Piping Design Factors. Consider the choice between
steel and copper piping based on estimated initial cost and life
cycle cost of each installation. For a safe pressure of piping
and fittings corresponding to working pressure and temperature,
refer to ASME B31.1, Power Piping. See Table 8.
Copper piping cannot be corroded by fluorinated
hydrocarbon refrigerants, even when this liquid is mixed with
moisture. Copper is entirely free of scaling effects. However,
steel pipe and fittings are less expensive than copper piping for
non-refrigerant systems with larger pipe sizes.
Pipe Friction Loss. For pipe friction loss, see
Figures 11 through 13 for water flow and Figures 18 through 21
for steam flow.
System Pressure Loss. Piping system pressure loss
calculations shall include the following considerations:
Pipe friction based on 10-year-old pipe;
b) Pressure loss of valves, fittings, and other
Equipment pressure loss;
Static lift in open systems.
Piping Layouts. Piping layouts shall provide for flow
control, subsystem isolation, pipe expansion, elimination of
water hammer, air removal, drainage, and cathodic protection.
Isolation valves are required in piping systems. To control
corrosion, provide cathodic protection as required due to
presence of dissimilar metals, stray currents, or soil
composition (if using direct burial pipe), as described in
MIL-HDBK-1004/10, Electrical Engineering Cathodic Protection.
Expansion. Preferred methods of accommodating thermal
expansion are by pipe geometry, e.g., offsets and changes in
direction, and pipe loops. Offsets that would cause torsion
should be avoided with screwed fittings to prevent the potential
for leaking joints. Use expansion joints only when space does
not permit proper geometry or installation of pipe loops. For
expansion as a function of temperature for steel and copper pipe,
and general expansion criteria, see Table 12 of MIL-HDBK-1003/8A,