IAGC Guidelines for Marine Small Boat Operations Appendix 1 - Small Boat Design

Transcription

1 IAGC Guidelines for Marine Small Boat Operations Appendix 1 - Small Boat Design September 2013

2 Guidelines for Marine Small Boat Operations Appendix 1 - Small Boat Design Table of contents 1. Introduction Purpose Definitions References 2 2. Stability and Buoyancy Stability Buoyancy 4 3. Hull General Safety Systems 6 4. Propulsion and Steering Propulsion Steering 8 5. Seismic Specific Equipment Winches, Reels and Towing Points Cable Lifters 9 6. References 10 Page 1 of Appendix 1

3 1. Introduction The design and construction of any small boat should be appropriate to the tasks and environmental conditions that it will exposed to. Any small boat not specifically designed for interacting with towed equipment should be limited to tasks that are appropriate to its design and function. Classification Societies will provide specific details on the standards for the design, construction and testing of boats. 1.1 Purpose Understanding how a small is boat designed will assist an organisation in the management of small boat operations. The following explanations are designed to provide an overview and where appropriate references have been included to provide further detailed explanations on particular subjects. All personnel who are assigned as small boat crews should have an understanding of small boat design. 1.2 Definitions Throughout this document the terms and definitions used are in accordance with OGP Glossary of HSE Terms, where possible company specific terminology for seismic equipment has been supplemented for generic terms or names. If you are in doubt of the meaning of a word or acronym in any part of this manual, ask your supervisor or HSE department to advise you. 1.3 References The references used in this appendix are listed in Section 6; it is the responsibility of the user to monitor the references in case of updates or changes to Legislation, Regulation, Conventions, Standards or Guidelines. Page 2 of Appendix 1

4 2. Stability and Buoyancy All boats are required to have Stability and Buoyancy Assessment carried out on it. Further details can be found in ISO 12217: Small Craft - Stability and Buoyancy Assessment and Categorisation 1. The assessment will have been carried out by a competent authority who will issue either a Statement of Compliance or a Boat Certificate. Rescue Boats will be issued a certificate in accordance with Chapter III of the international Convention for the Safety of Life at Sea (SOLAS) Stability Stability relies on the interaction between the boats Centre of Gravity (CG) and Centre of Buoyancy (CB) in three planes. The total weight of the vessel, including all the stores, fuel and equipment can be represented as acting through one point, the CG. Buoyancy acts on all the underwater parts of the hull. The total of this buoyant upward force can be represented as acting through one point, the CB. Vertical Centre of Gravity The first angle of plane is the Vertical Centre of Gravity (VCG). When a boat is in its normal upright position the CG and CB should be in vertical alignment. When the hull of the vessel tilts along this plane (providing that any load on the boat does not move) the CG remains in the same position, and the CB moves to fit the change in water displacement by the hull. Longitude Centre of Gravity The second plane of stability is the Longitude Centre of Gravity (LGC). When a boat is in its normal upright position the LCG and CB should be in vertical alignment this is called trim. The alignment between the CB and CG changes when the boat increases speed, or when cargo or people are placed onboard this change effects the boats trim and the boat will either pitch forward or aft. Forward pitching in boats with low freeboards may increase the likelihood of water entering the deck area; this may then further increase the forward pitch if bilge pumps or self-bailers are unable to operate. Transverse Centre of Gravity The third plane of stability is the Transverse Centre of Gravity (TGC). When a boat rolls gravitational force will initially try to force the hull back into its normal CG and CB alignment causing the boat to roll or heel, however if the hull is tilted further the buoyancy and gravitational forces start to create a movement that will capsize the boat. If any load on the boat shifts towards the roll the CG and CB is 1 ISO 12217: Small Craft - Stability and Buoyancy Assessment and Categorisation 2 IMO - Chapter III of the international Convention for the Safety of Life at Sea (SOLAS) Page 3 of Appendix 1

5 moved and the potential for capsize increases. Cable Lifters The alignment of a boats CG and CB may change if a cable lifting device is fitted and additional assessments should also be made as part of its stability and buoyancy assessment based on expected downward forces exerted by the tension of a streamer cable. The amount of downwards force on a cable lifter will change dependant on the location of the boat along the length of the streamer cable and the depth that the streamer is set. Tension on cable lifters will cause the TGC to shift which will in turn change the manoeuvring characteristics of the boat causing it to heel (See also section 5). Movement of Crew Deck space where crew are expected to move around is to be calculated to determine potential heeling of a boat. The standard of stability to be achieved by a new boat is dependent on its length, maximum number of persons permitted to be carried, whether cargo is to be carried and the area of operation. Boats fitted with a Deck Crane or Lifting Device A boat fitted with a deck crane or other lifting device should be a decked vessel and should be assessed to determine the maximum angle of heel and the minimum freeboard on the low side. The angle of heel should not exceed 7 or result in a freeboard on the low side of less than 250mm, whichever is the lesser angle. When an angle of heel is greater than 7 but not exceeding 10 a certifying authority may accept the lifting condition providing that additional criteria are satisfied when the crane or other lifting device is operating at its maximum load moment. 2.2 Buoyancy The buoyancy provided by the underwater parts of a boat, coupled with the combined weight of its hull, equipment, fuel, stores and crew will determine the stability of a boat. Down Flooding Downflooding Height All small boats will have their Downflooding Height assessed to determine where all openings that may allow water to ingress onto the boats deck or into its compartments are situated and to the type of drainage available to each area. The early stages of downflooding often go unnoticed as the boat sinks lower in the water and the buoyancy of the boat reduces. Freeboard The space or distance between the deck of a vessel and the waterline, a decked boat without a freeboard is treated as an open boat. Water Freeing Arrangements Boats fitted with bulwarks may trap water on deck and should be provided with efficient freeing ports. When a non-return shutter or flap is fitted to a freeing port it should have sufficient clearance to prevent jamming and any hinges should have pins or bearings of non-corrodible material. Where cargo is to be stowed on deck the stowage arrangement should be such as to not impede the free flow of water from the deck. Free Surface Effect Page 4 of Appendix 1

6 Flooded decks and compartments have the potential for Free Surface Effect (FSE) to occur. FSE is the movement of water or loads on an open deck or within a compartment which may effect the stability of the boat by making adverse changes to the boats CG and CB. 3. Hull 3.1 General A boat should be of strength to withstand the sea and weather conditions likely to be encountered in the area of operation. As a minimum, tests to verify strength of structure should include drop and towing. When lifting arrangements are provided to a boat, a lifting test should be carried out at ambient temperature with the boat loaded with the mass of the full complement of persons and equipment for which it is to be approved. Hull Integrity All small boats should undergo regular hull integrity inspections, this may include the weighing of the boat to identify potential water ingress into closed compartments. Weather-tight A weather deck should be of a weather-tight construction and drainage capable of efficient operation when the vessel is heeled to 10. When pipes, cables, etc. penetrate watertight bulk heads, they should be provided with valves and/or watertight glands as appropriate Electrical The electrical arrangements should minimise the risk of fire and electric shock. Tanks, machinery or other metallic objects which do not have good electrical continuity with the water surrounding the vessel should have special earthing arrangements to reduce such risks. Air Pipes Air pipes should be kept as far inboard as possible and/or have a height above deck sufficient to prevent downflooding. Engine air intakes identified during a Downflooding Height Assessment should where appropriate be fitted with manual or automatic self-closing system. Bilge A decked boat should be provided with efficient means for removal of bilge water entering any compartment below the weather deck with at least two bilge pumps systems (one may be power driven and the other by hand pump). The arrangements should be such that any single event hazard such as collision, flooding of one compartment, engine failure, blackout or fire, should not disable all the pumping systems. An audible and visual alarm at the control position should be fitted with an auto-start. Snag Points The crew should be aware of the potential snag points on the boat. The potential for incidents to occur during the interaction of a small boat with another small boat or larger vessel due to the fender arrangements of the other vessel or the vessels superstructure Prior to any interaction between the two boats the fender arrangements, hull design and stability of the vessel should be assessed. Crew Each small boat should be assessed for its minimum safe manning level and the level of competency training given to each position as defined in the IAGC Marine Small Boat Training and Competency Guidelines. Page 5 of Appendix 1

7 Personnel The maximum number of persons carried in addition to the crew should be identified and sitting and/or standing arrangements determined in order to maintain the stability of the boat during its launch, recovery or transit. Cargo The maximum load capacity of the small boat and the lifting capacity of the davit should be identified. The load distribution of any cargo should not adversely affect the trim and the CG or CB. The use of simple diagrams should be considered to ensure that passengers and crew are aware of the arrangements for crew, passengers and cargo. Limited Cargo with 3 crew and 2 passengers Cargo with 3 crew only Working Life The working life of the hull and lifting points should be identified and consideration given to the replacement of a boat or extending the working life dependant on rigorous inspection. Nondestructive testing follow SOLAS specifications for re-certifying should be considered for non SOLAS boats. 3.2 Safety Systems Safety System should be assessed for the type of boat and its expected operational environment. Boats that may operate remotely from its launching vessel may require additional safety systems to mitigate the additional hazards. Fire Detection Efficient smoke and/or heat detectors as appropriate to the hazards should be fitted in the machinery spaces. The detectors should provide an audible warning at the control position and indicate the location of the fire. Firefighting Appliances A boat should be provided with efficient firefighting equipment. Fixed fire extinguishing systems installed in a machinery space should be an approved type, appropriate to type and size of space being protected. Fuel systems should be provided to isolate switch/control to prevent the fuel from being fed to a fire in an engine space. The isolation switch/control should be capable of being closed from a position outside the engine space. Liferafts Inflatable liferafts, fitted with hydrostatic release units may be fitted to work boats based on the types of operations required of the boat and the associated hazards. Life Saving Appliances Firefighting appliances, liferafts and associated ancillaries fitted to a small boat which may not be included as part of the launching vessels Life Saving Appliances as described in the International Life-Saving Appliance Code 3 should be treated with the same diligence as those of the launching vessel. 3 International Life-Saving Appliance Code 3 Resolution MSC.48(66) Page 6 of Appendix 1

8 4. Propulsion and Steering A small boat is at its most vulnerable during launch, recovery and whilst interacting with towed equipment. The propulsion and steering capabilities of the boat should be assessed for the potential of failure, the principles of a Failure Mode Effects Analysis (FMEA) can be used to determine the level of redundancy or mitigation afforded to the boats design. 4.1 Propulsion Engine Changes in marine propulsion systems and the development of computer based engine management systems onboard a small boat should be assessed in order to determine any factors that may result in an automatic shutdown of engine without the crew being alerted and where appropriate the automatic shutdown system should be disarmed. The boats main propulsion and all auxiliary machinery essential to propulsion and the safety of the boat should operate when the vessel is in the upright and when inclined at any angle of heel and trim up to and including 15 and 7.5 respectively either way, under static conditions Exhaust Systems An engine exhaust outlet which penetrates the hull below the weather deck should be provided with a means to prevent back flooding into the hull through the exhaust system. The means; may be provided by system design and/or arrangement, built-in valve or a portable fitting which can be applied readily in an emergency. Kill Cords Kill Cords or Dead man's switch should be considered so that the engine is automatically shut down if the small boat capsizes or the coxswain leaves his position. A second kill cord should be held on the boat so that the engine can be restarted should the coxswain fall overboard. Whilst coming alongside or approaching a vessel that is towing equipment consideration should be given to preventing the Kill Cord from accidental activation that may cause the boat to lose propulsion and drift. Propulsion Guards should be considered to reduce the potential for fouling propellers or water jet systems Fuel Page 7 of Appendix 1

9 The marine geophysical industry has generally accepted the move away from petrol to diesel powered engines because of the potential risk involved with fuels with a low flash point. Changes in national and international environmental conventions, laws or regulations relating to emission may impact on future engine design and management systems. 4.2 Steering Steering Guards should be considered to reduce the potential for fouling propellers or water jet systems. Boat with the ability to have remote steering arrangements should have a secondary method of controlling the steering in the event of failure of the remote control. Page 8 of Appendix 1

10 5. Seismic Specific Equipment History has shown that most seismic small boat capsizes have occurred due to the boat being towed either in a sideward or rearward direction, this was demonstrated during tank test on a model of a typical seismic work boat. TANK TEST WAVE CHARACTERISTICS Irregular wave spectrum with significant wave height 2 meters and peak period 9.2 seconds The following result were determined during a tank test carried out on a work boat on the effects that towing from different angles may occur at a speed of 4.5nm: RESULTS Towing at 4.5 knots from aft (towing point 1): Stayed upright Towing at 4.5 knots from WaterJet (towing point 2): Stayed upright Towing at 4.5 knots from cable winch (towing point 3): Capsized Towing at 4.5 knots from cable winch (towing point 4): Capsized Towing at 4.5 knots from front (towing point 5): Stayed upright Towing at 4.5 knots from front with 200 kg in the cable lifter: Stayed upright Towing at 4.5 knots from front with 400 kg in the cable lifter: Stayed upright 4.1 Winches, Reels and Towing Points Winches Page 9 of Appendix 1

11 The use of winches onboard a small boat should assessed for their suitability and be load tested and marked accordingly to indicate their Safe Working Load (SWL). The lay of the rope should also be identified on the winch to ensure the maximum brake force can be applied. Storage Reels Storage reels may be confused with winches so should be clearly identified as a Reel. Towing Points A small boat designed to tow seismic equipment should be assessed for it maximum SWL and all towing points identified and marked accordingly. The boats bollard pull should also be assessed to ensure that the boat is not used to perform a task that is above its capability. Lashing points should be identified and marked so as not to cause confusion with towing points. 4.2 Cable Lifters Cable Lifting When designing future cable lifters, consideration should be made for additional safety features to prevent it from being operated outside its approved limits. The addition of safety features should be assessed to ensure that they do not create other hazards. Page 10 of Appendix 1

12 6. References IMO - International Life-Saving Appliance Code 1 Resolution MSC.48(66) IMO - Chapter III of the international Convention for the Safety of Life at Sea (SOLAS) ISO - ISO 12217: Small Craft - Stability and Buoyancy Assessment and Categorisation Page 11 of Appendix 1