morganwz
Mechanical
- May 21, 2024
- 5
Does anyone know of any publicly available standards, recommended practices, documents, studies, etc. that address the inspection and disposition of corroded threads on in use equipment? We are in the process of writing our own criteria and are looking to see what information is out there that we could build upon.
To give some background, we are an OEM manufacturer of subsea equipment and our products utilize a substantial number of fasteners, nuts, and load bearing retention collars with stub acme threads ranging in diameter from 3.0" to 6.5". Materials are 4130 75Kys, 4340 130Kys, and 8630 130Kys. Our customers have equipment that has been in the field for 15+ years, and when it comes back to us for 5 year inspections and NDE examination, oftentimes a significant number of these connections will have some amount of corrosion damage to the threads. This is not necessarily an automatic rejection because the design has excess capacity far above that which is required by code.
The problem is our current method of dispositioning the threads on these parts is incredibly subjective and relies on the judgement and experience of the person doing the inspection. Basically to simplify things, if it looks like garbage or at least a certain percentage of the threads are not fully intact and undamaged, we advise them to replace the component. This has received substantial pushback from customers who want a less subjective acceptance criteria that is measurable/quantifiable.
They are wanting to use G0/No-Go gauging to make this determination or to measure thread backlash. I have been pushing back pretty hard on this as theoretically I could take a bolt, cut out half the threads and still get it to pass a G0/No-Go gauge test. As long as some portion of the thread remains undamaged they will always measure good.
To give some background, we are an OEM manufacturer of subsea equipment and our products utilize a substantial number of fasteners, nuts, and load bearing retention collars with stub acme threads ranging in diameter from 3.0" to 6.5". Materials are 4130 75Kys, 4340 130Kys, and 8630 130Kys. Our customers have equipment that has been in the field for 15+ years, and when it comes back to us for 5 year inspections and NDE examination, oftentimes a significant number of these connections will have some amount of corrosion damage to the threads. This is not necessarily an automatic rejection because the design has excess capacity far above that which is required by code.
The problem is our current method of dispositioning the threads on these parts is incredibly subjective and relies on the judgement and experience of the person doing the inspection. Basically to simplify things, if it looks like garbage or at least a certain percentage of the threads are not fully intact and undamaged, we advise them to replace the component. This has received substantial pushback from customers who want a less subjective acceptance criteria that is measurable/quantifiable.
They are wanting to use G0/No-Go gauging to make this determination or to measure thread backlash. I have been pushing back pretty hard on this as theoretically I could take a bolt, cut out half the threads and still get it to pass a G0/No-Go gauge test. As long as some portion of the thread remains undamaged they will always measure good.
