July 8, 1991
MEMORANDUM FOR: DAVID GRAFTON
SOUTH BOSTON AREA OFFICE
THROUGH: CHARLES CULVER, Director
Office of Construction and Engineering
FROM: PATRICK FINN, Chief of Construction
Division Office of Construction and Engineering
SUBJECT: PROTECTION OF FLEXIBLE CORDS WHEN HUNG IN TUNNEL SHAFTS
In response to your telephone conversation with Bill Burke of this office
concerning the use of type "SO" flexible cords in tunnel shafts, OSHA
standard 29 CFR 1926.405(a)(2)(ii)(I) states "Flexible cords and cables shall
be protected from damage". Type "SO" flexible cords must be protected from
physical damage when mounted on the inside of a tunnel shaft. The insulation
on type "SO" flexible cords is not suitable protection against physical
damage when the flexible cord is subject to being struck by heavy objects.
The raising and lowering of the muck bucket through the shaft opening could
create this condition. Type "SO" Flexible Cord should be located outside of
the shaft, concealed behind "H" piles, or physically protected in another
fashion to limit the possibility of damage to the cord's insulation and
subsequent energizing of other conductive material. Although "SO" flexible
cords are suitable for hard and extra hard usage, these cords were not
manufactured to withstand this type of abuse.
Regarding your concern about running type "SO" flexible cord with utilities
in tunnel work, this is permitted under 29 CFR 1926.800(s)(1) if adequate
mechanical protection is provided to assure the integrity of the cord's
insulation and in such a fashion that any inadvertent damage to the cord's
insulation will not result in energizing of other utility systems.
If you have any further questions concerning the use of type "SO" flexible
cords in tunnel shafts, you may contact Bill Burke at FTS 523-1440.