Controls Safety

Electrical Safety

General Safety

The outline below provides Electrical safety precautions:

  • Only qualified technicians familiar with the system, using an up-to-date set of system schematics, should perform electrical/electronic system troubleshooting or maintenance.
  • Avoid wearing glasses that have a metal frame.
  • Avoid wearing necklaces, watches, bracelets, earrings, rings, or chains that are made of a metallic substance.
  • It must be always assumed that power is "ON" so all conditions must be treated as live. This practice develops a caution that may prevent an accident.
  • Ground connections cause fault currents to flow directly into the ground instead of flowing through the body into the ground. All electrical apparatus must be properly grounded.
  • Always use electrically insulated tools and utilize shock avoidance techniques.
  • Remove Load from circuit or equipment. Before performing maintenance or service on any part of the Electrical System, perform all applicable Lockout/Tagout (LOTO) procedures.
  • Before performing any work on the system, verify that power is removed from all circuits.
  • Electrical panels must not be opened if the ground light is on by anyone other than a qualified, authorized electrician for any reason.
  • Capacitors must be given time to discharge, otherwise it should be done manually with care using proper discharging tools.
  • Before any repair work is conducted on electrical circuitry, a voltage check using the proper test equipment must be made to ensure that dangerous voltages do not remain in the circuitry.

    Test equipment must be checked at regular intervals.

  • USE CAUTION when connecting test equipment probes to test points. Shock hazards could exist at the test points or in the test point area and/or transients induced by the probes could cause a machine action.
  • If it is necessary to perform troubleshooting with the power on, know where power is present and proceed with extreme caution. Whenever possible, use electrically insulated tools. When troubleshooting "LIVE" equipment, take the following precautions:
    • Make certain your tools and body are clear of potential grounds.
    • Use extra precaution in damp areas.
    • Be alert and work without any outside distraction.
    • When servicing electrical enclosures, follow all Personal Protective Equipment PPE. requirements per posted arc flash warnings in accordance with plant safety specifications.
    • Always use an appropriate fuse puller. Only regulation fuses, with their physical and electrical characteristics clearly specified, are to be used as replacements. Never attempt to replace a specified fuse with a higher-rated fuse (such as replacing a 5-amp fuse with a 10-amp fuse).
    • Before applying power to any equipment, establish, without any doubt, that all persons are clear.
    • The control panel doors shall be open only when it is necessary to check out the electrical equipment or wiring. After closing the door, make certain that the disconnecting means is operating properly with the disconnect handle mechanism.
    • All covers on junction boxes must be closed before leaving any job.
  • Before restarting equipment, read and understand all warnings, markings, and notices:
    • Read all markings such as nameplates and identification plates.
    • Do not alter circuits unless authorized to do so by the manufacturer.
    • Do not alter or bypass protective interlocks.
    • Do not place jumper wires across fuses or trip switches.
    • Do not alter over-current protective devices.
  • Refer to the LOTO Procedures to properly shut down the equipment and remove all energy from the source.
  • Before performing any maintenance or troubleshooting on the electrical system, ensure to fully understand and identify the Wire Color Coding used throughout the system. The Wire Color Code is listed below, but can also be found on Page three (3) of the Wiring Diagram:
    • Power Circuits 480/120 VAC = Black
    • Control Circuits 120VAC = Red
    • Control Circuits before Main Disconnect (Internally Supplied) = Yellow
    • Control Circuits before Main Disconnect (Externally Supplied) = Orange
    • Control Circuits 24 VDC = Blue
    • DC Circuits before Main Disconnect (Positive) = Blue/Orange
    • DC Circuits before Main Disconnect (Common) = White/Orange
    • Protective Conductor PE (Earth) = Green / Yellow
    • Neutral = White

Arcing Fault Hazards

Arcing fault hazards exist at all live electrical panels and precautions must be taken when opening any one of them.

An Arcing Fault is the flow of current through the air between phase conductors or between phase conductors and a neutral or ground, and can be caused by any number of things, ranging from faulty panel wiring to simply dropping a screwdriver or other tool inside a live panel. They can even occur when any conductive object gets too close to a high-amp current source or by simple equipment failure (i.e., opening or closing disconnects). The hazards of arcing faults come in multiple forms.

An Arc Flash is exposure to the tremendous thermal energy released by an arcing fault. Arc Flash can occur if a conductive object gets too close to a high-amp current source or by equipment failure (for instance, opening or closing disconnects). The arc can heat the air to temperatures as high as 35,000° F, so hot that even metal inside the panel can be vaporized. The heat of an arc flash can cause incurable third degree burns and can even ignite clothing from up to ten feet away.

An Arc Blast is exposure to the pressure blast released by an arcing fault. When conductive metals are vaporized by the immense heat of an arcing fault, they expand to 67,000 times their volume instantaneously. This rapid expansion results in an explosion of concussive forces that can propel molten metal and shrapnel away from the arc center.

Electrical maintenance personnel should be fully trained in arc flash safety and protection procedures before attempting any maintenance on electrical equipment.

Arc Flash Sequence

The above image shows sequential photos of one of many staged tests that helped to understand and quantify the effects of arcing faults on workers. In this test, mannequins with temperature and pressure sensors were placed in the test cell. This was a 480 volt, three-phase system with an available three-phase short-circuit current of 22,600 symmetrical rms amperes. A noncurrent limiting over current protective device was the nearest upstream protective device. An arcing fault was initiated in a combination motor controller enclosure. The arcing fault quickly escalated into a three-phase arcing fault in the enclosure. The current flowed for 6 cycles (1/10 second). The temperature recorders (with maximum temperature limit of 475 °F) on the neck and hand of the mannequin closest to arcing fault were pegged (beyond 457° F limit) (threshold for incurable burn is for skin to reach 205° F for 1/10 second).

The pressure sensor on this mannequin’s chest pegged the recorder at over 2160 lbs/ft² (the threshold for severe lung damage is 2160 lbs/ft2).

Arc Flash Safe Practices:

  • Always observe the safe working depth and clearance for turning on the disconnect switch.
  • Never face a disconnect when placing it into the open or closed position; stand off to the side of the panel and turn your body away from the disconnect.
  • Always wear PPE appropriate to the hazard present as dictated by established Flash Protection Boundaries (FPBs).
  • Be aware of all warning labels and understand them fully before attempting to service.
Typical Arc Flash Hazard Warning

NFPA 70E

An electrical incident can claim lives and cause permanently disabling injuries. Hundreds of deaths and thousands of burn injuries occur each year due to shock, electrocution, arc flash, and arc blast—and most could be prevented through compliance with NFPA 70E: Standard for Electrical Safety in the Workplace. Originally developed at OSHA's request, NFPA 70E covers the latest information about the effects of arc flash, arc blast, and direct current (DC) hazards as well as recent developments in electrical design and PPE.

110.16 FLASH PROTECTION: Switchboards, panel boards, industrial control panels, and motor control centers in other than dwelling occupancies that are likely to require examination, adjustment, servicing, or maintenance while energized, shall be field marked to warn qualified persons of potential electric arc flash hazards. The marking shall be located to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment.

FPN No. 1: NFPA 70E-2000: Electrical Safety Requirements for Employee Workplace, aids in determining severity of potential exposure, planning safe work practices, and selecting personal protective equipment.

FPN No. 2: ANSI Z535.4-1998: Product Safety Signs and Labels, provides guidelines for the design of safety signs and labels for application to products.

Mechanical Safety

The outline below provides Mechanical safety precautions:

  • Only qualified technicians familiar with the machine should perform mechanical maintenance, adjustments, or repairs.
  • If mechanical service does not require machine power, perform the appropriate Lockout / Tagout (LOTO) procedures to disconnect or dissipate energy sources.
  • Keep all moving parts of machinery and surrounding areas free of rags, dirt, and excessive oil or metal debris.

Extra caution must be exercised while working near an operating tool. Severe injury can result if personnel get in the way of moving parts while the machine is in any of its operating modes.

A machine must not be restarted until the system has been double-checked, safety guards reinstalled, safety gates and doors locked, and all personnel have been informed of impending start-up.

Pneumatic Safety

The work cell and associated equipment may feature multiple air drops and/or use components that are actuated by electrical, hydraulic, gravity, or other means. When working with the system, be aware of multiple possible sources of active power and motion. Follow all lockout procedures as posted on the equipment.

Use caution when working around air lines and components using compressed air. Principles of operating safely with pneumatic components are provided below:

  • Before locking out the air supply, secure any machine parts that could move when the air pressure is removed. Such motion can result in damage to the equipment and/or personal injury.
  • Shut off, depressurize, and lock out the system air prior to working on pneumatic devices, unless air is absolutely required to accomplish the maintenance.
  • When turning on air, ensure that all components are clear of obstructions and that any personnel in the area are aware of your intentions.
  • Some pneumatic circuits trap air. Check the pneumatic drawings for any possible trapped air circuits and relieve any trapped air before performing any maintenance on the system.
  • When repair is completed, make sure to tighten all fittings and connections before turning on the air.

Hydraulic Safety

When working with the system, be aware of multiple possible sources of active power and motion. Follow all lockout procedures as posted on the equipment. The work cell and associated equipment may feature multiple air drops and / or use components that are actuated by electrical, hydraulic, gravity, or other means.

While there are many potential hazards on a hydraulic system, careful maintenance, employee training, and working within the specifications and manufacturers recommendations for the equipment will greatly reduce the risks.

  • Only qualified technicians familiar with the machine and the hydraulic system should perform mechanical maintenance, adjustments, or repairs.
  • Always wear the proper personal protective equipment (PPE) for the work to be performed.

Hazards

The operators/ maintenance crews are subjected to hazards from high pressure liquids and large mechanical forces. Hydraulic systems store fluid under high pressure.

The maintenance personnel are exposed to following hazards:

  • Exposure to Hot Hydraulic Fluid - While hydraulic fluid is not always hot, when it is, the temperature alone can be dangerous. Should a connection or hydraulic line burst, hot fluids can be released, inflicting significant damage to human skin, eyes, and face.
  • Fluid Penetrating the Skin - Even more concerning than hot fluid is the extreme pressure that would release the oil in the event of a line break. The greater the pressure is, the greater the danger to operators. Because of the serious nature of fluid injections, it is imperative that an injected person go to the ER immediately. To help prevent fluid injection into the skin, never use a finger or any other body part to stop a fluid spray.
  • Fires Hazards - Keep fire extinguisher available when working on the hydraulic system.
  • Bruises, cuts, or abrasions from flailing hydraulic lines.
  • Injury due to sudden release of residual pressurized oil.
  • Slippage due to oily floor area. Always immediately clean up spills

Use caution when working around hydraulic lines and components.

Some basic principles of operating safely with hydraulic components:

  • Before locking out the hydraulic supply, secure any machine parts that could move when the hydraulic pressure is removed. Such motion can result in damage to the equipment, personal injury, or death.
  • When working around hydraulic equipment, it is important to have a proper blocking system in place for suspended loads.
  • Employees should never work under suspended loads unless proper blocking or a safety device is in place.
  • Shut off, depressurize, and lock out the system prior to working on the hydraulic system. Before someone begins working on a pressurized system, all precautions should be taken to ensure that the pressure is removed from the lines and that the machine is locked out so it cannot become live during maintenance.
  • For hydraulic systems with accumulators, it is forbidden to work on a hydraulic circuit without prior awareness, decompression, and depressurizing verification. Use the safety and shut-off block to release the pressure.
  • When any hydraulic line, connector, or component is replaced, they must conform to the manufacturer's specifications.
  • When turning on the hydraulic system, ensure that all components are clear of obstructions and that any personnel in the area are aware of your intentions.

With any pressurized system, there is a potential for the system to fail. Over time, without proper maintenance or replacement, the components of a hydraulic system will wear out and weaken. When these damaged places become thin, there is a much greater possibility of hydraulic oil leaks.

Contaminated fluids also run the risk of causing an entire system failure. A potential danger in this case would be an absence of pressure. In this case, it could cause hydraulic equipment to drop unexpectedly, damaging whatever is beneath its load.