Article by Eddie Guidry | Originally published at on September 29, 2017.

Minimum required lighting levels aren’t the only important criteria to consider.

When designing lighting layouts in a petrochemical plant, there are  many criteria the designer must look at. Among the basic safety  considerations are:

  1. What are the minimum required footcandle levels for each type of  area? Is the intent to provide enough lighting to safely work? Or, is  the minimum lighting level just intended to provide some visibility to  avoid tripping hazards?
  2. Is illumination required for an emergency means of egress for personnel?
  3. How will the electrician “tie off” while installing and servicing the luminaire?

The first consideration is a relatively simple one to solve. For  clients who may not have specific standards for illuminances, the  designer can use API RP 540, “Electrical Installations in Petroleum  Processing Plants.” This document is published by the American Petroleum  Institute. Among all the information for designing industrial  electrical systems in general, it also provides charts for common  illuminances in plants.

The second item on the list above requires input from the client, who  also typically serves as the Authority Having Jurisdiction (AHJ).  Depending on the location of the platform, deck, or operating areas at  grade level, there may be instances where during normal operating  conditions personnel will be present. In these cases, if the normal  lighting were to fail, there must be emergency lighting available to  assist the workers to see the means of egress. Vertical ladders up the  side of process columns or plant stairways may also fall into this  category.

Number three on the list requires some ingenuity and thought.  Installation and servicing of lighting for grade level may require the  use of a ladder or scaffolding. The electrician must tie off when  working over certain heights. These heights are dictated by OSHA 29 CFR  1926; however, the plant may have more stringent requirements. When the  luminaires are installed on elevated platforms and walkways,  consideration should be given to outfitting the stanchion mounted  luminaires with break-over type conduit stanchions or other variations  of such so that the luminaire can be lowered and accessed without having  to climb a ladder and then subsequently not having anywhere to tie off.  Likewise, for surface-mounted luminaires or column-mounted luminaires  at elevated heights, they should ideally be placed near a structural  member so that 100% tie off can be achieved while installing or  performing maintenance.

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