PowerPoint® Presentation
Chapter 1PLC Electrical Safety
Chapter 1PLC Electrical Safety
Programmable Logic Controllers • PLC Safety • Electrical Properties • Grounding • Force and
Disable Safety Considerations • Electrical Noise Suppression • Static Electric Charges • Electrical
Safety • Personal Protective Equipment • Lockout/Tagout • Inspecting a PLC System •
Chapter 1 — PLC Electrical Safety
PLC system programming is viewed by various devices that connect to micro-sized PLCs (8 to 10 inputs and outputs) or to large-sized PLCs that control thousands of inputs and outputs.
Chapter 1 — PLC Electrical Safety
Improperly installed and/or maintained PLCs can overheat, leading to fire or explosion.
Chapter 1 — PLC Electrical Safety
An advantage of a PLC controlling a process is that a PLC can be programmed and reprogrammed as process conditions change.
Chapter 1 — PLC Electrical Safety
An electric shock results anytime a body becomes part of an electrical circuit.
Chapter 1 — PLC Electrical Safety
Possible effects of electrical shock include the heart and lungs ceasing to function, and/or severe burns where the electricity (current) enters and exits the body.
Chapter 1 — PLC Electrical Safety
Current is the amount of electrons flowing through an electrical circuit and is measured in amperes.
Chapter 1 — PLC Electrical Safety
Voltage is the amount of electromotive force in a circuit and is measured in volts.
Chapter 1 — PLC Electrical Safety
Resistance is the opposition to the flow of electrons and is measured in ohms.
Chapter 1 — PLC Electrical Safety
Grounding provides a direct path for unwanted fault current to travel to earth without causing harm to technicians or equipment.
Chapter 1 — PLC Electrical Safety
Building grounding, equipment grounding, and electronic equipment grounding are used to create a safe working environment for technicians.
Chapter 1 — PLC Electrical Safety
Building grounding ensures that there is a low impedance (low resistance) grounding path for fault current (electrical short or lightning) to earth ground.
Chapter 1 — PLC Electrical Safety
Equipment grounding prevents electrical shock when a person comes in contact with electrical equipment or exposed metal of machinery.
Chapter 1 — PLC Electrical Safety
Electronic equipment grounding is used to provide a quality ground for electronic systems to enable better communication (less noise) with PLCs, process control equipment, and other facility operations.
Chapter 1 — PLC Electrical Safety
Ground resistance measurements are taken on grounding conductors used with service entrances, transformers, utility transmission, and communication (control circuit) grounds.
Chapter 1 — PLC Electrical Safety
PLC force and disable commands are used during system start-up and for troubleshooting.
Chapter 1 — PLC Electrical Safety
Electrical noise enters a PLC system through input devices, output components, and power supply lines.
Chapter 1 — PLC Electrical Safety
To prevent false signals from entering a PLC, input and output lines must cross at right angles (90°) and not run parallel to each other.
Chapter 1 — PLC Electrical Safety
A shielded cable uses an outer conductive jacket (shield) to block electromagnetic interference from the inner, signal-carrying conductors.
Chapter 1 — PLC Electrical Safety
Depending on the PLC application, an enclosure with a cooling unit can be required.
Chapter 1 — PLC Electrical Safety
Article 500 of the NEC® classifies hazardous locations according to the properties and quantities of the hazardous material that may be present.
Chapter 1 — PLC Electrical Safety
Electrical safety rules aid in the prevention of injuries from electrical energy sources.
Chapter 1 — PLC Electrical Safety
PLC safety begins with a sufficient number of emergency stops and a master control relay that removes power to the inputs and outputs of the PLC and stops all motion of the machine(s) or process.
Chapter 1 — PLC Electrical Safety
Personal protective equipment includes items that protect a technician from electrical and other hazards.
Chapter 1 — PLC Electrical Safety
Arc-flash protective clothing made of Nomex®, Basofil®, and/or Kevlar® fibers must be used when working with live high-voltage electrical circuits.
Chapter 1 — PLC Electrical Safety
The National Fire Protection Association (NFPA) specifies boundary distances that vary depending on voltage.
Chapter 1 — PLC Electrical Safety
Protective helmets are identified by class of protection. For example, Class E protective helmets protect against high-voltage shock and burns.
Chapter 1 — PLC Electrical Safety
Eye protection must be worn to prevent eye or face injuries caused by contact arcing, radiant energy, or flying particles.
Chapter 1 — PLC Electrical Safety
Ear protection is worn to prevent technician hearing loss caused by electrical systems, machinery, power tools, and HVAC equipment.
Chapter 1 — PLC Electrical Safety
Rubber insulating gloves have color-coded labels that represent voltage ratings for specific applications.
Chapter 1 — PLC Electrical Safety
Rubber insulating gloves must be air tested before each use and when there is cause to suspect damage.
Chapter 1 — PLC Electrical Safety
Insulated rubber-soled shoes are typically worn during electrical work to aid in the prevention of electrical shock.
Chapter 1 — PLC Electrical Safety
Lifting an object with the legs reduces the possibility of a back injury.
Chapter 1 — PLC Electrical Safety
When carried on the shoulder by one person, objects such as conduit must be transported with the front end down.
Chapter 1 — PLC Electrical Safety
Rubber insulating matting aids in protecting a technician from electrical shock when working on energized electrical circuits.
Chapter 1 — PLC Electrical Safety
Lockout/tagout kits contain reusable danger tags, tag ties, multiple lockout hasps, magnetic signs, and information on lockout/tagout procedures.
Chapter 1 — PLC Electrical Safety
Lockout devices resist chemicals, cracking, abrasion, and temperature changes and are available in colors to match American National Standards Institute (ANSI) pipe colors. Lockout devices are sized to fit standard industry equipment.
Chapter 1 — PLC Electrical Safety
A proper inspection of a PLC ensures safe control of an electrical system.