I. Main Types of Cast Iron Valves​​

1. ​​Gate Valve​​
   • ​​Features​​: Full open/full close, low fluid resistance, suitable for medium cutoff.
   • ​​Structure​​: Rising stem (e.g., Z45X-16Q), non-rising stem.
   • ​​Applications​​: Water supply, drainage, sewage treatment.
2. ​​Globe Valve​​
   • ​​Features​​: Flow regulation, good sealing, but higher flow resistance.
   • ​​Structure​​: Straight-through, angle-type (e.g., J41H-16C).
   • ​​Applications​​: Chemical, petroleum pipelines.
3. ​​Butterfly Valve​​
   • ​​Features​​: Compact size, flexible operation, suitable for large-diameter pipelines.
   • ​​Structure​​: Centerline type, double eccentric (e.g., D71X-16Q).
   • ​​Applications​​: Fire protection systems, HVAC.
4. ​​Check Valve​​
   • ​​Features​​: Automatically prevents backflow.
   • ​​Types​​: Swing type, lift type (e.g., H44X-10Q).
   • ​​Applications​​: Pump outlets, water supply systems.
5. ​​Ball Valve​​
   • ​​Features​​: 90° rotation for rapid on/off control.
   • ​​Material​​: Floating ball, fixed ball (e.g., Q41F-16C).
   • ​​Applications​​: Chemical, food processing industries.

​​II. Cast Iron Material Classifications​​

1. ​​Gray Cast Iron (HT200/HT250)​​
   • ​​Characteristics​​: Low cost, wear-resistant, but brittle.
   • ​​Applications​​: Low-pressure, ambient-temperature environments (e.g., water supply).
2. ​​Ductile Iron (QT450-10)​​
   • ​​Characteristics​​: High strength, good toughness, can replace steel valves.
   • ​​Applications​​: Medium-high pressure, high-temperature environments (e.g., chemical, fire protection).

​​III. Technical Parameters​​

1. ​​Pressure Ratings​​
   • ​​ISO​​: PN6/PN10/PN16/PN25 (equivalent to Class 150/300, etc.).
   • ​​ANSI​​: Class 150/300/600.
2. ​​Nominal Diameter (DN)​​
   • DN50–DN600 (large diameters common in municipal projects).
3. ​​Temperature Range​​
   • Gray cast iron: -10°C to 120°C; Ductile iron: -30°C to 200°C.
4. ​​Connection Types​​
   • Flange (most common), threaded, wafer, welded.

​​IV. Typical Applications​​

1. ​​Water Supply & Drainage​​
   • Gate valves, butterfly valves for water plants and pump stations.
2. ​​HVAC Systems​​
   • Butterfly valves, check valves for chilled water loops.
3. ​​Chemical/Petroleum​​
   • Globe valves, ball valves for corrosive media transport.
4. ​​Fire Protection​​
   • Butterfly valves, signal butterfly valves for pipeline control.

​​V. Valve Selection Guidelines​​

1. ​​Medium Properties​​
   • Corrosive media: Ductile iron with epoxy coating; particulate media: wear-resistant gate valves.
2. ​​Pressure & Temperature​​
   • High-pressure/high-temperature environments: Prefer ductile iron to avoid brittleness of gray cast iron.
3. ​​Installation Space​​
   • Large-diameter pipelines: Butterfly valves; space-constrained areas: Globe valves.
4. ​​Environmental Factors​​
   • Humid environments: Consider anti-corrosion (e.g., galvanized coating).