API RP 17O:2009 pdf download
API RP 17O:2009 pdf download.ecommended Practice for Subsea High Integrity Pressure Protection Systems (HIPPS).
3.1.18
safe failure fraction
5FF
Ratio of the average rate of safe failures plus dangerous detected failures of the subsystem to the total average failure rate of the component, as defined by IEC 61508, Part 2.
3.1.19
safety instrumented function
SIF
Safety function with a specified SIL which is necessary to achieve functional safety and which can be either a safety instrumented protection function or a safety instrumented control function.
3.1.20
safety integrity level
SIL
Discrete level (one out of four) for specifying the safety integrity requirements of the SIFs to be allocated to the SIS.
SIL 4 has the highest level of safety integrity; SIL 1 has the lowest.
3.1.21
shut-in pressure
SIP
Full internal product process pressure that shall be contained by the HIPPS at the seabed when the high-pressure source is abruptly isolated to protect lower pressure hardware downstream of the spec break.
3.1.22
specification (spec) break
Point at which equipment pressure rating changes from one RWP rating to a lower one (or vice versa) downstream.
NOTE These locations are defined by the normal operating conditions of a flow stream that allows the use of lower design pressure equipment.
3.1.23
subsea tieback
An offshore field developed with one or more wells completed on the seafloor, using subsea trees.
NOTE The wells are connected by flowlines and umbilicals—the pathways for electrical and hydraulic signals—to a production facility in another area.
3.1.24
systems integration test
SIT
A process conducted on land to verify the fit, form, and function between interfaces of all subsea equipment and associated running tools prior to offshore installation.
3.1.25
systematic failure
Failure related in a deterministic way to a certain cause, which can only be eliminated by a modification of the design or of the manufactunng process, operational procedures, documentation, or other relevant factors.
3.2 Acronyms, Abbreviations, and Symbols
— Controlled but Uncontained—ln this case, there is a pressure-relieving mechanism which minimizes the quantity of product released. An environmental remediation plan should be in place.
— Controlled and Contained—In this case, there is a pressure-relieving mechanism (preferably self-resetting) which contains the release. The capacity of the containment system shall be defined.
4.4 Process Hazard and Risk Analysis
The decision to utilize a HIPPS shall be based on a qualitative and quantitative risk analysis (QRA) carried out in accordance with industry standards. Risk analysis requires determining the frequency of the event (overpressure) and the ability of safeguards (HIPPS, etc.) to reduce the consequences, such that the likelihood of the event becomes tolerable.
A qualitative nsk analysis such as process hazard analysis shall be conducted using a defined methodology. The
process hazard is typically overpressure and the subsequent failure of downstream equipment, potentially resulting in
a loss of hydrocarbon containment. The nsk is the frequency, or possibility of, overpressunng the equipment and the
resulting consequences of equipment failure.
Quantitative analysis shall be performed [e.g. layer of protection analysis (LOPA)] as defined in IEC 61511. Risk thresholds shall be those mandated by the regulatory agency or the owner whichever is the most stringent.
4.5 Selection and Determination of SIL
SIL is a representation of the required safety unavailability [average probability of failure on demand (PFD)] of a safety instrumented function (SIF). The SIL is expressed as a Level 1 through Level 4, which corresponds with Table 1.
SILs are determined, either in a prescriptive manner where a preselected SIL may be used when the application meets the required criteria, or a quantitative manner where the required SIL is calculated based on the risk thresholds, initiating frequencies, and other layers of protection to determine the required SIL of the HIPPS.
Determination of the HIPPS SIL should consider additional safeguards that are installed:
— pressure switch high (PSH) at facility, upstream of BSDV;
— PSH at each individual pressure source, upstream of HIPPS;
— PSV at facility upstream of the BSDV sized for either leakage rate (partial protection) or full flow rate; and
— reinforced section at facility riser.
SIL analysis is primarily conducted for safety; however, additional consideration may be for environmental or economic impacts. In this case the consideration with the highest SIL requirement may be used as the design basis.
