Flowserve V-376 R4 Edward Valves - Manual (Page 5)

6
Flow Control Division
Edward V
alves
Seats Edward valve seats are of two types: screwed-in (with “O”- Ring Seal) or integral with the valve body
.
Screwed-in seats can best be repaired, if more than lightly damaged, by removal from the valve. If screwed-in seats are badly damaged, it may be more economi- cal to replace them with new seats; however
, if they are repairable, they may
be remachined on a lathe. The par
t should
be accurately centered in the lathe before machining. Seats can be cut with high- speed tool bits. Stellite-faced seats must be machined with tungsten-carbide tools or by grinding. In replacing a screwed-in seat in the valve body
, care should be taken that
the face on the body against which the seat shoulder rests is clean and true to pro- vide a tight seal. New “O”- Rings should always be used. Sur
faces should be blued
and checked for contact all the way around when replacing a seat. Care should be taken that reworking does not throw the sealing face between body and seat out of line with the seat threads.
Integral Seat
Integral valve seating sur
faces cannot be
removed for repair
. Once the valve has
been disassembled and thoroughly cleaned, deter
mine the best procedure
based on the extent of damage. Lightly damaged seats may simply be repaired by lapping with the valve disk assembly
.
Heavier damage may require the use of special lapping tools or removal of the valve body from the line for remachining. These valves should then be finish-lapped using the valve disk assembly (see below). Seat refinishing tools are also available for integral Stellite seat valves. Consult your Edward V
alves representative.
Complete instructions for the repair and fin- ishing of integral Stellite valve seats are contained in “Univalve Operation and Maintenance Manual” V
-370.
Seat Finishing After properly installing seats in valve bodies or reworking integral seat valves, the seat and disk should be lapped together
. T
o
preclude galling, caution should be t
aken
not to apply too much pressure in lapping
seats and disks. Lapping should be done with a light load, lifting the disk frequently to a new position and cleaning the lapping faces as required. See below:
Lapping with Lap or Abrasive Disk Lapping with V
alve Disk Assembly
The effectiveness of valve seat lapping can best be judged by blueing the disk and rotating it lightly in the seat. A full contact should be obtained around the circum- ference of the seat. A valve that shows this full contact should be pressure tight after assembly when proper stem load is applied.
Seats and Seat Finishing