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How It Works: Gate Valves
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All valves are designed to stop, allow, or throttle the flow of a process fluid. Gate
valves—one of the original valve designs—are ideally suited for on-off, primarily
liquid, service. A gate valve functions by lifting a rectangular or circular gate out of
the path of the fluid. When the valve is fully open, <a
href="http://www.mingyivalve.com/forged-steel-gate-valves/" target="_self">forged steel
gate valves </a>are full bore, meaning there is nothing to obstruct the flow because the
gate and pipeline diameter have the same opening. This bore diameter also determines the
valve size. An advantage of this fullbore design is very low friction loss, which saves
energy and reduces total cost of ownership.
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Gate valves can have a rising or nonrising stem design. Rising stems are attached
directly to the gate and provide a visual indicator of the valve position. Nonrising stems
are generally threaded into the upper part of the gate and have a pointer threaded onto
the top to indicate position. Nonrising stem designs are ideally suited for applications
where vertical space is limited, in well applications, and where scraping or pigging is
not required.
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Gate valves are designed with a sealing unit to provide a tight seal around the stem.
Our patented single loaded-spring (SLS) stem seal design, used in <a
href="http://www.mingyivalve.com/forged-steel-gate-valves/socket-welded-gate-valves/"
target="_self">thread and socket gate valve </a>and WKM Pow-R-Seal double expanding gate
valves, provides superior leak protection and a self-adjusting seal designed to reduce
maintenance.
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Bonnets
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Gate valves generally have one of four types of bonnets, which provide closure to
prevent fluids from leaking out of the valve. Screw-in bonnets are simple, durable sealing
units that use pressure to seal. Union bonnets provide easy access to the valve body for
applications that may require frequent maintenance or inspection. Bolted bonnets are
generally used for larger valves in higher-pressure applications. Pressure seal bonnets
are designed for services with pressure in excess of 2,250 psi [15 MPa].
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Applications
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Because of the diversity of construction materials, trim offerings, and design
combinations available with <a href="http://www.mingyivalve.com/forged-steel-gate-
valves/pressure-sealing-gate-valves/" target="_self">pressure sealing gate valves</a>,
they are appropriate for a wide variety of applications. From high-temperature coking
units to food and pharmaceutical services, gate valves can be trusted to reliably perform.
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The protected seat-face design of double expanding and slab gate valves eliminates
degradation of the seat face caused by debris in the process fluid, which makes them ideal
for liquid service. When additional protection is needed at points in pipeline
applications where operational integrity is vital and the consequences of environmental
exposure are higher, such as near waterways and municipalities, double expanding gate
valves are a particularly wise choice.
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