CSA Certified & UL Listed Explosion Proof Motors

Hazardous Location Classifications
Underwriters Laboratories Labeling
Special Construction Features
Substances & Atmospheres Charts
Special Information for User

Hazardous Location Classifications

There are three main categories of classification:

1. Division
2. Class
3. Group

Division: In real sense, it means location or area of the hazard. There are only two types of divisions:

Division 1	Hazard can occur under normal conditions
Division 2	Hazard can occur only under abnormal conditions Local safety authorities decide what are normal and abnormal conditions. Therefore, the first step is to contact local authorities to define the location if it is Division 1 or Division 2.

Class: Defines the type of hazard. There are three different classes.

Class I	Consists of chemical gases or vapors in the environment, such as gasoline or acetylene.
Class II	Consists of flammable dust in the environment, such as coke dust, grain dust, etc.
Class III	Consists of flammable lint or fibers in the area, such as textile, saw dust, etc.

Groups: Defines the principal chemical gas, vapor or dust present in the environment.
The term group comes from the various atmospheric mixtures which have been grouped together on the basis of their hazardous characteristics.

Groups A, B, C, and D are always in the form of gas or vapor. Therefore, these groups can exist only under Class I category.

Groups E, F, and G are always in the form of dust. Therefore, these groups can exist only under Class II category.

Top ^

Underwriters Laboratories Labeling

Underwriters Laboratories is the only safety agency recognized by the National Electrical Code for the approval of electric motors under hazardous locations.

It defines all the requirements for the manufacturers to make these motors after Division, Class, and Groups are defined by the user. The following chart should help understanding where U.L. label is required.

Top ^

 

Special Construction Features

1. Most are provided with thermal protection. Thermostats, or Thermistors
2. Most are made of cast iron frames.
3. Conduit boxes of the motors going in Division 1 are specially sealed.
4. Class I motors have longer lap joints, tighter fits, and longer flame paths so that if an explosion does occur in the motor, it’s contained in the motor and flames coming out through the joints are cooled enough to be extinguished. They may be bolted by hardened steel bolts.
5. Motors used in atmosphere of less than -25°C require still stronger construction features because of the extra stresses, also because of the increase in the density of the environment. The amount of energy required to cause an explosion is more, but the explosion is of much greater intensity. Standard explosion-proof motors are not useable below -25°C without special UL testing, approval, and marking.
6. Class II motors have bearing dust seals.
7. Non-sparking fan made of aluminum, bronze, or plastic is used to prevent friction sparks in case of any small stones or metal objects getting into the air stream and bouncing off fan blades, and to prevent the build-up of static electrical charge which could generate a spark.

Top ^

 

Substances and Atmospheres Chart

 

 

Top ^

 

Special Information for User:

U.L. does not offer any standards on Division 1 Class 1 Groups A and B.

U.L. does not offer any standards on Division 2 motors.

U.L. does not offer any standards on Class III motors.

U. L. does not offer any standards for motors used below ambient temperatures of -25°C, but will conduct individual tests at whatever low ambient is desired.

Motors rated ¾ HP and less may have internally mounted automatic thermal overload.  Caution should be observed when applying these to the machinery as automatic thermal overload resets and starts the motor.

Motors rated 1 HP and more may have thermostats on the windings which are pilot circuit devices only to be connected into the magnetic starter circuit.

Open motors can only be used in Division 2 location.

Operating temperature of space heaters must be considered when non-UL listed motors are applied in Division 2 locations. Any heater temperature below 200°C.

 

Conclusion

This paper provides the general everyday information. The user should be very careful about the special situations which are not covered by National Electrical Code tables. The main limiting factor is the surface temperature of the motor which should always be below the minimum ignition temperature of the environment. It should also be strong enough to contain any explosion inside.

 

Recognized UL Component Mark for Canada and the US

This new UL Recognized Component Mark, which became effective April 1, 1998, may be used on components certified by UL to both Canadian and U.S. requirements. Although UL had not originally planned to introduce a combined Recognized Component Mark, the popularity of the Canada/U.S. Listing and Classification Marks among clients with UL certifications for both Canada and the United States has led to the new Mark.

 

Special Information for User

The latest revisions of the U.L. Standards are primarily additional safety features and in no way affect the safe operation of U.L. labeled motors now in use. The most significant change in the revised Standards is that all motors must bear a marking indicating maximum operating temperature. This change, in effect, further subdivides each of the existing U. L. groups.

The marking to show maximum surface operating temperature must be in either degrees C or F, or by code, indicating the temperature range, i.e., a motor having a maximum surface operating temperature of 165°C may be marked 165°C or 329°F or coded T3B. All temperatures are on the highest temperature obtained in an ambient of 40°C (104°F) under all operating conditions, including overload, single-phasing, and locked-rotor operation. National Electrical Code (2002) Article 500-8(B) lists the preferred markings in part as follows:

Maximum Temperature
C°	F°	Temperature Class (T Code)
450	842	T1
300	572	T2
280	536	T2A
260	500	T2B
230	446	T2C
215	419	T2D
200	392	T3
180	356	T3A
165	329	T3B
160	320	T3C
135	275	T4
120	248	T4A
100	212	T5
85	185	T6

Top ^

For more information regarding CSA certified and U.L. listed explosion proof motors, contact us. We'll help you find the motor you need to fit quality and safety standards. Or request a quote today for Class 1, Groups A, B, C, & D motors or Class 2, Groups E, F, & G Motors.