One grade can be used through a considerable range
of temperature. This coating endured a 2,000-mile shipment successfully.
Each piece was carefully inspected along the trench, and any break in
the coating was thoroughly painted with hot asphalt. Enough of the
latter came in barrels, with the pipe, from the factory.
The first 37 miles of this pipe has been in service for two years.
Recent inspections show the coating to be in excellent condition and the
steel underneath to be bright and clean. In some cases, where the
initial pressure and leaking between the staves of the dry pipe were
great, the escaping air and water lifted the coating into bubbles. At
some points where this lifting was great enough to rupture the asphalt,
and the soil is heavily charged with alkali, some corrosion has begun.
The integrity and impermeability of this asphalt coat are quite as vital
as constant saturation. This coating protects the entire pipe from
exterior contact with destructive agencies. With such effective exterior
protection, a constantly full pipe is not so imperative. In the exterior
protection of the wood, this coated pipe has quite an advantage over
continuous stave pipe.
Each piece of pipe goes directly from the winder to the asphalt rolls,
then to an adjacent saw-dust table, then back to the rolls, then to the
table again, and then to the dry finishing rolls at the opposite end of
the table.
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