Charpy Impact Testing

[Valve123]

My backgound does not include a knowledge of metallurgy but does involve the specification and purchase of control valves and other equipment associated with chemical processes. My question is of a general nature;

For what reason would I require Charpy Impact Testing on control valves? Is this a metals (carbon steel, stainless steels) and pressure/temperature issue? What is a good guideline for requesting this test and to what extent?

I have read many articles about Charpy Impact Testing but do not fully understand when to request.

 

[metengr]

For what reason would I require Charpy Impact Testing on control valves? Is this a metals (carbon steel, stainless steels) and pressure/temperature issue? What is a good guideline for requesting this test and to what extent?

Charpy impact testing is a standard test method accepted by most Codes and Standards to evaluate the notch toughness behavior of metals. This is very important because certain metals (carbon and low alloy steels or even some grades of stainless steels) can exhibit a loss of toughness that can result in a sudden, catastrophic failure when exposed to low temperature service if there are flaws or stress risers. Normally, CVN impact testing is specified for service conditions below ambient temperature for pressurized components (like valve bodies, pipe and tube products).

The background on CVN testing can be found in the link below. Go the the article on "Brittle Fracture and Impact Testing"

http://www.key-to-steel.com/default.aspx?ID=Articles#p10

 

[metengr]

Valve123;
Regarding the answer to your last question; the requirements for Charpy impact testing will be mandated by the code of construction that you use for the application of your valves. For instance, if you follow the ASME Boiler and Pressure Vessel Code or even API, there are specific requirements for CVN impact testing based on service temperature, not pressure.

I presume you have an understanding of material specifications like those in ASTM when purchasing components. In some cases, international specifications like ASTM may have CVN testing requirements or supplemental testing requirements. Beyond this, the code of construction will specify additional requirements.

I hope this helps.

 

[arunmrao]

valve 123,
If you specify LCB grade and such other grade valve castings,you will need to specify impact test. The impact value at the operating temperature indicates the toughness of the valve parts and its resistance to brittle failure.

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