One major concern in every industrial plant is the potential occurrence of ignitions and explosions. Flammable gases, vapors, mists, and dusts are inevitably created in many processes. This is why there are countless standards, laws, and protective regulations to ensure the safety of hazardous areas. Many applications in various industries also require the use of explosion protected equipment.
Underwriters Laboratories Inc. (UL) is a global safety consulting and certification company. They have set one of these standards called UL 1203, which is the "Standard for Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations". This standard contains technical requirements needed for electrical equipment to be labeled as “explosion proof” and “dust-ignition proof”.
For this test, sample castings in groups of 6 are exposed to saturated vapors in air for the following chemicals: Acetic Acid (Glacial), Acetone, Ammonium Hydroxide (20% by weight), ASTM reference fuel C, Diethyl Ether, Ethyl Acetate, Ethylene Dichloride, Furfural, n-Hexane, Methyl Ethyl Ketone, Methanol, 2-Nitropropane, and Toluene. After 7 days of exposure to these vapors, all the samples are observed for discoloration, swelling, shrinking, crazing, cracking, leaching, and dissolving. The samples are also subjected to a crush test. For the crush test, the crushing force should be at least 85% of the original value.
Master Bond’s system EP41S-6 was tested in accordance with UL 1203 and passed the above specifications. EP41S-6 is suitable for use in Class I, Division 1, Groups A, B, C, and D, and Class II, Division 1, Groups E, F, and G, in accordance with the National Electrical Code, NFPA 70 (National Fire Protection Association). The NEC is the benchmark for safe electrical design, installation, and inspection to protect people and property from electrical hazards.
The NEC classifies potentially explosive environments into 3 distinct classes: fire or explosion hazards from:
- a) Class I – flammable gases, vapors or liquids
- b) Class II – combustible dusts
- c) Class III – ignitable fibers
The divisions are based on how likely the materials are to be present. Division 1 represents an area where flammable or hazardous conditions can exist under normal operating conditions. Division 2 represents an area where these materials are not likely to exist under normal operating conditions.
Groups – Materials are further divided into Groups for Class I, Divisions 1 and 2:
- A – Acetylene
- B – Hydrogen
- C – Ethylene
- D – Propane
Groups – Materials are further divided into Groups for Class II, Division 1 and 2:
- E – Metal Dusts (Div. 1 only)
- F – Carbonaceous Dusts
- G – Non-Conductive Dusts (flour, grain, wood, plastic, etc.)