SECTION 3 Marine Drilling Riser System

301. General

The marine drilling riser system consists of the followings.

(1) Riser tensioning system and equipment

(2) Telescopic joints

(3) Pup joints

(4) Riser joints

(5) Buoyancy devices

(6) Riser couplings

(7) Ball and flex joints

(8) Riser running and handling equipment

(9) Riser recoil

(10) Special equipment, including fill-up valves, mud boost system, drag reducing devices.

302. Riser tensioning system

1. The riser tensioning system typically consists of accumulators, air/nitrogen compressors, air/nitrogen dryers, control systems/consoles/panels, hydraulic cylinders, hydraulic power unit, piping, pressure vessels, tensioners, guideline, podline, wireline, sheaves for tensioners, telescopic arms, wire ropes, etc.

2. Component specific requirements

(1) The marine drilling riser system and associated components are to be designed and fabricated in accordance with applicable sections of API Spec 16F, API RP 16Q and API Spec 16R, and the additional requirements of this Section.

(2) The manufacturer is to establish a rated capacity through appropriate design analysis and proto-

type testing.

(3) Design analysis is to be submitted for review, showing that the drilling riser system and all as- sociated components will not be overstressed at the rated capacity, either in axial loading or

bending, overpressure at rated tensioning capacity in specified design conditions.

(4) Piping and hoses are to be in accordance with Ch 5.

(5) Materials are to be in accordance with Ch 3, Sec

1.

(6) Welding and non-destructive examination are to be in accordance with Ch 3, Sec 2.

3. (7) Load-carrying parts are to be in accordance with Ch 6, 603.

5.

(8) If the locking mechanism is in the load path, it is to be in accordance with Ch 6, 603. 5.

(9) Hydraulic and pneumatic cylinders are to be in accordance with Sec 8, 802.

Control systems for riser tensioning system

4. (1) Electrical systems are to be in accordance with Ch 6, Sec 1.

(2) Control systems are to be in accordance with Ch 6, Sec 2.

303.

1.

Marine drilling riser operating envelope

In order to provide a set of criteria for the drilling operation, an envelope of operating parameters is to be established, preferably in the form of a chart. The chart is to clearly show the limits not to be exceeded for each marine drilling riser type in use for any combination of applied loading conditions and the anticipated environmental conditions.

48 Guidance Relating to the Rules for the Classification of Mobile Offshore Drilling Units 2015

2. Where applicable, consideration is to be given to the limits on dynamically-positioned or tur- ret- moored drill ships and the heading change limitations imposed by the length of the choke and kill lines, and restrictions with the slip joint fluid ring.

3. The development of the chart is to take into consideration all applicable loading conditions, load effects, mechanical stops or other limitations on the marine drilling riser system and any component of the drilling riser.

4. The drilling riser is to be designed so that the maximum stress intensity for the operating modes, as described in API RP 16Q, is not to be exceeded.

5. The design limits or combination thereof for consideration in the design and structural analysis of the drilling riser system are to consider:

(1) Maximum stress

(2) Strain

(3) Maximum deflection or curvature

(4) Temperature

(5) Fatigue for service life

(6) Hydrostatic collapse

(7) Maximum loading on specific components

6. The drilling riser loads and load effects are to be considered in the design and structural analysis

of the marine drilling riser system in conjunction with the design limits rine drilling riser loads effects are categorized as follows:

(1) Functional

(A) Nominal top tension

indicated Par 5. The ma-

(B) Vessel constraints and/or offsets (DP, moored

(C) Internal pressure

(D) External hydrostatic pressure

(E) Internally run tools

(F) Thermal

(G) Installation

(H) Vortex-induced vibration

(I) Weight of riser

(J) Hang-off

(K) Inertia

(L) Weight of attachments and/or tubing

(M) Weight of tubing contents and annulus mud

(2) Environmental

(A) Waves

(B) Wind

(C) Vessel motions

(D) Seismic

(E) Current

(F) Ice

(3) Accidental

(A) Small dropped objects

(B) Partial loss of station keeping capability

(C) Normal handling impacts

(D) Emergency disconnect

(E) Tensioner failure

installations, etc.)

304.

Technical requirements

1. Marine drilling riser system is to be verified through global riser analysis.

2. The design analyses of the individual marine drilling riser components are loads obtained from a global drilling riser analysis.

to be performed using

3. The marine drilling riser system and components are to be evaluated for the design conditions and service life criteria as indicated in 303.

4. The individual components of the marine drilling riser system are to be adequately designed to

Guidance Relating to the Rules for the Classification of Mobile Offshore Drilling Units 2015 49

withstand stresses expected throughout the service life of the particular component. In design, con- sideration is to be given to the maximum stress, fatigue damage, maximum deflection and stability against column buckling.

5. The maximum permissible deflection of the drilling riser system is to be limited to that value which would cause interference with the passage of any downhole tools that would be used in the different operating modes.

6. The drilling riser running equipment, which includes the drilling riser running/handling tool, riser spider, gimbal and shock absorber (if applicable) is to be designed and rated in accordance with API Spec 8C and the additional requirements of this Annex.

7. The mud boost system is to be provided with safety relief valves capable of protecting system equipment with the lowest pressure rating, including the marine drilling riser.

8. Riser make-up and break-up equipment and procedures are to be subjected to the Society's review.

305. Design Documentation

Design documentation are to include the reports, calculations, plans, manuals and other doc- umentation necessary to verify the global riser analysis and structural integrity of the individual ris- er components. Additional documentation may be required based on the relative complexity of the marine drilling riser system or relevant conditions in the geographic area of operation.

(1) Reports

(A) Reports are to fully describe the loads and resulting stresses for the global drilling riser system, individual components, and the operating and environmental conditions that produce those loads and restrict the ability of the drilling riser system to meet its designed function.

(B) The environmental reports are to be based on appropriate original data. Data from analogous

areas may be considered. The information contained therein is to include all environmental phenomena that would affect the drilling riser system.

(C) Data presented is to include tables that summarize wave height vs. percentage of time,

wave height vs. direction, wave and overall current statistics for return periods of 1 year, 10 years and 50 years.

(D) Fatigue data are to be included.

(E) Design air and water temperature ranges are to be specified and to be suitable for operation of any system component.

(2) System Calculations

(A) Design analyses are to be submitted that clearly demonstrate the capability of the marine drilling riser system to withstand the imposed loads for the intended operating envelope.

(B) The operating envelope defines the range of individual operating conditions for which the

drilling riser system is suitable and which also defines the boundaries for combinations of operating conditions within the acceptable ranges of individual conditions (e.g., the combina- tion of offset, water depth, mud weight, etc.)

(C) Details of the slip joint and flex joints, location and extent of any concentrated loads, de- tails of riser joint are to be submitted to the Society.

(3) Arrangement plans and fabrication drawings