APPROXIMATE
EFFICIENCIES OF VARIOUS
COVERINGS REFERRED TO
BARE PIPES
+--------------------------------+
|+-------------------+----------+|
|| Covering |Efficiency||
|+-------------------+----------+|
||Asbestocel | 76.8 ||
||Gast's Air Cell | 74.4 ||
||Asbesto Sponge Felt| 85.0 ||
||Magnesia | 83.5 ||
||Asbestos Navy Brand| 82.0 ||
||Asbesto Sponge Hair| 86.0 ||
||Asbestos Fire Felt | 73.5 ||
|+-------------------+----------+|
+--------------------------------+
Based on one-inch covering.
The following suggestions may be of service:
Exposed radiating surfaces of all pipes, all high pressure steam
flanges, valve bodies and fittings, heaters and separators, should be
covered with non-conducting material wherever such covering will improve
plant economy. All main steam lines, engine and boiler branches, should
be covered with 2 inches of 85 per cent carbonate of magnesia or the
equivalent. Other lines may be covered with one inch of the same
material. All covering should be sectional in form and large surfaces
should be covered with blocks, except where such material would be
difficult to install, in which case plastic material should be used. In
the case of flanges the covering should be tapered back from the flange
in order that the bolts may be removed.
All surfaces should be painted before the covering is applied. Canvas is
ordinarily placed over the covering, held in place by wrought-iron or
brass bands.
Expansion and Support of Pipe--It is highly important that the piping be
so run that there will be no undue strains through the action of
expansion. Certain points are usually securely anchored and the
expansion of the piping at other points taken care of by providing
supports along which the piping will slide or by means of flexible
hangers. Where pipe is supported or anchored, it should be from the
building structure and not from boilers or prime movers. Where supports
are furnished, they should in general be of any of the numerous sliding
supports that are available. Expansion is taken care of by such a method
of support and by the providing of large radius bends where necessary.
It was formerly believed that piping would actually expand under steam
temperatures about one-half the theoretical amount due to the fact that
the exterior of the pipe would not reach the full temperature of the
steam contained. It would appear, however from recent experiments that
such actual expansion will in the case of well-covered pipe be very
nearly the theoretical amount. In one case noted, a steam header 293
feet long when heated under a working pressure of 190 pounds, the steam
superheated approximately 125 degrees, expanded 8¾ inches; the
theoretical amount of expansion under the conditions would be
approximately 9-35/64 inches.
[Illustration: Bankers Trust Building, New York City, Operation 900
Horse Power of Babcock & Wilcox Boilers]