“Carbon steel” or “stainless steel” describes a material family, but does not complete a purchase specification. Keep the material specification and grade separate from the product’s dimensional standard.
Write both requirements
Record the material specification with its grade, and the fitting standard with its edition. Add the product type, end sizes and wall requirement. For example, writing ASME B16.9 alone does not tell the supplier which material grade your project requires.
Use standards within their scope
ASME B16.9 covers factory-made wrought buttwelding fittings. Confirm that the chosen standard applies to the actual product and connection. A forged socket-weld fitting, a flange and a butt-weld fitting should not be assigned the same requirements merely because they belong to one piping order.
Handle substitutions explicitly
If the requested grade is unavailable, ask for a separately identified alternative and supporting documents. Have the project engineer review it before changing the order. Similar names, translations or appearance are not sufficient evidence that two materials are interchangeable.
Common question
Can I request “equivalent material”? Specify who must approve equivalence and what evidence is required. Keep the accepted grade and document requirements in the final order rather than leaving an open-ended substitution permission.