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Sec.7: Special Provisions for Production and Storage Units [Table of Contents] Sec.9: Special Provisions for LNG Import and Export Terminals (and LNG Production Units)

DNV-OS-A101 Safety Principles and Arrangements

[-] Sec.8: Special Provisions for Drilling Units

SECTION 8
Special Provisions for Drilling Units

Sec.8
A. General

Sec.8
A 100   Introduction

Sec.8 A
101   In addition to the provisions given elsewhere in this standard, the following requirements apply specially for floating drilling units.

Sec.8
B. Arrangement

Sec.8
B 100   General

Sec.8 B
101   Design and location of equipment shall take account of motion of the unit and the possible effects of green sea.

Sec.8
B 200   Mooring systems

Sec.8 B
201   Mooring systems, including winches, tensioners, chain stoppers etc. should be located in open, non-hazardous areas. Where this is not practicable, special precautions shall be taken to ensure that such items do not become a source of ignition.

Sec.8 B
202   Chain lockers and chain pipes should be arranged in a non-hazardous area. Where such location is not practicable, permanent facilities for gas freeing (e.g. flushing or purging) the chain lockers and chain pipes shall be provided.

Sec.8
B 300   Moonpools

Sec.8 B
301   Moonpools shall have adequate scantling and stiffening to avoid damage from impact from load handling.

Sec.8 B
302   For ship shaped drilling units, the moonpool for drilling shall be surrounded by a cofferdam. However, upon special consideration, cofferdams may be omitted in areas with an equivalent arrangement of ballast water tanks, drill water tanks etc., which are easily accessible for inspection immediately after being pumped out.

Sec.8
B 400   Production and well testing

Sec.8 B
401   Drilling units intending to utilise facilities for storage and offloading of crude oil are to satisfy relevant requirements for production and storage units.

Sec.8 B
402   Arrangement of areas for well testing equipment and burner booms shall be given special attention. See Sec.3 for general requirements for arrangement and location of flares, and Sec.4 and C for hazardous areas.

Sec.8
C. Hazardous Area Classification

Sec.8
C 100   General

Sec.8 C
101   These requirements are supplementary to general requirements given in Sec.4.

Sec.8 C
102   Typical drilling plants shall be classified in accordance with requirements in IEC 61892-7 and IMO MODU Code sec. 6.2.

Sec.8
C 200   Drilling plant

Sec.8 C
201   Drilling mud transported in piping systems after the last stage of degassing shall not normally be regarded as a source for hazardous area. Consequently, mud pump rooms and mud mixing rooms are not normally classified hazardous unless there are other sources in the area.

Sec.8 C
202   Drilling fluid should be considered as hazardous when it is flammable and is handled at temperatures above flash point, e.g. due to high formation temperatures.

Sec.8 C
203   Outlets from drilling diverter line and overboard line from kill and choke manifold shall be located at a safe distance from potential sources of ignition.

Sec.8 C
204   If data on expected flow rate is available, dispersion calculations should be applied to identify the actual size of the gas plume.

Sec.8 C
205   Where a cementing unit is used for well control (kill) operations and may use active mud, the space containing the cementing unit may require classification.

Sec.8 C
206   Areas containing well test equipment and associated flowlines and burner arrangements shall be classified in accordance with the same general principles as for equivalent production equipment.

Sec.8 C
207   The dedicated area for well test equipment and associated piping shall be indicated on area classification drawings that shall include temporary test equipment.

Sec.8 C
208   Deck drainage systems shall be segregated from drains from non-hazardous areas.

Sec.8
D. Electrical Installations in Hazardous Areas

Sec.8
D 100   General

Sec.8 D
101   Electrical cables are as far as possible to be routed outside areas containing drilling mud.

Sec.8 D
102   Cables that necessarily will have to be so located that they may come into contact with mud are to be constructed of materials resistant to oil based mud.

Sec.8
E. Shutdown

Sec.8
E 100   General

Sec.8 E
101   International requirements for a simplified shutdown hierarchy may be applied on agreement between yard and owner. The principles of Sec.5 D remain applicable for areas that are vulnerable to an emergency originating from plant for well testing.

Sec.8 E
102   At least two emergency control stations shall be provided. One of the stations is to be located near the drilling console and the second station is to be at a suitable manned location outside the hazardous areas.

Sec.8 E
103   The control stations are to be provided with:
—manually operated contact makers for actuating the general alarm system.
—an efficient means of communication between these stations and all manned locations vital to the safety of the vessel.
—emergency shutdown facilities.

Sec.8
F. Escape, Evacuation and Communications

Sec.8
F 100   General

Sec.8 F
101   At least one escape route from the drilling derrick and from driller's cabin should lead directly to a safe place without requiring personnel entry to the central drill floor area.
Sec.7: Special Provisions for Production and Storage Units [Table of Contents] Sec.9: Special Provisions for LNG Import and Export Terminals (and LNG Production Units)