Figure 13-11.--Critical dimensions of the Leslie top cap.
grooves and that the cylinder liner is smooth and free of
When you install the control valve and its bushing,
grooves, pits, and rust.
remember that the joint between the bottom of the
When installing the cylinder liner, be sure the top
bushing and its seat is a metal-to-metal contact. Install
of the liner does not extend above the top of the valve
the bushing tightly, and when it is all the way down, tap
body. The piston must work freely in the liner; if there
the wrench lightly with a hammer, to ensure a
is binding, the governor will not operate satisfactorily.
When the controlling valve is installed, you must
Renew the controlling valve spring and the main valve
check the clearance between the top of the valve stem
spring if they are weak, broken, or corroded, or if they
and the diaphragm. It is absolutely mandatory that this
have taken a permanent set. Renew all diaphragms if
necessary. If you use the old diaphragms, install them
If the clearance is less than 0.001 inch, the diaphragm
in their original position; do not reverse them.
will hold the control valve open, allowing steam to flow
Follow the instructions in the manufacturer's
to the main valve at any time the throttle valve is open.
technical manual when you reassemble the governor.
If the clearance is more than 0.002 inch, the diaphragm
All clearances must be as designed if the governor is to
will not fully open the control valve. This means the
operate satisfactorily. Check each moving part carefully
main valve cannot open fully, and the unit cannot be
to ensure freedom of movement.
brought up to full speed and capacity.
When you have reassembled the governor, test it as
When the main valve seating area is damaged, it
soon as possible so that you can make any needed
must be lapped in by the same process. ALWAYS lap in
the main valve with the piston in the cylinder liner to
Repairing Double-Seated Valves
ensure perfect centering.
If the damage to the seating surfaces is excessive,
On a double-seated valve, the extent of damage
you must install new parts. Use parts supplied by the
determines the kind of repairs you can do. Normally,
manufacturer if they are available.
you can lap it or weld-repair it and remachine it to fit
the body. The normal seat angles are the same as those
TOP CAP.--If the top flange of the top cap of the
in globe valves, and the spotting-in procedure is the
governor becomes damaged, you must be extremely
same. You can hold most valve disks on a spud or mount
careful when you machine it. Consult the manu-
them on a mandrel and cut them the same way as a globe
facturer's technical manual for the correct clearances.
valve. In this case as in the others, it is best to consult
local quality assurance directives and local procedures
All seating surfaces must be square with the axis of
when you repair this type of valve. Also, in most cases
the control valve seat threads and must have the
the blueprints will show ND (no deviations) and must
smoothest possible finish. Before you start the
be closely adhered to, as far as type of weld and quality.
reassembly, be sure that all ports in the top cap and the
In all cases, shop LPO's should be able to provide the
diaphragm chamber are free of dirt and other foreign
matter. Be sure that the piston rings are free in their