Grinding Cracks in Brittle Steel
Grinding Cracks in Brittle Steel
(OP)
We have an old pressure vessel analyzed to ASME Div 2, but not originally Code construction. Material is T1 steel, high strength but brittle. We found a spot where an old welded attachment was removed, and we suspect cracks. We will be checking with wet fluorescent mag particle and possibly replication. If we find some small cracks, we can grind about 0.2" without compromising thickness. We are worried that residual stress redistribution during grinding could cause the cracks to run. Any experience here in grinding out cracks, and whether they might get worse? Thanks in advance.....
Larry





RE: Grinding Cracks in Brittle Steel
You need to do two things - (1) verify the vessel material chemical composition and (2) see if you can obtain some hardness values. What was the past process application of the vessel?
Proceed with caution on placing old vessels into service. You need to conduct some type of condition assessment, which would include a review of prior operating history and repairs. Also, you need to assure current operating conditions are suitable for this vessel.
RE: Grinding Cracks in Brittle Steel
This particular vessel has been assessed, operating history and repairs are known, it's even been inspected by Hartford as a part of its sale to another user. We have material certs, and cut coupons out of a scrap vessel for analysis, which confirmed T1.
Customer is concerned that grinding will alter residual stresses and possible cause cracks to grow. That's the information I'm fishing for.
Larry
RE: Grinding Cracks in Brittle Steel
What was the vessel used for – operating temperature and pressure?
RE: Grinding Cracks in Brittle Steel
When checking on the code case be sure and check the dates as I recall there were some issues with chemistry and physical properties of T-1 before a certain date. There might be a reference to CBI as my boss at the time was working with them on some problems.
My notes from 1965 show ASME code case 1204
RE: Grinding Cracks in Brittle Steel
RE: Grinding Cracks in Brittle Steel
Larry
RE: Grinding Cracks in Brittle Steel
The ASME B&PV Code, Section II, subcommittee this week approved a code case for using all grades of ASTM A 514 plate in ASEM Section VIII, Div 3 applications. The limitations to this code case are 100 deg F service temperature, allowable stress limited to yield strength, and for a limited range of plate thicknesses, CVN tests, and no welding is permitted.