Cast iron valves or ductile iron valves, which is better?

Customers in all industries require a variety of valves to meet their demanding processes. Valves are available in a wide range of materials for any conceivable application. Some of these materials are PVC, carbon steel, stainless steel, cast iron, and ductile iron. This article focuses on cast iron valves and ductile iron valves.

 

Cast Iron Valves

Cast iron (also known as gray cast iron) is a metal that has been used for centuries. Cast iron is strong and usually does not break even after severe vibration. It is an alloy made of 96-98% iron, 2%-4% carbon, and a small amount of silicone. It has impressive temperature tolerance, with some cast irons able to withstand temperatures in excess of 2100F (1150C). In terms of pressure, the strength of cast iron depends on its pressure rating. The two most common are Class 125 and Class 250. At less extreme temperatures, Class 125 cast iron flanges are rated between 150 and 200 psi. Class 250 cast iron is much harder and is rated from 300 to 500 psi. these pressures will vary by end type. The main disadvantage of cast iron valves is that they are not very ductile at all.

 

Ductile Iron Valves

Ductile iron is a synthetic metal material invented in the mid-twentieth century as a type of iron used to make cast iron. By adding trace amounts of other elements to the iron, the carbon is made to form a spherical shape instead of flakes. This is what allows the material to change without fracturing. Ductile iron has excellent ductility, so it will not necessarily fracture when bent. Temperature limits are slightly lower than cast iron, but still quite high at 1350F (730C). In terms of pressure, ductile iron valves are also available in pressure grades: 150 and 300. 150 grade ductile iron can maintain a seal up to 250 psi at standard outdoor temperatures. 300 grade can withstand pressures up to 640 psi.