condensate level in the trap body. The bucket
valve is connected to the bucket in such a way that
the valve closes as the bucket rises. As condensate
continues to flow into the trap body, the valve
remains closed until the bucket is full. When the
bucket is full, it sinks and thus opens the valve.
The valve remains open until enough condensate
has blown out to allow the bucket to float, thus
closing the valve.
Figure 6-18 shows a ball-float steam trap. This
trap works much in the same way as the bucket
trap. Condensate and steam enter the body of the
trap, and the condensate collects at the bottom.
As the condensate level rises, the ball float rises
until it is raised enough to open the outlet valve
of the trap. When the outlet valve opens, the
condensate flows out of the trap into the drain
system, and the float level drops, shutting off the
valve until the condensate level rises again.
Figure 6-19.--Bimetallic steam trap.
Bimetallic Steam Traps
fastened to the top of the stem of the ball-type
Bimetallic steam traps of the type shown in
Line pressure acting on the check valve keeps
figure 6-19 are used in many ships to drain
the valve open. When steam enters the trap body,
condensate from main steam lines, auxiliary steam
the bimetallic element expands unequally because
lines, and other steam components. The main
of the different response to the temperature of
working parts of this steam trap are a segmented
the two metals; the bimetallic element deflects up-
bimetallic element and a ball-type check valve.
ward at its free end, thus moving the valve stem
The bimetallic element has several bimetallic
upward and closing the valve. As the steam cools
strips fastened together in a segmented fashion,
and condenses, the bimetallic element moves
as shown in figure 6-19. One end of the bimetallic
downward, toward the horizontal position, thus
element is fastened rigidly to a part of the valve
opening the valve and allowing some condensate
body; the other end, which is free to move, is
to flow out through the valve. As the flow of
condensate begins, an unbalance of line pressure
across the valve is created; since the line pressure
is greater on the upper side of the ball of the check
valve, the valve now opens wide and allows a full
capacity flow of condensate.
Orifice Steam Traps
Aboard ship, continuous-flow steam traps of
the orifice type are used in systems or services in
which condensate forms at a fairly steady rate.
Figure 6-20 shows one orifice-type steam trap.
Several variations of the orifice-type steam
trap exist, but all have one thing in common-
they have no moving parts. One or more restricted
passageways or orifices allow condensate to trickle
through but do not allow steam to flow through.
Besides orifices, some orifice-type steam traps
Figure 6-18.--Hall-float steam trap.