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GB/T 3836.5-2021 English PDF

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GB/T 3836.5-2021: Explosive atmospheres - Part 5: Equipment protection by pressurized enclosure 'p'
Status: Valid

GB/T 3836.5: Evolution and historical versions

Standard IDContents [version]USDSTEP2[PDF] delivered inStandard Title (Description)StatusPDF
GB/T 3836.5-2021English939 Add to Cart 8 days [Need to translate] Explosive atmospheres - Part 5: Equipment protection by pressurized enclosure 'p' Valid GB/T 3836.5-2021
GB/T 3836.5-2017EnglishRFQ ASK 7 days [Need to translate] Explosive atmospheres -- Part 5: Equipment protection by pressurized enclosure 'p' Obsolete GB/T 3836.5-2017
GB 3836.5-2004EnglishRFQ ASK 6 days [Need to translate] Electrical apparatus for explosive gas atmosphere -- Part 5: Pressurized enclosures “p” Obsolete GB 3836.5-2004
GB 3836.5-1987English279 Add to Cart 3 days [Need to translate] Electrical apparatus for explosive atmospheres--Pressurized electrical apparatusp Obsolete GB 3836.5-1987

PDF similar to GB/T 3836.5-2021


Standard similar to GB/T 3836.5-2021

GB/T 3836.34   GB/T 3836.33   GB/T 3836.35   GB/T 3836.11   GB/T 3836.13   GB/T 3836.2   

Basic data

Standard ID GB/T 3836.5-2021 (GB/T3836.5-2021)
Description (Translated English) Explosive atmospheres - Part 5: Equipment protection by pressurized enclosure "p"
Sector / Industry National Standard (Recommended)
Classification of Chinese Standard K35
Word Count Estimation 52,536
Issuing agency(ies) State Administration for Market Regulation, China National Standardization Administration

GB/T 3836.5-2021: Explosive atmospheres - Part 5: Equipment protection by pressurized enclosure "p"


---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Explosive atmospheres - Part 5.Equipment protection by pressurized enclosure "p" ICS 29.260.20 CCSK35 National Standards of People's Republic of China Replace GB/T 3836.5-2017, GB 12476.7-2010 Explosive environment Part 5.Equipment protected by a positive pressure enclosure "p" (IEC 60079-2.2014,Explosiveatmospheres-Part 2.Equipment Released on 2021-10-11 2022-05-01 implementation State Administration for Market Regulation Issued by the National Standardization Management Committee

Table of contents

Foreword Ⅲ Introduction Ⅵ 1 Scope 1 2 Normative references 1 3 Terms and definitions 2 4 Protection level 4 5 Structural requirements for positive pressure enclosures 6 6 Temperature limit 8 7 Safety measures and safety devices (except static positive pressure protection) 8 8 Safety measures and safety devices for static positive pressure 12 9 Supply of protective gas 13 10 Positive pressure housing with internal release source 14 11 Release conditions 14 12 Design requirements for built-in systems 14 13 Shielding gas with internal release source and positive pressure technology 15 14 Equipment capable of igniting 17 15 Internal hot surface 17 16 Type inspection and test 17 17 Routine test 20 18 logo 21 19 Operating Instructions 22 Appendix A (normative) Ventilation and dilution test 24 Appendix B (informative) Example of functional program diagram 25 Appendix C (informative) Examples of pressure changes in pipes and enclosures 27 Appendix D (informative) Information provided to users 31 Appendix E (Normative) Classification of Release Types in Enclosures 33 Appendix F (informative) Examples of the use of the principle of dilution zone 34 Appendix G (Normative) Applies to internal batteries and battery packs with "pxb" and "pyb" protection levels 36 Appendix H (Normative) Applies to internal batteries and battery packs with "pzc" protection level 42 Reference 44 Explosive environment Part 5.Equipment protected by a positive pressure enclosure "p"

1 Scope

This document specifies the structure and testing of electrical equipment used in explosive gas atmospheres or explosive dust environments protected by a positive pressure enclosure "p" The special requirements also stipulate the requirements for containing positive pressure enclosures that restrict the release of flammable substances. This document is applicable to electrical equipment protected by a positive pressure enclosure "p" intended to be used in an explosive gas environment or an explosive dust environment. This document does not apply to. ---Positive pressure enclosures where the built-in system may release the following substances. ● Air with oxygen content exceeding the normal value; or ● Oxygen is mixed with inert gas, and the proportion of oxygen exceeds 21%. ---Pressure room or analysis room, see GB/T 3836.17. ---A positive pressure enclosure used in an environment where explosives or fireworks are present. ---Used in the presence of gas/vapor and combustible dust mixed in the environment of the positive pressure shell. ---Use the positive pressure shell in an environment where there are self-igniting substances such as explosives or propellants that contain oxidants. ---Positive pressure shell with flammable dust release source inside. Note. When the user is a manufacturer, under normal circumstances, it is the user's responsibility to ensure that all relevant requirements of this document are applicable to the manufacturing and testing of the equipment. This document is a supplement and modification to the general requirements of GB/T 3836.1.When the requirements of this document conflict with those of GB/T 3836.1 In the event of an emergency, the requirements of this document shall take precedence.

2 Normative references

The content of the following documents constitutes an indispensable clause of this document through normative references in the text. Among them, dated quotations Only the version corresponding to the date is applicable to this document; for undated reference documents, the latest version (including all amendments) is applicable to This document. GB/T 2900.35 Electrical terminology equipment for explosive atmospheres (GB/T 2900.35-2008, IEC 60050-426.2008, IDT) GB/T 2900.83 Electrical terminology, electrical and magnetic devices (GB/T 2900.83-2008, IEC 60050-151.2001, IDT) GB/T 3836.1 Explosive environment Part 1.General requirements for equipment (GB/T 3836.1-2021, IEC 60079-0. 2017, MOD) GB/T 3836.4 Explosive atmosphere Part 4.Equipment protected by intrinsically safe "i" (GB/T 3836.4-2021, IEC 60079-11.2011, MOD) GB/T 3836.8 Explosive atmosphere Part 8.Equipment protected by "n" type (GB/T 3836.8-2021, IEC 60079-15. 2017, MOD) GB/T 4207 Method for determination of tracking resistance index and comparative tracking index of solid insulating materials (GB/T 4207-2012, IEC 60112.2009, IDT) GB/T 4208 Enclosure protection grade (IP code) (GB/T 4208-2017, IEC 60529.2013, IDT) GB/T 4942.1 Protection level (IP code) classification of the overall structure of rotating electrical machines (GB/T 4942.1-2006, IEC 60034-5. 2000, IDT) GB/T 9364 (all parts) small fuses [IEC 60127 (all parts)]

5 Structural requirements for positive pressure enclosures

5.1 Housing The positive pressure enclosure shall have a protection level in accordance with Table 2. For the "pxb" protection level of internal components that do not exceed the marked temperature group, as well as the "pyb" and "pzc" protection levels, non-metallic exterior The heat and cold resistance test (GB/T 3836.1) of the shell and the non-metallic parts of the shell does not have to be used for the positive pressure shell. This is because the degradation of the casing leads to an increase in the leakage rate, which can cause alarms and cut off the power of the circuit with the ability to ignite. Therefore, non-metal The pretreatment test of the enclosure and the non-metallic parts of the enclosure is not considered necessary. 5.2 Material The materials used for the housing, pipes and connectors shall not be adversely affected by the specified protective gas. 5.3 Doors and covers 5.3.1 Type I positive pressure enclosure The door and cover should. ---Use special fasteners that meet the requirements of GB/T 3836.1; or --- Interlocking is used so that when the door and cover are opened, the electrical equipment that is not protected by the equipment protection level (EPL) listed in 7.15 can be supplied The electric power can be cut off automatically, and the power cannot be re-energized before the door and cover are closed. At the same time, it should also meet the requirements of 7.7. 5.3.2 Class I positive pressure enclosure with static positive pressure protection Doors and covers should use special fasteners that meet the requirements of GB/T 3836.1. 5.3.3 Type Ⅱ positive pressure enclosure The requirements for special fasteners specified in GB/T 3836.1 do not apply. For the "pxb" protection level, doors and lids that can be opened without tools or keys should be interlocked so that when they are in an open state In the state, the power supply to the electrical equipment not listed in 7.15 protection can be automatically cut off, and the power can not be re-energized before the door and cover are closed. For the "pyb" and "pzc" protection levels, there is no requirement on whether to use tools or keys. It should be considered that when the fasteners are loosened, the high internal pressure may cause the door or cover to open suddenly. The following methods should be used to prevent operators And maintenance personnel were injured. a) Use multiple fasteners to safely vent the enclosure before loosening all fasteners; or b) Double-position fasteners are used to safely discharge pressure when the shell is opened; or c) Limit the maximum internal pressure to not more than 2.5kPa. 5.3.4 Positive pressure enclosures of category Ⅱ and Ⅲ with static positive pressure protection Doors and covers should only be opened with tools. 5.3.5 Type Ⅱ and Ⅲ. pxb type For positive pressure enclosures containing hot parts that require cooling time, they should not be easily opened without tools or keys. 5.3.6 Warnings for Class Ⅱ and Ⅲ Doors and Covers In order to prevent the explosive gas or dust from being ignited due to the opening of the enclosure, the door and cover should be marked. "Warning. It is strictly forbidden to open in an explosive environment" 5.4 Mechanical strength During normal operation, the positive pressure housing and its pipes and their connecting parts shall withstand the manufacturer's requirements when all vents are closed. The maximum positive pressure is 1.5 times the pressure, and the minimum pressure is.200Pa. If pressure that may cause deformation of the shell, pipeline or connecting parts occurs during work, a safety device should be installed to reduce the maximum internal positive pressure. The value is limited to a level below which may adversely affect the type of protection. If the manufacturer does not provide safety devices, the equipment explosion-proof certificate The number shall include the “X” suffix in accordance with the marking requirements in GB/T 3836.1, and the special use conditions listed in the explosion-proof certificate shall be stated in detail Specify the necessary information required by the user to ensure compliance with the requirements of this document. 5.5 Class Ⅰ and Ⅱ pores, partitions, partitions and internal components 5.5.1 The arrangement of air holes and partitions shall ensure effective ventilation. The unvented area can be eliminated by appropriately setting the inlet and outlet holes for the protective gas supply and the effect of the partition plate. For gas or vapor heavier than air, the inlet hole of the protective gas should be close to the top of the positive pressure shell, and the exhaust hole should be close to the top of the shell. bottom. For gases or vapors lighter than air, the inlet holes of the protective gas should be close to the bottom of the shell, and the exhaust holes should be close to the top of the shell. Air intake holes and exhaust holes are provided on opposite sides of the housing to promote front and rear ventilation. The internal partition (such as a circuit board) should be arranged so that the flow of the protective gas is not obstructed. The use of branch pipes or baffles can also improve obstacles The air flow around. The number of pores should be selected according to the structure of the equipment, especially considering that the electrical equipment may be divided into some small cavities for ventilation. 5.5.2 The inner compartment should be communicated with the main enclosure or be ventilated separately. For every 1000cm3, a vent hole with an area of not less than 1cm2 is provided, and a vent hole with a minimum diameter of 6.3mm is usually sufficient Proper ventilation. 5.5.3 Cathode ray tubes (CRTs) and other airtight devices do not require ventilation. 5.5.4 For components with a net internal volume less than 20cm3, as long as the total volume of all such components does not exceed 1% of the net internal volume of the positive pressure enclosure, It is regarded as an internal cavity that does not require ventilation. Note. 1% is based on 25% of the lower combustion limit (LFL) of hydrogen, see A.2. Electrical components that are considered to be sealed, such as transistors, microcircuits, capacitors, etc., are not included in the calculation of the total volume of the components. 5.6 Air holes of the static positive pressure protection enclosure The static positive pressure protection enclosure should have one or more air holes. After inflation and positive pressure protection, all air holes should be closed. 5.7 Insulation material For Class I electrical equipment, it can withstand the rated current greater than 16A (in switchgear such as circuit breakers, contactors, and isolators) The insulating material that is sufficient to generate electric arc stress in the air shall meet at least one of the following requirements. ---Comparative tracking index is equal to or greater than CTI400M in the GB/T 4207 standard. ---Set up an appropriate device, which can detect the dangerous situation that the insulating material inside the shell may decompose, and automatically on the power supply side Cut off the power supply to the enclosure. The installation and function of such devices shall be verified. ---The creepage distance of the live bare conductor conforms to the creepage shown by the equivalent voltage of the third-grade pollution-related materials in GB/T 16935.1 distance. 5.8 Seal All cables and conduits connected to the enclosure should be sealed to maintain the protection level of the enclosure. If it is not sealed, it is regarded as part of the housing. 5.9 Spark and particle baffle The pipes for the positive pressure shell and the protective gas should be equipped with spark and particle baffles to prevent hot particles from blowing into the dangerous place. Unless the working current of the on-off contacts is less than 10A, and the working voltage does not exceed 275V (AC) or 60V (DC), and the contacts should If there is an arc extinguisher, it is considered that no hot particles are generated, otherwise it should be considered that hot particles may usually be generated. If hot particles are not normally produced, it is not necessary to discharge into the normally closed decompression port where the equipment protection level is Gb or Mb. To spark and particle baffle. If hot particles are usually not produced, sparks and particles are not required at the exhaust port when the equipment is discharged into a place where the protection level of the equipment is Gc. Bezel. If the manufacturer does not provide spark and particle baffles, the equipment explosion-proof certificate number shall be included in accordance with the marking requirements in GB/T 3836.1 "X suffix, and the special conditions of use listed in the explosion-proof certificate shall specify the necessary requirements for the user to ensure compliance with the requirements of this document. information. 5.10 Batteries and battery packs "Pxb" and "pyb" protection level internal batteries and battery packs should meet the requirements of Appendix G, "pzc" protection level internal batteries and batteries The group shall meet the requirements of Appendix H.

6 Temperature limit

6.1 General Equipment should be grouped according to the temperature group requirements in GB/T 3836.1, and should be determined in accordance with 6.2 and 6.3. 6.2 For "pxb" or "pyb" protection level The temperature group should depend on the higher of the following temperatures. a) The maximum outer surface temperature of the enclosure; or b) Maximum surface temperature of internal components. Exception. Internal components can exceed the marked temperature group if. 1) Meet the relevant "small components" requirements in GB/T 3836.1; or 2) The positive pressure shell is "pxb" protection level, and meets the opening time requirements of GB/T 3836.1.If the positive pressure protection is interrupted, Appropriate measures should be taken to prevent the possibility of the Any flammable mixture that appears in contact with any surface of the heating element. The above requirements can be achieved through the design and structure of the positive pressure housing and pipe joints or other methods, for example, the auxiliary ventilation system Enter the working state or place the hot surface in the positive pressure shell in an airtight or encapsulated shell. In the "pyb" protection class enclosure, there should be no thermal element capable of igniting under normal operating conditions. 6.3 For "pzc" protection level The temperature group should be based on the highest outer surface temperature of the enclosure. When determining the temperature group, the explosion-proof equipment that is still live when the positive pressure system is disconnected should be considered. 7 Safety measures and safety devices (except static positive pressure protection) 7.1 Applicability of safety devices in hazardous locations All safety devices used to prevent ignition of electrical equipment for positive pressure protection shall not cause ignition by themselves (see 7.15) or be installed in Outside the hazardous area. 7.2 Integrity of safety devices The safety devices required by this document (see Table 3) constitute safety components related to the control system. The safety and integrity of the control system should confirm. Positive pressure system should be tested to verify the correctness of operation. 7.4.3 Positive pressure system with "pxb" protection level The positive pressure system shall include. a measure to control the lowest positive pressure value (such as a regulator) that meets the requirements of 7.11, and a verification of the lowest positive pressure value Measures (such as pressure sensors) and an automatic safety device, as well as an automatic control system that meets the requirements of 7.7 using flow sensors. If a regulator is used, and in the case of a single failure, all the pressure at the air inlet will be applied to the air outlet of the regulator, then use A measure to limit the pressure inside the enclosure to a specified value (such as a pressure relief port). This specified value is obtained by experiment or calculation and needs to be listed in In the instruction manual. If there are multiple regulators or pressure relief ports to choose from, then the specified value of each suitable regulator/pressure relief port should be Sure. The positive pressure system shall be tested to verify the correct operation including the functions of the automatic control system. 7.5 "pxb" program diagram For the "pxb" protection level positive pressure system, the functional program diagram should be provided by the manufacturer, such as truth table, state diagram, flow chart, etc. Determine the role of the control system. The program diagram should be clearly distinguishable and indicate the operating status and subsequent actions of the safety device. On request Functional test to verify whether it is consistent with the program diagram. These tests only need to be carried out under normal environmental conditions, unless otherwise specified by the manufacturer. Note. Appendix B gives an example of the information provided by the manufacturer. 7.6 Safety device ratings The manufacturer shall specify the maximum and minimum operating values and tolerances of the safety device. The safety device should be in the normal working range as specified by the manufacturer Used within. 7.7 Automatic ventilation of positive pressure enclosures of "pxb" protection class Ⅰ and Ⅱ An automatic control system with safety devices should be installed to prevent the electrical equipment in the positive pressure enclosure from being energized before the ventilation is completed. The operating procedures of the control system should be as follows. a) After the start of the procedures specified in this document, the ventilation flow through the positive pressure enclosure and the lowest positive pressure in the enclosure should be monitored; b) When the minimum flow rate of the protective gas is reached and the positive pressure value is within the specified range, the ventilation timer can be started; c) The electrical equipment can be energized after the time is up; d) If any step in the program fails, the circuit should be restored to the initial stage. 7.8 Ventilation requirements for positive pressure enclosures of type Ⅰ or type Ⅱ When the housing is opened or the positive pressure drops below the minimum value specified by the manufacturer, the manufacturer shall specify the conditions that require proper ventilation. a) For the "pxb" or "pyb" protection level, the manufacturer shall specify the minimum air exchange flow rate and air exchange time to meet the requirements of 16.4 or 16.5 Test requirements. Except for rotating electrical machines and equipment with complex shapes, no experiment is required to determine that the air exchange is sufficient, that is, the minimum air exchange The flow rate and time can be determined based on the air exchange rate of 5 times the shell volume. b) For the "pzc" protection level, in addition to rotating electrical machines and equipment with complex shapes, the manufacturer shall specify the minimum ventilation flow rate and time. In order to ensure that the positive pressure shell is equal to the amount of protective gas 5 times the volume of the shell for ventilation. If effective ventilation is according to 16.4 or 16.5 The test proves that the ventilation is effective, and the amount of protective gas can be reduced. Rotating motors and equipment with complex shapes can be tested based on similar or equivalent enclosures, and the ventilation time can be determined without testing. c) The ventilation flow rate should be monitored at the air outlet of the positive pressure enclosure. For the "pxb" protection level, the actual flow rate should be monitored. For "pyb" or The "pzc" protection level can be inferred from the flow rate, for example, from the housing pressure and the specified opening at the exhaust port. for The "pyb" or "pzc" protection level shall be provided with indication marks to allow the positive pressure enclosure to be ventilated before the electrical equipment is energized. Logo should be included Contains the following or similar content. "Warning. The power supply should not be reset after the shell is opened, and it can be reset only after the shell has been ventilated for minutes at the flow rate." Note. It is the user's responsibility to determine the free space of the associated pipes that are not part of the equipment, and to determine the additional ventilation time at a given minimum flow rate. 7.9 Cleaning of Type Ⅲ Positive Pressure Shell The equipment should be marked with a warning that combustible dust should be swept out of the equipment before powering on. The logo should contain the following or similar content. "Warning. The power supply should not be reset after the shell is opened. It can be reset only after the combustible dust accumulated in the shell is removed." 7.10 Requirements at the lowest flow rate When the manufacturer specifies the minimum flow rate of the protective gas (for example, if the temperature generated by the internal equipment is higher than the marked temperature group rating Value), one (or more) automatic safety devices should be provided so that the flow rate of the protective gas at the exhaust port is reduced to the minimum value specified. Next action. 7.11 Safety device for detecting the lowest positive pressure One or more automatic safety devices shall be provided so that when the positive pressure value in the positive pressure enclosure drops below the minimum value specified by the manufacturer action. The automatic safety device shall meet the following requirements. a) The sensor of the automatic safety device shall directly collect the signal from the positive pressure housing. b) There should be no valve between the automatic safety device sensor and the positive pressure housing. c) It should be possible to check whether the safety device can operate correctly. Its position and setting value should consider the requirements of 7.12. Note 1.The use of automatic safety devices (such as power failure or sound alarm, or other methods to ensure the safety of the equipment) is usually the user's responsibility. d) For the "pzc" protection level, if the positive pressure enclosure is equipped with an indicator instead of an automatic safety device, the following conditions should be met. 1) In order to maintain the lowest pressure in the positive pressure enclosure, the protective gas supply source should be equipped with an alarm device to display the protective gas supply. Failure when giving. 2) No other device should be equipped between the positive pressure shell and the alarm of the protective gas source, but the isolation valve and/or pressure or flow control Except the device. 3) The isolation valve should. ● Logo. "Warning. Shielding gas supply valve---please refer to the instruction manual before closing" ● It should be able to be sealed or fixed in the open position; ● With display of whether it is open or closed; ● Install directly near the positive pressure shell; ● It can only be used during the operation of the positive pressure enclosure. Note 2.This valve is expected to remain open all the time, unless there is no explosive gas environment in the known area or all equipment in the positive pressure enclosure has been powered off and cooled. 4) The pressure or flow control device, if it can be adjusted, should be operated with tools on request. 5) No filter should be arranged between the positive pressure housing and the protective gas system alarm. 6) In order to facilitate observation, an indicator should be installed. 7) The indicator should show the shell pressure. 8) The installation of indicator sampling points should consider the worst operating conditions. 9) The exclusion of non-metallic enclosures and non-metallic enclosures in 5.1 is not used. 10) No isolation valve should be arranged between the indicator and the positive pressure housing. If the flow meter is used to display the housing pressure and ventilation flow, it should be installed at the exhaust port. If the flow meter is only used to display pressure, it can be installed anywhere on the housing, except for the air inlet. Note 3.The flowmeter is installed at the air inlet only under exceptional circumstances to display the pressure of the housing or the flow through the housing. 7.12 Minimum positive pressure value The lowest positive pressure value that each part should maintain relative to the external pressure in the positive pressure shell and its pipeline that may cause leakage. "pxb" or The protection level of "pyb" is 50Pa, and the protection level of "pzc" is 25Pa. The manufacturer shall specify the minimum and maximum positive pressure values during operation, the maximum positive pressure values during ventilation, and the maximum leakage rate during the maximum positive pressure. Care should be taken when using positive pressure equipment with an internal closed cooling circuit assisted by an internal fan (such as a motor), because this type of fan It may generate negative pressure inside and cause gas or dust to be inhaled when the positive pressure stops (see Figure C.3). The distribution of pressure in each system and pipeline is illustrated in Figure C.1 to Figure C.4. The installation of the compressor and associated pipes or fans should not cause danger. Appendix D gives the basic information about the installation of the piping system. 7.13 Positive pressure protection of multiple enclosures When several separate positive pressure enclosures share a protective gas source, one or several safety devices can be shared, as long as the synthesis control is considered The most unfavorable arrangement of the shells of this group is considered. If a public safety device is installed, as long as the following 3 conditions are met, open the door or When the cover is closed, it is not necessary to close all the electrical equipment in the positive pressure enclosure or send out a signal alarm. a) For the "pxb" protection level, the power supply of the electrical equipment in the specific positive pressure enclosure should be disconnected before opening the door or cover. 7.15 allows Except for permission; b) The public safety device continuously monitors the positive pressure in all other positive pressure enclosures in this group, and monitors the airflow when necessary; c) Perform the ventilation procedures specified in 7.7 before supplying power to the electrical equipment in the specific positive pressure enclosure. 7.14 Safety device on door or cover For the "pxb" protection level, doors and covers that can be opened without keys or tools should be interlocked so that they do not follow the 7.15 mark when opened The power supply of electrical equipment is automatically cut off, and the power cannot be energized before the door and cover are closed. The requirements of 7.7 shall also apply. 7.15 Equipment that may be live For category Ⅰ or category Ⅱ positive pressure enclosures, the "pxb" or "pyb" protection class enclosure may still be charged when the enclosure is not in operation. For category Ⅰ EPLMa or Mb should be used for protection, and EPLGa or Gb should be used for type II protection. For type Ⅱ positive pressure enclosures, electrical equipment with "pzc" protection level enclosures that may still be charged when the enclosure is not in operation should use EPLGa, Gb or Gc to protect. For type III positive pressure enclosures, electrical equipment with "pxb" protection level enclosures that may still be charged when the enclosure is not in operation should use EPLDa or Db To protect. For type III positive pressure enclosures, electrical equipment with "pzc" protection level enclosures that may still be charged when the enclosure is not in operation should use EPLDa, Db or Dc to protect. 7.16 Equipment allowed in enclosures with "pyb" protection class The electrical equipment in the "pyb" protection class positive pressure enclosure shall be protected by EPLGa, Gb or Gc for Class II, and shall be used for Class III EPLDa, Db or Dc to protect.

8 Safety measures and safety devices for static positive pressure

8.1 Applicability of safety devices for hazardous locations All safety devices used to prevent explosions caused by electrical equipment protected by static positive pressure should not cause explosions themselves, and if installed The whole device is electrically operated, it should be protected by one of the explosion-proof types specified in GB/T 3836.1 or installed outside the hazardous location. 8.2 Shielding gas The protective gas should be an inert gas. 8.3 Internal release source There should be no internal sources of release. 8.4 Inflation procedure for type Ⅰ and type Ⅱ positive pressure enclosures The instruction manual should specify that the positive pressure enclosure should be filled with inert gas in a non-hazardous area using the inflation procedure specified by the manufacturer. 8.5 Inflation procedure for type Ⅲ positive pressure enclosure The operating instructions should specify that the positive pressure enclosure should be cleaned to ensure that there is no dangerous accumulation of combustible dust in the enclosure. In the instruction manual It should be specified that the positive pressure enclosure should be filled with inert gas in a non-hazardous area using the inflation procedure specified by the manufacturer. 8.6 Safety device For "pxb" or "pyb" protection level equipment, two automatic safety devices should be installed, and for "pzc" protection level, one automatic safety device should be installed. For the whole device, when the positive pressure drops below the minimum value specified by the manufacturer, the automatic installation device shall act. It should be possible to check safety while the equipment is running Whether the device is operating correctly. These automatic safety devices should only be reset using tools or keys. Note. The use of automatic safety devices (ie. power failure or sound alarm or other methods to ensure the safety of the equipment) is usually the user's responsibility. 8.7 Equipment that may be live When the explosion-proof type "p" is not in operation, the electrical equipment that may be charged in the positive pressure enclosure shall be at the equipment protection level (EPL) listed in 7.15 One to be protected. 8.8 Positive pressure The lowest positive pressure value should be greater than the maximum pressure loss measured in a cycle during normal operation, and this cycle should not be less than according to GB/T 3836.1 The medium opening time requires the internal components to be cooled to 100 times the required time, at least 1h. In the worst requirements for normal operation Under the conditions, the lowest positive pressure value should be at least 50Pa higher than the external pressure.

9 Supply of protective gas

9.1 Spare supply If a backup supply is required in the event of a failure of the main supply of shielding gas, then each supply should be able to be maintained independently Required pressure level or shielding gas supply rate. Two gas sources can share the same piping system or pipeline. Note. Where it is necessary to maintain the operation of electrical equipment, it may be recommended to use a backup power supply. 9.2 Independent supply When the enclosure of the equipment with ignition capability is protected by the "pzc" protection grade positive pressure enclosure, and the enclosure is also installed in a "pyb" When the protection level is in a positive pressure enclosure, the supply of protective gas should be independent of each other. 9.3 Shielding gas type The protective gas should be non-flammable. The instruction manual shall specify the type of shielding gas and the allowed type of substitute gas. If air or For other protective gases other than nitrogen, the protective gas should not reduce the explosion-proof type "p" due to its own chemical characteristics or possible impurities The protection effect of this product may seriously affect the normal operation and the integrity of the built-in equipment. When inert gas is used, there is a danger of suffocation. Therefore, appropriate warnings should be attached to the enclosure (see 18.9). Should be considered when opening the door It is a proper method to ventilate the shell to remove inert gas before and cover. 9.4 Temperature At the air inlet of the enclosure, the temperature of the protective gas should normally not exceed 40°C. In special circumstances, higher temperatures may be allowed or may be required Find a lower temperature. In this case, the temperature should be marked on the enclosure. 10 Positive pressure housing with internal release source Chapters 11~15 give the release conditions, built-in system design requirements, suitable positive pressure technology, equipment with ignition capability, and internal heat meter Noodle restrictions. 11 Release conditions 11.1 No release 11.1.1 When there is no fault in the built-in system, there is no internal release, see 12.2. 11.1.2 When the flammable substance in the built-in system is in a gas or vapor state, it runs between the specified temperature limit and the following two conditions When, it is considered that there is no internal release. a) The gas mixture in the built-in system is always below the lower combustion limit (LFL); or b) The minimum pressure specified for the positive pressure enclosure is at least 50Pa higher than the maximum pressure specified for the built-in system, and if it is under the pressure difference When it drops to 50Pa, the installed automatic safety device operates. Note. It is the user's responsibility to use the alarm signal of the automatic safety device (ie, power failure or sound alarm or other methods to ensure the safety of the equipment). The equipment explosion-proof certificate number shall be marked with "X" on the equipment in accordance with the marking requirements in GB/T 3836.1, and the explosion-proof certificate shall be listed Special conditions of use shall specify the necessary information required by the user to ensure compliance with the requirements of this document. 11.2 Limited release of gas or vapor The release rate of flammable substances entering the positive pressure enclosure under all fault conditions of the built-in system should be predictable, see 12.3.For this Document, the release of liquefied gas is regarded as released gas. 11.3 Limited release of liquids According to 11.2, the flow of flammable substances entering the positive pressure enclosure is restricted, but the conversion of liquid into flammable vapor is unpredictable of. The possible accumulation of liquid in the positive pressure enclosure and its consequences should be considered. If oxygen can be released from the liquid, the maximum flow rate of oxygen should be estimated, see 13.2.2. 12 Design requirements for built-in systems 12.1 General design requirements The design and structure of the built-in system will determine whether leakage is possible, and the worst operating conditions specified by the manufacturer shall be used as Base. The built-in system shall be fault-free or have a limited release in the event of a fault. If the flammable substance is liquid, there should be no normal release (according to Appendix E), And the protective gas should be an inert gas. Note. The shielding gas is an inert gas to prevent the released vapor from exceeding the dilution capacity of the shielding gas. The manufacturer shall specify the maximum inlet pressure of the built-in system. The manufacturer shall provide a description of the design and structure of the built-in system, which may include the type and operating conditions of flammable substances, and the expected interpretation. Discharge flow or release flow at a known location in order to classify the built-in system as a trouble-free built-in system (12.2) or a built-in with limited release System (12.3). 12.2 Trouble-free built-in system The trouble-free built-in system shall be composed of metal, ceramic, glass, conveying pipes, pipes or containers, without movable joints. The connection should be welded, Brazing, glass and metal sealing, or eutectic 1) connection. The use of low-temperature tin solder alloy solder, such as lead/tin, is not allowed. Manufacturers should consider damage to potentially vulnerable built-in systems due to adverse operating conditions. The instructions should provide appropriate instructions Guide to reduce the risk of damage under adverse operating conditions recognized between manufacturers and users, such as opening the door and access cover of the positive pressure enclosure Vibration, thermal shock and maintenance operations. 12.3 Built-in system with limited release The design of the built-in system with limited release should be able to predict the release rate of combustible substances of the built-in system under all fault conditions. release The amount of flammable substances placed in the positive pressure enclosure, including the amount of flammable substances in the built-in system and the flammability that enters the built-in system during the process The amount of substance. The flow should be limited to the expected rate through the corresponding flow limiting device, and the flow limiting device should be installed outside the positive pressure enclosure. However, if the built-in system goes from the inlet of the positive pressure housing to the inlet part of the flow restriction device, the air inlet of the flow restriction device is in In accordance with 12.2, the current-limiting device can be installed in the positive pressure housing. In this case, the current-limiting device should be permanently fixed and should not be detachable Unload parts. If the maximum release rate of flammable substances from the built-in system into the positive pressure enclosure can be predicted, it is not necessary to restrict access to the built-in system. Systematic technological process. This condition can be met in the following situations. a) When the built-in system is composed of connecting parts that individually meet the requirements of 12.2 and the connecting heads between the parts, it should be designed to be able to predict the built-in The maximum release flow of the system, and the connection head is permanently fixed; or b) The built-in system includes air holes or nozzles for releasing (e.g. flame) under normal operating parts, but other parts shall comply with 12.2 Require. If the current limiting device is not used as part of the equipment, the equipment explosion-proof certificate number should be included in accordance with the marking requirements in GB/T 3836.1 "X" suffix, and the special conditions listed in the explosion-proof certificate shall specify the necessary information required by the user to ensure compliance with the requirements of this document Information, including the maximum pressure and flow rate of flammable substances entering the built-in system. A positive pressure enclosure containing a flame should also be used when the flame has been extinguished assessment. The maximum amount of fuel/air mixture supplied to the flame shall be added to the release amount of the built-in system. Elastic seals, observation windows and other non-metallic parts of the built-in system are allowed, pipe threads, pressure connections (such as metal crimp attachments) Parts) and flange connections are also allowed. 1) A method of connecting two or more parts, usually metal parts. The use of bimetallic alloy or trimetallic alloy is lower than the lowest of all connected parts The curing is carried out at a constant temperature of the initial curing temperature. 13 Shielding gas and positive pressure technology with internal release source 13.1 General The choice of shielding gas depends on the possibility, quantity and composition of the release of the built-in system. See Table 4 for the list of allowable shielding gases. The design of the positive pressure enclosure with a built-in system and limited release should prevent the formation of explosive gas near the potential ignition source in the positive pressure enclosure. The physical environment, that is, outside the release area. Appendix F provides information on how to use internal partitions to ensure that potential ignition sources are outside the dilution zone.

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