Section 9 Riser systems
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, July 2022 - Part 7 Safety Systems, Hazardous Areas and Fire - Chapter 1 Safety and Communication Systems - Section 9 Riser systems

Section 9 Riser systems

Parent topic: Chapter 1 Safety and Communication Systems

9.1 General

9.1.1 The provisions laid down in Pt 3, Ch 5 Fire-fighting Units for the assignment of the special features class notation PRS are to be complied with.

9.1.2 The location where the riser(s) is situated, inboard of the installation or unit, is to be safeguarded by an appropriate fire and gas detection system complying with the requirements of Pt 7, Ch 1, 2 Fire and gas alarm indication and control systems. In the event that a fire or confirmed gas leakage is detected, effective automatic means of closing down the riser(s) are to be provided.

9.1.3 The riser system is to be equipped with an emergency shut-down valve, fitted as close to the waterline as possible, but above the splash zone. The valve is to be of the self-actuating type with its own localised control medium and interfaces with the installation ESD, as specified in Pt 7, Ch 1, 7 Emergency shutdown (ESD) systems.

9.1.4 Testing facilities which actuate the inboard riser valves are to be provided, and initiated periodically to ensure actuator breakout forces are achieved.

9.1.5 The riser system is to be provided with means of leakage monitoring and to ensure integrity of the riser system (Trunk and Infield Pipelines, as applicable). The leak detection system should take the following parameters into consideration:
  • Continuous mass balance (fiscal).
  • Continuous volumetric balance corrected for temperature and pressure (fiscal).
  • Continuous monitoring of rate of change of pressure.
  • Continuous monitoring of rate of change of flow.
  • Low pressure alarm or trip.
  • High flow alarms.
The leak detection system on Infield Lines should take the following parameters into consideration where relevant:
  • Subsea choke position.
  • Multiphase subsea flowmeter.
  • Infield metering (when installed).
  • Continuous monitoring of rate of change of pressure.
  • Continuous monitoring of rate of change of flow.
  • Low pressure alarm or trip.
  • High flow alarm.

9.1.6 Control of the riser system is to be effected from a clearly defined control centre, provided with sufficient instrumentation to indicate the conditions at each end of the riser system and to ensure effective control, shut-down and disconnection.

9.1.7 Where more than one control centre is provided, the arrangements are to be such that only one control centre can start up the riser system at a given time. Clear indication is to be provided to show which centre is in control.

9.1.8 Independent means of voice communication are to be provided between the single point mooring end of the riser system and the control centre(s).

9.1.9 Alarms displayed in a control centre are to be audible and visual. An alarm event recorder is to be provided.

9.1.10 The riser system is required to be safely disconnected when the design limits are exceeded. Self-closing devices positioned as close to the rapid disconnecting point as possible are to be fitted so as to ensure accidental spillage at the junction is minimised. A suitable alarm is to be provided, warning that the design limits are reached.

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