Section 2 Design of Process Systems

201. General

1. Process systems are to be arranged so that one single maloperation or malfunction will not lead to critical situations for personnel or the unit.

2. Due consideration is to be given to the well fluid properties, such as presence of hydrogen sulfide, carbon dioxide, etc., for selection of materials.

3. Equipment and piping of process system are to be designed with considering maximum pressure and temperature that may occur during operation, and corrosion property. In addition, the effects of operational conditions such hydrate formation, water hammers and slug are to be taken into account.

202. Separator system

1. The separators are to have sufficient capacity to separate the components of the well stream, and effective means for removal of sand and water.

2. Design of separator and separator control system shall include consideration for list and rolling of the unit, where relevant.

3. The separators are to comply with relevant requirements in 302. and 304.

203. Gas treatment and compression system

1. Liquid scrubbers with mist pad are to be installed immediately upstream of gas compressors. The compressor is to be tripped or otherwise protected if liquid levels reach an unacceptable level with- in an upstream scrubber.

2. Scrubbers are to comply with requirements in 302.

3. Gas coolers in systems with significant pressure differential between the gas and cooling medium side are to be fitted with quick acting relief devices in accordance with API RP 521.

4. Compressor seal systems are to be monitored for leakage. The compressor is to be automatically tripped and depressurised if unacceptable leaks or other malfunctions are detected.

5. Location of vent points from the glycol regeneration re-boiler is to include consideration of emis- sions of harmful substances and their effect on personnel.

204. Piping systems

1. Process piping design, selection of valves, fittings and flanges, are to be in accordance with API RP 14E, ASME B31.3 and other recognized standards.

2. Sections of piping systems that can be isolated with block valves are to be provided with thermal relief valves with set point at 120% of design pressure to protect the piping from overpressure caused by solar heating or exposure to fire.

3. Flexible hoses

(1) Hose assemblies may be installed between two points where flexibility is required and is to be type approved by the Society.

(2) Hoses carrying flammable fluids are to incorporate a single, double or more closely woven in-

tegral wire braid or other suitable material reinforcement.

(3) Hoses carrying flammable fluids are to be of fire-resistant type. Fire resistance is to be demon- strated by testing to Ch 3, Sec 17, Table 3.17.1 of Guidance for Approval of Manufacturing Process and Type Approval, Etc.

4. Plastic pipe

(1) Plastic pipe is to comply with Pt 5, Annex 5-6 of Rules for the Classification of Steel Ships.

(2) Plastic pipe used in the piping systems for conveying hydrocarbon fluid is to be Level 1 of fire endurance.

205. Electrical systems

Electrical systems are to comply with Ch 10, Sec 1.

206. Control systems

1. Control systems are to comply with Ch 10, Sec 2 in addition to requirements in this Article.

2. The process control system used to maintain process variables within normal operating ranges is to be capable of accommodating a reasonable range of abnormal or transient conditions without creat- ing an upset condition.

3. Essential process parameters such as flow rate, pressure, temperature and liquid level are to be au- tomatically monitored and controlled, and the abnormal conditions are to be alarmed with visual and audible devices.

4. For computer-based Systems, the computer system for monitoring alarms and control is to include redundancy arrangements in order to maintain continued operation of the hydrocarbon process system.

207. Safety systems

1. The safety system is to be provided with two levels of protection to prevent or minimize the ef- fects of an equipment failure within the process. The two levels of protection are to be independent of the control devices used in normal process operation. The two levels are to be provided by functionally different types of safety devices wider spectrum of coverage. The two levels are to be categorized by primary and secondary and to comply with API RP 14C, paragraph 3.4.

2. The emergency shutdown system for process systems is to be provided in accordance with 209.

and API RP 14C, Appendix C.

3. Safety Analysis Tables (SAT) and Safety Analysis Checklists (SAC) for each process component, in accordance with API RP I4C, are to be submitted to the Society.

4. Safety Analysis Function Evaluation (SAFE) Charts, in accordance with API RP I4C, are to be submitted to the Society.

208. Pressure relieving and hydrocarbon disposal systems

1. Pressure relief valves are to be installed to protect all pressure vessels and equipment from over- pressurization. Pressure relief valves are to be sized and installed in accordance with API RP 520 and ASME Section VIII, Division 1 Appendix M.

2. Pressure relief valves in hydrocarbon gas service are to discharge to one or more closed relief headers for atmospheric discharge at either a flare or vent. Such flare or vent discharges are to meet the requirements of Par 6.

3. Pressure relief valves in liquid hydrocarbon service are to discharge to a tank, pump suction or closed drain system.

4. The use of rupture discs is limited to the following:

(1) In gas or gas/liquid service, rupture discs may be utilized only as backup to pressure relief valves and they are sized for the maximum relieving conditions.

(2) In liquid service, rupture discs may be utilized only as backup to pressure relief valves that are

sized for the maximum relieving condition. They may be installed as primary relief devices for non-flammable, non-hazardous liquids at relieving pressures no greater than 1.0 MPa.

5. Vapor Depressurizing systems are to comply with the following:

(1) An emergency vapor depressurizing system is to be provided for all equipment processing light hydrocarbon with operating pressures of 1.75 MPa and above

(2) To gain rapid control of a situation in which the source of a fire is the leakage of flammable fluids from the equipment to be depressurized, the equipment is to be depressurized to 0.7 MPa. In cases where the equipment is handling high pressure and large inventories of hydrocarbon, and depressurizing to 0.7 MPa is impractical, it is acceptable to depressurize to 50% of the equipment design pressure if such depressurization is achieved within 15 minutes. Equipment is to designed with ample margin of safety to prevent the vessel from failing due to overheating.

6. Flares and Vents are to comply with the following:

(1) Flares and vents for hydrocarbon gas disposal are to be located with respect to prevailing winds. This is to limit exposure of personnel, equipment to vented gas, flare exhaust, or flame radiation.

(2) Worst-case atmospheric conditions are to be used for radiation and gas dispersion calculations.

Flame radiation calculations are normally to assume a strong wind as a worst-case condition. Dispersion calculations are normally to assume still air and low vent velocity as a worst-case condition.

(3) When a venting system is selected for disposal of hydrocarbon vapors, a vent snuffing system is to be provided to extinguish vented gases, should they ignite.

(4) The flare system is to be provided with means for purging sufficiently (below 5% of oxygen content) before ignition to prevent explosion inside the flare system.

209. Spill containment, open and closed drain systems

1. Spill containment

(1) Spill containment is to be provided in areas subject to hydrocarbon liquid or chemical spills, such as areas around process vessels and storage tanks with drain or sample connections, pumps, compressors, engines, glycol systems, oil metering units, and chemical storageareas.

(2) Where equipment is protected by a fixed foam fire extinguishing system, a minimum of 150

mm coaming is to be provided.

2. Open drain piping

(1) Each containment area, as well as any other plated deck or skid area subject to rainwater or other liquid accumulation, is to be equipped with drains connected to an open drain system, and installed and located so as to prevent the accumulation of standing liquid.

(2) Open drain piping is to be self-draining with a slope of not less than 1:100. Lines are to be sized for gravity drainage without backup or overflow.

(3) Cleanouts or flushing connections are to be provided for removal of sediment or solids from open drains subject to potential blockage.

(4) Open drains are to be piped to convey the fluids, by gravity or pumping, to oily water treat-

ment or final disposal location.

(5) Drains from classified and unclassified areas are to be separate.

3. Closed drain systems

(1) The drain vessel is to be provided with pressure relief valves, which are to be sized to handle the maximum flow of gas or liquid that could occur under blocked outlet condition.

(2) Drains or liquid relief from vessels containing non-toxic, non-flammable liquids, may be con- nected to an unclassified open drain piping system if the open drain system is sized to accom- modate these additional drains.

210. Packaged process units

1. Skid structures

(1) The skid structure is to be sufficiently rigid to support the mounted equipment and piping and, as required, to permit lifting during shipment without damage to the equipment or piping.

(2) Structural design calculations for skid units with a center of gravity height of more than 1.5 m , or a maximum operating weight in excess of 10 tons, calculated in dry conditions, are to be submitted to the Society for review.

2. Drip pans

(1) Drip pans are to be provided to contain liquid spills and leaks from skid mounted equipment and piping, and to drain the liquid with adequate slope into open drain systems.

(2) A minimum 150 mm coaming around the entire perimeter of a skid is to be provided.

(3) A spill containment with less than 150 mm coaming arrangement is subject to special

consideration.

(4) Calculations showing sufficient spillage containment for the skid are to be submitted to the Society for verification.

(5) Skid beams that extend above the drip pan may be considered as a part of the coaming, pro- vided that the drip pan is seal-welded to the skid beams.