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Valves shall be of the bonnetless knife gate valve type,
with pressure ratings as required by the customer. Flanges
shall be drilled and tapped to ANSI B16.1, 125 lb. Flanges
shall be raised face and machined with serrated-spiral or
serrated-concentric grooves with a 125-250 RMS finish. Valve
body shall have 304/316 stainless steel body liner, seat (if
metal to metal seat), packing box and raised faces (all wetted
parts) and carbon steel body flanges, exterior stiffeners,
packing gland and yoke.
Valves shall have 304/316 stainless steel gate. Gate shall
be of the design and thickness to withstand full design pressure
with out permanent deflection to the gate.
FOR METAL SEATED VALVES:
Seat and gate shall be machine finished for tight one way
shutoff. Two gate wedges shall be provided to assist seating
of the gate against the seat in the lower half of the valve
body. On valves 48" diameter and above, the gate will
be square bottom.
FOR RESILIENT SEATED VALVES:
Gate shall have a rounded bottom. The seat shall be positioned
to seal around the perimeter of the gate for drip tight bi-directional
shutoff in either direction and at any pressure up top the
design pressure. The resilient seat shall be a molded or extruded
elastomer with an internal stainless steel rod for stiffening.
Seat retainers shall be provided in the lower half of the
valve body to retain the seat and guide the gate during closing.
At least two gate guides shall be provided in the upper half
of the valve body.
The packing gland will be fabricated from carbon steel. Packing
shall be Teflon lubricated synthetic packing. Packing gland
bolts and studs shall be 304 stainless steel.
The valve yoke shall be fabricated carbon steel. The valve
stem shall be 304 stainless steel with full ACME threads.
The stem nut shall be bronze. The stem nut retainer shall
be of the enclosed type and shall be carbon steel.
Manually actuated valves shall be bevel gear operated.
Valves shall be designed, manufactured and tested to comply
with MSS SP-81, Standard Practice for "STAINLESS STEEL,
BONNETLESS, FLANGED,WAFER,KNIFE GATE VALVES".
Valves shall be A-C Valve Fig 76 knife gate valve (Metal
seat), Fig 77 knife gate valve (Resilent seat) or approved
equal.
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