住房城乡建设部关于发布《石油化工工程防渗技术规范》等7项工程建设标准英文版的公告

　　现批准《石油化工工程防渗技术规范》（GB/T50934-2013）、《石油化工安全仪表系统设计规范》（GB/T50770-2013）、《石油化工钢制低温储罐技术规范》（GB/T50938-2013）、《石油化工装置设计文件编制标准》（GB/T50933-2013）、《石油化工工厂布置设计规范》（GB50984-2014）、《石油化工用机泵工程设计规范》（GB/T51007-2014）、《石油化工建（构）筑物荷载规范》（GB51006-2014）英文版。工程建设标准英文版与中文版出现异议时，以中文版为准。

　　该7项工程建设标准英文版由住房城乡建设部组织中国计划出版社出版发行。

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　中华人民共和国住房和城乡建设部
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　2018年9月4日

1 General Provisions1.0.1 This code is developed to implement relevant national policies in the design, construetion andquality inspection of anti-seepage in petrochemical engineering,to protect the groundwater environment,tosan dd es a s a andcost-effectiveness.

1.0.2 This code is applicable to the design , construction and quality inspeetion of anti-seepage for thepetrochemical and coal chemical engineering , but it is not applicable to the storage, disposal and landfillof normal industrial solid wastes and hazardous wastes , and installation of long-distance pipelines.

1.0.3 In addition to the requirements stipulated in this code , design, construction and quality inspectiono s l e a s se d e a- etrelevant standards of the nation.住房城乡建设部

3 Basic Requirements

t s o - h heEIA (environmental impact assessment) approval document and the EIA report.

3.0.2 Prior to the start of the anti-seepage design, the geological and hydrogeological data of theproject shall be familiarized with, and the information on the sensitivity of the groundwater environmentin the site, the pollution characteristics of the aquifer and the antifouling properties of the vadose zoneshall be collected and studied.

3.0.3 Proper measures shall be taken for the construction projeets to prevent and reduce accidentalreleasing, emitting, dripping and leaking of contaminants.o e o as ss e- aet e- e teclassification of pollution prevention area.

3.0.5 Appropriate measures shall be taken to prevent the spread of contaminants from a pollutionprevention area to a non-pollution prevention area.

3.0.6 The impermeable barrier shall be made of the material in a permeability coefficient not largerthan 1.0× 10−cm/s and compatible with materials or contaminants in contaet.

3.0.7 The subgrade of the impermeable barrier shall be uniform.

3.0.8 The impermeable material and construction technology used shall meet the requirements of thehealth,safety and environmental (HSE),

3.0.9 The construction technical people shall be familiar with the technical requirements and qualitystandards for anti-seepage in the project.

3.0.10 In the process of construction, the specially appointed person in charge of quality control andconstruction records is necessary.

3.0.11 For anti-seepage design, no-pollution shall be guaranteed to the groundwater within the designworking life. When the design working life expires, the impermeable barrier shall be subject toinspection and verification, only the qualified one can be further used.

4 Permanent Loads4.0.1 The permanent load shall cover the self-weight of structural member, enclosure member, surfacecourse and decoration (including the surface course of anticorrosion and fire-proof) , self-weight ofequipment and piping, weight of equipment attachments (including the auxiliary piping and equipmentinstalled on equipment) , weight of insulation and lining of equipment and piping, soil pressure, waterpressure of still water level, prestress as well as other loads required to be considered as permanentloads.

4.0.2 The characteristic values of the structure self-weight are determined through calculation accordingto the design dimension of the structural member and the material unit weight.

4.0.3 The unit weight of the common material and member may take its average value; for the materialand member with larger self-weight variation(such as the insulation material and thin-walled concretestructural members fabricated at site) , the charaeteristic value of the self-weight shall take the upperlimit or lower limit according to the state unfayorable or favorable to the structure. The unit weight ofcommonly used materials and members may be adopted according to national standard GB 50009Load Code for Design of Building Structures4.0.4 The self-weight of fixed partition and fixed operation platform should be considered as permanentloads.浏览住房城乡

the following requirements:

1 The shape coefficient of round members should be taken as 0.7, and the shape coefficient ofother types of members may be taken as 1.3;

2 The shape coefficient of steel handrails should be taken as 1.3, the solid area of steel handrailsshould be taken as 0.26m²/m , and the shape coefficient of the handrails and handrail posts made of roundsteel pipes may be taken as 1.0;

3 The shape coefficient of steel ladders should be taken as 1.3, the total effective solid area ofwindward steel ladders without cages should be taken as 0.13m²/m, and total effective solid area ofwindward steel ladders with cages should be taken as 0.2m2/m;

4 The shape coefficient of steel stairs should be taken as 1.3, the total effeetive solid area of steelstair at lateral direction should be taken as 1.Om²/m at horizontal projeefed length,and the effective solidarea of steel stair at nominal direction should be the envelope width øfsteel stair multiplying half of thestair height.

7.4.4 The wind loads acting on pipe rack shall include the wind Joads acting on pipe rack members,pipes, cable trays and ladders with handrails. Wind loads aefing on pipe rack members, pipes and cabletrays shall be calculated according to the following requirements:

1 Effect of wind vibration may not be considered for pipe rack;

2 The wind loads acting on the pipe raek members and ladders with handrails may be calculatedaccording to the same method for determining the wind loads acting on structures, the shielding effectmay not be considered for single-bentordouble-bent pipe rack;

3 The wind loading shape coefficient of piping should be taken as 0.7 and the wind loading shapecoefficient of cable trays should be taken as 1.3;

4 The solid area of piping at radial direction should be calculated by the sum of the maximumdiameter of the pipes with insulation on the pipe rack beams plus 10% of bent width multiplying thebent spacing;

5 The effective sqlid area of cable trays arranged side by side at transverse direction should becalculated by the sum of the height of cable trays plus 10% of bent width multiplying the bent spacing;

6 The effective solid area of cable trays at transverse direction should be calculated by the totalheight of cable trays multiplying the bent spacing;

7 Wind loads along piping and cable trays may not be considered;

8 The effictive solid area of vertical pipe bends should be calculated by 90% of bent widthmultiplying the height of vertical pipe bends, the shielding between groups of vertical pipe bends maynot be considered, the shape coefficient of vertical pipe bends may be taken as 1.3;

9 Longitudinal wind loads may not be considered for the pipe rack without vertical pipe bends.

7.4.5 The effects of amplifying or shielding from the adjacent equipment shall be considered whencalculating the wind loads acting on equipment. The shape coefficient of vertical cylindrical equipmentarranged side by side shall be determined according to the following requirements:

1 If the wind acting direction is perpendicular to the equipment arrangement orientation , the windloading shape coefficient of the outer equipment should be determined based on the up-down doublepipes (double tower) or densely arrayed pipes (towers) as specified in the current national standardGB 50009 Load Code for Design of Building Structures , and the wind loading shape coefficient of innerequipment should be 1.2 times the shape coefficient of the outer equipment;

Materials4.1 General Requirements4.1.1 Steels used for low temperature steel storage tanks for petrochemical service shall be providedwith quality certificates supplied by the steel manufacturers.

4.1.2 The materials used to construct low temperature steel storage tanks shall be properly selectedbased on the tank operating conditions, the material performances and economic consideration.

4.1.3 The materials used to construct concrete components in low temperature environment shall havelow temperature resistant performance.

4.1.4 The steel of the primary container and secondary steel container shall be the killed steelproduced by oxygen converter or electric furnace. If the design metal temperature is lower than — 20℃,secondary refining shall be also used for the low temperature steel plates, the low temperature steelforgings and low temperature steel pipes.

4.1.5 The design metal temperature for each component shall be calculated based on the mostpessimistic assumption.

4.1.6 Any special requirements for steels, ifany, shall be specified in the design documents.Metallic Tank BodyPrimary and Secondary Liquid Containera e e s s s e s a s s s cal caservices shall be in accordance with Table 4.2.1.Table 4.2.1 Delivery states of steel plates used for low temperature steel storage tanksS/NSteel gradeApplicable code/Delivery stateMin.designDelivery thicknessstandardtemperature(℃)(mm)-20≤121Q245RGB 713Hot rolled, controlled rolled,normalized-100≤16≤34-20≤202Q345RGB 713Hot rolled, controlled rolled,-10≤25normalized0≤343Q370RGB 713Normalized-20≤34416MnDRGB 3531Normalized,normalized and-40≤34temperedNormalized,normalized and515MnNiDRGB 3531-45≤34tempered609MnNiDRGB 3531Normalized,normalized and-70≤34tempered

7 Insulation7.1 Selection, Performance and Testing of Insulation Materials7.1.1 The following factors shall be considered in the selection of the appropriate insulation materials :

1 The factor contributing to heat in-leak through the insulation system during normal operation ofthe tank.

2 The design thermal resistance for each component of insulation and the actual thermalresistance offered by the insulation under accidental conditions as wel as the designed duration of theaccidental condition.

3 The static and dynamic loads-applied to the insulation materials in all directions.

4 Tank insulation design inherent with the selected spegific insulation system , installation methodand type of containment.

7.1.2 Assessment of the performances of the insulationmaterials and their products shall include :

1 Thermal resistance: it shall include thermal conductivity and the possible heat in-leak throughradiation, convection and cold bridges.

2 Mechanical properties:it shall include short-term and long-term compressive properties, tensileand shear properties, and the adhesivestrength for insulation systems.

3 Temperature resistance it shall include the impacts of maximum and minimum servicetemperatures and possible temperature changes, expansion coefficient, tensile strength and tensilemodulus on the shrinkage, expansion and possible cracking in the design temperatures.4Resistance to water and water vapour:it shall include:

1)Closed cell content,permeability for water vapour and water absorption of the insulation;

2)Reduction of thermal resistance due to water and water vapour penetration, and the possiblestructural damage to the insulation by liquid water or by the process of freezing (possiblyfreeze/thaw cycles).

5 Influences of stored products on the insulation shall include:

1)Closed cell content of the insulation;

2)Absorption of product vapours and effect on other material properties;

3)Absorption of/and permeability for liquid product;

4)Effects of long—term liquid absorption on other material properties;

5)Desorption behavior:time/percentage.

6 An assessment shall be made of the compatibility between and/or possible chemical reactionsof insulation system , its environment and tank material and/or its coating in contact with the insulationsystem.

7 For fire risk during construction or in case of an external fire, the following properties ofinsulation shall be assessed:

1)For combustion performance, the flammability, fire retarding properties and toxic gasgeneration are the main aspects for assessment;

2)For the maximum temperature limits of the material, melting temperature, decomposition

3 Basic Requirements3.1 General Requirements3.1.1 The rotary machines used for petrochemical service shall be designed and constructed for aminimum service life of 20 years (excluding the wearing parts) , and the uninterrupted operation cyclesshall be no less than the service years indicated in Table 3.1.1.Table 3.1.1 Uninterrupted Operation Cycle of Rotary Machines Used for Petpochemical ServiceCategoryUninterruptedCategoryUninterruptedoperation cycle (years)operation cycle (years)Pumps3Reciproeating compressors3Hydraulic power recovery turbines3Rotary compressors3Vacuum pumps3General-purposes team turbines3Agitators2Special purpose steam turbines5Centrifugal fans3Expanders3Instrument air centrifugalGas turbines3compressorProcess centrifugal compressorsRoots blowers3CentrifugesNote: in special conditions,the uninterrupted operation cycle of rotary machines may bemutually agreed.

3.1.2 The rotary machines, shall be within the scope of their design and manufacture experience, andat least one same or similar model rotary machine have been running successfully under same or similaroperating conditions for two years or more.

3.1.3 On-lines pares shall be provided for the pumps, medium- and small-size fans/blowers, instrumentair centrifugal compressors and reciprocating compressors in continuous operation, one on-line spareshall be provided for the single pump (rotary machine) , and at least one on-line spare shall be provided forseveral pumps (rotary machines)arranged in parallel operation. Off-line spare parts shall be provided forthe agitators in continuous operation. On-line spares may not be provided for the large-size fans/blowers,centrifugal compressors and gas turbines, but long term parts should be provided as critical/capital spareparts for them.

3.1.4 When the medium contain H2S, chloride or other components that may result in stress corrosion,or the medium contain any components that may be subject to reaction with copper or copper alloy , theyshall be indicated in the datasheets or technical requisition documents. The construction materials ofrotary machines shall be suitable for the requirements for these medium.

3.1.5 The complete unit of rotary machine shall include all equipment, pipes, valves, electrical,instrument and control systems within the scope of supply.

3.1.6 The design pressure of steam jacket and cooling water jacket shall be no less than themaximum working pressure of their respective external supply systems.

3.1.7 The minimum temperature rise at the water side of cooling system shall comply with the

flanges may follow Appendix A of this code.

3.4 Materials3.4.1 The construction materials of rotary machines shall comply with the following requirements:

1 The material requirements for the pressure-containing parts and other main components ofrotary machines shall be specified in the inquiries or datasheets, final material selection shall be specifiedin the proposals of the manufacturers, and specific material codes shall be indicated in the datasheets.

2 Welded pressure-containing parts shall be subject to post weld heat treatment and nondestructivetest.

3 Except for cast steel parts, repair welding shall not be made on al pressure-containing castparts. If repair welding is required for cast steel parts ,it shall comply with Artiele 11.2.3 of this code.

4 If the specified minimum design metal temperature is lower than —20℃ , low temperatureimpact test shall be made for the base metal and welds of all pressure-containing steels except foraustenitic stainless steel.

5 If chlorides are present in the medium, the component materials in contact with the mediumshould not be aluminum and austenitic stainless steel.

6 When the medium contact with copper and then generate explosive copper compounds, copperor copper alloy shall not be used to fabricate the parts.

7 The materials exposed in acid environment or wet H2S-containing environment shall complywith the requirements specified in thecurrent national standard GB/T 20972.1 Petroleum and NaturalGas Industries-Materials for Use-in HS-containing Environments in Oil @nd Gas Production-Part 1:General Principles for Selection of Cracking-resistant Materials9 Hygroscopic materials shall not be used for sound insulation materials.

10 Material corrosion-resistant performance should not be enhanced by using surface plating andsurface coating.

11 Materials for lube oil, seal oil, seal flushing and dry gas seal piping and fittings shall be 304 or316 stainless steel.

12 For the welds that are impossible for inspection during fabrication or after fabrication , separatequality control methods shall be determined.

3.4.2 In addition to the requirements specified in Article 3.4.1 of this code, the construction materialsof pumps shall also comply with the following the requirements:

1 Cast iron shall not be used for pressure-containing parts of pumps for toxic, flammable andexplosive liquid services. Cast iron shall not be used for centrifugal pumps and rotary pumps for toxic,flammable and explosive liquid services, including seal less centrifugal pumps, and their bearinghousings.

2 Unless otherwise specified, the corrosion allowance of pump casings shall be at least equal to3.0mm.

3 The liners of canned pumps shall be made of nonmagnetic materials and shall have goodcorrosion resistance and high strength, stator liner should be Hastelloy alloy, its minimum thicknessshall be 0.4mm and corrosion allowance shall be 0.15mm. The containment shell of magnetic drivepump shall be high-resistivity materials, Hastelloy alloy and titanium alloy should be selected, its

4 The occupational health hazard pre-assessment report and its approval.

5 The names, numbers and approvers of design contract and PDP, and the names and numbers oflicensed technology contracts.

5.3 Process5.3.1 The BED deliverables for process shall include process design basis, process deseription, tie-inlist, piping list, process equipment list, PFD, UFD, P&.ID, UID, equipment datasheets, and datasheetsor specifications and lists for relief valves and rupture dises.

5.3.2 The process design basis shall include:

1 The plant capacity.

2 The process units/sections.E息

3 The specifications for feedstock, products and by-products4 The specifications for catalysts and chemicals.

5 The consumptions of feedstock,catalysts and chemicals.outputs of products and by-products.

6 The utilities specifications, consumptions and overall energy consumption.

5.3.3 The process description shall include:

1 The production modes and the process used, and the process features in terms of process,用equipment,control,operation and safety.

2 The brief description to process shall inelude:

1)The routing of fluids from/to the process equipment.

2)The temperature, pressure and flow rate ratio, and main control schemes. For batch operation,feed amount for each batch and the operation cycle shall be specified.

3)The process equipment for normal service and standby.

4) The recovery and reuse of by-products.

5)The quantities, compositions, sources and suggested treatment schemes of waste gases,liquids and solids.

3 The quantities of onshore and offshore ordered equipment defined per equipment categories.

4 The process energy and water conservation.

5 The risks and hazards of main materials in the process, and the measures used to control theresulted consequence.

5.3.4 The tie-in list shall indicate the conditions respectively for the feedstock, chemicals, products, by-products and utilities, and shall at least include the serial number, name, in/out, fluid state, transfermethod, continuous/intermittent, flow rate,pipe size,temperature and pressure.

5.3.5 The piping list shall at least include the tag number, nominal size, piping class, P&.ID number,piping from/to, fluid name, fluid state, operating conditions, design conditions, insulation and tracingrequirements.

5.3.6 The process equipment list shall indicate the tag number, name, quantity, operating conditions,design conditions, specifications, main materials and weight by categories. And the scope of supply shallbe indicated for the packaged equipment.

5.3.7 The PFD shall indicate the complete process, including the main process equipment, their tagnumbers and names, main process pipes, operating conditions, process control schemes and fluid data aswell as the heat duties of exchangers. Fluid data may be indicated in material and heat balance.

1)The particular requirements for equipment layout, and the spaces required for catalyst,chemical and packing loading/unloading operations.

2)Particular requirements for process and piping.

3)Particular requirements for instrument installation and arrangement.

4)Any other requirements.

5 The legends shall indicate the functions of various symbols and identifications, abbreviationsand codes, and describe the rules for determining the illustrative symbols and their codes for equipment,instruments,piping and pipe fittings.4

5.3.10 The UID shall indicate:

1 The equipment consuming or producing utilities.

2 The utility headers, run pipes and branch pipes, and the utility piping, pipe fittings and valvesfrom/to the equipment.

3 The instruments in the utilities piping shall be indicated. However, the utilities instruments thathave been repeatedly indicated in the P&ID shall be marked and noted.

5.3.11 The equipment datasheets shall indicate:

1 The datasheets for vessels and heat exchangers shall indicate the data required for mechanicaldesign, and shall include:

1)The design data shall include operatingparameters, design parameters, structure parameters,fluid names and their main properties, and the concentrations and corrosion allowances ofspecial fluids such as corrosive fluids.

2)The nozzle flange types pressure ratings, flange facing types and insulation requirements shallbe indicated. For special cases, the pressure and temperature eyclic variations, the surfacepolishing requirements, the recommended specifications and materials for the vessels or parts,and the expected service life of various vessels shall be indicated.

3)The simplified diagram shall indicate the main dimensions, supporting type, liquid level,nozzles and their'elevation , and the recommended structure types2 The heater datasheets shall indicate :

1)The operating parameters, fuel and combustion data, tube data, refractory and heat insulatingmaterial data, air pre-heater data, burner and soot blower data.

2)The simplified diagram for waste heat recovery system.

3 The rotary equipment datasheets shall indicate:

1)The tag numbers, quantity, fluid names and main properties of the fluids, operating conditions,site conditions and explosion-proof requirements.

2)The structure data, main materials and metering accuracy.

3)The auxiliary equipment requirements, and control and interlock requirements.

4)Standards, pressure ratings and facing types for nozzle flange.

5)The driver requirements.

6)The flushing methods, inspection and test requirements, and scope of supply.

4 The machine datasheets shall indicate:

1)The tag numbers, names, quantity, process parameters, environmental conditions, mainmaterials and structure requirements.

2)The process parameters, including the mechanical capacity, water, electric power, steam and

7 The area with shortage of water resources.

8 The zones with poor geological conditions such as heavy loess collapsible under overburdenpressure zone, recently deposited loess zone in large thickness and the saturated loess zone in highcompressibility.

9 The zone with poor natural ventilation in mountainous or hilly areas.

3.3 General Planning3.3.1 After site selection, general planning shall be first made for the plant and outside fence supportfacilities in the site.

3.3.2 General planning shall highlight the overall benefit and development of the project and the inter-relations of production,storage, transportation and management for proper integration and coordination.

3.3.3 General planning shall properly organize the logistics for gonvenient transportation andseparation of cargo access and pedestrian access based on the features of the plant and its supportfacilities.

3 d a ayd ay.

3.3.5 The arrangement for adjacent plants shall follow the principles below :

1 The administrative areas and other occupied buildings of adjacent plants may be arranged in acentralized area outside the plant areas.depot outside the plant areas.

3 The utilities and support facilities may be centralized based on their scope of services to provideservices for multiple plants.

4 The flare zone should be properly planned and serves for multiple plants or the plant areasconstructed at different stages.

5 The logistics methods, logistics routings, and public roads, railway, water ways and pipelineshould be planned in an integrated way.

6 The possible cross-pollution shall be avoided between adjacent plant areas.

3.3.6 The main substation outside fence shall be arranged in a safe location that shall facilitateinstallation of incoming/outgoing feeders and shall not interfere with the plant development in thefuture.

3.3.7 The water intake along river shall be located upstream of the pollution sources and at thelocation where river bed is stable, and the water intake facility shall not interfere with navigation.

3.3.8 The centralized wastewater treatment plant should be arranged in the low-lying zone andadjacent to the receiving waters.

3.3.9 The effluent outfall shall be located downstream of water source area, if the effluent outfall islocated at the river mouth, backflow shall be prevented from polluting water resource.

3.3.10 River, lake and sea areas shall not be selected as the site to store industrial wastes, while theareas with less impact on the surrounding environment and do not pollute natural water bodies andunderground water resources shall be selected. The waste storage area should be arranged at the upwindside of wind direction with minimum frequency throughout the year to residential communities.

3.3.11 The initial station and terminal station of the crude oil and gas transfer for the plant should belocated close to plant border to facilitate pipeline connection.The fire prevention distance from the initial

8.3 Auxiliary Facilities8.3.1 The arrangement of track scale shall be in accordance with the following requirements:

1 The location of track scale shall be fit for the shunting operation to enable easy weighing andavoid reverse;

2 The track scale should be located on dedicated segment of railway line, and it should not sharewith other lines for avoidance of obstructing wagon passing in case of maintenance;

3 Straight and level line segments shall be provided at the two ends of the track scale based on thetec s s s l bteless than 15m in case of difficulty;

4 The foundation pit of track scale shall be provided with good water drainage facilities.

8.3.2 The private locomotive depot shall be located easy for locomotive leaving and arriving, and ifprivate railway station is provided, it should be arranged near to the private railway station.

8.3.3 The tanker washing station shall be arranged in accordanee with the following requirements:

1 It shall be convenient for railway line connecting and tanker taking-out and placing-in, andshould be arranged near to the throat area of liquid loading/unloading bay;

2 It should be arranged at the upwind side of wind direction with minimum frequency throughoutthe year in the plant area, and convenient for wastewater treatment and drainage住房城乡

1 General Provisions1.0.1 This code is developed to prevent and mitigate the process risks, secure the staff and propertysafety and protect the environment in petrochemical plants.

1.0.2 This code is applicable to the engineering design of safety instrumented system for grassroots,revamp and expansion projects in petrochemical plants.with the current national codes and standards.

6 Sensors6.1 General Requirements6.1.1 Sensors include analogue and discrete sensors, and analogue sensors should be used for SIS.

6.1.2 Smart transmitters with HART protocol signals superimposed to 4mA-20mA DC signalsshould be used for sensors.

6.1.3 In explosion hazardous area, sensors shall be Ex d or Ex i type When Ex i system is used,isolated type safety barriers shall be used.

6.1.4 Ingress protection of field installed sensors shall not be lower than IP65.

6.1.5 Sensors shall not adopt fieldbus or other communication methods as the input signals for SIS.

6.1.6 The sensors and their taps should be independently provided.

6.1.7 Sensor performance and configuration shall comply with SIL requirements.

6.2 Separation Requirements for Sensors6.2.1 For SIL1 safety instrumented functión, sensors may be shared with the basic process controlsystem.

6.2.2 For SIL2 safety instrumented function, sensors should be independent from the basic processcontrol system.

6.2.3 For SIL3 safety instrumented function, sensors shall be independent from the basic processcontrol system.

6.3Redundancy Requirements for Sensors6.3.1 For SILI safety instrumented function, single sensor may be used.

6.3.2 For SIL2-safety instrumented function, redundant sensors should be used.

6.3.3 For SIL3 safety instrumented function, redundant sensors shall be used.

6.4 Redundancy Methods of Sensors6.4.1 When high safety is required, "OR" logic architecture shall be used.

6.4.2 When high availability is required, "AND" logic architecture shall be used.

6.4.3 When both high safety and high availability are required, 2003 logic architecture should be used.

6.5 Discrete Sensors6.5.1 Discrete sensors may include process variable switches, manual switches, push buttons andrelay contacts.

6.5.2 For the discrete sensors used for emergency shutdown, their contacts shall be in closed stateunder normal condition, and the contacts shall be in open state under abnormal condition.

6.5.3 The critical input loops should be provided with open circuit and short circuit failure detectionfunctions. Open circuit and short circuit failures of input loops should generate alarms and be recordedin SIS.