Horses for courses.
Gaps on guides on long runs of pipework which are keeping thermal growth stable need not be too accurate. However,gaps which are controlling growth such as limit stops need carefull consideration.
Two examples are:
1) Static analysis of Prv pipework with forces vectored into the analysis. The size of gaps here can have a huge effect on stress levels and nozzle loadings.
2)Equipment Calcs, in reducing loadings on pumps/nozzles etc, the gaps on the stops can greatly affect the forces/ moments etc.
So as stated in an earlier responce, i feel it is important to model the supports/pipework/gaps as accuratly as possible. Guides/linestops etc should be individually assesed for the criticallity of the gap.
If indeed the gap is crucial, the state clearly on the iso's and have it checked in the field.
In my opinion, 0(zero) gap supports should not be moddelled in Caesar. if a zero gap support is required for code compliance, then redesign the pipework as zero gap supports are impossible to engineer.
my twopeneth so it is!.
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Best Regards