Specific electrical hazards

Relays such as those used in this particular system can be extremely dangerous because the contact points can spark and very easily ignite a fuel rich atmosphere, which will cause an explosion. Keep the controller well away from the rest of the system, or house it in a pressurized unit with alarm or alert shutdown controls, or in a flanged explosion-proof enclosure. 

All wiring and electrical components used in any control system must be rated for the current and voltage carried. If they are not, there is a risk of overheating components and/or starting a fire on wire insulation, etc. All electrical connections whether mechanical or soldered need to be done well so that shorts do not occur between wires, terminals or soldered joints. 

---

The overall intent of electrical area classification is to provide for safety of personnel and equipment. This is achieved by the elimination of electrical ignition sources near combustible gases or vapors that could explode or bum. The specific reasons for classifying facilities into electrical hazardous areas typically are ... 

Some specific internationally recognized electrical hazardous location equipment testing agencies are listed in Table 16 below. 

Fixed systems are classified in the manner they are stored. Low pressure 2,068 kPa (300 psi) or high pressure 5,860 kPa (850 psi) systems can be specified. Low pressure systems are normally provided when the quantity of agent required exceeds 907 kgs (2,000 lbs ). Protection of electronic or electrical hazards usually requires a design concentration of 50% by volume. NFPA 12 provides a table specifying the exact concentration requirements for specific hazards. As a guide, 0.45 kgs (1 lb.) of CO2 liquid may be considered to produce 0.23 cubic meters (8 cu. ft. ) of free gas at atmospheric pressure. 

This section can only touch upon the broad topic of safe laboratory working procedures because of the immense scope of the subject. The procedure to be followed here is to provide generic approaches to most of the hazards covered rather than discuss specific instances in which a given hazard could occur. Some of the more common areas which offer the potential for mishaps will be covered in some detail, but undoubtedly there will be areas that are considered comparably important by many that will be touched upon lightly or not at all. Sections will be devoted to a small number of the more hazardous chemicals to illustrate the precautions that need to be taken when working with such materials. In addition to physical hazards, such as fire, electrical hazards, and explosions, health risks will be discussed in some detail, since in many... 

In addition, this section specifically addresses the requirements for vehicle-mounted elevating and rotating work platforms. It specifically states "Unless otherwise provided in this section, aerial devices (aerial lifts) acquired on or after July 1,1975, shall be designed and constructed in conformance with the applicable requirements of the American National Standard for Vehicle-Mounted Elevating and Rotating Notk Platforms, ANSI A92.2-1969, including appendix." The employee training, personal protective equipment required, boom operation around electrical hazards, and inspection and maintenance of equipment are also discussed. 

E) Other work that exposes an employee to electrical hazards greater than, or equal to, the electrical hazards posed by operations listed specifically in paragraphs (b)(3)(i)(A) through (b)(3)(i)(D) of this section. 

OSHA has requirements for safe work practices at 1910.333. By not complying with these work practices employees performing work near or on equipment or circuits (which are or may be energized) could be exposed to electric shock or other injuries resrdting from either direct, or indirect, electrical contacts. Your company-specific safety-related work practices must be consistent with the nature and extent of the electrical hazards. 

OSHA requires employees working in areas where there are potential electrical hazards to be provided with and use electrical protective equipment appropriate for the specific parts of the body to be protected and work to be performed. 

Equipment is varied in cleanrooms. It is impractical to try to highlight even the most common. Each piece of equipment needs to be specifically reviewed for generic hazards. This would involve the materials of construction being handled, electrical hazard and interconnections. 

---