Posted in
Electrical Distribution -
Power Factor
As companies look for ways to become greener power factor correction is providing opportunities to be a better environmental steward, but also to potentially save some cash along the way. Here's how companies are saving green by being green.
Posted in
Maintenance Methods -
Maintenance Programs
There are several definitions or meanings of preventive maintenance, however all preventive maintenance management programs are time-driven. What this means is, performed maintenance procedures are derived on an elapsed time or hours of operation method. Below depicts the statistical life of a typical machine-train. 
The mean-time-to-failure (MTTF) also commonly referred to as the bathtub curve illustrates that a recently installed machine has a higher likely hood of failure because of installation issues that occur during the first few weeks of commissioning. After this initial period, the possibility of failure is comparatively low for an extended period. After this typical machine life period, the probability of failure increases drastically with elapsed time. When it comes to preventive maintenance management, equipment repairs or rebuilds are determined based on the MTTF statistic.
Posted in
Maintenance Methods -
Maintenance Programs
This outlines eight simple steps that should be at the heart of an electrical preventive maintenance. These key steps are plan, inspect, clean, tighten, lubricate, test, record, and evaluate. The following article briefly describe each step and illustrate the part that they play in a good preventive maintenance program.
Posted in
Health & Safety -
Arc Flash
Maintenance and testing is also essential to ensure proper protection of equipment and personnel. With regard to personnel protection, NFPA 70E and OSHA require a flash hazard analysis be performed before anyone approaches exposed electrical conductors or circuit parts that have not been placed in an electrically safe work condition. In addition, it requires a flash protection boundary be established. All calculations for determining the incident energy of an arc, and for establishing a flash protection boundary, require the arc clearing time. This clearing time is derived from the engineering coordination study which is based on what the protective devices are supposed to do. If, for example, a low-voltage power circuit breaker had not been operated or maintained for several years and the lubrication had become sticky or hardened, the circuit breaker could take several additional cycles, seconds, minutes, or longer to clear a fault condition. The following are two specific examples that illustrate the important role protective trip devices play in the calculation of incident energy:
For the example, flash hazard analyses will be performed using a 20,000 A short circuit with the worker being 18 in. from the arc for a condition “arc in a cubic box” as described in Appendix D.6.2 of NFPA 70E-2004:
Posted in
Health & Safety -
Arc Flash
Every year many workers are treated in burn centers with severe arc flash injuries.
The flash is immediate, but the devastating effects can potentially last forever.
What is an Arc Flash?
". . . a dangerous condition associated with the release of energy caused by an electric arc."
As defined by NFPA
What is an Electric Arc?
- An electric arc is a short circuit current passing through the air
What are the Causes of Electric Arcs?
Arcs can be initiated by:
- Glow to Arc Discharge
- Dust and Impurities
- Corrosion
- Condensation of Vapor and Water
- Spark Discharge
- Accidental Touching
- Dropping or Leaving Tools
- Rodents and other Animals
- Over Voltages across Narrow Gaps
- Failure of Insulating Materials
- Improper Work Procedures
