Sec III vs VIII rupture disk stamping

[vanmorrison]

Section VIII requires that the Code Symbol is applied on a rupture disk nameplate. Reference UG-129 (e).

To the best of my knowledge Section III SS NB does not specify the requirement for the Code Symbol to be applied to the nameplate. Reference Section III NB 7811.

Do I understand this correctly? Why do the marking requirements differ between VIII and III? If the Code stamp is a critical requirement for Section VIII why is it not for Section III?

 

[vpl]

VanMorrison

You're correct in that Section III, Division 1 - NB does not require a Code Symbol for a Rupture Disk, per Section III NB-7821. A Code Symbol is required for a Pressure Relief Valve per Section III NB-7811 and for a Rupture Disk under Section VIII, Division 1, Section UG-129(e).

You asked "Why the difference" -- the short answer is "Different Codes, different committees, different requirements." I'm not sure there is really is any specific reason why the marking requirements are different.

One of the reasons -- and this is pure speculation on my part -- might lie in NB-7610(a): since a rupture disk can't be used alone under Section III, the Code Symbol on the pressure relief valve might have been considered sufficient for both the rupture disk and the valve.

However, in the end, the components have to meet the Code under which they're designed, not any other Codes that have other requirements.

Patricia Lougheed

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[vanmorrison]

VPL,
Thanks for your response and kind correction to my incorrect reference #.

I have also noted that Class NC & ND does not require Code stamping on the rupture disks nameplate. Unlike Class NB they can be a sole device as in Section VIII. They do not do not need to be use with a PRV with the exception that Class ND requires regulator approval to use as a sole device.

One suggestion provided to me was that Class NB might consider RD's as a fitting and that Class NC & ND deems them as system components.

As you have stated I will chalk it up to "Different Codes, different committees, different requirements"

 

[vpl]

I was thinking about the question of rupture disks in nuclear service on the drive home last night, racking my brain for where rupture disks were used on the nuclear side. I couldn't think of anything within the reactor coolant pressure boundary (which I think of as the boundary for the "NB" components). We'd pretty much want all components within that boundary to be able to close/recover pressure integrity.

I don't believe that the NRC would ever consider a rupture disk as a "fitting," but I can wander upstairs tomorrow and ask one of the real Code experts.



Patricia Lougheed

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[vanmorrison]

It is the weekend...do you or your contacts "upstairs" ever rest?