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Thermoplastic Valves Product Guide & Engineering Specifications
Valve Types
Made in the U.S.A. Suitable for Oil-Free air handling to 25 psi, not for distribution of compressed air or gas Page 712
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Swing Check Ball Valves
Swing check ball valves are a special design that combines the basic function of a ball valve and a swing check valve
for use in general purpose applications where an in-line ball and check valve configuration is required.
Gate Valves
Gate valves perform an on/off function accomplished by means of a flow-controlling gate centered in the valve body
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etween the inlet and outlet sides of the valve. The gate moves along a vertical stem axis, perpendicular to the flui
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stream, thereby blocking the flow in the closed position and variably increasing the flow as the gate is moved to the
full open position. Spears
®
gate valves use either a cylindrical plug (Plug Gate Valves) or a wedge-shaped gate an
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sealing surface design (regular Gate Valves). Both provide positive shut off when engaged with the valve body in the
closed position and feature non-rising type stem. This provides vertical movement of the gate without extension o
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the stem above the valve body.
Butterfly Valves
Butterfly valves are rotary valves in which a disc is rotated 90° to open or close the flow passage. In the full close
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osition, the disc seals against an elastomer seat. Flow control can be accomplished by varying the degree to which
the disc is opened. Spears
®
Standard and True Lug type Butterfly Valves utilize a special offset disc and low contac
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seat designed. Spears
®
Wafer style Butterfly Valve incorporates a special low contact, disc-mounted seat and centere
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disc. These designs minimize operation torque and improve sealing capabilities over conventional rubber seated valves.
Diaphragm Valves
Diaphragm valves utilize a moveable elastomeric membrane, or “diaphragm”, to constrict the flow passage throug
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the valve, thereby controlling or throttling fluid flow. The diaphragm additionally isolates system fluids from internal
moving parts of the valve. In the Weir-Type design, a raised area in the center of the waterway serves as a seal-of
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oint for the elastomeric diaphragm. When installed in a horizontal position, this additionally facilitates drainage
of fluid from the valve. From the full-open position, operation of the valve is accomplished by rotating the handle
to vertically move a compressor unit on a threaded shaft. This compresses the attached elastomeric diaphragm to
constrict the waterway and finally seal-off flow. Spears
®
diaphragm valves provide an indicator in the center o
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the handle for 360° visibility of valve position, and a special stop on the compressor to prevent damage from over-
tightening. The T-Style “Zero Dead-Leg” Diaphragm Valve is a special configuration incorporating a Tee fitting a
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one end of the valve. This design maintains close proximity of the valve to the fluid mainline to minimize “dead leg”
of potential fluid accumulation, where required by specific application.
Globe Valves & Y-Pattern Valves
Globe valves are characterized by a partition separating the two halves of the body with a center passage that is
opened and closed by a screw-down/screw-up seat mounted at right angle to the body. The “Globe” name was derive
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from the original spherical body design for these valves. Globe valves offer excellent flow regulating characteristics,
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ut have a high resistance due to the turning flow path. The Y-Pattern Valve (aka, “oblique valves”) is a hybrid globe
valve incorporating an angled stem. This less restrictive flow path design improves flow while maintaining the same
excellent throttling characteristics as a globe valve.
Needle Valves
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eedle valves are small sizes of globe valves fitted with a tapered plug. The tapered plug or “needle” is screwed in o
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out of a mating orifice in the body and thus controls the effective orifice size. Needle valves are excellent for metering
and other fine adjustment flow control applications. Spears
®
Needle Valves use PTFE stem seals and no elastomers
for optimum chemical resistance. These are produced in both a conventional “globe” pattern and convenient right-
angle pattern design for application versatility.