Transcript
ANNEXURE-6.1
6.1.1 GENERAL The PLANTS shall in all respects conform to International standards. Applicable codes and standards listed in this section are intended to be OWNER's minimum quality requirements. Platforms and walkways, stairs and ladders shall be provided in design to ensure easy and safe access to valves, instrument components, etc. Battery Limit PLANT is defined as the boundaries of the PLANT where supply of raw materials, utilities & other inputs for the PLANT would be made available and where CONTRACTOR shall deliver products & other outputs from the PLANT and are identified as follows All raw materials, utilities and PLANT outlet lines (except WNA product line) shall end at its BATTERY LIMIT, BATTERY LIMIT valve/s and companion flanges at either sides are in the scope of the CONTRACTOR Detailed Mechanical Design Philosophy / Specifications enclosed at here in is intended to be OWNER's minimum quality requirements for equipment, machinery, piping, inspection and the PLANT design. In general, pumps and other rotating equipment, except major compressors, shall be equipped with stand-by units as specified under „Drive Pattern‟ in Detailed Specifications. Lube-oil coolers and filters shall be provided with 100% standby. Only proven and modern speed governing shall be provided for the steam-turbines. Steam condenser design vacuum shall be minimum 0.14 Bar (abs) and temperature maximum 52 deg C. Adequate provisions shall be made for isolation of equipment without causing a shutdown, so that maintenance or repair work can be carried out on such items. (e.g. block valves on rotating equipment standby units, block valves and bypass on control valves, etc.). All control valves on Ammonia or any other hazardous fluid shall be provided with double block & bleed system. All isolation valves for various sections of the plants, process/steam vents, drains, etc. as may be required during start-up/shut-down and during PLANT upsets shall be provided. 6.1.2
LIST OF STATUTORY REGULATIONS, CODES & STANDARDS The design of the PLANT shall comply with the International standards, laws, regulations, rules and codes applicable A list of some important applicable International laws, rules, regulations and codes (with amendments as applicable from time to time) is given below. This list is not exhaustive. Pressure Vessels: ASME Sect. VIII Div. 1 & 2 latest ed. IS-2062
High Pressure Vessels: Heat Exchangers: Shell & tube exchangers
Special Heat Exchanger
ASME Sect. VIII Div. 1 & 2 or A-D Merkblatter or Manufacturer design ASME sect. VIII Div. 1 & 2 TEMA-R TEMA-C (in case of light duty only) Including UHX design As per country of origin standards
Steam Generation and Superheating: ASME Sect. VIII Div. 1 & 2., IBR Boilers : ASME Sect.I ASME Sect.IX ASMESect.II ANSI B 31.3 IBR Steam Turbine for Fan API 611 Gears
Storage tanks
ABMA
API 650 API 620 Piping ANSI or ASA B 31.3 Material Specification ASTM, BS, DIN, IS Electrical Relevant country Standards, Act/Rules Instrumentation 15 A-NBC-BSS or equivalent ASA-ASME for sizing of metering orifices API PR 550 Centrifugal pumps for process services A PI610 8th edition Centrifugal pumps for general services: ASME B73.1M latest edition or relevant non API codes Centrifugal compressor: API 617 API 614 (Lube oil - Seal oil system) Reciprocating compressor: API 618 Reciprocating pumps: Manufacturer's Standards Steam turbines & Tail Gas Expander API 611 (for general purpose) API 612 (for special purpose) High Speed Gear: API-613 Fire fighting System: NEPA Standards Fire protection system shall be in line with LPA to meet GNFC standard insurance condition. Buildings, Plumbing, Sanitation: Relevant country Standards
Noise Level STATIC EQUIPMENT
Relevant country Standards HEI API 661 API 662 API 941 EJMA NACE etc. ROTATING MACHINERY ANSI/ ASME B 73.1 M Horizontal, End Suction centrifugal Pumps for Chemical Process International Standard Horizontal Centrifugal Pumps for Clear Cold Water API 616 Gas Turbines for Petroleum, Chemical and Gas Industry Services API 619 Rotary Type Positive Displacement Compressors for General Refinery Service API 670 Vibration, Axial-Position, and Bearing- Temperature Monitoring Systems API 671 Special Purpose Coupling for Refinery Services, Petrochemical and Gas Industry API 672 Packaged, Integrally Geared Centrifugal Compressor for General Refinery Service. API 673 Special Purpose Centrifugal Fans for General Refinery Service API 674 Positive Displacement PumpsReciprocating API 675 Positive Displacement PumpsControlled Volume API 676 Positive Displacement PumpsRotary API 682 Shaft sealing Systems for Centrifugal and Rotary Pumps AGMA 420 Practice for Enclosed Reducers or Increasers using Spur, Helical, Herringbone and Spiral Bevel Gears. AGMA 421 Practice for High Speed Helical Gear Units NEWA SM 23 Steam Turbine for Mechanical Drive Turbine Other applicable code and standards shall be mutually agreed upon between CONTRACTOR & OWNER. All codes & standards should be of latest edition, unless otherwise, specifically mentioned herein.
6.2.0
Process Design Philosophy
6.2.1
Columns and Vessels: Given below are the minimum equipment design condition requirements.
6.2.2
Design Pressure Factors like pump shut-off conditions, pressure drops in recycle loop etc. shall be considered for fixing design pressure. Pump shut-off shall be calculated at 1.25 x rated differential pressure + max. Suction pressure. Equipment which could have to bear the shut-off pressure of a pump in case of a valve closing (either control valve or block valve) is designed for the following pressure: Design pressure = Design pressure of the suction vessel + liquid height at vessel HLL at pump suction + 125% of pump differential pressure. The above calculated design pressure must be checked with the shutoff pressure based on vendor data and higher of the two shall be considered. When operating pressure is less than or equal to 100 kg/cm2g, design pressure shall be equal to normal operating pressure plus 10% (min. 2.0 kg/cm2). When operating pressure is more than 100 kg/cm2g, design pressure shall be equal to normal operating pressure plus 5% (min 10 kg/cm2). All steam handling / condensate vessels shall be designed for full vacuum conditions also. All vessels / columns subject to internal pressure shall be designed to withstand a minimum external pressure of 0.175 kg/cm2 abs. Minimum design pressure for all equipment shall be 3.5 kg/cm2g. Full vacuum will be specified for isolable equipment containing fluid having a vapor pressure lower than atmospheric pressure at ambient temperature. For equipment subject to pressure and temperature swings, the magnitude and frequency of these swings will be given on the specification sheet. When several pieces of equipment are protected by the same relief valve, each piece of equipment will be designed at least for the pressure imposed by the discharge conditions of the relief valve in case of emergency. For columns, the reference design pressure shall be taken as that at the bottom of the column. The equipment normally working under vacuum or subjected to steam out during start-up etc. shall be designed for full vacuum. Additionally, such equipment shall be designed with the highest pressure it can experience on account of vacuum failure, or maximum operating
pressure or steam pressure, which ever is higher as operating pressure plus the standard over design. 6.2.3
Design temperature For the unfired pressure vessels and their interconnecting piping, which operate at temperatures between zero and 400°C, the design temperature will be equal to maximum anticipated operating temperature plus 30°C. The same will be considered at 28°C, if the vessel operates above 400°C. Conditions like steam-out (for handing out vessel to maintenance) will be considered while specifying design temperature. For vessels operating at ambient temperature, 65° C will be used for mechanical design. For operating temperatures below 0° C, design temperature shall be minimum operating temperature - 5° C or minimum ambient temperature, whichever is lower.
6.2.4
Liquid Residence Time Following criterion of minimum residence time (as defined between low liquid level and high liquid level) shall be followed for vessels sizing. Service Residence Time Reflux 5 minutes Column feed 15 minutes on flow control Or 8 minutes on cascade level / flow control Reboiling by heater 10 minutes on feed to heater Reboiling by thermo siphon 10 to 30 seconds Product to storage 2 minutes Product feeding another unit 15 minutes on flow control Or 8 minutes on cascade level / flow control Feed surge drum 30 minutes In the case of pumps ensuring several services such as reflux and liquid distillate to storage, the residence time of the corresponding vessel will be whichever is greater from the above list.
6.2.5
Other Specifications Vessels will be sized according to inside diameter and 2:1 elliptical heads or hemispherical heads. Minimum inside diameter shall be 500 mm. Top cover shall be flanged if the ID is equal or less than 900 mm. All connections shall be flanged. Minimum nozzle size in vessels shall be 2". 24" manhole shall be used for all vessels with internal diameter more than 900 mm. Columns of internal diameter below 900 mm shall be flanged at one head for access with a 12 " hand hole on the other end. Other vessels of internal diameter below 900 mm shall also be flanged at one head, however, a 6" hand hole shall be provided on the other end.
Larger size manhole will be specified when required to accommodate internals or critical for vessel entry. In tray columns, manholes will be provided above the top tray, at the feed tray, at any re-distribution level and below the bottom tray. A manhole will be provided at any tray with removable internals. Minimum numbers of manholes in the tray columns shall be 3. One manhole for every 6000 mm or 10 trays, whichever is less, will be provided in all tray columns. A manhole shall be provided on the column bottom partition wall, if applicable. For packed columns, manholes shall be provided above and below each packed bed. All vessels will be provided with vent and drain nozzles. Other than for process reasons, the vent and drain sizes will be specified as defined in 'Special Design Requirements'. Where ever intended, separate permanent steam-out connections will be specified for the vessels. In vertical vessels with demister, manholes shall be provided on to access both sides of the demister. In horizontal vessels, the manhole shall be located on one of the heads, which is away from internals such as displacers, baffles etc. The vent connection on the horizontal vessels shall be on the opposite end of the manhole. Large vessels with diameter of more than 3000 mm TI- TI, an additional 4" vent nozzle with blind shall be provided. For small diameter towers (diameter < 900 mm), tower internals shall be cartridge type, which can be removed from one end. Necessary end flanges shall be provided. where necessary, along the tower.
6.2.6
Trays & Packing All columns shall be sized to correspond to 110% of normal flow rates. Trays: Valve trays in stainless steel construction will be used. Valve tray columns will be specified with a maximum flooding factor of 70 for all applications. Operating range for the trays will be at least 50 to 110% of normal loads. Trays will be numbered from the bottom. Packing: Random packing shall be considered, only where it is absolutely necessary. For random packing, a 12" hand hole shall be provided at bottom of packing.
6.3.0
Heat Exchangers / Condensers / Reboilers:
6.3.1
General Guidelines
6.3.2
Plate type heat exchanger shall not be used generally except critical services like Combustion Air Pre-heater and cryogenic conditions. Straight tube length for all shell & tube heat exchangers shall be optimized for the duty. Following criterion for tube diameter & thickness shall be followed as a minimum The tube diameter and thickness for Carbon Steel and low alloy (up to and including 5 Cr, ½ Mo) tubes shall be 20 x 2 mm (minimum) and 25 x 2.5 mm (minimum) respectively. The tube diameter and thickness for high alloy (above 5 Cr ½ Mo and Austenitic) tube shall be 20 mm & 25 mm x t to suit design. No copper or its alloys shall be used as tube material. The tube pitch shall be square pitch in fouling services (Shell side fouling > 0.0004 h C m2 / kcal) For all water-cooled heat exchangers, back-flushing facilities shall be provided with a minimum size of 4". Return Water line from each cooler shall be provided a globe valve and a water sample connection. All wetted parts of Lube Oil exchangers shall be of SS. Cooling Water exchangers shall have SS tubes wherever CW is in tube side.
Shell and Tube heat exchangers Thermal design of shell & tube heat exchangers shall be done according to TEMA 'R' / “C” specifications. The pressure parts and tube sheets shall be designed as per ASME Section VIII Div. 1 UHX latest edition. For utility fluids, following fouling factors shall be considered – Cooling Water - 0.0004 h.m2.oC/Kcal Steam - 0.0002 h.m2.oC/Kcal BFW - 0.0002 h.m2.oC/Kcal Following minimum fouling factors, if not specified otherwise, shall be used based on heat exchanger type : Shell side fouling Tube side fouling Heat Exchanger Type (h.m2.oC/Kcal) (h.m2.oC/Kcal) > 0.0002 > 0.0002 Floating < 0.0002 > 0.0002 Fixed T / sheet > 0.0002 < 0.0002 U-tube bundle < 0.0002 < 0.0002 Fixed T/sheet or U-tube bundles For stacked heat exchangers, maximum two shells shall be stacked. Only if the shell diameter is less than 500 mm, a stack of three shells will be permitted. A minimum cooling water velocity of 1.0 m/s shall be maintained while designing the water cooled heat exchangers. The cooling water pressure drop across heat exchanger shall not exceed 0.5 kg/cm2. Corrosion allowance
Unless otherwise specified, corrosion allowance for all exchangers should be as per TEMA standard (Class R / Class C). For U tube exchanger, minimum radius of U bend shall be at least 3 1.5 times of the tubes OD.
6.3.3
Design pressure for heat exchange equipment When operating pressure is less than or equal to 100 kg/cm2g, design pressure shall be equal to normal operating pressure plus 10% (min. 2.0 kg/cm2). When operating pressure is more than 100 kg/cm2g, design pressure shall be equal to normal operating pressure plus 5% (min 10 kg/cm2). Exchangers that are subject to pump shut off, in general, shall have design pressure equal to maximum shut off pressure as follows. Equipment which could have to bear the shut-off pressure of a pump in case of a valve closing (either control valve or block valve) is designed for the following pressure: Design pressure = Design pressure of the suction vessel + liquid height at vessel HLL at pump suction + 125% of pump differential pressure. The above calculated design pressure must be checked with the shutoff pressure based on vendor data and higher of the two shall be considered. In case exchanger is operating under vacuum or in steam service, the design shall be for full vacuum. In addition to above criteria, design pressure of an exchanger shall also reflect the location and set pressure of the safety relieving valve protecting it. For high differential pressure, the design pressure of lower pressure side shall be at least 0.77 x higher pressure side design pressure.
6.3.4
Design temperature for heat exchange equipment Exchangers operating between zero to 400°C shall be designed for the maximum anticipated operating temperature plus 28° C but not less than 75°C. In case of possible loss of flow of cooling media, the tubes may be subjected to full process inlet temperature with no margin. These components shall be designed for maximum process anticipated temperature of hotter medium. Exchangers operating at 0°C and below shall be designed for minimum anticipated temperature. For operating temperatures below 0°C, design temperature shall be minimum operating temperature - 5° C or minimum ambient temperature, whichever is lower. The effect of auto-refrigeration due to depressurization to atmospheric pressure will be taken into consideration (LPG systems for example).
6.4.0
Pumps: Spare philosophy: 100% spare for continuous service and critical intermittent service, unless other wise specified specifically. Drive of pumps: Electric Motor, unless otherwise specified for process/safety reasons. Centrifugal pumps shall be as per API 610 8TH edition. For NPSHa calculations, minimum liquid level, minimum upstream vessel operating pressure, maximum operating temperature for vapor pressure and maximum rated capacity for friction losses shall be considered. A margin of at least 1.0 m between NPSH available and required NPSH shall be applied. In case of requirement of lower difference, concurrence of Owner / PMC shall be obtained. Equipment which could have to bear the shut-off pressure of a pump in case of a valve closing (either control valve or block valve) shall be designed for the following pressure: Design pressure = Design pressure of the suction vessel + liquid height at vessel HLL at pump suction + 125% of pump differential pressure. The above calculated design pressure must be checked with the shutoff pressure based on vendor data and higher of the two shall be considered. A minimum flow bypass (back to the upstream vessel / drum / separator) with flow control valve for centrifugal pumps shall be specified for the following cases: high differential pressure multistage pumps (water differential head > 360m) large pumps with driver power > 180 kW for process reason (turndown), flow rate < 30% of max flow rate The control valve at the pump discharge with 'fails in close' specification or controlled by upstream vessel level. Minimum flow of pump being more than the process minimum flow. Normal driver shall be electrical motor. Critical service drivers will be connected to electrical emergency network. Common spares can be specified whenever appropriate for metering pumps. All pumps shall be provided with bridle cooling water lines (for bearing cooling, gland cooling, seal cooling), as per vendor information. The cooling water return from pumps shall be collected in an underground concrete sump and the same shall be pumped to the main return header. The size of cooling water lines to / from each pump shall be minimum 1" NB. Pump vendor's battery limit for cooling water shall be 1" NB ASME B16.5 flange with counter flanges, gaskets, fasteners for both CWS and CWR lines at individual pumps.
Sight glass for cooling water flow at pump (bearing housing, seals etc.) shall be ball type. Drains from pump base plates shall be routed, through an open funnel and pipeline, for each individual pump, to nearest oily water sewer catch point. Temporary strainers shall be provided on all pumps for start-up. Basket type strainers shall be provided for Hydrocarbon / MDEA solution Pumps. Pumps provided for waste water like, BBD, CW blow down, open / close drain pit, shall be designed with sufficient head so that discharge reaches relevant treatment unit.
6.5.0
Process Control and Instrumentation:
6.5.1
Control Room The state-of-the-art, control room arrangements shall be built by the CONTRACTOR in existing NPP control room to accommodate new installations for this new Weak Nitric Acid PLANT. All process and product streams shall be measured and recorded. Level alarms, wherever required, shall be used. For Thermocouples in Temperature Control Loop, closed loop, temperature compensation / correction loop or connected to PLC, Temperature Transmitters shall be used. For other open loop Temperature indications, 'K' type thermocouples with connection to DCS shall be used.
6.5.2
Control Philosophy The plant shall be operated through DCS Consoles along with Console panel with dedicated Instruments, Recorders, Annuniciators etc. and a Console desk having selector switches, push buttons & status indicators. The Interlocks (LOGIC) for the unit shall be performed in PLC capable of communicating with DCS. 2-out-of-3 voting logic is envisaged for all critical interlocks.
6.5.3
Instruments All alarm points, Software and hardwired shall be indicated in P&ID with proper legend as per ISA symbol. All specification data sheets shall be as per ISA. For security interlocks, transmitters shall be used as field instruments connected to Analog Input card of PLC directly. No switches shall be used. For all field instrument of pressure, Temp, flow, level etc. only transmitters shall be used and switches shall not be used. For all temperature closed loops & interlock loops, temperature compensation/correction loops, field mounted temperature transmitters shall be used and head mounted shall not be used.
6.6.0
1 ½” flanged type thermowell with minimum flange rating of 300# shall be considered. Screwed type thermowell will not be used. Dedicated field instruments (Transmitters) shall be used for trip activation and critical alarms. Separate nozzle / tapping shall be used for such instruments. Limit switch : proximity type limit switch shall be used. The symbols to be used will be in accordance with ISA. Alarms and shutdown devices: Alarms and shutdown devices will be specified where required for process, safety or equipment protection considerations. Shutdown device connections except flow shall have independent primary elements and independent connection. All safety related interlocks shall be connected to a PLC (Programmable Logic Controller). Non-critical logics shall be through DCS. 2 out of 3 voting logic with field instruments shall be provided for all critical parameters. For shut down valves, the valve position shall be made available in DCS through proximity switches. Instrument impulse lines shall be insulated / traced, wherever required, to avoid condensation /congealing. Critical rotating equipment to have vibration monitoring system with control room indication. All vents from all instruments in lighter hydrocarbon shall be connected to suitable flare network. All drains from all instruments in hydrocarbon service shall be connected to closed slop system. PG and PT tapping shall be withdrawn separately.
Safety Valves All hydrocarbon / combustible gases and vapors shall be relieved to a closed flare system. Nitrogen shall be provided in all dead ends of flare header for continuous purging. The permanent nitrogen connections shall be provided with double block valves (one isolation valve and one controlling), spectacle blind, rotameter and a bleeder (with valve and blind). Double safety valves shall be provided with isolation valves, such that on-stream isolation and maintenance of a safety valve is possible without affecting unit operational safety requirements. This shall be considered for all operation failure cases (guided or no-guided). All isolation valves of pressure safety valves shall be lock open/close type. All pressure safety valves shall be provided with a bypass line with double block valve and a spectacle blind in between. No bypass is
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required, when depressurization of the upstream equipment to flare is possible through accessible valves & suitable piping. Pressure relief valves are normally installed on the equipment. All relief valves load and size shall be calculated according to the following mentioned codes: API RP 520 API RP 521 API 526 API 527 API 2000 IBR Following typical over pressure conditions shall be considered : Blocked Discharge Cooling Water Failure Loss of Air Cooler Fans. Loss of Instrument Air or Electric Power Reflux Failure Heat Exchanger Tube Failure Trapped Liquid Expansion External Fire Where ever vacuum conditions in the system are likely to occur, the system shall be designed for full vacuum. The following guidelines shall be applied for safety valve selection and line sizing: Valve selection will be based on maximum operating temperature and relief valve set pressure. Conventional type relief valves shall be used for the cases where the built-up back pressure and the variable superimposed backpressure doesn't exceed 10% of the set pressure. For the cases, where it exceeds 10%, but is below 30 % of the set pressure, balanced bellow type relief valves shall be used. For the cases, where the total back pressure is between 30 & 50% of the set pressure, the balanced bellow type relief valves may be used subject to confirmation from the manufacturer that there is no decrease in the capacity of the pressure safety valve due to high back pressure. Relieving device discharge lines shall be sized based on the back pressure data. The sizing shall be done so as to limit the maximum back pressure at the discharge of a PSV up to 30% of its set pressure. However, if it exceeds 30% but is below 50% of the set pressure, necessary confirmation, as defined above, from manufacturer must be obtained. The discharge velocities shall not exceed 0.5 mach no. PSV discharge shall be free draining to flare header. PSV inlet shall be free draining towards the source. The inlet lines to safety devices shall be sloped back to the protected equipment and the discharge lines
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6.7.0
from safety devices shall be sloped towards the respective knock out drum. These lines shall be without pockets. Pilot operated relief valves shall be used for the systems where maximum set point accuracy is required. Such relief valves shall be installed in equipment, which operate very close to the set pressure. Safety valves on column circuits shall preferably be located at the highest point in the overhead vapors lines. In case, these are located at a lower elevation on the overhead vapor line, the inlet line of the safety valves must be self draining to prevent any liquid accumulation and the pressure drop in the inlet circuit of the safety valve must meet the API guidelines for maximum allowable pressure drop. Pressure drop in a PSV inlet line must not exceed 3% of the set pressure of the PSV. PSV inlet and outlet line sizes shall be equal or greater than the PSV nozzle sizes. Inlet and outlet isolation valves of PSVs shall be full port. All relief valves, which are susceptible to plugging, shall be steam traced and have a rupture disc installed under them. Staggered pressure setting may be specified to minimize losses. For atmospheric relief, the open end of discharge will be located 30m from any source of ignition. Discharge shall be 3m higher than any equipment or manholes (ladder, platform etc.) within 15m radius, or 2 meters above the top most technological platform, which ever is higher. The relief valves on storage tanks shall be as per API codes to take care of over filling also. Thermal Safety Valves (TSV) shall be provided for the protection of equipment and lines, where ever there is possibility of blocked liquid getting heated up on account of another heating medium or direct sun light. The discharge of TSVs shall be appropriately routed to local drain for cooling water and slop system for hydrocarbons. The flare header shall be sized according to pressure drop constraints. The discharge line of all liquid safety valves discharging to atmosphere shall be routed to appropriate drain system. All drains on safety valves (wherever provided) shall be connected to the slop system. The discharge piping of safety valves shall be provided with safely routed small drain line at lowest location to remove any condensed/carried liquid. All safety valves shall normally have carbon steel body with stainless steel trim. Bronze or cast iron bodied valves shall not be used.
Control Valves As a default, control valves up to 8" size and in steam service shall be provided with a manifold of block and bypass valves. Bypass valves shall be globe valves. For control valves above 8”size, block and bypass requirement shall be decided on case to case basis. However,
Control valves not having block and bypass provision shall be provided with hand wheel for manual operation. Control valves shall be designed considering instrument air pressure at 4.0 bar g. All control valves shall be provided with a minimum ¾ " drain connection with valves, which shall be provided as: Upstream and downstream of all control valves Drain valve shall be capped (In non-hydrocarbon & non-IBR LP steam service) Drain valve shall be blind flange (In all Hydrocarbon, toxic / hazardous chemicals & IBR steam service). Shut down valves connected with ESD system shall not be provided with block and bypass valves. The control valve pressure drop should be the greater of the following – 50 -60 % of the total frictional loss excluding the control valve 0.7 Kg/cm2 15 % of the pump differential head For control valves installed in extremely long or high pressure drop lines, the percentage drop across control valve may be lower, but at least 15 % up to 25%, where possible, of the system friction drop. The selected control valve must allow maximum operating flow through it at 80% opening (maximum) and minimum operating flow at 15 to 20% opening minimum. Control valves must be evaluated for flashing / cavitation and choked flow condition before selection. All critical control valves shall have smart positioners with position transmitter. For non-critical control valves, conventional E/P positioners shall be provided. 6.8.0
Flow Indication: Flow indications with totalizer for the following streams entering / leaving the battery limit shall be available in the control room over and above those required for process control of the unit: All hydrocarbon /N2 inputs to the units All hydrocarbon/Syn Gas/CO2 /Steam outputs & off gases from the units. The steam flow indication at battery limit shall be pressure and temperature compensated for accuracy. Battery limit flow measurement for NG / R – LNG and Product Ammonia Syn Gas shall be high accuracy type for guarantee purposes.
6.9.0
Level Instruments: Standpipes with a default size of 2" NB shall be considered for only clean, non-viscous and non-crystallizing services. Standpipes shall be used if more than 4 vessels nozzles are anticipated for mounting all the level instruments in a given service. When directly mounted, LG and LT tappings shall be provided on different nozzles. Level nozzle size shall be minimum 2". Standpipes bottom tapping shall be from side only. Standpipe bottom tapping shall not have any low pocket in order to ensure free draining of standpipe liquid into the vessel. All standpipes shall have drain and vent connections. The isolation valves shall be provided for isolation of stand pipe from the vessel and isolation of each instrument connected to the standpipe. Following specific requirements for standpipes are to be followed: Standpipe shall not have instruments other than for level. Standpipe accommodating level gage / transmitter shall be separate from standpipe / vessel nozzles for level switches for alarm and trip. Standpipe shall not be connected to process lines. All standpipes shall have isolation valves at top and bottom tapping. Standpipe bottom tapping shall have slope towards the vessel. Standpipe connections shall be on sides only. DP type level measurement shall be used in Test Tanks and radar type level measurement shall be specified for critical product Tanks. All remote seal type level transmitters shall have 3" nozzle size only.
6.10.0
Standard Heat Exchanger Instrumentation The following shall be followed as a minimum for all heat exchangers – Isolation valves shall be provided at both inlet & outlet lines in cooling water service. Isolation and bypass line with valves shall be provided for exchangers, which need to be taken out for maintenance when plant is running DCS TI at cooling water outlet of each exchanger. DCS TI at process inlet and outlet of each service DCS PI at process inlet & outlet of each service Local PI at cooling water outlet of each exchanger TSV at cooling water return line of each exchanger with isolation valves. Sample connection on cooling water return line of each exchanger Vent connection with valve & blind at cooling water outlet. On line back flushing arrangement for exchangers using cooling water (size of at least inlet cooling water piping).
6.11.0
Safety Recommendations: Shutdown of pumps by low level in upstream vessel
Automatic shutdown of the pumps by low level in upstream vessel shall be specified for all pumps in continuous service. For pumps in intermittent service. The automatic shut down of the pumps on low level in upstream vessel shall be decided on case to case basis during detail engineering. Automatic isolation valves between process vessel and pumps Automatic remote operated isolation valves shall be provided at the outlet pipe of all critical products and Test Tanks. High level in feed drum To avoid overfilling, an independent high level alarm (LAH) shall be specified. The feed surge drum high level alarm will be provided with an interlock to close the upstream on-off valve. Seals on pumps Dual mechanical seals (pressurized or un-pressurized according to process considerations) shall be considered for all Hydrocarbons. Single mechanical seal shall be considered for water service. Additional safety requirements Additional push buttons housed in protected case or similar arrangement for stopping critical motors shall be provided at a safe location with protection from spurious operation, at least 15 m away from the fire-zone of respective motors and in control room. This is in addition to normal start-stop push buttons provided for such motors. Additional stop push button for air coolers shall be located at grade level in addition to start-stop button near the fan at platform. Suction / discharge valves and suction strainer shall be close to the pump in order to avoid fluid wastage during strainer cleaning and pump maintenance. All valves located on flare lines shall be installed in horizontal line. Flare line isolation valve at unit battery limits shall be installed only in the horizontal line with stem in vertical downward position to avoid free fall of gate and blockage of flare system. Each flare header leaving a unit shall be provided with such isolation valves to facilitate maintenance of flare piping and pressure relief valves within the unit. Critical Pumps shall have a DCS stop facility in central control room along with running lamp indication. Emergency trips if specified for HT motor shall be wired directly to switch gear in addition to control room. Double isolation valves with spectacle blind & bleed shall be provided at each battery limit in all the process & utility lines. All the valves and Instruments shall be provided at approachable height with suitable platforms ensuring accessibility, safety and ease of operation. Flame arrestors shall be provided on Hydrocarbon Tanks and Product Test Tanks.
6.12.0
Utility Stations, Safety Showers & Eye wash Drinking water shall be used for eyewash and safety showers. The locations shall be located strategically during detail engineering. The drinking water lines shall be laid above ground and without insulation. Each utility station shall be provided with LP steam, plant air and service water outlets. Nitrogen connection shall also be provided at all utility stations, but will be located little away from the other outlets. A dedicated LP steam header shall be considered for supplying LP steam to Utility stations if required. All utility outlets at utility stations shall terminate with a hose connection of minimum size 1”. Assuming a maximum hose length of 25m, utility stations for LP steam, plant air and service water shall be provided at the following locations : At grade to serve all equipment within maximum 25m radius At all platforms of structures At those platforms of self-standing towers - Where man-holes/hand holes are located. - Top and bottom platform - Every alternate platform However, only a single riser for LP Steam, Service Water and Plant Air shall be installed with single utility station at above mentioned locations. The riser will have facility to connect through hose to anyone of the above services at the bottom of the self standing tower. For nitrogen, it will be a separate permanent connection at all the above mentioned locations. At top platforms of drums located at the grade Near the pumping stations and tanks Technological Platform -two (minimum) per platform level including grade, beyond 15 m length/width, provide additional utility point. A permanent Nitrogen connection will be provided to the utility connection of all the columns.
6.13.0
Material Selection Philosophy Suitable material to be selected for equipments, items, machinery etc., for various sections of the PLANT, which under normal operating conditions will not be subject to material related failures. Materials shall be specified according to the relevant design code ASTM/ASME/API or equivalent. No parts bearing Copper/Cu alloys shall be used for the PLANT. In the material selection the operation conditions including start up and shutdown, site conditions etc are to be considered. Following items may influence the material selection Mechanical, thermal and cyclic conditions Safety, plant availability Material Delivery Situation. If more than one material are suitable, the most economical choice will be taken.
6.14.0
The selected material shall not be susceptible to undue localized corrosion or stress corrosion cracking under normal operating conditions of the PLANT. General Corrosion will be taken into consideration by provision of sufficient Corrosion Allowance (CA). Materials for high temperature applications are normally calculated with their 100,000 h creep rupture strength values. Materials for low temperature service have to show adequate ductility at the lowest design temperature. In the case of cyclic loads on pressure bearing equipment, fatigue calculations will be performed to prevent pre-mature failures. In the case of carbon steel heat exchanger tubes the life time of heat exchanger is to be optimized between corrosion aspects and heat transfer requirements. If not specified separately carbon and low alloy steels are suitable with yield strength < 370 N/mm2 (53 ksi) and tensile strength < 500 N/mm2 (72 ksi), minimum values each according to the material standard used. The carbon content according to the ladle analysis shall be < 0.23% for piping material supplied by the Contractor. If not specified separately unsterilized austenitic CrNi-steels like Tp 304 or Tp 316 may be used for welded components up to a wall thickness of 6mm, above 6mm low carbon grades like Tp 304L , Tp 316L or stabilized materials like Tp 321 shall be used. In systems in low temperature service, unsterilized austenitic CrNi-Steels may be used for all thickness. Austenitic stainless steels shall be free from annealing colors, ferritic inclusions etc. The alternative use of CS with SS cladding shall be considered for all high pressure SS vessels. Design of PLANT components those will be in contact with CW with consideration that CW is operated in a cycle (circulated) and is treated in a manner that the corrosion rates for CS are < 0.1 mm per year. The CW treatment shall be specified by the Contractor accordingly. Owner prefers to have cooling water on tube side of the heat exchanger. Tube bundle of Heat Exchangers and inter-coolers / after-coolers, Lube oil coolers etc. with cooling water services must be of stainless steel to prevent future corrosion and fouling problems. These specifications are applicable to package units also. All ladders and platforms in the pit shall be of SS 304.
IBR Requirement Steam generators/steam users shall meet IBR regulations. Major IBR requirements are summarized below: Vessels: Any closed vessel exceeding 22.75 liters {five gallons) in capacity which is used exclusively for generating steam under
pressure and include any mounting or other fittings attached to such vessels, which is wholly or partly under pressure when steam is shutoff. Piping: Any pipe through which steam passes and if: - Steam system mechanical design pressure exceeds 3.5 kg/cm2 {g) or - Pipe size exceeds 254 mm internal diameter The following are not in IBR scope - Steam Tracing - Heating coils - Heating tubes in tanks - Steam jackets All steam users {heat exchangers, vessels, condensate pots etc.) where condensate is flashed to atmospheric pressure i.e. downstream is not connected to IBR system are not under IBR and IBR specification break is down at last isolation valve upstream of equipment. All steam users where downstream piping is connected to IBR i.e. condensate is flashed to generate IBR steam are covered under IBR. IBR starts from BFW pump discharge. Safety valves / Relief valves on IBR system shall have isolation valves as per general philosophy. All Nitric acid line valves shall be of plug type IGC tested with third party inspection. TSP, Hydrazine, Hydrogen service piping and components shall be of SS. TSP, Hydrazine tanks shall have motorized agitator. Material Certificate All items which are part of steam piping i.e. pipes, valves, fittings, traps, safety valves must have material certificates, countersigned by the local boiler inspectors. For imported items -Certificates issued by an authority empowered by Central Boilers Board {As per IBR) or under the law in force in a foreign country in respect of boilers manufactured in that country may be accepted. In case of imported boiler IBR items, prior advice, Drawing approval for fabrication from Director of Boiler, Gujarat State and Boiler Board, New Delhi, India shall be obtained. All drawings coming under purview of IBR shall be certified by Local Boiler Inspector. 6.15.0
Special Design Requirements In case of remote operated valves, (critical service} indication of valves position shall be available in the control room. Shut down valves shall be operable from control room. Instrument and electrical cables shall be above ground. The following non-standard line sizes shall not be used unless approved by OWNER / PMC ¼” , 2 ½", 3 ½", 5", 7", 9"
The following guidelines for minimum line / nozzle sizes shall be applied – 2" NB Minimum nozzle size for vessels, tanks and heat exchangers 2" NB Minimum process (hydrocarbon) line size 1 ½ ”NB Minimum utility line size ¾ ”NB Minimum bridle drain or pump casing vent / drain ½ " NB Minimum chemical injection line size. Tubing size to be 10 mm 1 ½ " NB Minimum on pipe rack 4" NB Minimum for underground lines The following roughness coefficients shall be used unless stated otherwise –
Material Roughness (inches) Carbon Steel 0.0018 Flare / Vent headers (Heavily corroded) 0.018 Stainless Steel Pipe 0.001 Glass Reinforced Epoxy Pipe 0.0001 Vents & Drains in Heat Exchangers If high point vent and low point drain are not available, 2" NB x 300# (min.) flanged vents and drains shall be provided at high and low points respectively on all heat exchangers. All vents and drains shall be having valves and blinds. Exchangers in total condensing service shall be provided 2" vent connection at the opposite end of the shell inlet. All heat exchangers shall be provided with a multi-purpose connection on all the nozzles. Sizes of multi-purpose connections and pressure gauge connections on exchanger nozzles shall be 1” NB x 300# (min.) for below 12" nozzles and 2" NB x 300# (min.) for 12" & above nozzles. Vents & Drains in Piping Pipe Size in Inches Vent Size, inches Drain Size, Inches 4 & below ¾ ¾ 6 to 10 ¾ 1 12 & above 1 1½ Vents & Drains in Pump Casing For non-volatile services, casing vents and pump drains shall be routed to appropriate sewer or closed drain system. For volatile services, casing vents and drains shall be routed to the relief header and sewers. Double Block Valves Philosophy Double block valves with blind and bleed shall be provided for the following conditions All incoming & outgoing lines to/from the unit with bleed and spectacle blind For cases where cross contamination can't be tolerated.
6.16.0
For vents and drains in ANSI Class 600 rating and above For drains containing C5 or lighter hydrocarbons. In this case, the double block valves must be minimum of 1000 mm straight pipe apart. Where high pressure (above ANSI 300# rating) is likely to be removed on the run; e.g. spare machinery or equipment For gas stream > 100 bar g or liquid systems > 60 bar g or gas/liquids which are potentially toxic. For the equipment, which may be opened for maintenance on the run e.g. filters Block valves of 12" diameter & above shall be gear operated. Injection Points and Sample Connections Sample connections shall consist of a NPS ¾ " shut-t T valve. For applications, where throttling is required, a secondary throttling (globe) valve shall be installed. Sample connections shall be installed in the side of the pipe rather than the top or bottom. Provisions shall be made to collect excess fluid from the sample point in a drain or sump. Sample coolers shall be provided for all sampling connections from piping or equipment when the service temperature is 77°C (170°F) or higher. Sample lines shall be as short as feasible and braced to protect them from mechanical damage. The sample lines shall be brought to ground level to avoid hazardous situation. Injection points where a fluid (such as additive, corrosion inhibitor, etc.) is to be injected into a line shall be designed so the fluid is injected into the centre of the pipe. The location of the injection point shall be from the top of line and shall not be immediately upstream of an elbow. Check valves shall be provided at all chemical injection points to Process systems to prevent process fluid from entering in to the chemical system. SAFETY, HEALTH & ENVIRONMENT
CONTRACTOR shall provide Hazardous area classification. HAZOP study is included in the scope of the CONTRACT. HAZOP study shall be jointly conducted by OWNER, CONTRACTOR / Technology supply from abroad and all changes, additions, etc. Agreed during HAZOP study shall be incorporated by the CONTRACTOR without extra cost. Introduction While considering the execution and operating of the Project, the Safety, Health and Environment (SHE) Management policy becomes key issue and elaborate the arrangement CONTRACTOR has to make. OWNER also has policy related to Plant Safety, Health and Environment which complies with the referenced legislation, regulations, standards, policies and procedures prescribed by the Government or any regulatory authorities.
