Editing Safety engineering (section)

=== Oil and gas industry offshore (API 14C; ISO 10418) ===
The offshore oil and gas industry uses a qualitative safety systems analysis technique to ensure the protection of offshore production systems and platforms. The analysis is used during the design phase to identify process engineering hazards together with risk mitigation measures. The methodology is described in the [[American Petroleum Institute]] Recommended Practice 14C ''Analysis, Design, Installation, and Testing of Basic Surface Safety Systems for Offshore Production Platforms.''

The technique uses system analysis methods to determine the safety requirements to protect any individual process component, e.g. a vessel, [[Pipeline transport|pipeline]], or [[pump]].<ref name=":0">API RP 14C p.1</ref> The safety requirements of individual components are integrated into a complete platform safety system, including liquid containment and emergency support systems such as fire and gas detection.<ref name=":0" />

The first stage of the analysis identifies individual process components, these can include: flowlines, headers, [[pressure vessel]]s, atmospheric vessels, [[Industrial furnace|fired heaters]], exhaust heated components, pumps, [[compressor]]s, pipelines and [[heat exchanger]]s.<ref name=":1">API RP 14C p.vi</ref> Each component is subject to a safety analysis to identify undesirable events (equipment failure, process upsets, etc.) for which protection must be provided.<ref name=":2">API RP 14C p.15-16</ref> The analysis also identifies a detectable condition (e.g. [[high pressure]]) which is used to initiate actions to prevent or minimize the effect of undesirable events. A Safety Analysis Table (SAT) for pressure vessels includes the following details.<ref name=":2" /><ref name=":3">API RP 14C p.28</ref>
{| class="wikitable"
! colspan="3" |Safety Analysis Table (SAT) pressure vessels
|-
!Undesirable event
!Cause
!Detectable abnormal condition
|-
|Overpressure
|Blocked or restricted outlet

Inflow exceeds outflow

Gas blowby (from upstream)

Pressure control failure

Thermal expansion

Excess heat input
|High pressure
|-
|Liquid overflow
|Inflow exceeds outflow

Liquid slug flow

Blocked or restricted liquid outlet

Level control failure
|High liquid level
|}
Other undesirable events for a pressure vessel are under-pressure, gas blowby, leak, and excess temperature together with their associated causes and detectable conditions.<ref name=":3" />
[[File:Vessel_level_instrumentation.jpg|thumb|Vessel level instrumentation]]
Once the events, causes and detectable conditions have been identified the next stage of the methodology uses a Safety Analysis Checklist (SAC) for each component.<ref>API RP 14C p.57</ref> This lists the safety devices that may be required or factors that negate the need for such a device. For example, for the case of liquid overflow from a vessel (as above) the SAC identifies:<ref>API RP 14C p.29</ref>

* A4.2d - High level sensor (LSH)<ref name="ISO-14617-1:2005">{{cite web |title=ISO 14617-1:2005 Graphical symbols for diagrams — Part 1: General information and indexes |url=https://www.iso.org/standard/41838.html |publisher=[[International Organization for Standardization]]}}</ref>
** 1.  LSH installed.
** 2.  Equipment downstream of gas outlet is not a flare or vent system and can safely handle maximum liquid carry-over.
** 3.  Vessel function does not require handling of separate fluid phases.
** 4.  Vessel is a small trap from which liquids are manually drained.
[[File:Vessel_pressure_instrumentation.jpg|thumb|Vessel pressure instrumentation]]
The analysis ensures that two levels of protection are provided to mitigate each undesirable event. For example, for a pressure vessel subjected to over-pressure the primary protection would be a PSH (pressure switch high) to shut off inflow to the vessel, secondary protection would be provided by a [[Safety valve|pressure safety valve]] (PSV) on the vessel.<ref>API RP 14C p.10</ref>

The next stage of the analysis relates all the sensing devices, shutdown valves (ESVs), trip systems and emergency support systems in the form of a Safety Analysis Function Evaluation (SAFE) chart.<ref name=":1" /><ref>API RP 14C p.80</ref>
{| class="wikitable"
! colspan="4" rowspan="2" |Safety Analysis Function Evaluation  (SAFE) chart
|Close inlet valve
|Close outlet valve
|Alarm
|-
|ESV-1a
|ESV-1b
|
|-
|Identification
|Service
|Device
|SAC reference
|
|
|
|-
| rowspan="5" |V-1
| rowspan="5" |HP separator
|PSH
|A4.2a1
|X
|
|X
|-
|LSH
|A4.2d1
|X
|
|X
|-
|LSL
|A4.2e1
|
|X
|X
|-
|PSV
|A4.2c1
|
|
|
|-
|etc.
|
|
|
|
|-
|V-2
|LP separator
|etc.
|
|
|
|
|}
X denotes that the detection device on the left (e.g. PSH) initiates the shutdown or warning action on the top right (e.g. ESV closure).

The SAFE chart constitutes the basis of Cause and Effect Charts which relate the sensing devices to [[Shut down valve|shutdown valves]] and plant trips which defines the functional architecture of the [[Plant process and emergency shutdown systems#Process shutdown (PSD)|process shutdown]] system.

The methodology also specifies the systems testing that is necessary to ensure the functionality of the protection systems.<ref>API RP 14C Appendix D</ref>

API RP 14C was first published in June 1974.<ref>{{Cite book|chapter-url=https://www.onepetro.org/conference-paper/SPE-7147-MS|chapter=Impact of API 14C on the Design And Construction of Offshore Facilities|doi=10.2118/7147-MS |access-date=7 February 2019|title=All Days |year=1978 |last1=Farrell |first1=Tim }}</ref> The 8th edition was published in February 2017.<ref>{{Cite web|url=https://global.ihs.com/doc_detail.cfm?document_name=API%20RP%2014C&item_s_key=00010460|title=API RP 14C|access-date=7 February 2019}}</ref> API RP 14C was adapted as ISO standard ISO 10418 in 1993 entitled ''Petroleum and natural gas industries — Offshore production installations — Analysis, design, installation and testing of basic surface process safety systems.''<ref>{{Cite web|url=https://www.iso.org/standard/38067.html|title=ISO 10418|access-date=7 February 2019}}</ref> The latest edition of ISO 10418 was published in 2019. <ref>{{Cite web|url=https://www.iso.org/standard/55440.html|title=ISO 10418|access-date=2 January 2025}}</ref>