This appliance, which is also called an interceptor or catch water, is
generally a T shaped pipe.
[Illustration: Fig. 90.]
This, although not a boiler fixture or fitting, is intimately connected
with them: it is an appliance fast coming into use both for land and
marine engines, to guard against the danger to steam engine cylinders
arising from “the priming” of the boilers when the steam is used at a
high pressure with high speed of the piston.
The separator is usually placed in the engine room, so as to be well
in sight. The steam is led down the pipe round a diaphragm plate and
then up again to the engine steam pipe. By this means any priming or
particles of water that may be brought from the boiler with the steam
will fall to the bottom of the interceptor or catch water, from whence
it can be blown out, according to the arrangement of the pipes, by
opening the drain cock fixed on the bottom. It has a water gauge fixed
on the lower end, so as to show whether water is accumulating; and the
engineers attention is required to see that this water is from time to
time blown off.
In the illustration, Fig. 90, is shown the simplest form in which the
device can be made. The arrows exhibit the direction in which the steam
travels, the aperture whence the water is to be blown out and the
place for attachment of a water column. In practical construction the
separator should have a diameter twice that of the steam pipe and be
2-1/2 to 3 diameters long. It is often made with a round top and flat
bottom and sometimes with both ends hemispherical. The division plate
should extend half the diameter of the steam pipe below the level of
the bottom of the steam pipe.
In Fig. 91 is shown an improved form of a steam separator which
consists of a shell or casing in which there is firmly secured a
double-ended cone. On this cone there are cast a number of wings,
extending spirally along its exterior. On entering the separator the
steam is spread and thrown outward by the cone and given a centrifugal
motion by the spiral wings. These wings are constructed with a curved
surface.
It will be noticed that the steam on entering the separator is
immediately expanded from a solid body into an annular space of equal
volume to the steam pipe, whereby its particles are removed from the
centre and thus receive a greater amount of centrifugal motion. The
entrained water or grease, etc., is thus precipitated against, and
flows along the shell of the separator, and is collected in a well of
ample proportions at base of separator, where it is entirely isolated
from the flow of dry steam.
[Illustration: Fig. 91.]