Fact  Fact Sheet

HOT WORK  ON  HOLLOW  STRUCTURES

Hot work on hollow structures located on a vessel or on a dock can
present a hazard

to both the worker and vessel/facility on which the hot work is being
performed.  OSHA defines hot work to mean riveting, welding, flame
cutting, or other fire or spark producing operation (See 29 CFR
1917.152(a)).

Hollow structures can be drums, inaccessible voids, sealed bulkheads,
hatches, coamings, skegs, bilge keels, rudders, fairwaters, pipe
stanchions, masts, booms, lamp posts, crane pedestals, crane portal
beams, doubler-plates, railings, rub rails, mooring bitts, bollards,
vents, container frames, box girders, cargo lids, sponsons, pontoons,
floats, buoys and many others. Hollow structures should not be confused
with tanks or confined and enclosed spaces.  Hot work in these spaces is
addressed in 29 CFR 1917.152 (b) and 1917.152 (f).

Known hazards of hollow enclosed structures:

May contain flammable or toxic gases, liquids, or residue;

Commonly filled with combustible preservatives;

Often contaminated with saltwater, fuel oils, solvents, degreasers, or
cleaning chemicals.

May contain high pressure or vacuum effects due to fluctuation from
temperature. 

Recommended control measures prior to hot work on hollow enclosed
structures:

Always wear proper PPE, clothing, gloves, and eye protection during
drilling, cutting and hot work operations (See 29 CFR 1917 Subpart E and
the applicable regulations for the specific type of work being
performed).

Check and make sure that the structure will not radiate heat to the
other side (e.g. sealed insulation in a sealed bulkhead).

Open all sampling ports to drain residual products and have a Qualified
Individual test for the presence of flammable or combustible gases or
liquids.

Hollow structures that have contained flammable or combustible
substances shall either be filled with water or cleaned (e.g.
pressure-wash, degreasing or steaming) and shall be ventilated (29 CFR
1917.152(c)(8)(i)).  Another option may be to purge with an inert gas. 

Before heat is applied to a hollow structure, an opening to release
built-up pressure during heat application shall be provided (29 CFR
1917(c)(8)(ii)).

When a sampling port is not available, drill a small hole into the
structure to facilitate air sampling and testing.  Use new bits and
blades, and always lubricate the drilling bits and metal blades with
cutting oil or soapy water to minimize the generation of heat and
sparks.

If any flammable gases, liquids or preservatives are detected and gas
reading is above 10% LEL, consult a Qualified Individual.  Carefully
drill a second hole further away to ventilate by blowing compressed air
through the structure.  After the structure is ventilated, retest again
to ascertain 0% LEL is sustained prior to any hot work.

