Section 1 General requirements

1.1.1 Gas from the unit’s process plant may be utilised as fuel in gas turbines/engines and auxiliary boilers/fired heaters, and crude oil/slops may be used in auxiliary boilers/fired heaters, provided the requirements of this Chapter are complied with. Diagrammatic plans showing ventilation arrangements, piping system layout and safety devices should be submitted for approval in each case.

1.1.2 Boilers, turbines, etc. which are arranged for burning gas or crude oil/slops are to be located within designated non-hazardous areas such as a boiler or turbine room or enclosure.

1.1.3 The design and construction of turbines, boilers, burners, etc. is to be suitable for operation on gas or crude oil as appropriate, effectively maintaining stable and complete combustion under all operating conditions.

1.1.4 The design of gas-burning internal combustion reciprocating engines and turbines will be specially considered in each case. For special requirements relating to boilers/fired heaters burning gas or crude oil/slops, see Pt 5, Ch 16, 1.6 Special requirements for boilers/fired heaters.

1.1.5 Consideration will be given to special cases or to arrangements which are equivalent to those required by these Rules.

1.1.6 The relevant requirements of Rules and Regulations for the Classification of Ships using Gases or other Low-flashpoint Fuels, July 2022 are to be complied with as applicable

1.2.1 Gas which is taken directly from the process plant is to be treated before distribution. The system should include suitable treatment equipment to provide well-mixed, liquid-free gas at constant pressure.

1.2.2 The gas treatment system is to be located within a designated hazardous area. This area is to be separated from the boiler room or machinery space by a gas-tight bulkhead.

1.2.3 Liquid drains from the treatment equipment are to be led to a closed drain recovery system. Gas lines downstream of the treatment equipment should be heat traced or insulated as necessary to prevent condensation and hydrate formation.

1.2.4 A separate and independent gas supply line is to be provided for each gas burning unit and each line is to be provided with a fuel gas master valve arranged to close automatically if gas leakage is detected, or on loss of the required ventilation from the pipe duct or casing, or loss of pressurisation of the double-walled piping, see Pt 5, Ch 16, 1.4 Piping requirements 1.4.2.

1.2.5 The fuel gas master valves and pressure regulators/reducing valves are to be located external to the boiler room or machinery space.

1.2.6 The gas supply line to each gas burning unit is to be fitted with a double block-and-bleed system utilising three automatic valves comprising two valves in series enabling the gas supply to be shut off and vented via a third valve to atmosphere at a safe location. These valves are to be arranged so that failure of the required ventilation, flame failure at the burners, abnormal gas supply pressure or loss of the valve actuating medium will cause the two valves in series to close and the vent valve between them to open. The valves are to be arranged for manual reset.

1.2.7 All master valves and block-and-bleed valves are to be arranged for remote operation from a location outside the boiler room or machinery space, and for local operation from the boiler or turbine control console.

1.2.8 The operation of the master valves or block-andbleed valves is to activate an alarm in the machinery space and in the central control room.

1.2.9 For long runs of high pressure gas piping, consideration should be given to the fitting of a self-closing ‘safety block valve’ between adjoining all-welded sections of piping, which would automatically isolate the gas supply in cases of pipe fracture.

1.2.10 Provision is to be made for gas-freeing and inerting that portion of the fuel gas piping system located in the boiler room or machinery space.

1.2.11 Suitable arrangements are to be made for change over between gas and oil fuel so that change over can be accomplished quickly and easily.

1.3.1 Crude oil or slops may be taken directly from the unit’s storage tanks, or from other suitable tanks. Such tanks are to be separated from non-hazardous areas by means of cofferdams with gas-tight bulkheads. Where crude oil/slops in tanks is preheated, its temperature is to be automatically controlled and a high temperature alarm and cut-out fitted.

1.3.2 The crude oil/slops transfer and treatment system (pumps, strainers, separators, etc.) is to be located within a designated hazardous area, such as a pump-room. This area is to be separated from the boiler room and other machinery spaces by gas-tight bulkheads.

1.3.3 Where crude oil/slops is heated by steam or hot water, the outlet from the heating coils is to be led to a separate, closed observation tank located within a designated hazardous area, together with the transfer and treatment components. This tank is to be fitted with a vent pipe led to atmosphere at a safe location, and the vent outlet fitted with a suitable flame arrester.

1.3.4 Pumps are to be fitted with a pressure relief valve in closed circuit discharging to the suction side, and are to be capable of being stopped from the machinery control room and from near the boiler front, as well as locally in the compartment in which they are situated.

1.3.5 Prime movers for pumps, etc. (excluding hydraulic motor drives) are to be located in a non-hazardous machinery space. Where drive shafts pass through a pump-room bulkhead or deck, gas-tight glands are to be fitted. These glands are to be effectively lubricated from outside the pump-room, see also Pt 5, Ch 15 Piping Systems for Oil Tankers of the Rules and Regulations for the Classification of Ships.

1.3.6 The crude oil piping is, as far as practicable, to be installed with an inclination rising towards the boiler so that the oil naturally returns towards the pumps in the case of leakage or failure in delivery pressure.

1.3.7 Crude oil delivery and return pipes are to be fitted with fail-close, shut-off master valves located external to the boiler room and remotely controlled from a position near the boiler fronts and from the machinery control room. These valves are to be arranged to close automatically on failure of duct ventilation or on detection of crude oil leakage within the duct.

1.3.8 The crude oil supply line to each burner unit is to be fitted with an automatic shut-down valve arranged so that failure of the forced draught fan, boiler hood exhaust fan, flame failure at the burner or loss of the valve actuating medium will cause the valve to close. The valves are to be arranged for local operation and for manual reset.

1.3.9 The operation of the master valves or burner shutdown valves is to activate an alarm in the boiler room and in the central control room.

1.3.10 Provision is to be made for gas-freeing and inerting that portion of the crude oil piping system located in the boiler room or machinery space.

1.3.11 Suitable arrangements are to be made for change over between crude oil/slops and fuel oil so that change over can be accomplished quickly and easily.

1.4.1 Fuel gas and crude oil piping is to be entirely separate from other piping systems and is not to pass through accommodation, service spaces or control stations. Such piping within the boiler room or machinery space is to be enclosed in a ventilated, gas-tight duct or be doublewalled as per either Pt 5, Ch 16, 1.4 Piping requirements 1.4.2 or Pt 5, Ch 16, 1.4 Piping requirements 1.4.3 respectively. For piping external to the boiler room or machinery space, or passing through enclosed non-hazardous spaces, see Pt 5, Ch 16, 1.4 Piping requirements 1.4.6.

1.4.2 The piping is to be installed within a ventilated, gas-tight duct, and this duct is to be connected to the bulkhead where it enters the boiler room or machinery space and to the burner unit(s) enclosure. The duct is to be provided with mechanical ventilation having a capacity of at least 30 air changes per hour and arranged to maintain a pressure less than atmospheric pressure. The ventilation outlet is to be located at a safe location where no gas-air mixture could be ignited. The duct ventilation is to be in continuous operation when fuel is in the piping. Continuous gas monitoring is to be provided in the duct to detect leaks, and arranged to automatically close the master valve in accordance with Pt 5, Ch 16, 1.2 Fuel gas supply arrangements 1.2.4 or Pt 5, Ch 16, 1.3 Crude oil supply arrangements 1.3.7

1.4.3 Alternatively, the piping may be a double-walled piping system with the fuel contained in the inner pipe and the annular space between pipes pressurised with inert gas to a pressure greater than the fuel pressure. Alarms are to be provided to indicate loss of pressure between the pipes and the master valves arranged to automatically close in accordance with Pt 5, Ch 16, 1.2 Fuel gas supply arrangements 1.2.4 or Pt 5, Ch 16, 1.3 Crude oil supply arrangements 1.3.7

1.4.4 Piping connections are to be reduced to the minimum required for installation and machinery maintenance. All piping is to be suitably and adequately supported so as to avoid vibration.

1.4.5 The piping for conveying fuel gas or crude oil/slops, and for the drainage pipes from the tray specified in Pt 5, Ch 16, 1.6 Special requirements for boilers/fired heaters 1.6.3, is to have a minimum wall thickness as specified for fuel oil systems in Pt 5, Ch 12 Piping Design Requirements.

1.4.6 Gas and crude oil/slops supply and return pipes which are located external to the boiler room or machinery space in open or semi-enclosed non-hazardous areas are to be of seamless heavy gauge steel with a minimum wall thickness of Sch 80, and have fully radiographed, full penetration, butt welded joints. Pipe connections are to be of the heavy flange type. This piping is to be clearly identifiable by means of a suitable colour code. Piping passing through enclosed non-hazardous spaces will be specially considered.

1.5.1 Ventilation of the boiler rooms and machinery spaces is to be at a pressure above atmospheric pressure by a separate ventilation system independent of all other ventilation systems, and providing at least 12 air changes per hour. At least two 100 per cent capacity fans are to be fitted. If the boiler, turbine, etc. is installed in a confined part of the boiler room or machinery space, the ventilation requirements apply to that part of the space only. For particular requirements relating to gas turbine ventilation, see Pt 7, Ch 2, 6.5 Gas turbine ventilation.

1.5.2 The ventilation system is to ensure good air circulation in all spaces, and in particular to prevent the formation of stagnant pockets of gas within the space. Gas detectors are to be fitted at appropriate locations in these spaces, particularly where air circulation may be restricted.

1.5.3 Where released gases are likely to be heavier than air as in the case of crude oil systems, extraction ducts should be located at a low level within the boiler room. Open mesh floor plates should be utilised as required to ensure efficient extraction of gases.

1.5.4 The ventilation air intakes are to be from an external non-hazardous area, at least 3 m from the boundary of any hazardous area. Ventilation outlets are to be led to atmosphere at a safe location.

1.5.5 Boilers and turbines are to be fitted with a suitable hood or casing, arranged so as to enclose as much as possible of the burners and associated valves and pipes, but without restricting the air flow to the burner registers. The hood or casing should be installed to ensure that the ventilating air sweeps across the enclosed valves, etc. and be fitted with doors as necessary for inspection of, and access to, the burner units, valves and pipes.

1.5.6 The boiler/turbine hood is to be fitted with a ventilation duct led to atmosphere at a safe location, and with the vent outlet fitted with a suitable flame-proof wire gauze. At least two 100 per cent capacity extraction fans with sparkproof impellers are to be fitted to maintain the pressure inside the hood less than that of the boiler room or machinery space. The fans are to be arranged for automatic change over to the standby fan on failure of the operational fan. The fan prime movers are to be placed outside the duct with gastight drive shaft penetration through the duct casing.

1.5.7 Means of continuous gas detection is to be provided in way of the hood and gas pipe ducting and arranged to provide an audible and visual alarm at 30 per cent lower explosive limit and shut-down of the fuel supply before the gas concentration reaches 60 per cent of the lower explosive limit.

1.6.1 The arrangement of boilers and burner systems is to comply, in general, with the requirements of Pt 5, Ch 14 Machinery Piping Systems, as applicable. The whole of the boiler casing is to be gastight and each boiler is to have a separate uptake.

1.6.2 The arrangement of burner units and all associated valves is to be such that the fuel gas or crude oil/slops is ignited by the flame of the fuel oil burner. A flame scanner is to be installed and arranged to ensure that the fuel supply to the burner is cut off unless satisfactory ignition has been established and maintained. A manually operated shut-off valve and flame arrester is to be fitted to each burner unit.

1.6.3 Boilers for burning crude oil/slops are to be fitted with a tray or gutterway of suitable height placed in such a way so as to collect any possible oil leakage from burners, valves or connections. The tray or gutterway is to be fitted with a drain pipe discharging into a separate, closed collecting tank in the boiler room, pump-room or other suitable location. This tank is to be fitted with a vent pipe led to atmosphere at a safe location, and with the vent outlet fitted with a suitable flame arrester, and with provision for drainage to a suitable tank outside the machinery space.

1.6.4 Means are to be provided for the boiler to be automatically purged before firing or relighting. Arrangements are also to be provided to allow manual purging, but interlocking devices should be fitted to ensure that purging can only be carried out when the burner fuel supply valves are closed.