Confined Spaces: Aircraft fuel tank work poses unusual risks

Confined Spaces Aircraft fuel tank work poses unusual risks By David D. Wagner and Roger J. Wells October 2001 David Wagner is responsible for all phases of product management for Industrial Scientific Corporation’s portable and...

Confined Spaces

Aircraft fuel tank work poses unusual risks

By David D. Wagner and Roger J. Wells

October 2001

It’s a space only experienced spelunkers could enjoy — dark, cramped and fraught with danger. But while the payoff for cave crawling enthusiasts is visual splendor, for aircraft maintenance technicians, it’s what they can’t see within an aircraft fuel tank that’s most deadly: potentially hazardous atmospheric conditions. For technicians, entry into aircraft fuel tanks is a unique and difficult form of work. It’s required during major maintenance and to rectify emergent problems, such as fuel leaks, sensor replacement, fuel boost pump failure, wiring trouble or other problems, or to inspect engine struts and structural damage to wings.
ImageBecause of its constricted environs, working within a fuel tank presents exceptional challenges. Within a DC-9, for example, the largest fuel cell is beneath the fuselage. It measures about 2-1/2 ft. high, 4-1/2 ft. wide and 4-1/2 ft. long. Because an average size man cannot sit upright without bumping his head, he must cross his legs in order to enter. Once inside, the worker may navigate through four separate compartments, carefully maneuvering through baffle holes to reach those compartments. He also must be mindful of his movements, as he must follow the same motions to exit.
Wing tanks are even smaller and require the ability of a contortionist to enter, legs first, with a partner supporting the entrant’s trunk. Many tank spaces become progressively smaller until a technician is forced to lie on his stomach or back, with just inches of headroom.
Confined Space Rules of Entry
According to statistics compiled by California State University, Fullerton, about 2.1 million workers enter confined spaces every year. Thirty-nine of those workers never make it out alive. Another 6,000 workers are injured. Most confined space fatalities and injuries occur because employees are unaware of the inherent dangers, and are not properly equipped to handle hazardous situations.
The Occupational Health and Safety Administration (OSHA) has established guidelines for operating within a confined space. According to OSHA’s rule, 29 CFR Part 1910.146, a confined space is "an area large enough to bodily enter and perform work, has limited means of entry or exit and is not designed for continuous human occupancy." Additionally, OSHA requires that permits be obtained before entering certain types of spaces. A permit-required confined space has one or more of the following characteristics:
• Contains, or has a known potential to contain, a hazardous atmosphere.
• Contains material with potential for engulfment.
• Has an internal configuration such that an entrant could be trapped or asphyxiated in inwardly converging walls, or a floor that slopes and tapers to smaller sections.
• Contains any other recognized serious safety or health hazard.
Confined space entry training is an important factor in OSHA regulations and applies to all employees — including supervisors — who are required to enter a space with restricted entry or exit, and which has the potential of accumulating dangerous gases or reduced oxygen levels. OSHA regulation 1910.146 requires that all employees who enter restricted spaces receive training and information on the following topics:
• Expected duties of the attendant, authorized entrant and entry supervisor
• Contents, location and availability of the organization’s
confined space entry plan
• Atmospheric conditions
• Entry/exit access
• Engulfment conditions
• Specific confined space entry procedures
• Operating and rescue procedures
• Confined spaces entry permit forms and authorization
• Test equipment procedure and calibration/maintenance
Employees must be trained prior to their initial assignments into confined spaces, before a change in assigned duties and before changes in operations or when deviations occur in procedures. Records of confined space locations and testing results should be maintained for five years as part of the overall program. Canceled permits must be maintained for at least one year as part of the standard’s requirement for an ongoing review process.
While OSHA regulations clearly outline training required by law, keep in mind that these are minimum requirements. Always be aware of confined spaces to be entered and the operations going on in and around those spaces.
For more information, and for a sample confined spaces program, visit the OSHA confined spaces section at its Web site:
Or, refer to the following publications:
Permit-Required Confined Spaces, Final Rule; OSHA, 29 CFR Part 1910.146; Federal Register 63: 66018-66036, December 1, 1998.
A Guide to Safety in Confined Spaces (NIOSH Publication Number 87-113), July 1987.
Safety Requirements for Confined Spaces, American National Standards Institute, Z117.1-1989.

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