Motors explosion protected

Explosion, Protection in. A review of approved electric switches, motors, meters, recorders and other gear suitable for use in areas where explosives are handled. Being spark proof, they minimize explosion hazards Ref H. Busch, "Die Schutzarten im Explo-sionsschutz (Types of Protection in Explosion Protection), Explosivstoffe 1958, 54—9 (9 refs)... 

The rule described above forms a basis for the secondary type of explosion protection, which results in the avoidance of ignition sources, e.g. by using either a flameproof enclosure of a commutator motor or the pressurized enclosure of a gas analyser, or by limiting the electrical values in intrinsically safe circuits. 

Table 3.12 summarizes IEC members and associates. Within the IEC, technical committees and subcommittees are involved in standardization work covering all aspects of electrical engineering, e.g. insulating materials, semiconductors, wires and cables, lamps, motors, generators, transformers, and, of special interest, electrical apparatus for explosive atmospheres. This is the responsibility of Technical Committee TC 31 and eight subcommittees (see Table 3.13). Table 3.14 gives a survey of IEC documents and standards covering the field of explosion protection of electrical apparatus. 

Figure 6.6 Synchronous motor for ELENAC ethylene compressor Explosion protection according to EN 50016 - Pressurization - Group II.

Table 6.22 Comparison of a non-explosion protected motor with (E)Ex eh design (rated synchronous speed 1500 min-1, frame number 132,50cps, totally enclosed/fan cooled) (by courtesy of Loher GmbH, Ruhstorf/Germany)...

Figure 6.86 Longitudinal section drawing of a cage induction motor with identical frame number (132) to that shown in Fig. 6.87 motor not explosion protected.

The reduced noise of water-cooled motors has opened a field of application far away from the domain of explosion protection as an electric drive in suburban trains. 

Following the philosophy of explosion protection, the piping for cooling water shall be considered as empty and, as a part of the environment, filled with the gas-air mixture according to the grouping of the motor. (This is the practice when type testing such a motor for flameproofness.)... 

If safety programs have stalled on a plateau of acceptance, professionals should zero in on the causes of most work fatalities motor vehicle safety, truck fleet safety, workplace violence prevention, and fire and explosion protection (fatal work injuries resulting from fires and explosions rose from 113 in 2009 to 187 in 2010, an increase of 65 percent, according to the BLS. 

Mineral-insulated, metal-sheathed (MIMS) cable is suitable for use in most environments, but it is not so suitable for use where there may be vibration. In an old paint spray booth which predated the Highly Flammable Liquids and Liquefied Petroleum Gases Regulations, a spider-frame-mounted, electrical extractor fan had been positioned at the mouth of the extract duct and connected by MIMS cable. The fan motor was totally enclosed and explosion-protected as the paints used were flammable. The maintenance was poor and paint accumulations were allowed to build up on the fan blades causing an imbalance and vibration. This led to embrittlement of the copper sheath of the cable, which cracked and broke. Then one of the conductors fractured and sparking occurred between the ends. Ignition of the spray started a fire in the paint accumulations on nearby surfaces and the factory was burnt down. 

Except for areas with fire or explosion hazards (hazardous areas), motor enclosures are designed to provide protection to the internal working parts. The development or improved insiilating materials and finishes has affec ted the required degree of protection and consequently the design and classification of enclosures. Examples of several types of enclosures are shown in Fig. 29-4. 

Rotating electrical machines starting performance of single-speed three-phase cage induction motors for voltages up to and including 690 V Electrical apparatus for explosive gas atmosphere. Increased safety protection e 8789/1996 6381/1991 BS EN 60034-12/1996 BS 5501-6/1977... 

Bifurcated fan An axial flow fan that directs the airstream around the motor, which is enclosed in a protective casing. It is used for handling corrosive, high-temperature, and explosive dusts, vapors and gases. 

Type and specifications on fan driver, gear types, pow er voltage, phase, cycles. Motors should at least meet specifications equivalent to totally enclosed, fan cooled, or if in explosive hazardous area, TEFC Class I, Group D (except this not acceptable in hydrogen or acetylene atmosphere). Due to moisture conditions around this equipment, it should be protected against moisture penetration and corrosion. 

One can view samples from an explosion scene as belonging to one of two work streams (i) clean and (ii) dirty. Separation between these work streams needs to be established at the earliest possible moment in the process with appropriate laboratory facilities to handle each. The clean work stream contains items which are to be examined for invisible chemical traces of explosives. Such items need protection from any external contamination to a degree commensurate with the sensitivity of the chemical analysis techniques to be employed. The dirty work stream contains items that do not require trace analysis precautions, e.g., scene debris for physical searching. Nonetheless, such items still need to be handled in a way which protects their evidential integrity. Some items can start in the clean stream and then be transferred to the dirty stream, e.g., damaged motor vehicles may first be examined for explosive traces, and then transferred out of the trace examination area to be searched for physical evidence. 

Refs 1) W. Veicl, Explosivstoffe 1956, 102—04 (Protection of electrical wiring and switches in explosion-exposed buildings) 2) E. Diancourt, Ibid 1957, 209—13 (Electric motors in explosion-exposed rooms) 3) H. Busch,... 

---