Industrial valves are critical control components in fluid delivery systems, with various classification methods primarily based on function, pressure, temperature, and actuation methods. Below are common classification approaches and typical valve types:
Classified by Function
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Shut-off Valves: Used to connect or block media flow, such as gate valves, globe valves, ball valves, butterfly valves, and plug valves.
Example Products:- Pneumatic manual slide gate valve (DN150, flange connection, suitable for pipeline hydraulic control)
- Stainless steel flange ball valve (DN125, soft seal, used for flow cutoff)
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Check Valves: Prevent backflow of media, such as lift check valves and swing check valves.
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Control Valves: Regulate media pressure and flow, such as pressure reducing valves and throttle valves.
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Safety Valves: Provide overpressure protection by discharging excess media.
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Diversion Valves: Distribute or mix media, such as three-way plug valves and steam traps.
Classified by Nominal Pressure
- Low-pressure valves: PN ≤1.6 MPa
- Medium-pressure valves: PN 2.5–6.4 MPa
- High-pressure valves: PN 10–80 MPa
- Ultra-high-pressure valves: PN ≥100 MPa.
Classified by Operating Temperature
- High-temperature valves: t >450°C (require special materials like chrome-molybdenum-vanadium steel, with extended bonnets and seal ring welding processes)
- Medium-temperature valves: 120°C ≤ t ≤450°C
- Normal-temperature valves: -40°C ≤ t ≤120°C
- Low-temperature valves: -100°C ≤ t ≤-40°C
- Ultra-low-temperature valves: t <-100°C.
Classified by Actuation Method
- Manual valves: Such as manual ball valves and rising-stem soft-seal gate valves
- Power-actuated valves: Including electric, pneumatic, and hydraulic types, such as pneumatic on-off cut-off valves.
Other Classification Methods
- By connection type: Flanged, welded, or compression fittings.
- By port size: Small (DN<40mm), medium (DN50–300mm), and large (DN≥350mm).
The above classifications provide a basic framework for industrial valves. Actual selection should be based on specific working conditions (e.g., media properties, pressure, and temperature requirements).
Common Valve Materials
Industrial valve materials vary widely, and selecting the appropriate material is crucial based on the working medium, temperature, and pressure conditions. Below are common valve materials and their characteristics:
Common Body Materials
- Gray Cast Iron
- Suitable for nominal pressures PN ≤1.0 MPa and temperatures -10°C to 200°C in water, steam, air, and other media.
- Low cost but with lower tensile strength and moderate temperature resistance (recommended below 200°C).
- Malleable Cast Iron
- Suitable for PN ≤2.5 MPa and temperatures -30°C to 300°C in water, steam, and oil media.
- Better strength and toughness than gray cast iron, with good wear resistance.
- Ductile Iron (Nodular Cast Iron)
- Suitable for PN ≤4.0 MPa and temperatures -30°C to 350°C in water, steam, and oil.
- Mechanical properties approach those of steel, with high tensile strength and toughness.
- Carbon Steel (e.g., WCB)
- Suitable for PN ≤32.0 MPa and temperatures -30°C to 425°C in high-pressure environments, such as petroleum and steam.
- Good overall performance, with strong pressure and impact resistance.
- Stainless Steel
- Austenitic Stainless Steel (e.g., 304/316): Excellent corrosion resistance. 304 is suitable for general environments, while 316 is suitable for chloride-containing corrosive media.
- Widely used in chemical and food industries.
- Copper Alloys
- Suitable for PN ≤2.5 MPa in water, seawater, oxygen, and other media, with temperatures -40°C to 250°C.
- Low-Temperature Steel
- Suitable for PN ≤6.4 MPa and temperatures ≥-196°C in liquefied natural gas, liquid nitrogen, and other cryogenic applications.
- Plastics / Lined Rubber / Lined PTFE
- Good corrosion resistance, suitable for low-pressure, low-temperature, or highly corrosive media.
Sealing and Packing Materials
- Sealing Surfaces: Must be corrosion and wear-resistant, commonly made of PTFE (Teflon) or metals (e.g., 1Cr13, 1Cr18Ni9).
- Packing: Typically PTFE or asbestos rope, selected based on medium, temperature, and pressure.
Key Selection Considerations
- Medium Characteristics: For corrosive media, prioritize stainless steel (e.g., 316L) or lined valves.
- Temperature & Pressure: High-temperature and high-pressure environments require carbon or alloy steel, while cryogenic applications need low-temperature steel.
- Cost-Effectiveness: In harsh conditions, high-corrosion-resistant materials (e.g., 316) may be more economical.
For further details on specific materials (e.g., differences between 304 and 316 stainless steel) or sealing materials, refer to the following resources:
- Stainless Steel Valve Selection Guide (Video tutorial)
- Detailed Explanation of Valve Materials and Temperature Relationships (Technical article)