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Gate valves are linear-motion isolation valves used to start or stop fluid flow. They are widely used in water systems, oil & gas, steam, chemical plants, HVAC, and power plants because they provide minimal pressure drop when fully open.

Main Types of Gate Valves

1. Solid Wedge Gate Valve

The most common type. Uses a single solid wedge-shaped disc.

Technical Details

• Disc Type: Solid wedge

• Sealing: Metal-to-metal or resilient seat

• Pressure Class: ANSI 150 to 2500

• Temperature Range: Up to ~600°C depending on material

• Materials: Cast iron, carbon steel, stainless steel, alloy steel

• Standards: API 600, ASME B16.34, BS 1414

• Applications: Steam, oil, gas, high-temperature service

Advantages

• Strong and simple design

• Good for high pressure/temperature

Limitations

• Sensitive to thermal expansion

• Can jam in high-temperature service

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2. Flexible Wedge Gate Valve

Uses a split wedge that can flex slightly to improve sealing.

Technical Details

• Disc Type: One-piece disc with flexible cut

• Pressure Rating: ANSI 150–2500

• Seat Design: Self-aligning

• Temperature: Suitable for thermal cycling

• Standards: API 600, API 6D

Advantages

• Better seat alignment

• Reduced sticking due to temperature changes

• Improved sealing

Applications

• Steam systems

• Thermal power plants

• Hydrocarbon pipelines

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3. Split Wedge Gate Valve

Uses two separate disc halves for improved seating.

Technical Details

• Disc Type: Two-piece split discs

• Pressure Class: ANSI 150–1500

• Seating: Mechanical expansion

• Materials: Carbon steel, stainless steel

Advantages

• Good sealing reliability

• Handles temperature fluctuations well

Applications

• Steam lines

• Condensate systems

• Refineries

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4. Parallel Slide Gate Valve

Uses parallel discs instead of wedge-shaped discs.

Technical Details

• Disc Type: Parallel discs

• Operating Pressure: Medium to high pressure

• Temperature: High-temperature capable

• Standards: API 6D, ASME standards

Advantages

• Less seat wear

• Suitable for high-temperature service

Applications

• Steam turbines

• Boiler feed systems

• Nuclear plants

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5. Rising Stem Gate Valve (OS&Y Type)

Stem rises visibly when valve opens.

Technical Details

• Stem Design: Outside Screw & Yoke (OS&Y)

• Visual Position Indicator: Yes

• Maintenance: Easier stem lubrication

• Pressure Standards: ANSI 150–2500

Advantages

• Easy to determine open/close status

• Better for corrosive environments

Applications

• Fire protection systems

• Industrial pipelines

• Refineries

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6. Non-Rising Stem Gate Valve

Stem rotates but does not move upward.

Technical Details

• Stem Movement: Internal only

• Space Requirement: Compact

• Common Sizes: DN50–DN1200

• Materials: Ductile iron, bronze, stainless steel

Advantages

• Requires less vertical space

• Good for underground installation

Applications

• Water distribution systems

• Underground piping

• Municipal networks

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Based on Body Bonnet Construction

Type	Description	Common Use
Bolted Bonnet	Bolted body connection	General industry
Pressure Seal Bonnet	Self-sealing at high pressure	Power plants
Welded Bonnet	Fully welded body	Hazardous fluids
Union Bonnet	Compact threaded bonnet	Small valves

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Based on Seat Design

Metal Seated Gate Valve

• Suitable for:

  • High temperature

  • Steam

  • Abrasive fluids

Resilient Seated Gate Valve

Uses rubber-coated wedge.

Specifications

• Seat Material: EPDM/NBR rubber

• Pressure Rating: PN10 / PN16 / PN25

• Applications: Drinking water, sewage

Advantages

• Bubble-tight sealing

• Corrosion resistant

• Low maintenance

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Common Gate Valve Specifications

Parameter	Typical Range
Size	½ inch to 72 inch
Pressure Class	ANSI 150–2500
End Connections	Flanged, threaded, welded
Operation	Manual, gearbox, pneumatic, electric actuator
Leakage Standard	API 598
Face-to-Face	ASME B16.10
Flange Standard	ASME B16.5 / B16.47
Testing Standard	API 598 / ISO 5208

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Common Materials

Component	Materials
Body	Cast iron, ductile iron, WCB, CF8, CF8M
Stem	SS410, SS304, SS316
Seat	Stellite, PTFE, EPDM
Packing	Graphite, PTFE

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Gate Valve Selection Criteria

Choose based on:

1. Fluid type

2. Pressure & temperature

3. Corrosion resistance

4. Required shutoff tightness

5. Space availability

6. Manual vs automated operation

7. Industry standard requirements

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Typical Industrial Standards

• American Petroleum Institute — API 600, API 6D, API 598

• ASME — B16.34, B16.10, B16.5

• International Organization for Standardization — ISO 5208

• American Water Works Association — Water service valves

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Typical Applications by Industry

Industry	Preferred Gate Valve
Oil & Gas	Flexible wedge / API gate valve
Water Supply	Resilient seated
Steam Service	Solid or flexible wedge
Power Plants	Pressure seal bonnet
Chemical Plants	Stainless steel gate valve
Fire Fighting	OS&Y gate valve

 

A gate valve works on a simple linear motion principle: a flat or wedge-shaped “gate” moves up and down perpendicular to the flow to either fully block or fully allow fluid passage.

It is designed primarily for ON/OFF operation, not flow regulation.

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🔧 Gate Valve Working Principle

1. Fully Open Position (Flow Allowed)

When the handwheel is rotated, the stem lifts the gate fully upward.

What happens:

• Gate is completely lifted into bonnet

• Flow path becomes straight and unobstructed

• Very low pressure drop

• Minimal turbulence

✔ Fluid flows freely
✔ Almost no energy loss

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2. Fully Closed Position (Flow Blocked)

What happens:

• Gate moves downward until it tightly contacts the seat

• Flow passage is completely blocked

• Provides tight shutoff sealing

✔ No flow passes
✔ Designed for leak-tight isolation

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3. Intermediate Position (Not Recommended)

What happens:

• Gate is partially raised

• Fluid passes through a restricted opening

• Causes:

  • Turbulence

  • Vibration

  • Erosion of seat and wedge

❌ NOT recommended for flow control
❌ Causes premature valve damage

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⚙️ Step-by-Step Working Mechanism

1. Handwheel Rotation

• Operator turns handwheel clockwise or anti-clockwise

2. Stem Movement

• Converts rotary motion → linear motion

• Stem moves gate up or down

3. Gate Movement

• Gate slides inside valve body guides

4. Flow Control

• UP = OPEN (flow allowed)

• DOWN = CLOSED (flow blocked)

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📊 Simple Working Diagram (Conceptual)

OPEN POSITION:

  Flow →
 ┌───────────────┐
 │               │
 │     ─────     │  ← Gate lifted
 │               │
 └───────────────┘


CLOSED POSITION:

  Flow X
 ┌───────────────┐
 │      ███      │  ← Gate blocks passage
 │      ███      │
 └───────────────┘

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🧠 Key Engineering Principle

The gate valve operates on:

➤ Linear Motion Sealing Principle

• Stem converts rotation into vertical displacement

• Wedge or parallel disc provides sealing force against seat

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⚠️ Important Design Note

Gate valves are designed for:

• ✔ Fully open or fully closed service

• ❌ Not for throttling or flow regulation

Using them partially open leads to:

• Seat erosion

• Cavitation

• Leakage over time

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🏭 Typical Applications

• Oil & gas pipelines

• Water distribution systems

• Steam isolation lines

• Industrial process shutoff systems

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