Section 3 Production, process and utility systems

The list above is not exhaustive. LR reserves the right to request any additional documents considered necessary for design appraisal.

This Section also applies to marine and machinery systems and storage and offloading systems that have a direct interaction or that are shared with the process plant.

3.2.1 The design and construction of the piping systems, piping and fittings forming parts of such systems are to be in accordance with a recognised Code or Standard, see Pt 3, Ch 8, 1.5 Recognised Codes and Standards, and if the Owner has decided to class the process plant facility in full compliance with Pt 3, Ch 8 Process Plant Facility, are also to comply in full with the remainder of this Section.

3.2.2 Piping systems for the process plant facility are, in general, to be separate and distinct from piping systems essential to the safety of the production unit. Notwithstanding this requirement, this does not exclude the use of the production unit’s main, auxiliary and/or essential services for process plant operations in suitable cases. Attention is drawn to the relevant Chapters of Pt 5 Main and Auxiliary Machinery, when such services are to be utilised. Substances which are known to present a hazard due to a reaction when mixed are to be kept entirely separate.

3.2.3 In cases where marine, storage, loading and offloading systems are integrated with the process plant facility systems, i.e. instrument air, nitrogen, cooling water, cargo, etc., there shall be an interface isolation valve preferably located at the topsides in an accessible location. This valve shall allow the isolation of the process plant section in cases in which the process plant may impair the safety and integrity of the marine system and consequently the overall safety of the production unit. Where it can be demonstrated through the use of a risk assessment (see ISO 31010: Risk management, Risk assessment techniques) that the safety and integrity of the marine system is not compromised, this valve will not be required.

3.2.4  The valve referenced in Pt 3, Ch 8, 3.2 General requirements for process and utilities piping systems will also act as the break point between the process plant facility systems under Rules and Regulations for the Classification of Offshore Units, July 2022 (see Pt 3, Ch 8, 1.3 Scope 1.3.3 and Pt 3, Ch 8, 1.3 Scope 1.3.4) and class system under Rules and Regulations for the Classification of Ships, July 2022.

3.2.5 All piping systems are to be suitable for the service intended and for the maximum pressures and temperatures to which they are likely to be subjected inclusive of transient conditions such as surge, depressurisation and relief when applicable.

3.2.6 The number of detachable pipe connections in hydrocarbon production and process piping is to be minimised to those which are necessary for installation and maintenance. The pipe connections are to be suitable for the intended use.

3.2.7 Soft-seated valves and fittings which incorporate elastomeric sealing materials installed in systems containing hydrocarbons or other flammable fluids are to be of a fire-tested type.

3.2.8 The production and process system piping is to be protected from the effects of fire, mechanical damage and other factors such as erosion and corrosion, vibration, hydraulic hammering and pressure surges. Corrosion coupons or test spool pieces are to be designed into the system. Spool pieces are to be fitted in such a manner as to be easily removed or replaced. Sand probes and filters should be provided where necessary for extraction of sand or reservoir fracture particles.

3.2.9 The corrosion allowance for hydrocarbon production and process piping of carbon steel is not to be less than 2 mm unless a corrosion assessment appropriate to the expected operating/design conditions of the process plant systems demonstrate allowance could be reduced.

3.2.10 Piping for services essential to the production and process operations, and piping containing hydrocarbon or other hazardous fluids is to be of steel or other approved metallic construction. Piping material for H₂S-contaminated products (sour service) is to comply with the NACE MR0175/ISO15156 - Petroleum and Natural Gas Industries – Materials for use in -containing Environments in Oil and Gas Production, see Pt 12, Ch 1 Recognised Codes and Standards.

3.2.11 The process plant, inclusive of process and utility systems that can contain flammable or toxic fluids, shall be divided into isolatable sections through the use of shutdown valves that are operated from the ESD system. The criteria to determine the extent of an isolatable section shall as a minimum be based on the characteristic of the plant layout, volume of inventory, operating conditions, fire zones and depressurisation zones.

3.2.12 Arrangements are to be made to isolate the unit from the supply and discharge of produced oil and gas by the provision of suitable shut-down valves on the unit and at the receiving installation. The valves on board the unit shall be operated from the control stations as well as locally at the valve.

3.2.13 If a single failure in the supply from utility systems such as compressed air or cooling water which are essential to the operation of the process plant facility could cause an unacceptable operating condition to arise, an alternative source of supply is to be provided unless it is demonstrated that the unit could be safely shut down.

3.2.14 Process vessel washout connections are to be fitted with non-return valves in addition to the shut-off valves.

3.2.15 The locking open/closed of valves is to be by means of a suitable keyed locking device or a similar system operated under a permit-to-work system.

3.2.16 For process vessels which periodically require isolation prior to gas-freeing and personnel entry, pipelines which connect the vessel to a source of pressure and/or hazardous fluid are to be provided with isolating valves, bleed arrangements and means to blank off the open end of the pipe. For systems containing significant hazards, consideration is to be given to double block and bleed valves and blanking-off arrangements (see Pt 3, Ch 8, 3.2 General requirements for process and utilities piping systems 3.2.12 for further guidance).

3.2.17 Arrangements appropriate for the safe isolation of the process plant and its equipment shall be provided for those process and utility systems containing high pressure, toxic or flammable fluids that require to be opened for maintenance or any other intervention while other connected sections of the process plant remain in operation or pressurised. Reference for guidance is made to UK HSE Safe Isolation of Plant and Equipment together with any other particular requirements that are referenced within these Rules.

3.2.18 For ship units and other surface type units, the design of piping systems should take into consideration the effect of hull girder bending in addition to any relative movement between modules.

3.2.19 A complete stress analysis is required for those process and utility systems determined as critical for the safety and integrity of the production unit; it should be performed in accordance to ASME B31.3. The analysis is to consider factors such as acceleration loads, pressure surge, reaction forces induced by PSVs, blast, extreme environmental conditions, hull bending and inclination of the production unit as per the damaged condition (see Pt 3, Ch 8, 1.4 Plant design characteristics 1.4.4).

3.2.20 Evaluation of piping systems required to maintain their integrity in an explosion event shall be performed. Normal operating conditions should be considered, including the blast drag load. The maximum allowable stress in the blast case shall be the minimum of 2,4S_h or 1,5S_Y, where S_h is the ASME B 31.3 hot allowable stress limit (at design temperature) and S_Y is the pipe material yield stress (at design temperature). The potential deformation of module structures and decks, including the movement of the equipment and pipe supports, shall be considered in the load case. However, for the primary load case (which in general would be gravitational load, functional load, environmental load and pressure load) inclusive of blast load, the stress level shall be limited to 1,8S_h.

3.2.21 Flange leakage check shall be carried out against operating load inclusive of blast load, with the allowable stress of bolts not to exceed more than the yield stress at design temperature.

3.2.22 Small bore piping shall be appropriately supported to prevent fatigue failure due to FIV and AIV. An assessment is to be performed in accordance with a recognised methodology (see Energy Institute Guidelines for the Avoidance of Vibration Induced Fatigue Failure in Process Pipework).

3.3.1 Flexible piping elements approved for their intended use may be installed in locations where rigid piping is unsuitable or impracticable. Such flexible elements are to be accessible for inspection and replacement, and are to be secured and protected so that personnel will not be injured in the event of failure.

3.3.2 Short lengths of flexible hose may be utilised to allow for limited misalignment or relative movement. All flexible hoses are to be manufactured to a recognised Code or Standard, and a prototype hose with end fittings attached is to have been burst-tested to the minimum pressure stipulated by the appropriate standard. Protection against mechanical damage is to be provided where necessary.

3.3.3 Means are to be provided to isolate flexible hoses if used in systems where uncontrolled outflow would be critical.

3.4.1 The christmas tree shall be designed for the maximum shut-in wellhead pressure that the reservoir can develop. The appropriate design conditions shall be in line with the predicted reservoir conditions inclusive of an appropriate safety margin.

3.4.2 The christmas tree is to have at least one remotely-operated, self-closing master valve and a corresponding wing valve for each penetration of the tree. In addition, there is to be a closing device for each penetration at a level higher than the wing outlets.

3.4.3 Additional wing outlets such as injection lines are to penetrate the christmas tree above the lowest remotely-operated master valve, and be fitted with a remotely-operated, self-closing control valve and a check valve installed as close as possible to the injection point. The injection point for hydrate inhibitor may be fitted below the lowest self-closing master valve if the christmas tree is fitted with valve(s) below this point.

3.4.4 All valves in the vertical penetrations of the christmas tree are to be capable of being opened and kept in the open position by means of an external operational facility independent of the primary actuator.

3.4.5 Valves that are important in connection with the emergency shut-down system such as the master and wing valves are to be fitted locally with visual position indicators.

3.4.6 Where exposure to -contaminated products is likely, materials and welds shall meet the requirements of the NACE MR0175/ISO15156 – Petroleum and Natural Gas Industries – Materials for use in -containing Environments in Oil and Gas Production.

3.5.1 Process and utilities vessels, equipment and piping (inclusive of HP/LP interfaces) and cargo storage tanks integral to the hull are to be provided with pressure-relieving devices to protect against system pressures exceeding their maximum allowable pressure such that the system will remain safe under all foreseeable conditions, unless the system is designed to withstand the maximum pressure which can be exerted on it under any circumstances. Where appropriate, sections of the production, process and utilities systems and storage and offloading are to be protected against underpressure which may result due to credible scenarios leading to this condition.

3.5.2 The pressure-relieving devices are to be sized to handle the expected maximum relieving rates due to any single failure or fire incident; potential overpressure scenarios are to be properly described, documented and governing scenarios selected, an appropriate review of the different operational modes inclusive of start-up and maintenance should be assessed to identify any potential scenario capable of overpressurise the system or equipment. A similar assessment requires to be performed for the underpressure case. The rated discharge capacity of any pressure-relieving device is to take into account the maximum back pressure that could be developed in the vent or relief system due to simultaneous releases that may be present.

3.5.3 Overpressure and underpressure protection design for cargo tanks of the production unit which is in compliance with IMO conventions and codes shall consider any other scenario imposed into them by the process plant facility; those scenarios require to be properly considered and, when not covered by any of the IMO conventions and codes, they require to be in compliance with API Std 2000 or any other suitable code/standard. Fire case on the deck and sides of those tanks shall be considered.

3.5.4 For protected items or sections of the system not in continuous service, a single pressure-relieving device is acceptable. Block valves for maintenance purposes, where fitted, in the pressure relief lines are to be interlocked with the source of pressure or spare relief valves as applicable to ensure that a relief path is always available.

3.5.5 For any particular item or section of the system in continuous service at least two pressure relief devices are to be provided for operational and maintenance purposes. In this case, each pressure relief device is to be designed to handle 100 per cent of the maximum relieving rate expected unless alternative systems are available or short-term shutdown is acceptable. Where the equipment has redundancy and can be properly isolated without compromising the safety of the facility or the personnel, a single pressure relief device is acceptable.

3.5.6 If more than two pressure relief devices are provided on any particular item or section of the system in continuous service, and any pressure relief device is designed to handle less than 100 per cent of the maximum relieving rate expected, the arrangements are to be such as to allow any one device to be isolated for operational and maintenance purposes without reducing the capacity of the remaining devices below 100 per cent of the maximum relieving rate.

3.5.7 Block valves fitted in pressure relief lines for isolation purposes are to be of the full bore type, capable of being locked in the fully open position. Where isolating valves are arranged downstream and upstream of a relief device, they are to be interlocked with each other in order to ensure 100 per cent capacity of the maximum required relieving rate.

3.5.8 The arrangement in Pt 3, Ch 8, 3.5 Overpressure and underpressure protection 3.5.5 or Pt 3, Ch 8, 3.5 Overpressure and underpressure protection 3.5.6 is to ensure that all relief possibilities cannot be isolated from the system at the same time, by interlocking the block valves using an approved keyed method of interlocking or a similar system operated under a permit-to-work system.

3.5.9 The set pressure for all pressure-relieving devices should generally not exceed the design pressure of the weakest component on the protected system or equipment. Pressure relief valves are to be sized such that any accumulation of pressure from any source will not exceed 110 per cent of the design pressure; exception to this Rule is a fire case in which the accumulated pressure will not exceed 121 per cent of the design pressure.

3.5.10 Bursting discs fitted in place of, or in series with, a pressure relief valve are to be rated to rupture at a pressure not exceeding the design pressure of the protected system or equipment at the operating temperature. However, in the case of a bursting disc fitted in parallel with a relief valve(s), such as in vessels containing substances which may render a pressure relief valve inoperative or where rapid rates of pressure rise may be encountered, the bursting disc is to be rated to burst at a maximum pressure not exceeding the maximum accumulated pressure as identified in Pt 3, Ch 8, 3.5 Overpressure and underpressure protection 3.5.9 at the operating temperature.

3.5.11 Bursting discs are only to be used for pressure vessels located in open areas or if fitted in conjunction with a relief line led to an open area. Where a bursting disc is fitted downstream of a safety valve, the maximum bursting pressure is also to be compatible with the pressure rating of the discharge system. Bursting discs are to be non-fragmenting type.

3.5.12 Pressure-relieving devices are normally to be connected to the flare and relief header to minimise the escape of hydrocarbon fluids, and to ensure their safe collection and disposal. Where appropriate, vent and discharge piping arrangements are to be such as to avoid the possibility of a hazardous reaction between any of the fluids involved.

3.5.13 In circumstances where hazardous vapours (toxic or flammable) are released directly to the atmosphere, the outlets are to be arranged to vent to a safe location where personnel would not be endangered; the determination of this safe location is to be confirmed through the development of gas dispersion and unexpected ignition analysis (see API Std 521 Section 5.8).

3.5.14 The inlet piping to a pressure relief device should be sized so that the pressure drop from the protected item to the pressure relief device inlet flange does not exceed three per cent of the device set pressure.

3.5.15 Pressure-relieving devices and all associated inlet and discharge piping are to be self-draining. Open vents are to be protected against ingress of rain or foreign bodies.

3.5.16 Relief piping supports are to be designed to ensure that reaction forces during relief are not transmitted to the vessel or system, and to ensure that relief devices are not used as pipe supports or anchors where the resultant forces could interfere with the proper operation of the device.

3.5.17 The design and material selection of the pressure-relieving devices and associated piping is to take into consideration the resulting low temperature, vibration and noise when gas expands in the system.

3.5.18 Positive displacement pumps and compressors for hydrocarbon oil/gas service are to be provided with relief valves in closed circuit, set to operate at a pressure not exceeding the maximum allowable pressure of the pump or equipment connected to it, and adequately sized to ensure that the pump output can be relieved without exceeding the system’s maximum allowable pressure. Proposed alternatives to relief valves may be considered and full details should be submitted.

3.5.19 Relief valves may also be required on the suction side of pumps and compressors when recycling from the discharge side is possible.

3.5.20 Where pumps or pressure surges due to the suddenly closure of valves or the shutdown of pumps are capable of developing pressures exceeding the design conditions of the system, effective means of protection such as pressure relief devices or equivalent are to be provided.

3.5.21 Pressure relief devices are to be type tested to establish their discharge capacities at their maximum rated design pressures and temperatures in accordance with an approved Code or Standard.

3.5.22 Provision of instrumented protection systems as alternatives to pressure-relieving devices could be accepted in a case-by-case basis, i.e. high integrity pressure protection systems (HIPPS); when proposed, it should follow guidelines described in standards such as API Std 521 Annex E and API RP 17O.

3.5.23  Balanced pressure relief valves in toxic service shall have the bonnet vent discharge to a safe location; it shall be demonstrated by dispersion analysis that the toxic gas levels that may be discharged from the bonnet vent or associated vent tubing are acceptable where personnel may be located.

3.6.1 Facilities for gas flaring and oil burning are to be adequate for the flaring requirements during well control, well testing and production operations conducting the disposed fluids to a safe location. Scenarios for individual relief loads as well as simultaneous flare loads due to common modes of failure, during normal operation, upset conditions and emergency, are to be considered when designing and sizing the relief system and associated flare or vent.

3.6.2 For well testing, at least two flare lines are to be arranged through which any flow from the well can be directed to different sides of the unit; for turret moored or dynamic positioning units this point should be evaluated in a case by case basis.

3.6.3 The flare system is to be designed to ensure a clean, continuous flame. Provision is to be made for the injection of make-up gas into the relief system to maintain steady flaring conditions. A means of cooling the flare burners when used for well testing is to be available.

3.6.4 The flare burners are to be located at a safe distance from the unit. This distance, or protection zone, is to be determined by consideration of the calculated thermal radiation levels. For limiting thermal radiation levels, see Pt 3, Ch 8, 3.9 Flare and radiation levels .

3.6.5 For well test systems, any flare line or other line downstream of the choke manifold is to have an inside diameter not less than the inside diameter of the largest line in the choke manifold.

3.6.6 Production and process plant relief systems are to be led to a liquid separator or knock-out drum to remove any entrained liquids which cannot be safely handled by the flare. The liquid accumulation capacity of this vessel is to be based on the sizing method described in API Std 521 for a minimum time of 20 minutes of liquids that may be disengaged from the released streams during the governing scenario for liquid release. The releases that may contribute for maximum liquid accumulation should be documented. If liquid or two-phase fluids are released into the relief system, adequate provision is to be made in the design for the effects of back pressure for vapour flash-off when the pressures are reduced and slug loading during these transient events.

3.6.7 The flare system is to be capable of controlling any excess gas pressures resulting from emergency depressurising conditions.

3.6.8 Disposed fluids are to be properly segregated to prevent mixed potential hazardous scenarios such as hydrate formation, chemical reactions, etc., as well as reducing the use of low temperature material etc. Headers can be segregated by HP sources, LP sources, cold fluids, hot fluids, water wet fluids, etc.

3.6.9 Relief tail lines and sub-headers are to be provided with a minimum slope of 1:200 towards the main headers, whilst main headers are to be provided with a minimum slope of 1:400 towards the knock-out drum, or to a low drain point, in order to prevent liquid accumulation. Installation trim as well as roll and pitch of the production unit shall be considered on the determination of the final slope.

3.6.10 Relief lines laterals should be interconnected, preferable at 45º on top of sub-headers or main headers.

3.6.11 Main headers and sub-headers shall be continuously purged with inert gas or dry fuel gas to prevent air ingress within the system and the formation of flammable mixtures within. A backup system in case of failure of the main purge source is to be provided.

3.6.12 Relief piping systems should be sized to limit the maximum velocity to Mach 0,7 on tail pipes and depressurisation lines, and to Mach 0,6 on main headers and sub-headers. Backpressures are required to be checked and be consistent with the overall design of the relief system.

3.7.2 The emergency depressurising system in a fire scenario is to be designed to reduce pressures to a level and in a time suitable to prevent rupture of the pressure-containing envelope as a result of the material strength reduction due to overheating. As a minimum requirement for open pool fires, the depressurising system is to be designed to ensure that the pressure is reduced to half the equipment’s maximum allowable working pressure or 6,9 bar g within approximately 15 minutes; for different fire types, i.e. jet fires or enclosed pool fires, a study in which a tolerable time to rupture based in the mechanical properties of the systems shall be performed. In a leak scenario, depressurisation to 6,9 bar within approximately 15 minutes should be considered to prevent escalation.

3.7.3 The cooling effect due to throttling of large volumes of high pressure gas in the discharge piping and valves during the depressurising period is to be evaluated for appropriate material selection, inclusive of a 0,6 m minimum section upstream of the pressure reduction orifice to allow for any heat transfer due to conduction. Where temperatures below minus 29°C are expected, the piping and valve material is to have specified average Charpy V-notch impact values of 27J minimum at the calculated lowest operational temperature.

3.7.4 The relief system design should ensure that allowance has been given to the possibility of high dynamic forces at pipe bends and supports during emergency depressurisation.

3.7.5 For large production plants where the relief loads may require a large disposal relief and flare system, a sequential depressurisation may be considered. A proper assessment of escalation between plant modules/zones should be performed in order to define the blowdown zones and its sequences for isolation of hydrocarbons inventory.

3.7.6 Depressurisation should start automatically on confirmed fire and gas detection. A time delay to allow the closure of ESD valves and shutdown of the process plant should be provided, and manual initiation from the ESD system should also be provided. If sequential depressurisation is required, the requirements of Pt 3, Ch 8, 3.7 Depressurising system 3.7.8 shall be met.

3.7.7 Depressurisation valves shall fail to the open position; however, when sequential depressurisation is to be provided and the flare could be overloaded, an air accumulator is to be provided for each depressurisation valve to prevent its opening in case of loss of the main air supply.

3.7.8 Where simultaneous depressurisation is not practicable, sequential depressurisation may be considered. The order of sequential depressurisation is to be controlled by the Integrated Control and Safety System (ICSS). The initial depressurisation zone is to be initiated in accordance with the requirements of Pt 3, Ch 8, 3.7 Depressurising system 3.7.6. Subsequent zones are to be initiated in a pre-programmed sequence in the ICSS based on the fire assessment of adjacent zones, until all zones are depressurised to the required pressure. The duration of each stage of the depressurisation system is to be such as to ensure that the pressure in that particular zone is reduced to a figure in which its mechanical integrity is not compromised (Pt 3, Ch 8, 3.7 Depressurising system 3.7.2) and the capability of the flare is to be such as to prevent its overloading when the sequence moves to the next pre-determined zone. All depressurisation valves for a single zone are to be controlled from one instrument room. The design of hardware, software, communications and Uninterruptible Power Systems (UPS) systems shall ensure that there is no single point of failure in the depressurisation sequence.

3.8.1 A cold/atmospheric vent is acceptable only if it is determined that the gas release will not create any danger to the production unit. Due consideration should be given to the prevailing wind to ensure that gases do not flow down around operating areas. Where cold venting is provided, the arrangement is to minimise:

• Accumulation of toxic and flammable gases.
• Ignition of vent gases from outside sources.
• Flashback upon accidental ignition of the vent gases.
• Asphyxiation in the case of non-flammable/non-toxic gases.

An analysis is to be performed in which dispersion of vented gases as well as its unexpected ignition and submitted for approval to confirm that the safety of the personnel and facility are not jeopardised (see API Std 521 Section 5.8). An appropriate set of atmospheric conditions should be selected for it.

3.8.2 Cold/atmospheric vents in which there may be continuous/intermittent venting such as cargo vents, in order to avoid continuous burning of the vent gases in the case of an accidental ignition, are to be provided with an extinguishing system using a suitable inert gas. The extinguishing system should be sized to extinguish the maximum flow expected from the leakage of a single source on the vent and capable of three successive discharges. The operation of this system can be either manual or automatic.

3.8.3 The dew point of the gases is to be such that they will not condense at the minimum ambient temperature. In the case of liquid condensation in the cold vent piping, a drain or liquid collection system is to be provided to prevent accumulation of liquid in the vent line and a possible rainout (see API Std 521 Section 5.8 for further guidance).

3.9.1 The flare and its ancillaries shall be designed to provide a safe, reliable, efficient discharge and combustion of the released hydrocarbons vapours and liquids (liquids applies for well control flares only). The location, height, type and size of the flare are to take into consideration the minimum and maximum governing relief scenarios, local environmental conditions, location of accommodation spaces noise levels and the levels of thermal radiation to ensure that exposure of personnel, structure and equipment is acceptable even under unfavourable wind conditions

3.9.2 Under normal operating circumstances and continuous flaring, the intensity of thermal radiation, in unprotected areas where personnel wearing appropriate work clothes may be continuously exposed is not to exceed 1,58 kW/m₂ in calm conditions. Solar radiation as per the facility location is to be added. Allowance for the cooling effect of wind in unsheltered areas may be taken into consideration in determining the radiation levels.

3.9.3 Under emergency flaring conditions, the intensity of thermal radiation at muster stations and in areas where emergency actions of short duration may be required by personnel is not to exceed 4,7 kW/m² in calm conditions.

3.9.4 Suitable radiation screens, water screening or equivalent provision should be utilised to protect personnel, structure and equipment as necessary.

3.9.5 An analysis in which radiation levels, dispersion of combustion gases and dispersion of vented gases in case of flame-out of the flare is to be performed and submitted for approval to confirm that the safety of the personal and facility are not jeopardised. An appropriate set of atmospheric conditions should be selected for this assessment.

3.9.6 Flares shall be provided with reliable continuous type pilots. The number of pilots should be appropriate for the type and size of the flare tip. A reliable pilot ignition system is to be provided, inclusive of a back-up bottled gas supply for flame front generators (FFGs). Power supply from emergency power is to be provided in case of high energy spark type. In general, flare and ancillaries are as a minimum to comply with API Std 537 or ISO 25457 requirements, suitably modified and/or adapted for the marine environment.

3.10.1 The requirements of this Section are applicable to all types of fired equipment associated with the process plant. The equipment is to be designed, constructed, installed and tested in accordance with a relevant Code or Standard and in compliance with the equipment categorisation (see Pt 3, Ch 8, 1.6 Equipment categories).

3.10.2 Details of the design and construction of the fuel gas burning equipment for steam boilers, oil and gas heater furnaces, etc., are to be in accordance with agreed Codes, Standards and specifications normally used for similar plants in land installations, suitably modified and/or adapted for the marine environment. Ignition of the burners is to be by means of permanently installed igniters, or properly located and interlocked pilot burners and main burners arranged for sequential ignition.

3.10.3 Proposals to burn gas or gas/air mixtures having relative densities compared with air at the same temperature greater than one will be specially considered in each case. See also Pt 5, Ch 16 Gas and Crude Oil Burning Systems.

3.10.4 Proposals for the furnace purging arrangements prior to ignition of the burners are to be submitted. Such arrangements are to ensure that any accidental leakage of product liquid or gas into the furnace, from a liquid or gas heating element, or from the accidental ingestion of flammable gases and/or vapours, does not result in hazardous conditions.

3.10.5 Compartments containing fired pressure vessels, heaters, etc., for heating or processing hazardous substances are to be arranged so that the compartment in which the fired equipment is installed is maintained at a higher pressure than the combustion chamber of the equipment. For this purpose, induced draft fans or a closed system of forced draught may be employed. Alternatively, the fired equipment may be enclosed in a pressurised air casing.

3.10.6 The fired equipment is to be suitably lagged. The clearance spaces between the fired equipment and any tanks containing oil are to be not less than 760 mm. The compartments in which the fired equipment is installed are to be provided with an efficient ventilating system.

3.10.7 Smoke box and header box doors of fired equipment are to be well fitted and shielded, and the uptake joints made gastight. Where it is proposed to install dampers in the uptake gas passages of fired equipment, the details are to be submitted. Dampers are to be provided with a suitable device whereby they may be securely locked in the fully open position.

3.10.8 Each item of fired equipment is to have a separate uptake to the top of the stack casing. Where it is proposed to install process fired equipment with separately fixed furnaces converging into a convection section common to two or more furnaces and/or a secondary radiant section at the confluence of the fired furnace uptake to the convection section, the proposed arrangements, together with the details of the furnace purging and combustion controls, are to be submitted.

3.11.1 Drainage systems are to be provided to collect and direct drained or escaped liquids to a location where they can be safely handled or stored. In general, the process plant facility is to be provided at least with:

• Closed drainage system to collect produced liquids from equipment and piping;
• Hazardous open drainage system to collect leaks and spillage from designated hazardous areas;
• Non-hazardous open drainage system to collect leaks and spillage from designated non-hazardous areas;
• Chemicals drainage system to collect leaks and spillage from areas in which chemicals will be handled or stored; and
• Cryogenic drainage system to collect produced cryogenic liquids from equipment and piping.

These systems are to be entirely separate and distinct in order to prevent a route for the migration of a fire, flammable liquids or vapours from one hazardous area to another, or to non-hazardous areas.

3.11.2 The hazardous drainage systems are to be kept separate and distinct from those of the main and auxiliary machinery systems or any other non-hazardous drainage. Consideration will be given to directing the process facilities hazardous drains to the facilities oil storage tanks or dirty slop tanks. The hazardous drains fluids should not be allowed to free-fall into the tank. In units equipped with an inert gas system, a U-seal of adequate height, or equivalent method, should be arranged in the piping leading to the oil storage tanks.

3.11.3 Provision is to be made for protection against overpressurisation of a lower pressure drainage system when connected to a higher pressure system.

3.11.4 Untreated overboard discharges from the process plant facility should be prevented. National or Flag Regulations are to be complied with as applicable to the production unit.

3.11.5 Drain lines flowing by gravity are to be provided with a minimum slope of 1:100 towards the drain tank in order to prevent liquid accumulation. Installation trim as well as roll and pitch of the production unit shall be considered on the final slope.

3.11.6 Appropriate flushing connections and rod out points are to be provided for those systems subject to potential blockage due to solids or sediments, i.e. mud and/or sand, that may be present on the drained area.

3.11.7 A proper philosophy is to be developed for the collection or diversion to the sea of leaks and spills of cryogenic or any other fluid which are otherwise vapours at ambient conditions.

3.11.8 The provision of a dedicated drain system for instruments or its routing to the closed drain or open drain systems will not be practical in all cases. For such cases an appropriate philosophy should be developed for drainage where required during operation. Considerations of the fluid properties are to be accounted for. In addition, drainage from instruments is to be considered for the classification of hazardous areas.

3.12.1 Where, during operation, the production plant spaces contain, or are likely to contain, hazardous and/or toxic substances, they are to be kept separate and distinct from the unit’s main bilge pumping system. This does not, however, preclude the use of the unit’s main bilge system when the production plant is shut down, gas freed or otherwise made safe.

3.12.2 The bilge and effluent pumping systems handling hazardous and/or toxic substances should, wherever possible, be installed in the space associated with the particular hazard. Spaces containing pumping systems that take their suctions from a hazardous space will also be designated as hazardous spaces unless all associated pipelines are of all-welded construction without flanges, valve glands and bolted connections, and the pump is totally enclosed.

3.12.3 Bilge and effluent piping systems related to the production plant are to be constructed of materials suitable for the substances handled, including any accidental admixture of such substances.

3.12.4 Arrangements are to be provided for the control of the bilge and effluent pumping systems installed in production and process plant spaces from within the spaces and from a position outside the spaces.