Grounding Overhead Cranes: What do the standards Require?
As we enter into 2016, over 10 years have passed since the NEC code added the requirement for overhead cranes to have grounded power bar or festooning. Unfortunately, Hoosier Crane's service and sales teams continue to see customers put their employees at risk by not upgrading their older cranes to be in compliance with the current safety regulations.
Back in 2005, the revised edition of ANSI/NFPA 70 National Electric Code grounding requirements changed. Article 610, Cranes and Hoists, Section 610.61 Grounding clearly states, “The trolley frame and bridge frame shall not be considered electrically grounded through the bridge and trolley wheels and its respective tracks. A separate bonding conductor shall be provided.” The terms “ shall and shall not ” make the fourth conductor for ground mandatory. It does not matter if the electrification is festoon cable or insulated conductor bar.
The upgrading of power bar systems to comply with these requirements often does not require the complete replacement of a power bar system. A fourth rail of grounded power bar and new collector shoes are typically all that needs to be added to most systems. The grounded power bar must be green as is noted in the December 5th, 2001 OSHA Letter of interpretation.
An OSHA letter of interpretation explains and clarifies requirements set forth in statutes, standards and regulations as they apply to a specific situation. In this letter regarding the grounding of overhead cranes the third question clarified states:
Question 3: In crane applications, can a separate grounded conductor (neutral) or an equipment grounding conductor be the same color as the other conductors (e.g., can all conductors including the grounded and equipment grounding conductors be red)?
Response: No. As previously stated, 29 CFR 1910.179(g)(1)(i) requires crane installations to comply with 29 CFR 1910. Subpart S. In Subpart S, OSHA has two separate provisions, 29 CFR 1910.304(a)(1)(i) and (a)(ii), which requires that a grounded conductor and an equipment grounding conductor, respectively, must each be identifiable and distinguishable from all other conductors. In general, as noted in the NEC at 200.6 and 250.119, grounded conductors are white or natural gray in color or markings, and equipment grounding conductors are bare (uninsulated) or are green in color or marking.
Some crane owners will argue that they do not need to upgrade their crane because it was produced prior to the introduction of the overhead crane grounding standards. Interpreting overhead crane standards or OSHA standards in general can be confusing. Part of this confusion comes from something called Incorporation by Reference.
OSHA 1910.6 Incorporation By Reference
The standards of agencies of the U.S. Government, and organizations which are not agencies of the U.S. Government which are incorporated by reference in this part, have the same force and effect as other standards in this part. Only the mandatory provisions (i.e., provisions containing the word "shall" or other mandatory language) of standards incorporated by reference are adopted as standards under the Occupational Safety and Health Act.
ANSI/ASME B30.2.0-67 Safety Code for Overhead and Gantry Cranes, IBR approved for §§1910.179(b)(2); 1910.261(a)(3)(xii), (c)(2)(v), and (c)(8)(i) and (iv).
What this means is that the OSHA code for Overhead Cranes 1910.179 incorporates the ASME ( American Society of Mechanical Engineers) standard B30.2 into their requirements. In turn the ASME B30.2 standards incorporates Article 610 of ANSI/NFPA No. 70, National Electrical Code.
ASME B30.2 SECTION 2-1.13: ELECTRICAL EQUIPMENT
(a) Wiring and equipment shall comply with Article 610 of ANSI/NFPA No. 70, National Electrical Code.
NEC Article 610
All exposed non–current-carrying metal parts of cranes, monorail hoists, hoists, and accessories, including pendant controls, shall be bonded either by mechanical connections or bonding jumpers, where applicable, so that the entire crane or hoist is a ground-fault current path as required or permitted by Article 250, Parts V and VII.
Moving parts, other than removable accessories, or attachments that have metal-to-metal bearing surfaces, shall be considered to be electrically bonded to each other through bearing surfaces for grounding purposes. The trolley frame and bridge frame shall not be considered as electrically grounded through the bridge and trolley wheels and its respective tracks. A separate bonding conductor shall be provided.
As you can see above, this does apply to all forms of electrified lifting equipment. You are required to ground overhead cranes, monorail hoists, hoists and their accessories. Hoosier Crane designs and builds all our new equipment to comply with the above standards. We also have an experienced sales and service team that can help you safely ground overhead cranes and hoists. If you need help identifying or finding parts to add grounding to your existing system, our parts team will be happy to help. We can also offer full installation of power bar systems, along with other crane modernization services.