safety offshore - the work of imo* introduction · pdf filesafety offshore - the work of imo*...

Safety offshore - the work of IMO*

E.E. Mitropoulos

Maritime Safety Division, International Maritime

Organization, 4 Albert Embankment, London SE1 7SR, UK

Introduction

The first mobile drilling platform for the oil industry was launched in 1949and thereafter the industry took many steps to improve the design, con-struction and equipment of drilling units to ensure they were stable, mobileand cost effective. Their research led to the evolution of truly mobile (self-propelled) floating drilling units and, through the 1960s, the drilling fleetexpanded in size and type. Four generic forms of mobile offshore drillingunits (MODUs) evolved, i.e. submersibles and jack-ups, which are bottomsupported and drill ships and semi-submersibles, which are free-floating.

The submersible is designed as a bottom-supported drilling unit and itsoperation is limited to water depths of up to 52 metres. The 'self-elevating'or jack-up rig is one of the most widely used platforms in today's offshoredrilling industry and the current designs can accommodate depths up to120 metres.

The benefits of self-propulsion allow drill ships to operate in deep water,with the assistance of either conventional mooring or dynamic positioningsystems; however they tend to be restricted to regions having small waveheights and low wind velocities.

The semi-submersible consists of a deck supported by a number of ver-tical columns, cross braces and pontoons, which have sufficient buoyancyto float the entire structure. This arrangement makes this mobile offshoredrilling unit very stable and reduces the effects of wave action, since muchof the vessel is below the surface of the sea while drilling.

* Views expressed in this paper are those of the authors and should not be construedas necessarily reflecting the views or policies of the International Maritime Organizationor its Secretariat.

Transactions on the Built Environment vol 1, © 1993 WIT Press, www.witpress.com, ISSN 1743-3509

The 1979 MODU Code

IMO followed swiftly the development of new marine vehicles and, in 1979,adopted the Code for the Design and Construction of Mobile OffshoreDrilling Units (MODU Code). In that Code, the mobile offshore drillingunit is defined as a vessel capable of engaging in drilling operations for theexploration for or exploitation of resources beneath the sea bed. The Codeprovides a level of safety for such units and their personnel equivalent tothat required for conventional types of ships engaged in international voy-ages by the International Conventions for the Safety of Life at Sea, 1974(SOLAS Convention) and on Load Lines, 1966, (LL Convention) but doesnot include requirements for drilling or procedures for the control of subseawells.

The Code regulates safety matters related to construction; subdivision,stability and freeboard; machinery and electrical installations; fire safety;life-saving appliances; and radiocommunications similar to the SOLAS andLL convention ships. It also regulates lifting devices, helicopter facilitiesand the operation of the units.

The Code applies to new units built after its adoption by a flag State.Surveys are provided for as well as the issue of Mobile Offshore DrillingUnit Safety Certificates intended to facilitate the international movementand operation of units. Coastal States may, however, impose additionalrequirements regarding operational aspects of industrial systems not dealtwith by the Code. The 1979 MODU Code has thus far been implementedby a number of maritime administrations.

The 1989 MODU Code

The 1979 Code was kept under review by IMO to take account of experi-ence gained in its application and lessons learned from accidents such as theALEXANDER KIELLAND and the OCEAN RANGER. It was extensivelyrevised in 1989.

The 1989 MODU Code, which is based upon sound design and engi-neering principles and operational experience, was developed to provide aninternational standard for mobile offshore drilling units constructed on orafter 1 May 1991 so that its application would facilitate the internationalmovement and operation of such units and result in a level of safety forsame and for personnel on board equivalent to that required for conven-tional ships engaged on international voyages by the SOLAS and Load LineConventions. The new Code covers the same subjects as the 1979 one.

Any existing unit, which complies with the provisions of the 1989 MODUCode, should be considered eligible for a safety certificate in accordance withthat Code. Use of an existing unit simply because its design, constructionand equipment do not conform to the requirements of the new Code is not


prohibited.

The 1989 MODU Code has been the subject of further review in the lightof technological advancements and amendments to it already approved orunder consideration by IMO's Maritime Safety Committee (MSC) are dis-cussed later on.

As its predecessor, the 1989 MODU Code does not include requirementsfor the drilling or procedures for the control of the subsea well. The drillingoperations are subject to control by the coastal State concerned.

Safety training of MODU personnel

As in all industries, the human element plays a large and important partin the offshore industry. In 1983 the Assembly of IMO adopted a recom-

mendation on maritime safety training of personnel on mobile offshore units(resolution A.538(13)), which also addresses personnel on accommodationunits and other units such as those engaged in construction, maintenance,lifting, pipe-laying and fire-fighting operations. It also covers survival drillsin emergency situations. The categories of personnel considered by the rec-ommendation embrace visitors, seafarers, where required, as well as regu-larly or non-regularly assigned special personnel, the former with or withoutspecial responsibility for the survival of others. In the context of the rec-ommendation, special personnel means all persons not being seafarers orpassengers connected with the special purpose of the unit.

Specialized training and certification for essentialmaritime functions

Furthermore, by resolution A.712(17), the IMO Assembly adopted, in Novem-ber 1991, recommended standards of specialized training, qualifications andcertification of key personnel assigned responsibility for essential marinefunctions on mobile offshore units (MOUs), thus ensuring that the humanelement on board such units has the requisite skills to perform their dutiescompetently and safely.

Safety of offshore exploration areas

The safety of offshore exploration areas, in particular where IMO trafficseparation schemes and other routeing measures exist, is another impor-tant matter. By resolution A.340(IX) IMO adopted a recommendation onthe establishment of fairways through offshore exploration areas, includingguidelines for adjustment of a traffic separation scheme when temporarypositioning of an exploration rig cannot be avoided. Further recommenda-tions were issued on charting and manning of drilling rigs and platforms,establishment of safety zones in offshore exploration areas, on ships' route-


ing and guidelines for vessel traffic systems.In addition, the MSC, having been informed of infringements of the

safety zones around fixed and floating offshore installations by commercialships and fishing vessels, prepared measures to prevent such infringements,which were eventually adopted by an Assembly resolution in 1989 (Reso-lution A.671(16) on Safety zones and safety of navigation around offshoreinstallations and structures).

Offshore support vessels

For the servicing of offshore units a number of specialized vessels are neededsuch as offshore supply vessels, crew boats, standby vessels and pontoons.An offshore supply vessel is generally defined as a vessel primarily engagedin the transport of stores- materials and equipment to offshore installationsand which is designed with superstructure forward and an exposed deck aft.

IMO recognised that both the design and normal operation of offshoresupply vessels differ from those of conventional ships and that, by virtueof this, the application of the 1974 SOLAS Convention is, in many ways,inappropriate for such vessels. The IMO Assembly, therefore, adopted, by

resolution A.469(XII), guidelines for the design and construction of offshoresupply vessels. These guidelines apply to new decked vessels with a lengthof 24 metres and over but not more than 100 metres, as far as requirementsfor stability in the intact or damaged condition of the vessels and their sub-division are concerned. Offshore supply vessels of 500 gross tonnage should,otherwise, comply with the requirements for cargo ships of the 1974 SOLASConvention, as amended.

Special stability requirements are needed for off-shore support vesselsbecause they are designed with low freeboards and large beam to providethe required platform for the deck cargo. Special guidelines applicable tooffshore support vessels for the transport and handling of limited amountsof hazardous and noxious liquids were adopted in 1991 by Assembly resolu-tion A.673(16). As low energy collisions may occur between offshore supplyvessels and offshore units, subdivision is required for both crafts.

IMO has also issued interim Guidelines on intact stability requirements

for pontoons (MSC/Circ.348 and MSC/Circ.503).

Safety of diving systems

With the increase in use of diving systems in connection with the explo-ration and exploitation of mineral resources offshore, IMO, being concernedwith the improvement of safety measures for such systems, considered desir-able to provide standards of safety for the design, construction and surveyof diving systems to facilitate their movement and operation internationally.

Eventually, IMO adopted, by resolution A.536(13) in November 1983,


the Code of Safety for Diving Systems to provide minimum safety standardsfor systems fixed on ships and floating structures. The Code provides for

Diving System Safety Certificates to document satisfactory compliance with

the provisions of the code. Items covered by the Code are, for example: sur-face compression chambers, diving bells and pressure vessels not intendedfor occupation, pipes and accessories, breathing gas systems, diving bellhandling systems, diving system/ship interface, fire safety, electrical, con-trol and communication systems. It is intended to complement the Codewith requirements for portable diving systems when some experience hasbeen gained with the fixed system standards. Currently, the Code is beingrevised to take account of technological advancements in its field.

Damage stability criteria for MODUs

A difficulty in most current damage stability regulations is that they assessdownflooding only on the basis of the static inclination caused by the dam-age and a specified wind force. They do not take into account the motionof the semi-submersible and the action of waves on it. Current stabilityrules require a MODU to be designed so that, under the specified extent ofdamage and wind conditions, it will not list beyond the angle of downflood-ing, which by definition is the angle at which an unprotected opening in thestructure reaches the mean sea level. Because rig motion and wave actionmay cause downflooding long before that point is reached, the matter hasbeen under consideration at IMO for the MODU Code to include, inter alia,provisions for assigning freeboard to potential downflooding points or, forreliable weathertight closures, to protect openings that may be immersed.

As a consequence of this work, the MSC, at its fifty-seventh session in April1989, approved:

• alternative intact stability criteria for twin pontoon column stabilizedunits; and

• alternative damage stability criteria for column stabilized semi-submersible units,

which were subsequently adopted by Assembly resolutions A.650(16) andA.651(16) respectively.

Removal of offshore platforms

After a number of years of service, many offshore platforms become idle,either for economic reasons or due to the depletion of the oil wells. Theinternational maritime community, realising that obsolete and abandonedoffshore platforms pose a serious risk to navigation and, in certain cases,to the marine environment, brought the matter before IMO, whose Sub-Committee on Safety of Navigation considered it during the late 1980s.


Following general discussion on the removal of disused offshore platformsand the effects this could have on the safety of surface and sub-surfacenavigation, including the safety of fishing vessels, the MSC, at its fifty-fifthsession in April 1988, prepared guidelines and standards for the removalof offshore installations and structures in the exclusive economic zone andon the continental shelf and an MSC circular was issued pending furtherrevision in light of experience gained in the application of the guidelines,which were later adopted by the Assembly as resolution A.672(16).

Various points, which should be considered by a coastal State havingjurisdiction over the installation or structure, were tentatively identified inthe guidelines as were also actions which should be taken by the coastalState concerned when authorization is given for an offshore installation orstructure or part thereof to remain on the seabed. The following basic

standards (contained in resolution A.672(16)) should be taken into accountwhen a decision is made regarding the removal of an offshore installation orstructure:

"All abandoned or disused installations or structures standing inless than 75 metres of water and weighing less than 4,000 tonnesin air, excluding the deck and superstructure, should be entirelyremoved. All abandoned or disused installations or structuresemplaced on the seabed on or after 1 January 1998, standing

in less than 100 metres of water and weighing less than 4,000tonnes in air, excluding the deck and superstructures, should beentirely removed."

MARPOL and offshore platforms

The International Convention for the Prevention of Pollution from Ships,1973, as amended by the 1978 Protocol relating thereto (MARPOL 73/78),applies and contains specific requirements related to offshore platforms andstructures. To start with,MARPOL 73/78 defines a 'ship' as a 'vessel ofany type whatsoever operating in the marine environment and includes hy-drofoil boats, air-cushion vehicles, submersibles, floating craft and fixed orfloating platforms'.

Special MARPOL requirements for drilling rigs andother platforms

In accordance with Regulation 21 of Annex I of MARPOL 73/78, fixedand floating drilling rigs, when engaged in the exploration, exploitation andassociated offshore processing of seabed mineral resources, must complywith the requirements of Annex I applicable to ships of 400 tons grosstonnage and above other than oil tankers, except for certain provisions ofregulations 11, 16 and 17 of Annex I and the oil discharge record book.


There are three categories of discharges associated with the operationof offshore platforms when engaged in the exploration and exploitation ofmineral resources, i.e.:

1. platform drainage;

2. production water discharge; and

3. displacement discharge.

Only the discharge of platform drainage is subject to MARPOL 73/78.

Under Annex V of MARPOL 73/78, the disposal of garbage is, subject tocertain provisions related to distance from the nearest land, prohibited fromfixed and floating platforms.

The GMDSS into the MODU Codes

In accordance with resolution A.649(16), the MSC adopted, in 1991, amend-ments to chapters 10 and 11 of the 1989 MODU Code in order to introducethe global maritime distress and safety system (GMDSS) into offshore plat-forms. Similar amendments were also adopted in respect of the 1979 MODUCode.

In addition, the Committee recommended that Governments encour-age the fitting of all MODUs with the GMDSS equipment specified in theamendments to the MODU Code and ensure that all MODUs comply with:

1. section 10.13 of the amendments to resolution A.649(16) not laterthan 1 February 1995; and

2. chapter 11 of the amendments to resolution A.649(16), as applicableto their mode of operation, not later than 1 February 1999.

Extension of the Code on Alarms and Indicators tothe 1989 MODU Code

The Code on Alarms and Indicators was adopted by the IMO Assembly atits 17th session in November 1991 by resolution A.686(17) and was primarilydirected to ships covered by the 1974 SOLAS Convention and associatedcodes (IBC, IGC, and Gas Carrier). By MSC/Circ.618, the Committee, atits 62nd session in May 1993, approved the extension of that code to coverthe 1989 MODU Code and the Code of Safety for Diving Systems andinvited Member Governments to apply them in the interim period beforetheir expected formal adoption in May 1994.

The MODU Code does not fully address the 'petroleum activity' ofthe unit and therefore does not call for alarms such as the 'Prepare toabandon platform alarm' and the 'Toxic gas alarm'. The only common


alarm addressed in the code is the 'General alarm' and, for harmonizationpurposes, the Code on Alarms and Indicators has been amended in respectof MODUs by the addition of a new paragraph 5.6 to section 5 of the AlarmCode as follows:

"5.6 On MODUs, where supplemental visual alarms are installedfor general emergency alarms, the colour of these supplementalalarms may be amber, provided they flash with a pulse frequencyof at least 4Hz."

The Code on Alarms and Indicators is a recommendatory documentintended to promote uniformity of systems between ships and MODUs withthe purpose of improving crew safety and training. For the benefit of de-signers and operators, it consolidates in one document the references to

priorities, grouping, locations and types, including colours, symbols, etc. ofshipboard alarms and indicators. The Code applies on ships constructedon, or after, 1 July 1992. It will also apply to MODUs after adoption of theamendments by the MSC in May 1994.

Helidecks on MODUs

Currently, IMO's Sub-Committee on Ship Design and Equipment (DE), to-gether with ICAO, is revising chapter 13 - Helicopter facilities - of the 1989MODU Code in order to harmonize the requirements of annex 14, volume IIof the ICAO Convention, with the two-tier approach with respect to climaticconditions contained in the IMO MODU Code. In support for a single setof requirements for offshore helidecks, the ICAO Secretariat has proposedrevised texts for paragraph 13.3 on the construction of helidecks. After de-tailed discussion at its last session in February 1993, the DE Sub-Committeeagreed that the new text proposed by ICAO, together with an amendmentsuggested by the Netherlands to delete any reference to phase-out datescontained therein, could form the basis of an agreement. Comments wereinvited from Members for consideration at the next DE session in February1994, when the matter is expected to be finalized.

HSSC into the MODU Code

The 1989 MODU Code is also under amendment for introduction of theharmonized system of survey and certification (HSSC) into it. At its 35thsession the DE Sub-Committee agreed, in principle, with the draft amend-ments to the 1989 MODU Code and invited comments on whether the 1979MODU Code should also be amended. At its 36th session there was no sup-port for the extension of the HSSC to MODUs covered by the 1979 MODUCode. A final text of draft amendments to the 1989 MODU Code, in orderto harmonize its survey and certification requirements and safety certificates


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Marine Engineering 163

with the requirements of the 1988 SOLAS and Load Line Protocols and a

draft MSC resolution for adopting the amendments with an entry into force

date on the same date as the HSSC Protocol, is expected to be agreed by

the DE Sub-Committee in February 1994.

Guidelines on dynamic positioning and anchoring

systems for MODUs

The DE Sub-Committee has been discussing papers since its 33rd sessionin 1990 on standard calculation methods for anchor positioning systemsfor MODUs and for dynamic positioning for MODUs and ships engaged insimilar operations. A working group is currently examining the availabletechnical literature, reports, research data and guidelines issued by the in-dustry and is developing two sets of draft guidelines on the above mentionedsubjects for the consideration of the Sub-Committee at its 37th session inFebruary 1994. Once finalized, the guidelines will be of great help to de-

signers and operators.

ILO-sponsored tripartite meeting on offshore safety

and related issues

One of the conclusions adopted by the ILO-sponsored tripartite meeting onsafety and related issues pertaining to work on offshore petroleum installa-

tions held at Geneva in April 1993 is as quoted below:

"Governments should take action to promote safety on mobile

drilling units by endorsing the recommendations for design cri-teria, construction standards and other safety measures con-tained in the International Maritime Organization (IMO) Codefor Construction and Equipment of Mobile Offshore DrillingUnits (MODU Code), 1979 and 1989 editions, and their subse-quent amendments. The 1989 Code applies to units constructedafter May 1991. Operators should take action to achieve alevel of safety at least equivalent to that intended by the rec-ommendations contained in 1979 or 1989 Code as appropriate.Governments and employers' and workers' organizations shouldtake note of the work of the IMO concerning maritime safetyand emergency preparedness training for personnel working onmobile offshore units and should clarify what additional safetytraining and other requirements are necessary on such units forsafety matters not covered by IMO resolutions or other stan-

dards."


164 Marine Engineering

Conclusions

The technological advancements in the offshore industry of the last twodecades have been rapid. This pace of change demands that the standardssafety of MODUs be constantly reviewed and mechanisms set up nationallyfor the implementation of all appropriate safety measures and the exerciseof effective and speedy relevant control.

The International Maritime Organization, a specialized agency of theUnited Nations dealing exclusively with maritime affairs, started consid-ering offshore safety matters in the early 70s and has, ever since, beenreviewing and updating international regulations for the construction andequipment of mobile offshore drilling units, for the prevention of marinepollution from the units and for ensuring safety in other related matters

including training of MODU personnel. However, safety cannot be ensuredby having regulations alone; it is their strict implementation that mattersmost. IMO, its Member Governments and the industry must work togetherin order to ensure the highest practicable standards of safety on MODUsand in offshore activities.


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