Hazardous Areas
Introduction to Purge and Pressurization
Comark utilizes purge and pressurization as the method of protection for hazardous area locations to ensure that the interior of an electrical enclosure is free of flammable gas or combustible dust and fibers. Pressurization is generally used for electrical equipment that cannot be protected by other means, either because it is too large to be made explosion-proof, or too high-powered to use intrinsic safety.
Purge controlled and pressurized enclosures provide an equivalent degree of safety to Flameproof (Explosion-proof) or Intrinsic Safety techniques. It also offers significant advantages of safety and durability. The pressurization process is very simple. Purge gas, normally compressed air, keeps the internal pressure of an enclosure above the pressure outside. External flammable gas cannot enter the enclosure while it is pressurized.
Before power can be switched on, the enclosure must be purged to remove any flammable gas that my have entered the enclosure before it was pressurized. Purging is the action of replacing the air inside an enclosure with air known to be free of flammable gas.
Applications where purge kits can be used include:
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Products shown below can be purge protected to meet your needs
| IEC/EN (ATEX) | ATEX Cat. | Code | USA (NEC500) FM & UL | Canada (CEC) CSA | Gas | Dust | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Protection Method | Ex code | Gas | Ex code | Dust | ||||||||
| Intrinsic Safety | ia ib ic |
60079-11 60079-11 60079-11 |
Zone 0 Zone 1 Zone 2 |
iaD ibD |
61241-11 61241-11 |
Zone 20 Zone 21 |
1 2 3 |
IS | FM3610/UL913 | C22.2 No 157 | Class I, Div 1 | Class II, Div 1 |
| Flameproof | d | 60079-1 | Zone 1 | 2 | XP | FM3615/UL1203 | C22.2 No 30 | Class I, Div 1 | Class II, Div 1 | |||
| Enclosure | tD | 61241-1 | Zone 20, 21, 22 | FM3611/UL1604 | C22.2 No 25 | Class II, Div 2 | ||||||
| Purge & Pressurization | px py pz |
60079-2 60079-2 60079-2 |
Zone 1 Zone 1 Zone 2 |
2 2 3 |
Type X Type Y Type Z |
FM3620/NFPA 496 FM3620/NFPA 496 FM3620/NFPA 496 |
CSA TIL 13A CSA TIL 13A CSA TIL 13A |
Class I, Div 1 Class I, Div 1 Class I, Div 2 |
Class II, Div 1 Class II, Div 1 Class II, Div 2 |
|||
| Pressurized | pD | 61241-4 | Zone 21,22 | 2 | X, Y, Z | As above | ||||||
| Increased Safety | e | 60079-7 | Zone 1 | |||||||||
| Encapsulation | ma mb |
60079-18 60079-18 |
Zone 0 Zone 1 |
maD mbD |
61241-18 61241-18 |
Zone 20 Zone 21 |
1 2 |
UL1604 | C22.2 No. 213 | Class I, Div 2 | ||
| Oil Immersion | o | 60079-6 | Zone 1 | 2 | ||||||||
| Powder Filled | q | 60079-5 | Zone 1 | 2 | ||||||||
| Non Incendive | nA, nC, nL, nR | 60079-15 | Zone 2 | 3 | NI | FM3611/UL1604 | C22.2 No. 213 | Class I, Div 2 | ||||
| Rooms (draft) | p | 60079-13 | Zone 1 | 2 | NFPA 496 | |||||||
| Optical Radiation | oP | 60079-28 | Zone 0 | 1 | ||||||||
| General Requirements | 60079-0 | 61241-0 | NEC 500-3 | |||||||||
| Class. Of Hazardous Areas | 60079-1 | |||||||||||
| Electrical Installations | 60079-14 | |||||||||||
| Inspection & Maintenance | 60079-17 | |||||||||||
| Gas, Dust, or Fiber | IEC/Europe Canada (CEC) | USA NEC (505) | Canada (CEC) USA NEC (500) |
|---|---|---|---|
| Acetylene | Group IIC | Class I, Group IIC | Class I, Group A |
| Hydrogen | Class I, Group B | ||
| Ethylene | Group IIB | Class I, Group IIB | Class I, Group C |
| Propane | Group IIA | Class I, Group IIA | Class I, Group D |
| Methane | Group I | Not within CEC/NEC | |
| Metal Dust | Class II, Group E (Div 1 only) | ||
| Coal Dust | Class II, Group F | ||
| Grain | Class II, Group G | ||
| Fibers | Class III |
| Dust | Temp °C (Cloud) | Temp °C (Layer) |
|---|---|---|
| Cellulose | 520 | 410 |
| Coal | 380 | 225 |
| Cocoa Powder | 580 | 480 |
| Flour | 490 | 340 |
| Grain | 510 | 300 |
| Polythene | 420 | Melts |
| Sugar | 460 | 435 |
| Tea | 510 | 300 |
