 
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:
Products shown below can be purge protected to meet your
needs
Hazardous Locations Chart
| 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
Groupings
| 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 |
|
IEC/ATEX
Dust
| 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 |
|
Available Purge Kits
|
|
Pharmaceutical
manufacturing 
