If a piping system after operating with a successful service period(operating from Jan'97) gets relocated without significant change in supporting or layout, to some location having similar wind speed, is clause 319.4.1(a) of ASME B 31.3 allowing designer to do away with formal analysis ?

Regarding seismic loading of this relocated piping of non-lifeline systems , as per clause 319.4.2(b) of ASME B 31.3 some simlified/approximate comparison of wind loading & seismic loading will be attempted & some representative, random-selected liquid/gaseous lines of large diameters in existing pipings will be re-analysed for relocated plant's seismic & wind loading data. Moreover, as per IBC for I=1, only pipe support seismic qualification (IBC 1621.6.10) is required, not for piping itself.

From the lessons learnt from this pipe stress community, it may be possible to demonstrate the structural integrity of relocated plant's unaltered piping system without going through the painful process of repeating the same calcs done by engineers 10 years ago. This will save time, human efforts in design & subsequent unnecessary rework due to differences in the approaches of the earlier & present analysts.

regards,

sam

Hi Sam,

Yours is an interesting question.

I think (just my opinion) that the systems as you describe them can for the most part be requalified per B31.3 paragraph 319.4.1(a). DO NOT attempt to qualify any piping system to paragraph 319.4.1(c) as you will notice that the "Warning" footnote effectively disqualifies any "real world" piping system.

There are some issues that you should evaluate:

Check to see if there have been any changes in the Code (from the original Code of record to the latest issues of the Code) especially regarding allowable stresses (stress ranges) for the materials of construction.

There may be a difference in the soil bearing capacity that would have to be reconciled with the pipe support designs (e.g., if you are going to erect a new pipe rack system at an undeveloped site). Be alert to the possibilities of differential settlement displacements associated with the equipment to which the piping is to be attached (i.e, the soil may not be fully compacted).

Be alert to the possibilities that the displacements (thermal and settlement) of the piping terminal equipment may not be the same after the piping has been "relocated" (e.g., if the piping is attached to a heat exchanger the supports for the HX may have the "anchored" end and sliding end switched in the new arrangement.

Consider what is really meant by "duplicates" an existing design. Exactly how close to the "as analyzed" system does the "relocated" system have to be? This is an age old question. A few years ago a committee considered this question (what are acceptable "tolerances" for slight differences in dimensions, support locations, locations of concentrated loads, etc.) and their work resulted in the issuance of an EPRI document (for electric generating plants but nevertheless it is a thought provoking document) EPRI-NP-5639, EPRI Guidelines for Piping System Reconciliation, NGIG-05.

Certainly there other issues to consider and our compeers will likely weigh-in with their thoughts


Regards, John.

Hi Sam,

I agree with all the above comments and would like to add the following points.
Generally most plants are designed for a 20 year fatigue life, therefore for code compliance the stress range reduction factor 'f' used in the stress calculation should be equal to 1, i.e. for 7000 cycles which is approximately one cycle per day for twenty years. If your plant has been working for eight years (since 1997) then it probably has twelve years life in it in the new location,however if the design life has been extened ( say by another 8 years or more)at the new site then all the stress critical lines will have to be re-evaluated to comply with the ASME B31.3 piping code by using a lower stress range reduction factor in the new calculations.

Regards A

Most plants never come close to 7000 cycles. While I, too, have been fed the line that 7000 cycles is about 1 cycle a day for 20 years, virtually no system, certainly not in a refinery, cycles nearly that often.

Just about every refinery on the Houston ship channel has been operating since long before I was born (1972 - Yes John, you are getting old...so am I). I wouldn't be too concerned with that aspect, as the plant is just as likely to have run for another 30 years at it's present location as at the new one.

I worked on a relocation project about 5 years ago. As the code indicates, it is the owners responsibility to insure that a facility is safely designed and operated and they were comfortable with not doing any analysis of the relocated piping.

But, I did spend a good bit of analysis time working the pipe rack lines than ran to the battery limits and all the new OSBL piping, as that part of the old unit was not relocated. The new plant had it's own utility and flare systems that we were hooking up to and that was the focus of stress work for the project.