On explosion-proof standards in the petrochemical industry
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Hello everyone. I am looking for an explosion-proof instrument for the petrochemical industry and would like to know the relevant standards. Could you please provide some standard numbers? Those from both domestic and international sources would be great. Thank you
This post was last edited by lmsa613 on 2012-2-15 at 13:44. Additional information: ANSI/API RP500-1998, GB 50058-92; also, China’s electrical explosion-proof marking standard GB3836-2000 (not sure if it’s the latest version)
In fact, you can select the table according to the explosion-proof areas defined in the general layout. Of course, it’s best to be able to master some standards!
The national explosion protection rating standard is \"GB3836.1-2000 Electrical equipment for use in explosive gas environments\", and this standard will be supplemented or modified by the following special standards for various explosion protection types. GB 3836.2 Electrical equipment for use in explosive gas environments – Part 2: Flameproof type “d” GB 3836.3 Electrical equipment for use in explosive gas environments – Part 3: Increased safety type “e” GB 3836.4 Electrical equipment for use in explosive gas environments – Part 4: Inherently safe type “i” GB 3836.5 Electrical equipment for use in explosive gas environments – Part 5: Positive pressure type “p” GB 3836.6 Electrical equipment for use in explosive gas environments – Part 6: Oil-immersed type “O” GB 3836.7 Electrical equipment for use in explosive gas environments – Part 7: Sand-filled type “q” GB 3836.9 Electrical equipment for use in explosive gas environments – Part 9: Encased type “m” GB 7957 Safety helmet lamps for use in mines. The above standards and this standard do not apply to medical electrical equipment, detonators, detonator testers, and ignition circuit testers. Common symbols include “ExdⅠ/Ⅱ BT3”. “Ex” is a general symbol meaning “explosive” (this is my personal interpretation); “d” indicates that the explosion protection type is “flameproof type d”. “Ⅰ” or “Ⅱ” denotes the classification of the electrical equipment – Ⅰ refers to electrical equipment used in coal mines, while Ⅱ refers to equipment used in other explosive gas environments besides coal mines. Among them, flameproof type “d” and inherently safe type “i” electrical equipment are further divided into categories ⅡA, ⅡB, and ⅡC. “T3” indicates the temperature group. For specific classifications and their meanings, please refer to “GB3836.1-2000 Electrical equipment for use in explosive gas environments”. I. Concept of explosion protection 1. Three necessary conditions for an explosion to occur; when all three conditions are met, an explosion takes place. Energy required for ignition, source of migration ； Air or oxygen air or oxygen ； Flammable air, flammable dust. 2. To prevent explosions, it is necessary to consider three essential conditions; by restricting any one of these conditions, the occurrence of an explosion can be prevented. In industrial processes, handling of flammable and explosive environments is usually approached from the following three aspects. 1) Prevent or minimize the possibility of leaks of flammable substances ； 2) Avoid using, or use as little as possible, electrical components that are prone to generating sparks ； 3) Use methods such as nitrogen filling to maintain an inert state. II. Classification of Hazardous Areas, Explosion Protection Classification of Electrical Components, and Allowable Temperature Ranges
1. Classification of Hazardous Areas
Zone 0: Explosive gases are present at all times or for extended periods.
Zone 1: Flammable gases may occur or be present during the normal operation of instruments.
Zone 2: Under normal conditions, no flammable gases are present; even if they do occur occasionally, their presence is brief.
Comparison between International Standards and American Standards for Hazardous Area Classification
I.E.C. N.E.C.
Gases: Zone 0 – Class I, Division I; Zone 1 – Class I, Division I; Zone 2 – Class I, Division II
Dusts: Zone 10 – Class II, Division I; Zone 11 – Class II, Division II
I.E.C.: International Electrotechnical Commission
N.E.C.: National Electrical Code, U.S.A.
2. Explosion Protection Classification of Electrical Components
1. General protection – EN50.014
2. Immersion protection – 0 – EN50.015
3. Pressurized protection systems – p – EN50.016
4. Powder filling – q – EN50.017
5. Flame-retardant enclosures – d – EN50.018
6. Increased safety factors – e – EN50.019
7. Intrinsic safety protection – i – EN50.0120
8. Airtight protection – h – Not standardized
9. Pressure relief protection – n – Not standardized
10. Special measures – s – Not standardized
3. Allowable Temperature Ranges for Electrical Equipment
Temperature class code of electrical components | Maximum allowable surface temperature (°C) | Ignition point of gas (°C)
T1 | 200 | T | 450 | 450
T2 | 200 | T | 300 | 300
T3 | 135 | T | 200 | 200
T4 | 100 | T | 135 | 135
T5 | 85 | T | 100 | 100
T6 | T | 85 | 85
III. Explosion Properties of Some Common Substances
Name | Ignition point (°C) | Temperature class | Explosion group number
—— | —— | —— | ——
Propane | 540 | T1 | IIA
Acetylene | 305 | T2 | IIC
Acetic anhydride | 330 | T2 | IIA
Benzene | 555 | T1 | IIA
Butane | 365 | T2 | IIA
n-Butanol | 340 | T2 | IIA
Benzenochloride | 590 | T1 | IIA
Ethanol | 425 | T2 | IIA
Ethyl acetate | 460 | T1 | IIA
Methanol | 455 | T1 | IIA
*** | 430 | T1 | IIA
n-Pentane | 285 | T3 | IIA
Propane | 470 | T1 | IIA
Toluene | 535 | T1 | IIA
Hydrogen | 560 | T1 | IIC
Hydrogen sulfide | 270 | T3 | IIB
Carbon disulfide | 102 | T5 | IIC
IV. Power Supply Restrictions for Intrinsic Safety Sensor Circuits
Power supply restrictions are mainly reflected in the following three aspects:
1. Isolating the power supply from electronic components. 2. Take measures to prevent external interference from coupling electromagnetic fields into electronic components via the relay or current output terminals. 3. Limiting the operating power supply and voltage of the sensing circuit. Intrinsic safety circuits can be divided into two categories: ia and ib. Ib intrinsically safe circuits must ensure that the circuit components do not catch fire or explode, both under normal operating conditions and in the event of a fault within the system. Intrinsic safety circuits require that components do not catch fire or explode under normal operating conditions as well as in the presence of two faults. V. Main explosion-proof standards followed by EH instruments: 1. IEC/CENELEC/EUROPE and NORTH AMERICA/FM standards are commonly used, whereas the CANADA/CSA standard is hardly used in China. Example: CENELEC: Eex de/Eex d ib IIC T2-T6 FM: NI/I/Z/ABCD DIP/II, III/1/EFG XP/I/1/ABCD DIP/II, III/1/EFG CSA: Class I, Div 2, ABCD. The new European explosion-proof standard ATEX100a will replace the previous CENELEC standards (as of 2003). ATEX 100a: II IG Ee*a IIB T6 I II 1G Zone 0 1D, 2D, 3D – dust explosions; Mining, other applications. 2G Zone 1 – Industrial applications. 3G Zone 2. VI. Classification of protection levels for instrument enclosures: For instruments used in explosive hazard areas, it is also necessary to specify the protection level of their enclosures, which is indicated by a code, namely the IP rating. The enclosure protection rating specified by IEC144 is represented by a code that corresponds to its resistance to impact and penetration by external objects as well as its water resistance. For example: Intrinsic safety instruments used for measuring circuit boards should not be removed from their enclosures, as this would violate the minimum requirements specified by IP40. The protection rating consists of two digits, preceded by the word IP. IP1 2: First digit, second digit – Resistance to impact by external objects, waterproofing capability. 0: No resistance to penetration; 0: No waterproofing capability. 1: External object size greater than 50 mm (very large); 1: Water droplets falling vertically. 2: External object size greater than 120 mm (medium); 2: Water droplets at an angle of -15°. 3: External object size greater than 2.5 mm (small); 3: Water sprayed at a 60° angle. 4: Granular external objects with a particle size greater than 1 mm; 4: Spraying from all directions. 5: Hazardous dust; 5: Water jet of 50 liters per minute. 6: Penetrating dust (applicable only to special enclosures); 6: Water jet of 100 liters per minute. 7: Immersion in water at a speed of 1 meter per minute; 8: Immersion in water in a pre-agreed manner. 1: Category, grade, and temperature group of explosion-proof electrical equipment. 1.1 Classification of hazardous areas in explosive gas environments: Zone 0: An environment where explosive gas mixtures are present continuously or for extended periods of time. Zone 1: An environment where explosive gas mixtures may occur during normal operation. Zone 2: An environment in which explosive gas mixtures cannot exist under normal operating conditions, or in which such mixtures exist only for short periods of time. Zone 0 generally exists only within the gas-filled spaces inside sealed containers, storage tanks, etc. In actual design processes, Zone 1 is also rare; in most cases, it falls under Zone 2. 1.2 Explosion-proof electrical equipment is divided into two categories: Category I – electrical equipment used in coal mines; Category II – electrical equipment used in locations other than mines. 1.3 Electrical equipment of Category II is further divided into three subcategories – IIA, IIB, and IIC – based on their maximum allowable safety gap or minimum ignition current when exposed to explosive gas mixtures ； And they are divided into six groups, T1 to T6, according to their highest surface temperature. 1.4 Explosive gas mixtures are classified according to their ignition temperature, as shown in Table 1. 2. Noun predicates 2.1 Flameproof electrical equipment: Electrical equipment whose enclosure is capable of withstanding the explosion pressure of explosive gas mixtures inside, and preventing the spread of an internal explosion to the explosive mixtures surrounding the enclosure; such equipment is marked with “d”. 2.2 Increased safety electrical equipment does not generate arcs, sparks, or high temperatures that could ignite explosive mixtures under normal operating conditions; structural measures are taken to increase safety margins in order to prevent the occurrence of arcs, sparks, or high temperatures under normal and permitted overload conditions. Such equipment is marked with the symbol “e”. 3. Explosion prevention principle: There are two reasons why electrical equipment can ignite a flammable gas mixture: one is the sparks and arcs generated by the electrical equipment, and the other is the heating of the surface of the electrical equipment (i.e., the surface in contact with the flammable gas mixture). To achieve explosion protection, the components of the equipment that can generate arcs or sparks during normal operation should be placed within an explosion-proof enclosure, or other explosion-proof designs such as encapsulation, sand filling, oil filling, or positive pressure systems can be employed. Safety-enhanced electrical equipment refers to devices that do not generate arcs, sparks, or dangerous high temperatures under normal operation. By implementing additional protective measures in their design, it is possible to ensure that such devices do not experience arcs, sparks, or overheating under normal operating conditions or under approved overload conditions, thereby further enhancing their safety and reliability. Therefore, such equipment has no ignition source when operating normally, and can be used in explosive hazardous environments. 4. Examples of explosion-proof markings 4.1 If the electrical equipment is of IIB classification, explosion-proof type T3, the marking will be Exd II BT3. 4.2 If the electrical equipment is of Type II increased safety type, with a temperature group of T2, the marking shall be Exe II T2. 4.3 If an electrical device adopts more than one composite protection type, the main explosion protection type shall be indicated first, followed by the other protection types. For example, if the main type is enhanced safety with internal IIC classification explosion-proof components and the temperature group is T4, the marking will be Exed II CT4. 4.4 If the electrical equipment is of dust-proof and explosion-proof type, Group T11. The identifier is: DIPDPT11.
1. Classification of Hazardous Areas
Zone 0: Explosive gases are present at all times or for extended periods.
Zone 1: Flammable gases may occur or be present during the normal operation of instruments.
Zone 2: Under normal conditions, no flammable gases are present; even if they do occur occasionally, their presence is brief.
Comparison between International Standards and American Standards for Hazardous Area Classification
I.E.C. N.E.C.
Gases: Zone 0 – Class I, Division I; Zone 1 – Class I, Division I; Zone 2 – Class I, Division II
Dusts: Zone 10 – Class II, Division I; Zone 11 – Class II, Division II
I.E.C.: International Electrotechnical Commission
N.E.C.: National Electrical Code, U.S.A.
2. Explosion Protection Classification of Electrical Components
1. General protection – EN50.014
2. Immersion protection – 0 – EN50.015
3. Pressurized protection systems – p – EN50.016
4. Powder filling – q – EN50.017
5. Flame-retardant enclosures – d – EN50.018
6. Increased safety factors – e – EN50.019
7. Intrinsic safety protection – i – EN50.0120
8. Airtight protection – h – Not standardized
9. Pressure relief protection – n – Not standardized
10. Special measures – s – Not standardized
3. Allowable Temperature Ranges for Electrical Equipment
Temperature class code of electrical components | Maximum allowable surface temperature (°C) | Ignition point of gas (°C)
T1 | 200 | T | 450 | 450
T2 | 200 | T | 300 | 300
T3 | 135 | T | 200 | 200
T4 | 100 | T | 135 | 135
T5 | 85 | T | 100 | 100
T6 | T | 85 | 85
III. Explosion Properties of Some Common Substances
Name | Ignition point (°C) | Temperature class | Explosion group number
—— | —— | —— | ——
Propane | 540 | T1 | IIA
Acetylene | 305 | T2 | IIC
Acetic anhydride | 330 | T2 | IIA
Benzene | 555 | T1 | IIA
Butane | 365 | T2 | IIA
n-Butanol | 340 | T2 | IIA
Benzenochloride | 590 | T1 | IIA
Ethanol | 425 | T2 | IIA
Ethyl acetate | 460 | T1 | IIA
Methanol | 455 | T1 | IIA
*** | 430 | T1 | IIA
n-Pentane | 285 | T3 | IIA
Propane | 470 | T1 | IIA
Toluene | 535 | T1 | IIA
Hydrogen | 560 | T1 | IIC
Hydrogen sulfide | 270 | T3 | IIB
Carbon disulfide | 102 | T5 | IIC
IV. Power Supply Restrictions for Intrinsic Safety Sensor Circuits
Power supply restrictions are mainly reflected in the following three aspects:
1. Isolating the power supply from electronic components. 2. Take measures to prevent external interference from coupling electromagnetic fields into electronic components via the relay or current output terminals. 3. Limiting the operating power supply and voltage of the sensing circuit. Intrinsic safety circuits can be divided into two categories: ia and ib. Ib intrinsically safe circuits must ensure that the circuit components do not catch fire or explode, both under normal operating conditions and in the event of a fault within the system. Intrinsic safety circuits require that components do not catch fire or explode under normal operating conditions as well as in the presence of two faults. V. Main explosion-proof standards followed by EH instruments: 1. IEC/CENELEC/EUROPE and NORTH AMERICA/FM standards are commonly used, whereas the CANADA/CSA standard is hardly used in China. Example: CENELEC: Eex de/Eex d ib IIC T2-T6 FM: NI/I/Z/ABCD DIP/II, III/1/EFG XP/I/1/ABCD DIP/II, III/1/EFG CSA: Class I, Div 2, ABCD. The new European explosion-proof standard ATEX100a will replace the previous CENELEC standards (as of 2003). ATEX 100a: II IG Ee*a IIB T6 I II 1G Zone 0 1D, 2D, 3D – dust explosions; Mining, other applications. 2G Zone 1 – Industrial applications. 3G Zone 2. VI. Classification of protection levels for instrument enclosures: For instruments used in explosive hazard areas, it is also necessary to specify the protection level of their enclosures, which is indicated by a code, namely the IP rating. The enclosure protection rating specified by IEC144 is represented by a code that corresponds to its resistance to impact and penetration by external objects as well as its water resistance. For example: Intrinsic safety instruments used for measuring circuit boards should not be removed from their enclosures, as this would violate the minimum requirements specified by IP40. The protection rating consists of two digits, preceded by the word IP. IP1 2: First digit, second digit – Resistance to impact by external objects, waterproofing capability. 0: No resistance to penetration; 0: No waterproofing capability. 1: External object size greater than 50 mm (very large); 1: Water droplets falling vertically. 2: External object size greater than 120 mm (medium); 2: Water droplets at an angle of -15°. 3: External object size greater than 2.5 mm (small); 3: Water sprayed at a 60° angle. 4: Granular external objects with a particle size greater than 1 mm; 4: Spraying from all directions. 5: Hazardous dust; 5: Water jet of 50 liters per minute. 6: Penetrating dust (applicable only to special enclosures); 6: Water jet of 100 liters per minute. 7: Immersion in water at a speed of 1 meter per minute; 8: Immersion in water in a pre-agreed manner. 1: Category, grade, and temperature group of explosion-proof electrical equipment. 1.1 Classification of hazardous areas in explosive gas environments: Zone 0: An environment where explosive gas mixtures are present continuously or for extended periods of time. Zone 1: An environment where explosive gas mixtures may occur during normal operation. Zone 2: An environment in which explosive gas mixtures cannot exist under normal operating conditions, or in which such mixtures exist only for short periods of time. Zone 0 generally exists only within the gas-filled spaces inside sealed containers, storage tanks, etc. In actual design processes, Zone 1 is also rare; in most cases, it falls under Zone 2. 1.2 Explosion-proof electrical equipment is divided into two categories: Category I – electrical equipment used in coal mines; Category II – electrical equipment used in locations other than mines. 1.3 Electrical equipment of Category II is further divided into three subcategories – IIA, IIB, and IIC – based on their maximum allowable safety gap or minimum ignition current when exposed to explosive gas mixtures ； And they are divided into six groups, T1 to T6, according to their highest surface temperature. 1.4 Explosive gas mixtures are classified according to their ignition temperature, as shown in Table 1. 2. Noun predicates 2.1 Flameproof electrical equipment: Electrical equipment whose enclosure is capable of withstanding the explosion pressure of explosive gas mixtures inside, and preventing the spread of an internal explosion to the explosive mixtures surrounding the enclosure; such equipment is marked with “d”. 2.2 Increased safety electrical equipment does not generate arcs, sparks, or high temperatures that could ignite explosive mixtures under normal operating conditions; structural measures are taken to increase safety margins in order to prevent the occurrence of arcs, sparks, or high temperatures under normal and permitted overload conditions. Such equipment is marked with the symbol “e”. 3. Explosion prevention principle: There are two reasons why electrical equipment can ignite a flammable gas mixture: one is the sparks and arcs generated by the electrical equipment, and the other is the heating of the surface of the electrical equipment (i.e., the surface in contact with the flammable gas mixture). To achieve explosion protection, the components of the equipment that can generate arcs or sparks during normal operation should be placed within an explosion-proof enclosure, or other explosion-proof designs such as encapsulation, sand filling, oil filling, or positive pressure systems can be employed. Safety-enhanced electrical equipment refers to devices that do not generate arcs, sparks, or dangerous high temperatures under normal operation. By implementing additional protective measures in their design, it is possible to ensure that such devices do not experience arcs, sparks, or overheating under normal operating conditions or under approved overload conditions, thereby further enhancing their safety and reliability. Therefore, such equipment has no ignition source when operating normally, and can be used in explosive hazardous environments. 4. Examples of explosion-proof markings 4.1 If the electrical equipment is of IIB classification, explosion-proof type T3, the marking will be Exd II BT3. 4.2 If the electrical equipment is of Type II increased safety type, with a temperature group of T2, the marking shall be Exe II T2. 4.3 If an electrical device adopts more than one composite protection type, the main explosion protection type shall be indicated first, followed by the other protection types. For example, if the main type is enhanced safety with internal IIC classification explosion-proof components and the temperature group is T4, the marking will be Exed II CT4. 4.4 If the electrical equipment is of dust-proof and explosion-proof type, Group T11. The identifier is: DIPDPT11.
The full set of GB3836 standards was also finalized in recent years, based on ATEX95 and 137.