12
STEAM INJECTION INSTALLATION, OPERATION, AND MAINTENANCE MANUAL
OVERVIEW
Inverted bucket steam trap
Check valve (swing type)
5' (1.5 m)
maximum
Elevated condensate return main
1/2" pipe thread (DN15)
Condensate return flow
Pitch 1/2" per 10' (0.4%)
DC-1064
In certain installations, it is not possible to drain the humidifier steam trap by gravity. The condensate must be lifted.
Generally, lifting condensate is not recommended, but it can be done successfully by observing the following rules:
•
Steam pressure
. Theoretically, one pound (6.9 kPa) of steam pressure will lift condensate about 2' (0.6 m). But
in practice, because of pipe friction, pressure drop through a steam trap, and back pressure in a return line, we
recommend maximum lift of 6" per pound (0.2 m per 6.9 kPa) of steam pressure at the trap. For example, a
steam pressure of 5 psi (34.5 kPa) will provide a maximum lift of 2.5' (0.76 m). Lifting condensate more than 5'
(1.5 m) should not be attempted.
•
Steam trap
. When lifting condensate, use an inverted bucket steam trap. Float and thermostatic (F&T) traps are
more prone to water hammer damage with a flooded trap, which may occur when lifting condensate.
•
Pipe size
. The size of the vertical portion of the piping should be 1/2" pipe thread (DN15).
•
Check valve
(swing type). A low-pressure differential swing check valve should be installed adjacent to the trap.
This will prevent backflow of condensate into the humidifier during periods of little or no steam pressure. Failure
to do so could result in accumulated backflow discharging from the humidifier when steam pressure is resumed.
Spring-type check valves are not recommended, as they can reduce pressure available for condensate lifts.
Condensate lifting recommendations:
1. Condensate can be lifted for all steam jacket piping.
2. Condensate could be lifted for connection to separator, but performance could vary based on variable pressure at
the separator.
3. Condensate cannot be lifted for connection on headers for Multiple-tube humidifiers (including Maxi-bank option).
Pressurized steam piping guidelines
mc_051011_1530
FIGURE 12-1: ELEVATING CONDENSATE FROM A STEAM INJECTION HUMIDIFIER
