Underground Heat Distribution Systems
How To Protect A System
Specifications are the only way a designing mechanical engineer can be assured the final project
will have met his required standards and be of the
quality the owner bought.
Three major elements make up an underground
heat distribution system: an inner pipe to convey
steam, high temperature hot water, chilled water,
condensate, etc., (type and size depending upon
project requirements); the insulating of the inner
pipe to minimize heat loss; and the outer casing to
protect the insulation and inner pipe.
The outer casing has to be specified in such a way
that it will provide positive protection against moisture entrance and accumulation. Saturated insula-
Testing welded joints by applying a soap solution with the casing
under 25 p.s.j.g.
tion, of course, equals low efficiency. Moisture, pres-
ent constantly in buried pipe, accelerates corrosive
action which is amplified in acidic and electrolytic
To be positively leak tight the casing must be
tested air tight. The engineer should specify a 25
p.s.i.g. air test on the casting for two consecutive
hours without a drop in pressure.
In order to prevent accumulation of moisture, the
casing should be specified with a smooth interior.
Impact from above and earth back fill weight is
a problem the engineer resolves by specifying a 14
gauge steel casing with a spiral lockseam for added
Now knowing that his casing is impact and water
proof he protects the casing by specifying an anticorrosive compound that will withstand a 15,000
volt spark test and have a permeability of .05 perms
With the casing and joints sealed leak tight and
protected against electrolysis and sub-soil acids he
needs only one bit of ...
Any system should be selected with .this thought
"That some moisture will find a way into the system such as a rain storm prior to installation."
Therefore, to protect the system against any moisture that may get inside prior to final assembly, he
specifies "that an annular uninterrupted air space
must run the entire length of the system." With this
feature and openings at ends of casing for draining
and venting, he can force ventilate the system and
dry it out. By necessity, the insulation must, of
course, have an insoluble binder and be capable of
returning to its original insulating efficiency when
dry, even after a thorough saturation.
For a free 24 page catalog with facts and figures
for designing and specifying underground heat distribution systems, write: E. B. Kaiser Co., 2114
W. Lake Ave., P. O. Box 47, Glenview, Illinois.
rr• •• for highest quality"