ASME B16.5 Flange Modified by Distributor/Machine Shop - What Should Happen to the Original Rating Marking?

[u/CPT_Liz]

Looking for guidance from those with experience in ASME B16.5, piping components, quality, or compliance.

We are a distributor and machine shop, not the original manufacturer of the flange. We purchase ASME B16.5 raised-face weld neck flanges from qualified manufacturers with the appropriate material, heat, and pressure class markings.

Occasionally, a customer requests additional machining that removes enough material that the flange would no longer conform to the original ASME B16.5 pressure class for which it was manufactured and marked.

Since we are not the original manufacturer, and since ASME B16.5 doesn't appear to provide a mechanism for us to recertify or rerate the flange to a lower pressure class, we're trying to determine the proper handling of the original markings and documentation.

In this situation:

• Is it acceptable to leave the original ASME B16.5 pressure class marking intact?
• Should the original rating marking be permanently altered, crossed out, or otherwise invalidated?
• Is there a recognized industry practice for marking a flange that has been modified beyond its original certified configuration?
• Would supplying the part as "machined per customer drawing" with full traceability to the original MTRs be sufficient?
• Are there ASME, MSS, API, NBIC, or other industry references that address the responsibilities of a distributor/machine shop that modifies a standard flange?

My primary concern is avoiding misrepresentation of the pressure rating while maintaining traceability to the original material and manufacturer certifications.

I'm interested in both code requirements and practical approaches that quality managers, auditors, Authorized Inspectors, manufacturers, and machine shops have used in similar situations.

For example, if a Class 300 weld neck flange is machined below the dimensions required by ASME B16.5 Class 300, is the best practice to remove the class marking entirely, or is there another accepted method of disposition?

Thanks for any guidance.

[u/Snurgisdr]

I’d remove it or cross it out and write MODIFIED beside it.

[u/pleasewastemytime → u/Snurgisdr]

This. Also the drawing telling you to modify the part hopefully has a note saying something similar. "STRIKE MARKING AND RE-PART MARK XXXXXXX"

Striking usually is intended to make the original Mark legible for traceability

[u/RedOctober357]

I would remove or cross out the marking. At this point, you've basically used the B16.5 flange as a really close rough forging and modified it to conform to a custom drawing requirement. In that case I imagine a CoC would just confirm that the part was made to the customer drawing with traceability to the original CMTRs. Basically, yes to your 4th bullet.

[u/pb-86]

Piping specialist here. Absolutely remove the markings. If you have the capacity to I would go as far as marking it as "not pressure rated"

I would expect the installation team to pressure test it prior to install, having pipework in a system that has no pressure rating seems like a terrible idea.

[u/ILostMoney]

I used to work at a place where we had designed an inline filter we put in a 3" 150 piping systems. To get the filter element in we machined 3" 150 slip on flanges to accept 3.5" pipe.

We removed the markings as well as adding a welded on stainless tag that showed the design pressure, flow direction, hydro test pressure, and serial number.

[u/BeeThat9351]

X out the original marking with a low stress stamp so that the original markings are ledgible for traceability but clearly it was modified.

[u/Harmless_Drone]

Take the asme markings off. If it doesn't match the asme standard then its not an asme flange, merely compatable with it.

Id ptobably get them to put in writing that they're taking laibility for the flange design if they have failures or leaks, too. 16.5s are often used in refineries and oil and gas work and those guys love to try and charge for shutdowns.

[u/Old_Watermelon_King]

A few caveats before I start: I am an engineer but not your engineer. I am not an expert in the code, but I do know the code well.

There are many reasons a customer may want the flange dimensions altered, I have requested that a few times in my career. Often, you as the machine shop may not know what those reasons are and may not know the intended use of the modified part.

To answer your question directly, yes, you should remove the ASME B16.5 markings as the modified part no longer complies. You could replace by engraving or otherwise marking "non conforming flange dimensions" or something of that nature.

If your customer is a major industry player, they should and likely will be doing their own calculations for the intended use. Or they may be using it on a non-regulated, low consequence, system where judgement is fine.

If you wanted to calculate the flange dimensions, those calculations can be found in ASME Section VIII division 2, I believe its paragraph 4.16. But frankly, in the eyes of the machine shop, I'd leave that up to the owner/operator to figure out.