Construction

Obstruction Clearances Behind Vertical Ladders

Oct. 13, 2014

Be mindful where you run conduit and supports on vessel ladders

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Not all requirements needed to make a safe installation are found in the National Electrical Code (NEC). Many rules for safety in the United States are found in Occupational Safety and Health Administration (OSHA) regulations. One such rule that is encountered on nearly every industrial electrical installation is maintaining adequate space behind ladder rungs when running conduit up a vessel, tank, or tower.

It’s common practice to use a vertical ladder on a vessel or tank to support lighting and instrument conduit, but there are some important rules to follow when doing so. First, the ladder has to be substantial enough to accept the weight of the conduit and support hardware. Second, adequate toe space must be maintained behind the ladder so personnel will not step on the conduit or supports or catch their toes on these components while climbing the ladder.

In the U.S., OSHA CFR 29, Part 1910, Subpart D, Section 1910.27(c)(4) addresses toe clearance behind ladder rungs. As a general rule, 7 in. of free and clear space must be left between the backside of the ladder and any conduit or other obstruction such as conduit support materials. Where it is impossible to maintain 7 in. of clear space, the Figure (reprinted from OSHA.gov) illustrates an acceptable variance.

To access all of the OSHA regulations, visit https://www.osha.gov/law-regs.html.

About the Author

Eddie Guidry | Senior Fellow

Eddie Guidry is a senior fellow with Fluor Enterprises, Inc., Sugar Land, Texas. He is highly skilled in electrical and control systems for industrial construction, design, and engineering (both domestic and abroad). The majority of Eddie’s 38 years of experience includes upstream and downstream portions of petrochemical plants and refineries. He is also heavily experienced in water and wastewater treatment facilities. Eddie is very active in the development of U.S. national (ANSI) and international codes and standards, and has been a principal member of the National Fire Protection Association (NFPA) National Electrical Code (NEC) committee since 1999 and NFPA’s National Advisory Committee on Electrical Safety Research since 2008. Eddie, who has also developed and conducted many electrical courses and seminars over the years, currently holds the corporate Master Electrician license for Fluor Corporation in the State of Texas and is also an ICC/IAEI certified electrical inspector.