Technical choice

[chtimi]

I have the choice between grey cast iron as A48cl35 and a carbon steel as A216 WCB for a use @ 40°C max in gasoline, petrole.( casing for centrifugal pump)
I would like to know what is the best choice in regard of properties of this kind of steels.

Thank for your help.

JLuc

 

[NickE]

I'm a big fan of Grey Iron castings where possible, they are generally less expensive and can have some really great properties for many applications. That said I really dont know if corrosion would be an issue.

nick

 

[Metalguy]

CI should be OK as long as the pump never gets hit by anything.

 

[PAN]

Should we consider the pressure?

 

[unclesyd]

I would not ever consider CI for a gasoline pump unless it was submerged in a tank. A CI pump installation requires too many special considerations.
Our internal specifications would not permit CI in flammable service. DI was permitted in some flammable services after a thorough review.
I think some local codes prohibit CI in flammable service.

 

[NickE]

thx Unclesyd- Is it the catastophic failure mechanism of GCI that is the concern?

 

[unclesyd]

NickE,
That is my main cosideration. Internally I've seen 3 catastrophic failures of CI pump housings, none in flamable service. 2 were due to external loading from piping and the other was from what we suspect was water hammer event.

I have seen 2 failures of CI pumps that caused major damage due to the resulting fires. The failed housings were sent to a metallurgical lab for failure analysis, but were suddenly withdrawn with no explanation. These pumps were pumping tolune and tolune and water. The most amazing thing about this was after the these fires the company continued to use CI pumps in this service.

 

[moltenmetal]

I agree with unclesyd- grey cast iron is too brittle and too likely to catastrophically fail if it's loaded by something unexpected (like a dropped sledgehammer etc...)

I'd use it for water services happily, but not for flammables.

What about ductile/malleable iron as an alternative to grey cast iron or cast steel?

 

[InspEngr]

At our refinery, cast iron was "outlawed" in hydrocarbon service many years ago due to brittle fracture concerns (and past problems). Steel is the material of choice unless, of course, process conditions require a different material.