
  • at the top of the wireline stuffing box of a wireline BOP.
Regulation 2, paragraph 14, DCR Guidance Source: Oil & Gas UK, Guidelines on subsea BOP systems, Issue 1, July 2012, Global Standards
PLT

PLT

Definition(s)

PLT

production logging tool. Source: Oil & Gas UK, Guidelines on subsea BOP systems, Issue 1, July 2012, Global Standards
OSCR

OSCR

Definition(s)

OSCR

The Offshore Installations (Safety Case) Regulations, 2006 Source: Oil & Gas UK, Guidelines on subsea BOP systems, Issue 1, July 2012, Global Standards
MEWP

MEWP

Definition(s)

MEWP

maximum expected wellhead pressure. Source: Oil & Gas UK, Guidelines on subsea BOP systems, Issue 1, July 2012, Global Standards
LPR

LPR

Definition(s)

LPR

Lower pipe ram. Source: Deepwater Well Control Guidelines. IADC Guidelines Source: Oil & Gas UK, Guidelines on subsea BOP systems, Issue 1, July 2012, Global Standards
EHBU

EHBU

Definition(s)

EHBU

electo hydraulic back-up. Source: Oil & Gas UK, Guidelines on subsea BOP systems, Issue 1, July 2012, Global Standards
DECC

DECC

Definition(s)

DECC

Department of Energy and Climate Change. Source: Oil & Gas UK, Guidelines on subsea BOP systems, Issue 1, July 2012, Global Standards
CA

CA

Definition(s)

CA

Hydrodynamic added mass coefficient. Source: API Specification 16Q, Design, Selection, Operation, and Maintenance of Marine Drilling Riser Systems, Second Edition, April 2017. Global Standards

CA

Certifying authority. Source: Oil & Gas UK, Guidelines on subsea BOP systems, Issue 1, July 2012, Global Standards  

CA

Condition on behalf of the flag administration. Source: Rules for Classification – Offshore units, DNVGL-OU-0101, Offshore drilling and support units, DNV GL, July 2015. Global Standard
Nonconformity

Nonconformity

Definition(s)

Nonconformity

Non-fulfilment of a requirement. Source: ISO/IEC 27000:2014, Information technology — Security techniques — Information security management systems — Overview and vocabulary, Third Edition, January 2014. Global Standards

Nonconformity

Non-fulfilment of a requirement [ISO 9000:2005, definition 3.6.2]. Source: ISO 19011:2011 (E) – Guidelines for auditing management system. Global Standards
Conformity

Conformity

Definition(s)

Conformity

Fulfilment of a requirement. [ISO 9000:2005, definition 3.6.1. Source: ISO 19011:2011 (E) – Guidelines for auditing management system. Global Standards  

IEC 27000:2014, Information technology

Fulfilment of a requirement. Note 1 to entry: The term “conformance” is synonymous but deprecated. Source: ISO/IEC 27000:2014, Information technology — Security techniques — Information security management systems — Overview and vocabulary, Third Edition, January 2014. Global Standards