MIL-HDBK-1003/8A
Change 2, 30 December 1991
e) Pumped Water Pipe. Pitch pumped water pipes (condensate, HTW,
MTW, LTW, CHW, or condenser water) up or down in direction of flow at a
minimum slope of 2-1/2 inches (64 mm) per 100-foot (30.5 m) length. Place
drain valves at all low points and vents at high points.
4.2.6.2
Drips and Vents.
Provide drips and vents as follows:
a) Drip Legs. Provide drip legs to collect condensate from steam
piping and compressed air piping for removal by automatic moisture traps, or
by manual drain valves for compressed air piping when practicable. Locate
drip legs at low points, at the bottom of all risers, and at intervals of
approximately 200 to 300 feet (61 to 91.5 m) for horizontally pitched pipe
where a trap is accessible, and not over 500 feet (152.5 m) for buried
underground pipe systems. On gas piping, drip legs are not usually required
where dry gas is provided. Where there is moisture in the gas, provide drip
legs and sediment traps in accordance with NFPA 54. Automatic traps are not
utilized.
b) Water Piping. Vent piping, especially high-temperature water
piping, at distribution piping high points.
c) Fuel Gas Piping. Provide capped dirt traps in vertical risers
upstream of gas-burning devices.
4.2.6.3
Condensate Systems.
Condensate systems are as follows:
a) Furnish a complete system of drip traps and piping to drain all
steam piping of condensate from drip legs. Ensure drip piping to traps is the
same weight and material as the drained piping.
b) Preferably, run a condensate line from a trap separately to a
gravity condensate return main or to a nearby flash tank. (Refer to ASHRAE
Handbooks - Systems and Applications for flash tank details and specific trap
applications. Additionally, refer to Naval Civil Engineering Laboratory
(NCEL) UG-0005, Steam Trap Users Guide.) However, a trap may be discharged
through a check valve into the pumped condensate line if pressure in the trap
discharge line exceeds the back pressure in the pumped condensate line during
standby time of an intermittently operated pump. If the pumped condensate
line is RTRP pipe, install a condensate cooling device, similar to that shown
in Figure 10, to limit temperature of the condensate entering the line to less
than 250 degrees F (121 degrees C).
c) Select traps using a safety load factor no greater than 2. The
condensate load should be indicated on design drawings and may be determined
for aboveground lines by using Table 13. The condensate load for underground
distribution lines is determined from maximum heat loss as indicated by the
design. With the tight safety load factor for sizing traps, an alternate
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