Material Mill Test Certificate

Not much, unless you have a failure that causes personal injury. Then your insurance company (if you have one) will not cover the accident. And you, by signing off on an uncertified job, will be liable. Depending on local laws.

Since we have no way of knowing where you are we can't help much.

I am sorry, but as per our standards we insist on the material mill certificate and even the re-test and others are not enough for us. And this is not only for our pressure vessels but for other critical fabrications (with high stress) too.

Not knowing what country your are in, or what area, MTR's are a basic requirent of most Quality control certifications. These qc programs are most usually governed by a ruling body administered by local and federal government. A manufacturer must supply these and can be traced by heat numbers assigned to material. If they are welded fittings, design requirements must meet a required Carbon co-efficient. these are listed on the MTR's. If not it is up to the governing body as to wheter this lack of information is acceptable, probably not. Check with the governing body in your area on welded materials as with the contractors own Quality Control Program.