I essentially agree with the statement posted by vanmorrison for most situations. We ran into a situation on some very large tube and shell reactor heads that were originally designed with 2 24" reverse buckling disks on each head. Due to the fact that it was very easy to exceed the stoichiometric ratio of air to butane which would cause a big bang it was deemed that 4 additional 24" disks on each head were needed to prevent a catastrophic over pressure of the reactor. I wasn't involved in the discussions with the insurance carrier but there was quite a discussion about the loss of area in the head proper. I never saw the closing report on the discussion even though I was tasked to install the four addition nozzles in each head. The only noticeable change in the original design was the 24" nozzle that held the RD holder was increased to Sch 80 in lieu of the original Sch 40.
I'll try to contact the AI at the time and checkout his memory.
Here is short video of the transporting an identical reactor in Germany. From some close up pictures there was no correction to some areas that gave us a lot of headaches.
The video is at the bottom of the page. I noticed one thing when you glimpsed the heads there are no large rupture disk nozzles.
Per Code, a rupture disk is a Pressure Relieving Device. It is assumed, by its nature, to be part of the pressure boundary and also a required Safety Device. Thus the reason that they are indipendantly tested in an ASME/NBIC approved labatory prior to being certified as proper for use.
Duwe,
I agree with you that it is a Pressure Relieving Device, it is required to be qualified and that it holds up to a specified pressure and therefore is a pressure retaining item. However, if the disk has ruptured it will not retain pressure. It is in this context that I said the disk was not pressure boundary (or pressure retaining). It is not external pressure boundary. I may have missed the context of Alex2010’s post.
Is the disk itself considered a PRD or is it the disk in conjunction with the holder? It is the disk holder forms part of the pressure retaining piping.
Is pressure retaining material required to be Code Material? Rupture disks do not need to be Code Material.
The disk itself does not require individual registration (in my world these are registered) but the disk holder requires the registration.
Some sections of the CODE require that the disk is stamped with the UV symbol and other sections do not.
Some sections of the Code require the use another PRD in line with the disk whereas other sections do not.
The reasons for the differences between the various sections of the CODE noted above are unknown to me. I have posted in thread292-284594. Any insight there would also be appreciated.
