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YARWAY HARDSEAT AND SEATLESS TANDEM BLOW-OFF VALVE SERVICE AND
OPERATION MANUAL
HARDSEAT VALVE
For cleaning, all internal parts of the hardseat
valve may be removed without disconnecting
the body from the line. If the inside of the valve
must be cleaned, or if a foreign body lodged in
the valve prevents proper seating of the disc,
disassemble as follows:
(1) loosen the gland flange and remove the split
gland bushing
(2) turn the handwheel past its full open position
to jack the packing and stuffing box
(3) break the tack weld on the yoke bushing and
back out this bushing
(4) remove the internal parts through the top of
the yoke.
When the valve is reassembled, the yoke must
be tack welded in place to prevent accidental
loosening of the bushing while the valve is in
service. It is also advisable to keep the disc
clear of the seat during reassembly of the yoke
bushing.
SEATLESS VALVE
Item Description
1 Body assembly
2 Yoke
2A Lubrication fitting
3 Lower packing ring assembly
4 Upper packing ring assembly
5 Lower gland
6 Upper gland
8 Plunger assembly
9 Stem
11 Ball thrust bearing
12 Handwheel
13 Stop screw
13A Stop screw gasket
14 Springs
15 Yoke studs
15A Yoke stud nuts (4 per set)
HARDSEAT SEAT VALVE
Item Description
1 Body assembly
19 Gland
20 Disc
21 Split gland bushing
22 Disc nut
23 Stuffing box bushing
24 Yoke bushing
25 Stem
26 Gland bolts
27 Handwheel
28 Packing
31 Disc insert
SEATLESS VALVE
Packing ring adjustment yoke nuts (15A) should
be tightened at regular intervals. The yoke
springs (14) will maintain a constant load on the
packing, but the packing rings will relax slightly
during use and an adjustment may be required.
To adjust the packing, back the plunger off
slightly by turning the handwheel (do not allow
flow to occur) and then tighten the yoke nuts.
¼ to ½ turn should be sufficient. Reseat the
plunger against the upper gland.
NOTE:
If the valve has not been operated for a long period,
the packing nuts should be ajusted prior to blowing
down the boiler.
Reseating hardseat valve
A specially designed Yarway reseating tool
cuts a new surface on a worn or damaged seat
without removing the unit-tandem valve from
the line. There are cutters of various sizes to
assure that all seats are cut at the proper angle
without lapping the seat and disc. Prices and
complete details are available.
Seatless valve
Hardseat valve
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