Ductile iron is widely used in the oil and gas industry due to its high strength, toughness and corrosion resistance.
Application scenarios of ductile iron valves
Low-pressure oil and gas transportation and distribution
Urban gas pipeline (low pressure)
- Ductile iron valves (such as EN-GJS-400/500) can be used in low-pressure natural gas distribution systems (≤PN16/Class 150), such as:
- Low-pressure pipelines after pressure regulating stations
- Residential and commercial gas inlet pipelines
- Auxiliary pipelines of gas storage and distribution stations
Oilfield water injection system
For low-pressure (≤PN25) water injection pipelines, ductile iron has better corrosion resistance than ordinary cast iron, but water quality (such as additional protection when containing chloride ions and H₂S) still needs to be considered
Medium and low pressure processes in non-acidic environments
Compressed air and inert gas systems
Applicable to compressed air or nitrogen pipelines with pressure ≤ PN40 (Class 300), such as:
Instrument air system
Oil field gas lift auxiliary pipeline
Water treatment and fire protection system
For cooling water and fire water pipelines in oil fields or refineries, ductile iron gate valves and butterfly valves are more common.
Low temperature and low pressure LNG auxiliary system
Low pressure water and nitrogen system of LNG receiving station
Ductile iron valves can be used in non-low temperature key parts (such as fire water and cooling water), but are not suitable for LNG media below -46℃ (requires low temperature steel or stainless steel).
Advantages of ductile iron valves
Mechanical properties are better than gray cast iron
High tensile strength (≥400 MPa), good toughness (elongation ≥10%), and can withstand certain impact loads.
Suitable for medium and low pressure vibration environments (such as pump outlet auxiliary pipelines).
Good corrosion resistance
Corrosion resistance can be improved by surface treatment (epoxy coating, zinc plating, nickel-phosphorus plating), suitable for mildly corrosive environments.
Ductile iron has better sulfate corrosion resistance than carbon steel (WCB).
Cost-effective
Priced lower than carbon steel and stainless steel, suitable for volume use in non-critical applications.
Manufacturing flexibility
Easy to cast complex structures (such as large diameter butterfly valve bodies).
Comparison of alternatives
| Working conditions | Recommended materials | Ductile iron applicability |
|---|---|---|
| （Class 600+）High-pressure natural gas transmission | Carbon steel (WCB) or stainless steel | Not applicable |
| （含H₂S）Acidic oil and gas (including H₂S) | Duplex steel（2205） | Not applicable |
| （PN16）Low pressure city gas | Ductile iron（QT400） | Applicable |
| （-162℃）LNG cryogenic storage tank | Stainless steel (CF8M) | Not applicable |
Summary
The application of ductile iron valves in the oil and gas industry is mainly concentrated in low-pressure, non-acidic, non-cryogenic conditions, such as city gas, oil field water injection, compressed air and other auxiliary systems. Its advantages are low cost, high strength, and better corrosion resistance than gray cast iron, but carbon steel, stainless steel or special alloy valves are still required in high-pressure, acidic environments or critical safety systems.
