|Advantages of the inverted bucket steam
The inverted bucket steam trap can be made to withstand
Like a float-thermostatic steam trap, it has a good tolerance
to waterhammer conditions.
Can be used on superheated steam lines with the addition
of a check valve on the inlet.
Failure mode is usually open, so it’s safer on those
applications that require this feature, for example turbine
Disadvantages of the inverted bucket steam trap
The small size of the hole in the top of the bucket means
that this type of trap can only discharge air very slowly.
The hole cannot be enlarged, as steam would pass through
too quickly during normal operation.
There should always be enough water in the trap body to
act as a seal around the lip of the bucket. If the trap
loses this water seal, steam can be wasted through the outlet
valve. This can often happen on applications where there
is a sudden drop in steam pressure, causing some of the
condensate in the trap body to 'flash' into steam. The bucket
loses its buoyancy and sinks, allowing live steam to pass
through the trap orifice. Only if sufficient condensate
reaches the trap will the water seal form again, and prevent
If an inverted bucket trap is used on an application where
pressure fluctuation of the plant can be expected, a check
valve should be fitted on the inlet line in front of the
trap. Steam and water are free to flow in the direction
indicated, while reverse flow is impossible as the check
valve would be forced onto its seat.
The higher temperature of superheated steam is likely to
cause an inverted bucket trap to lose its water seal. A
check valve in front of the trap should be regarded as essential
under such conditions. Some inverted bucket traps are manufactured
with an integral check valve as standard.
The inverted bucket trap is likely to suffer damage from
freezing if installed in an exposed position with sub-zero
ambient conditions. As with other types of mechanical traps,
suitable lagging can overcome this problem if conditions
are not too severe. If ambient conditions well below zero
are to be expected, then it may be prudent to consider a
more robust type of trap to do the job. In the case of mains
drainage, a thermodynamic trap would be the first choice.