What is Gate Valve?
A gate valve can be defined as a type of valve that used a gate or wedge type disk and the disk moves perpendicular to flow to start or stop the fluid flow in piping.
A gate valve is the most common type of valve used in any process plant. It is a linear motion valve used to start or stop fluid flow. In service, these valves are either in a fully open or fully closed position.
When the gate valve is fully open, the disk of a gate valve is completely removed from the flow. Therefore virtually no resistance to flow. Due to this very little pressure drops when fluid passes through a gate valve.
To achieve proper sealing, when the valve is fully closed, 360° surface contact is required between disk and seats.
Gate valves should not be used for regulation or throttling of flow because accurate control is not possible.
The high velocity of the flow in the partially open valve may cause erosion of the disc and seating surfaces and also creates vibration and noise.
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Valve Type
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CS / SS GATE VALVE - FL / BW
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Design Std
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BS EN ISO 10434 [BS 1414] / API 600 / API 602 / API 603/ASME B16.34
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Size Range
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40 DN to 400 DN [1 1/2” to 16”]
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Body
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[CS - ASTM A 216 Gr. WCB] [SS - ASTM A 351 Gr.CF8 / CF8M]
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Trim
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AISI 410 / 304 / 316
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Seat / Wedge
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13% Cr. Steel / AISI 410 / 304 / 316
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Design Features
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Bolted Bonnet, OS & YT, HW & Gear operated
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Prorating
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ASME - Class 150 / 300 / 600
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Face to Face
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ASME B 16.10 / EN 558 -1 / API 6D
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End Connection
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Flanged
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ASME B16.5, CLASS 150 / 300 / 600
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Butt weld
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ASME B16.25
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Testing Std.
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BS EN 12266 - 1 [BS 6755-1] / API 598
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Optional
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Lantern Ring / indicator & Locking Device/ Renewable Seat / Stellite Hard facing / Jacketed Provision / RTJ Flanges / By Pass Arrangement / Higher Sizes / Special MOC: Austenitic and Duplex Stainless Steels
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Types of Gate Valves
There are three ways to classify the gate valve.
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Types of Disk
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Solid taper wedge
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Flexible wedge
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Split wedge or Parallel disks Valve
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Types of Body Bonnet Joint
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Screwed Bonnet
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Bolted-Bonnet
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Welded-Bonnet
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Pressure-Seal Bonnet
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Types of Stem movement
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Rising Stem or OS & Y Type (Outside Stem and Screw Type)
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Non-rising Stem type
Gate Valve Applications
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Gate valves are used in almost all fluid services such as air, fuel gas, feedwater, steam, lube oil, hydrocarbon, and all most any services.
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Some special gate valve is used in slurry and powder product also such as knife gate valve
Advantages of Gate Valve
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Gate valve provides good
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Pressure drop during operation is very less.
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Most of the gate valve can be used as bi-directional
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They are suitable for high pressure and temperature application and required less maintenance
Flexible Wedge Gate Valve
The flexible wedge is a one-piece solid disk with a cut around the perimeter. These cuts vary in size, shape, and depth. A shallow, narrow cut on wedge perimeter gives less flexibility but retains strength. A cast-in recess or deeper and wider cut on wedge perimeter gives more flexibility but compromises the strength.
This design improves seat alignment and offers better leak tightness. It also improved performance in situations where thermal binding possible. Flexible wedges Gate valves are used in steam systems.
Thermal expansion of the steam line sometime causes distortion of valve bodies which may lead to thermal blinding.
The flexible gate allows the gate to flex as the valve seat compresses due to thermal expansion of the steam pipeline and prevents thermal blinding.
The disadvantage of flexible gates is that line fluid tends to collect in the disk.
These may result in corrosion and ultimately weaken the disk.
