IP First number - Protection against solid objects
0 | No protection. |
1 | Protected against solid objects up to 50mm, e.g. accidental touch by hands. |
2 | Protected against solid objects up to 12mm, e.g. fingers. |
3 | Protected against solid objects over 2.5mm (tools and wires). |
4 | Protected against solid objects over 1mm (tools, wire, and small wires). |
5 | Protected against dust limited ingress (no harmful deposit). |
6 | Totally protected against dust. |
IP Second number - Protection against liquids
0 | No protection. |
1 | Protection against vertically falling drops of water e.g. condensation. |
2 | Protection against direct sprays of water up to 15o from the vertical. |
3 | Protected against direct sprays of water up to 60o from the vertical. |
4 | Protection against water sprayed from all directions o limited ingress permitted. |
5 | Protected against low pressure jets of water from all directions o limited ingress. |
6 | Protected against low pressure jets of water, e.g. for use on ship decks - limited ingress permitted. |
7 | Protected against the effect of immersion |
IP Third number - Protection against mechanical impacts (commonly omitted)
0 | No protection. |
1 | Protects against impact of 0.225 joule (e.g. 150g weight falling from 15cm height). |
2 | Protected against impact of 0.375 joule (e.g. 250g weight falling from 15cm height). |
3 | Protected against impact of 0.5 joule (e.g. 250g weight falling from 20cm height). |
4 | Protected against impact of 2.0 joule (e.g. 500g weight falling from 40cm height). |
5 | Protected |
Substance | LEL | UEL |
Acetone | 3% | 13% |
Acetylene | 2.5% | 82% |
Benzene | 1.2% | 7.8% |
Butane | 1.8% | 8.4% |
Ethanol | 3% | 19% |
Ethylbenzene | 1.0% | 7.1% |
Ethylene | 2.7% | 36% |
Diethyl ether | 1.9% | 36% |
Diesel fuel | 0.6% | 7.5% |
Gasoline | 1.4% | 7.6% |
Hexane | 1.1% | 7.5% |
Heptane | 1.05% | 6.7% |
Hydrogen | 4% | 75% |
Hydrogen sulfide | 4.3% | 46% |
Kerosene | 0.6% | 4.9% |
Methane | 4.4% | 17% |
Octane | 1% | 7% |
Pentane | 1.5% | 7.8% |
Propane | 2.1% | 9.5% |
Propylene | 2.0% | 11.1% |
Styrene | 1.1% | 6.1% |
Toluene | 1.2% | 7.1% |
Xylene | 1.0% | 7.0% |
· Classes or Zone
· Zone is used for Europe
· Zone 0 = Flammable material always present
· Zone 1 = Intermittent available and for long hours (>10 hours)
· Zone 2 = Not always available and for short durations only (<10 hours)
· Class is used in US
· Rosemount transmitters use
· Gas group
· Refers to a group of gas which has similar propertie as the group gas. The main property is the ignition energy
· Group I = Methane
· Group IIA = Propane
· Group IIB = Ethylene
· Group IIC = Hydrogen
· Temperature Classes
· Each gas has an auto ignition temperature
· An area can be classified from T1 and T6. T1 has the highest auto ignition temperature hence it is safest.
· An equipment can be certified as T1 to T6. This is the worst case temperature the equipment can get hot
· Ex ‘d’ = Flame proof – Not designed to be gas tight, energy is released through flame path, Large design to prevent explosion.
· Ex ‘o’ = oil immersion – used for transformers, Zone 1 and 2
· Ex ‘p’ = Pressurized – used for analyzers, Zone 1 and 2 – Equipment needs to be powered off if the enclosure is opened. This is why purging is ‘’not usually recommended
· Ex ‘q’ = Powder field – weighing machines, Zone 1 and 2
· Ex ‘ma’ = encapsulation – Zone 1 and 2
· Ex ‘d’ = Flame proof , explosion is confined within box– DC motors, Zone 1 and 2
· Ex ‘e’ = Increased safety, it is not possible for explosion to happen. The box is designed in such a way to prevent
· Connections oversized
· Terminations more robust
– Induction motors, instrument JB, Zone 1 and 2
· Ex ‘ia’ = instrinsic safety – if 1 component fails, IS can still retain - Zone 0,1,2
· Ex ‘ib’ = intrinsically safe, Zone 1 and 2 only