Part Drawings 381
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d:\N-Design\Des19-1.pm5
19.4.2 Steam Stop Valve
The function of a steam stop valve is to regulate the amount of steam passing through the steam
pipe. It is operated manually.
Figure 19.18 shows one design of a steam stop valve. The valve seat 7 is screwed into the
valve body 1. The valve 6 is attached to the spindle 8 by a collar 9 and a pin. The cover 2 is
attached to the body along with the stuffing box, by studs and nuts 11. A bridge 5 is attached to
the cover, by means of two studs with collars 12. The spindle is screwed into the bridge and a
hand wheel is kept in position at the end of the spindle by a nut 13. When the hand wheel is
operated, the valve moves perpendicular to the seat and allows the steam to pass from the left to
the right side of the valve.
19.4.3 Ramsbottom Safety Valve
In Ramsbottom safety valve, spring load is used to lift the valves, when excess pressure of steam
is built-up. It is mostly used in a locomotive boiler. Whenever steam pressure exceeds the designed
value of the spring force, the excess pressure lifts the valves, allowing steam to escape till the
pressure decreases to the permissible value.
Figure 19.19 shows the assembly drawing of a Ramsbottom safety valve. It consists of two
valve chests provided in cast iron housing 1. There are two valves 2 of the same size and shape,
which are held in position against their seats 3 by the pivots of lever 5. The lever is loaded by
means of spring 6, placed centrally between the chests. One of the pivots 4 is pinned to the lever,
whereas the other is forged integral with the lever itself.
19.4.4 Diaphragm Regulator
Figure 19.20 shows the assembly drawing of a diaphragm regulator. This is used on gas lines to
regulate the outlet pressure of the gas. The gas enters the regulator at A and leaves from B. The
line pressure of a gas is indicated by the pressure gauge (not shown in figure) provided at C.
Similarly, the outlet pressure is shown by the guage to be provided at D.
When the gas is let into the regulator, it forces the diaphragm assembly, to find its passage
through B. For obtaining the required pressure of the gas at the outlet of the regulator, load on
the spring 4 is adjusted. The spring is located on the screw 6, by means of a locator 5 and
connected to the diaphragm assembly 2, by screwing the cover 3 onto the body 1. The required
adjustment is thus obtained by operating the screw 6, observing the outlet pressure guage located
at D.
19.4.5 Angle Plummer Block
Plummer blocks, when they are solid, are used mainly for end supports for the shafts and cannot
be used as intermediate supports, because of the interference of the other shaft mountings, such
as gears and pulleys. The split type of plummer block, whether the plane of splitting is horizontal
or inclined, is more flexible in its use and may be used as intermediate shaft support or even as
end support.
The angle plummer block shown in Fig. 19.21, consists of a cast iron pedastal or base with
inclined surface at 30° to the vertical. It also consists of a cast iron cover 2, which is used for
adjustment of wear in the brasses 3 and for the renewal of the brasses. This also facilitates easy
installation of the bearing. The brasses are supported in the base and they are prevented from
rotation by a snug provided in the bottom brass. The brasses are also prevented from moving
axially, by the collars provided at the ends. The cover is bolted to the base by means of two studs
4 and nuts 5. For reducing the friction between the brasses and the shaft, lubricating oil is
applied through the bush 6.
