Standard Interpretations - Table of Contents|
| Standard Number:||1926.803; 1926.803(e)(5); 1926.803(m)(3)|
July 23, 2010
Bulkheads used to contain compressed air shall be tested, where practicable, to prove their ability to resist the highest air pressure which may be expected to be used.
As described in your letter of February 9, 2010, modern tunnel-boring machines (TBMs) can pressurize the face area up to 261 psig. To access this area for repairs or inspection, workers must enter the area through a decompression chamber. When they finish their work, they must reenter the decompression chamber. Chamber operators then reduce the atmospheric pressure on the workers in a controlled manner, following an prescribed decompression schedule. Current §1926.803 does not address these working conditions.1 However, the general-duty clause specified by Section 5(a)(1) of the Occupational Safety and Health Act of 1970 (29 U.S.C. 654) requires:
Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees.
ANSI developed national consensus standard A10.16-2009 ("Safety Requirements for Tunnels, Shafts, and Caissons") to address the recognized hazards associated with using improperly designed and fabricated chambers to decompress workers. Section 12.3.2 of this standard states:
Except where a lock in a tunnel is constructed by bulk heading a length of the tunnel, all air locks shall be designed and fabricated in accordance with the provisions of Sections VIII and IX of the ASME Boiler and Pressure Vessel Code.2
A footnote to the 2010 ASME Boiler & Pressure Vessel Code, Section VIII, Division 1, Paragraph U-1(c)(2)(j) provides the specific requirements for pressure vessels for human occupancy, as follows:
Requirements for pressure vessels for human occupancy are covered by ASME PVHO-1.
OSHA recognizes the ASME PVHO-1 standard as specifying the construction industry's usual and customary practices for preventing death and serious injury associated with worker exposure to the recognized hazards of decompression from pressurized workplaces; therefore, OSHA would enforce the standard under the general-duty clause. Accordingly, decompression chambers associated with pressurized TBMs and used for decompressing workers must meet the requirements of ASME PVHO-1, or provide an equivalent means of worker protection.
1 for example, §1926.803(e)(5) states, "No employee shall be subjected to pressure exceeding 50 pounds per square inch except in emergency." [back to text]
2 The term "air locks" includes decompression chambers. [back to text]
|Standard Interpretations - Table of Contents|