Sir/s

Good day.

Is there any document stating that level gauges(including stanpipe and equipment nozzle) need not to evaluate the stress? Because when I do stress analysis, some of the level gauge fails in the nozzle or standpipe connections.

Thanks in advance.

No, just ignore it.

Wait a minute though, it's connected to a big vessel. If the standpipe fails you will be mopping up the vessel contents way past home-time.

But really, ANY pipe should be properly supported and restrained such that it is not over-stressed. If that needs a stress calc then do it.

Whilst simple instrument bridles are often self-supporting, some instruments are very heavy and require decent supports for standpipes and attachments.