check valve
A check valve (non-return valve) is a one-way valve that allows fluid (liquid or gas) to flow in only one direction and automatically prevents backflow. They are widely used in water systems, oil & gas, chemical plants, HVAC, and pumps.
Below are the main types of check valves, along with their technical specifications and engineering details.
🔧 1. Swing Check Valve
➤ Working Principle
A hinged disc swings open with forward flow and closes by gravity or reverse flow pressure.
➤ Technical Details
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Size range: 15 mm to 1200 mm (½" to 48")
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Pressure rating: PN10 – PN40, ANSI 150 – 600
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Temperature: -29°C to 425°C (material dependent)
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Body materials: Cast iron, carbon steel, stainless steel, bronze
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Seat leakage class: Class IV–VI (API/ANSI)
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Cracking pressure: Very low (~0.05–0.3 bar)
➤ Applications
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Water pipelines
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Sewage systems
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Low-pressure steam lines
➤ Key advantage
Low pressure drop
➤ Limitation
Not suitable for pulsating flow (may cause water hammer)
🔧 2. Lift Check Valve
➤ Working Principle
A disc or piston lifts vertically when flow enters; gravity or reverse pressure closes it.
➤ Technical Details
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Size range: 15 mm to 300 mm
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Pressure rating: ANSI 150–2500
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Temperature: up to 600°C (high-pressure versions)
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Body materials: Forged steel, stainless steel
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Seat type: Metal-to-metal or soft seat
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Cracking pressure: 0.1–1 bar
➤ Applications
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High-pressure steam systems
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Oil & gas pipelines
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Boiler feed lines
➤ Advantage
Better sealing than swing type
➤ Limitation
Higher pressure drop
🔧 3. Ball Check Valve
➤ Working Principle
A spherical ball moves to block reverse flow and rolls away during forward flow.
➤ Technical Details
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Size range: 8 mm to 300 mm
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Pressure rating: PN10 – PN25
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Temperature: up to 200°C (depends on elastomer)
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Ball material: Rubber-coated steel, stainless steel
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Body material: PVC, cast iron, stainless steel
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Cracking pressure: 0.05–0.5 bar
➤ Applications
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Wastewater systems
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Slurry handling
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Chemical dosing systems
➤ Advantage
Handles dirty fluids well
➤ Limitation
Not suitable for high pressure/high temperature
🔧 4. Dual Plate (Wafer) Check Valve
➤ Working Principle
Two spring-loaded half-discs open with flow and close rapidly when flow reverses.
➤ Technical Details
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Size range: 50 mm to 1200 mm
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Pressure rating: PN10 – PN40, ANSI 150–300
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Temperature: -196°C to 550°C
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Body materials: Cast steel, stainless steel
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Face-to-face: Compact wafer design
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Cracking pressure: 0.1–0.3 bar
➤ Applications
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Pump discharge lines
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HVAC systems
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Fire protection systems
➤ Advantage
Fast closing → reduces water hammer
➤ Limitation
Higher cost than swing check
🔧 5. Piston Check Valve
➤ Working Principle
A piston moves in a guided cylinder and closes against a seat under reverse flow.
➤ Technical Details
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Size range: 15 mm to 300 mm
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Pressure rating: ANSI 150–2500
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Temperature: up to 600°C
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Body: Forged steel
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Design: Guided piston with damping chamber
➤ Applications
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Steam systems
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High-pressure oil pipelines
➤ Advantage
Excellent for pulsating flow
➤ Limitation
Expensive and complex
🔧 6. Diaphragm Check Valve
➤ Working Principle
A flexible diaphragm bends to allow flow and returns to close the passage.
➤ Technical Details
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Size range: 15 mm to 200 mm
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Pressure rating: PN6 – PN16
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Temperature: up to 120°C
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Material: Rubber (EPDM, NBR), PTFE lining
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Body: Plastic or lined metal
➤ Applications
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Pharmaceutical industry
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Food processing
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Corrosive fluids
➤ Advantage
Highly corrosion resistant
➤ Limitation
Low pressure and temperature range
🔧 7. Nozzle (Axial Flow) Check Valve
➤ Working Principle
Flow moves axially through a spring-loaded disc; closes instantly when flow reverses.
➤ Technical Details
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Size range: 15 mm to 600 mm
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Pressure rating: ANSI 150–2500
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Temperature: -196°C to 500°C
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Material: Stainless steel, alloy steel
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Closing time: milliseconds (very fast)
➤ Applications
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Turbine protection
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High-pressure pump discharge
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Nuclear systems
➤ Advantage
Very low water hammer risk
➤ Limitation
High cost
📊 Summary Table
| Type | Best For | Pressure Range | Key Feature |
|---|---|---|---|
| Swing | Water pipelines | Low–Medium | Low pressure drop |
| Lift | Steam/high pressure | High | Better sealing |
| Ball | Dirty/slurry fluids | Low–Medium | Handles solids |
| Dual Plate | Pump discharge | Medium | Fast closing |
| Piston | Steam systems | High | Stable in pulsation |
| Diaphragm | Chemicals/pharma | Low | Corrosion resistant |
| Nozzle | Critical systems | Very High | Instant closure |
⚙️ Key Engineering Parameters (All Types)
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Cracking pressure: 0.05–1 bar (depends on design)
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Leakage class: API 598 / ANSI FCI 70-2
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Face-to-face standards: ASME B16.10 / API 594
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End connections: Flanged, threaded, wafer, butt weld
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Design codes: API 6D, ASME B16.34
Here are clear images of different types of check valves so you can visually understand their structure and working:
🔧 Types of Check Valves (With Images)
1. Swing Check Valve
👉 A hinged disc swings open with forward flow and closes by reverse flow.
2. Lift Check Valve
👉 A disc or piston lifts vertically to allow flow and drops back to seal.
3. Ball Check Valve
👉 A ball moves away during forward flow and blocks reverse flow.
4. Dual Plate (Wafer) Check Valve
👉 Two spring-loaded plates open and close quickly (used in pumps).
5. Diaphragm Check Valve
👉 A flexible diaphragm bends to allow flow and seals back automatically.
6. Nozzle (Axial Flow) Check Valve
👉 Very fast closing valve used in high-pressure systems to prevent water hammer.
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