Flat Gate Valve

Product Overview

The Flat Gate Valve with Diversion Hole is a parallel‑type gate valve with a slab gate that has a centrally located diversion hole. It is designed only for ON‑OFF (open/close) service – not for flow regulation. The diversion hole equalizes upstream and downstream pressure when the valve is partially opened, significantly reducing operating torque and making the valve easier to operate. This valve is suitable for clean media such as natural gas, crude oil, and refined products, especially in high‑pressure, large‑diameter applications requiring frequent operation.

The valve uses a floating or fixed seat design, relying on media pressure to press the gate against the downstream seat for sealing. It features bidirectional sealing, a full‑bore flow path, and fast open/close action. The valve has flanged connections, with nominal diameters from DN50 to DN600, pressure ratings PN16 to PN160 (Class 150–900), and body materials including carbon steel and stainless steel. It is widely used in long‑distance pipelines, tank farms, and gas distribution stations.

Product Structure

The Flat Gate Valve with Diversion Hole mainly consists of the following parts:

1. Body: Cast or forged body in carbon steel (WCB), stainless steel (CF8/CF8M), alloy steel, etc. Flanged ends conforming to GB/T 9113, ANSI B16.5, EN 1092‑1, etc. Full‑bore flow path with no restriction.

2. Gate (Slab): One‑piece or split slab gate made of stainless steel (304, 316, 17‑4PH) or alloy steel, with optional Stellite hardfacing or chrome plating. A diversion hole of diameter equal to the pipe bore is provided in the center of the gate.

3. Seats: Floating or fixed seats, typically metal‑to‑metal sealing, with soft sealing (PTFE, PEEK) optional. Floating seats are pressed against the gate by media pressure, providing bidirectional sealing.

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4. Stem: Stainless steel trapezoidal‑thread stem, moving the gate up and down. Available in rising stem or non‑rising stem design.

5. Bonnet: Bolted or pressure‑seal bonnet, housing the packing box.

6. Packing Box: Contains PTFE or flexible graphite packing, compressed by a packing gland to prevent external leakage. Low‑emission packing optional.

7. Spring or Preload Mechanism (optional): Springs behind the seats provide initial sealing force.

8. Drain / Vent Ports (optional): Provided on the top and bottom of the body to drain accumulated media or check seal integrity.

9. Actuator: Handwheel, bevel gear, electric, pneumatic, or hydraulic.

The diversion hole allows pressure equalization during opening, significantly reducing operating torque.

Function

1. Pressure Equalization for Low Torque: When opening from the closed position, the diversion hole first connects upstream and downstream, equalizing cavity pressure and greatly reducing opening torque – making manual operation easier or allowing a smaller actuator.

2. Bidirectional Sealing: The floating seat design ensures that media pressure from either side presses the seat against the gate, providing bidirectional zero leakage (soft seal meets ANSI Class VI).

3. Full‑Bore Low Flow Resistance: When fully open, the gate diversion hole aligns with the body bore, matching the pipe inner diameter for minimal pressure loss.

4. Fast Open/Close: Short gate stroke (equal to the port height) allows quick operation.

5. Wear Resistance: The gate and seat sealing faces can be hardfaced with Stellite or other hard alloys for media containing small amounts of particles.

6. Bidirectional Pressure Capability: The body and sealing construction withstand media pressure from either side; flow direction is not restricted.

7. In‑Line Drain / Vent: Bottom drain ports remove accumulated solids; top vent ports check seal integrity.

8. Multiple Actuator Options: Manual, electric, pneumatic, or hydraulic actuators to meet different automation requirements.

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Working Conditions

1. Applicable Media: Natural gas, crude oil, refined products, water, steam, clean chemical liquids (not suitable for crystallizing, high‑viscosity, or heavily particle‑laden media because the diversion hole may clog).

2. Temperature Range: –29°C to +200°C (soft seal); –29°C to +550°C (metal seal).

3. Pressure Rating: PN16, PN25, PN40, PN63, PN100, PN160 (Class 150, 300, 600, 900).

4. Nominal Diameter: DN50 – DN600 (2″ – 24″); larger sizes available on request.

5. Installation Orientation: No strict limitation (bidirectional sealing), horizontal installation with stem vertical recommended.

6. Typical Applications:

   1. Main line shut‑off in long‑distance natural gas pipelines

   2. Pump station inlet/outlet in crude oil and refined product pipelines

   3. Tank farm root valves

   4. Pressure regulating stations in city gas high‑pressure networks

   5. Clean chemical liquid pipelines (non‑crystallizing, non‑viscous)

   6. Boiler feedwater systems in power plants

   7. Offshore platform oil and gas pipelines

Summary

The Flat Gate Valve with Diversion Hole, with its pressure‑equalizing hole, bidirectional floating seat zero‑leakage sealing, and full‑bore low flow resistance, is an ideal bidirectional shut‑off valve for clean media pipelines such as natural gas, crude oil, and refined products. The diversion hole equalizes upstream and downstream pressure during opening, significantly reducing operating torque and making large‑bore, high‑pressure valves feasible for manual operation.

Compared with flat gate valves without a diversion hole, this design offers much lower operating torque, but the hole can trap media and is not suitable for crystallizing, high‑viscosity, or particle‑laden services. With flanged connections, a full‑bore flow path, and optional manual or automated actuators, the Flat Gate Valve with Diversion Hole is an efficient and economical solution for ON‑OFF pipeline systems that require reliable bidirectional shut‑off, low operating torque, and clean fluid media.