SECTION 5 Bulk Storage, Circulation and Transfer Systems

501. General

The bulk storage, circulation and transfer system equipment can be categorized as follows:

(1) Bulk storage and transfer system

(2) Cementing system

(3) Mud return system

(4) Well circulation system

502. Bulk storage and transfer system

1. Bulk storage and transfer system typically consist of bulk storage vessels, utility air system and transfer piping.

2. Provisions are to be made so that utility air used to transport cement or bulk mud is dried to a water dew point of at least 7°C below the minimum ambient air temperature.

3. All utility air piping is to be designed to be purged with dry air prior to transfer operations.

4. The utility air transfer piping is to be fitted with relief valves set at a pressure not greater than the working pressure of the bulk storage tanks.

5. Bulk storage vessels are to be fitted with safety relief valves or rupture disks piped to a safe relief area. Unless they are fitted with a relief line to an open area, the use of rupture disks is to be limited to tanks installed in open areas.

6. A P&ID or equivalent schematic of the bulk transfer system is to be clearly posted at the operator station to facilitate operation of the system during well kill circulation.

7. Piping systems are to be in accordance with Ch 5.

8. Materials are to be in accordance with Ch 3, Sec 1.

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

10. Electrical systems are to be in accordance with Ch 6, Sec 1.

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

503. Cementing system

1. The cementing system typically consist of cement pump, centrifugal pumps for mixing cement, pip- ing to and from cement pumps, pulsation dampeners and safety valves.

2. The cement pumps are to be arranged to be capable of emergency well kill circulation, using drilling fluid transferred from the mud pits.

3. Cement pump installations or modifications to existing installations are to be subjected to

the the

Guidance Relating to the Rules for the Classification of Mobile Offshore Drilling Units 2015 51

Society's review.

4. The interconnect lines between systems that are used only for emergency well kill circulation are to be fitted with blind or spectacle flanges, lockable valves or similar devices that can be opened as needed, but positively isolate the systems during normal operations. These flanges are to be clearly identified and labeled on the P&ID.

5. The cement manifold is to be rated to the ram-type BOPs pressure rating.

6. Pressure-retaining equipment is to be in accordance with Sec 8.

7. Piping systems are to be in accordance with Ch 5.

8. Materials are to be in accordance with Ch 3, Sec 1.

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

10. Electrical systems are to be in accordance with Ch 6, Sec 1.

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

504. Mud return system

1. Mud return system typically consists of agitators, chemical mixers, degassers, shale shakers, desand- ers, desilters, centrifuges, mud tanks and piping systems.

2. The mud circulating piping system is to be arranged so that the mud reconditioning system may be run in a series with the degasser, desander, desilter and centrifuge.

3. Degasser

(1) Degasser is to be provided to separate entrained gas bubbles in the drilling fluid which are too small to be removed by the mud-gas separator.

(2) Degasser is to be designed and manufactured in accordance with ASME Section VIII Boiler

and Pressure Vessel Code and Sec 8.

(3) Typically, the degasser is designed so that it can be operated under partial vacuum to assist in removing the entrained gas.

(4) Provisions are to be provided to vent gas to the appropriate location.

(5) The drilling fluid inlet line to the degasser is to be placed close to the drilling fluid discharge line from the mud-gas separator to reduce the possibility of gas breaking out of the drilling flu- id in the pit.

4. Pressure-retaining equipment is to be in accordance with Sec 8.

5. Piping systems are to be in accordance with Ch 5.

6. Materials are to be in accordance with Ch 3, Sec 1.

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

8. Electrical systems are to be in accordance with Ch 6, Sec 1.

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

505. Well circulation system

1. Well circulation system typically consist of circulating head, kelly, kelly cock, mixing pump, mud pump, standpipe, standpipe manifold, standpipe manifold, rotary hose, swivel and piping systems.

2. High-pressure mud pumps are to be fitted with safety relief valves whose maximum setting is no higher than the maximum allowable pressure of the system. Relief lines from the mud system are to be self-draining.

3. Where rupture disk type pressure relief devices are installed, rupture disks are to be certified to meet a recognized standard and the disk assembly is to be subjected to survey in accordance with the manufacturer’s specifications.

4. Rotary hoses in well circulation system are to be designed and constructed in accordance with Ch 5, 204. and「API Spec 7K」.

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

5. Piping systems are to be in accordance with Ch 5.

6. Materials are to be in accordance with Ch 3, Sec 1.

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

8. Mud, cement and kill pumps

(1) Fluid ends, pressure-retaining components, and mechanical load-bearing components including, but not limited to, gears, shafting, clevis linkages, gears of all types, keyways, splines, etc. are to be in compliance with API Spec 7K or equivalent recognized standard, and the additional re- quirements of this Annex.

(2) Materials, Welding and non-destructive examination used for major pressure-retaining equipment of the fluid ends and mechanical load-bearing components are to be in accordance with Ch 3.

(3) The fluid end and associated manifolds (suction and discharge) are to be hydrostatically tested as required by Ch 2, 203.

(4) Motor couplings and shafting are to comply with a recognized standard and be suitable for in- tended service in terms of maximum power and minimum operating temperature.

(5) Materials used for discharge manifold components on mud pumps designated as kill pumps must also comply with Ch 3, 103. 4 (2) regardless of minimum design temperature

(6) The mud pumps are to be equipped with pulsation dampening devices.

(7) Discharge high pressure piping to comply with ASME B31.3, or equivalent recognized standard, and Ch 5.

(8) The prime movers are to be in accordance with Sec 9.