c) Common Pump Discharge Mains. Size common pump discharge mains
to serve the sum of their capacities. Use the Hydraulic Institute (HI) Pipe
Friction Manual for steel pump discharge pipe sizing of new clean steel pipe,
6 feet per second (fps) (1.83 m/s) maximum velocity, and a correction factor
of 1.85 to provide for increased pressure drops when the pipe becomes dirty
and rough with age. Friction plus static heads shall not exceed the pump
characteristics of standard pump and receiver units.
High Temperature Water (HTW) Piping.
High temperature water piping
is as follows:
a) Sizing Piping. Use pipe friction charts in ASHRAE 1985
Handbook Fundamentals. These charts are based on the rational flow formula
using clean pipe. A reasonable average velocity is approximately 5 fps
(1.53 m/s). The minimum allowable velocity is 2 fps (0.61 m/s).
b) Venting and Draining. For methods of venting high points of
and Dehumidifying Systems. Piping must have drainage means at low points.
Chilled Water Piping. Use the standards of the Hydraulic Institute
Pipe Friction Manual for sizing new clean pipe, unless water is renewed
annually, in which case a correction factor of 1.41 for pressure drop is also
to be used. For recommended velocities, refer to DM-3.03.
Condenser Water Piping. Use the standards of the Hydraulic
Institute Pipe Friction Manual for pipe sizing, multiplying the pressure drop
by a factor of 1.85 to correct for the increase of pipe roughness with age.
For recommended velocities, refer to DM-3.03. No correction faction is
required for RTRP pipe.
Natural Gas Piping. Apply criteria in DM-3.01, Plumbing Systems,
for sizing pipe inside buildings. Use Figure 8 for low volume flow rates and
Figure 9 for high volume flow rates in sizing distribution piping. Using
these figures will simplify design of piping by indicating required diameter,
maximum rate of flow, permissible pressure drop, initial pressure, or final
pressure when the rest of these values are known. These charts are based on
the Weymouth formula for rate of flow in cubic feet of gas per hour. (The
chart is based upon the following conditions: gas at 60 degrees F (15.5
degrees C) and specific gravity of 0.60, with air = 1.0.). Exterior
distribution piping usually stops 5 feet (1.53 m) outside of buildings.
Compressed Air. For criteria on distribution piping, refer to DM-
3.5, Compressed Air and Vacuum Systems.
Piping Specifications and Codes.
Piping specifications and codes
are as follows: