TM 9-4940-444-14 & P
5. Fan Inlet Size:
The size of inlet to the airflow. producing equipment should be approximately the same inside diameter as the
inside diameter of the header pipe. However, the inlet to the air flow producing equipment shall as a general rule
never be less than the header pipe.
E. Supports for Piping Systems.
1. Horizontal Runs:
All headers and horizontal runs of piping shell be supported on not over 22 ft centers and fastened securely to
some substantial portion of the building structure or other permanent support. The supports should be of V
construction and made from band steel not less in size than the band steel surrounding the piping. The size of the
band steel clamped to the piping shall be as follows:
Diameter or greatest Dimension
Size of Connecting
of Rectangular Pipe
Bolts in Pipe Band
Up to 12" inclusive
1 1/4" x 1/8"
Over 12" to 20" inclusive
1 1/2" x 3/16"
Over 20" to
2" x 3/16"
Each horizontal run of branch pipe extending more than three ft horizontally from the header pipe shall be
supported by means of 1" x 3/16" band steel support, preferably of "V" construction and bolted to a 1" x 3/16" band
steel around the branch pipe.
2. Branch pipe:
Branch pipe subject to vibration and movement on account of the equipment being exhausted shall be supported
laterally by band steel or rods to prevent displacement.