Sequence of Pressure and Temperature Instruments

I should, though, add that installation geometry for flow instruments is more important. Thermowells in particular, and perhaps pressure ports in some cases, may need to be located some distance away from flow sensors, to minimize turbulence.

I think the general point is if they affect each other then the effect should be allowed in the layout.

Pressure devices in my experience are just a side branch - small with just a small eddy effect on the flow.

Temp devices again in thermowells or other will create different eddies. Technically these eddies might impact the pressure measurement but not to the extent that is significant or measurable on an industrial plant.

So probably Pressure then Thermowell. This also seems sensible if the PI is there to indicate the performance of the pump (in an installation downstream of pump) and so you would want it as close as possible to the pump outlet.

BUT if you have some lunking great device then think about what you are trying to measure and ensure that you can measure those things without impact.

Overall I would be surprised if it had an impact and in 20 yrs have never worried about the order.

HOWEVER double plus agree with Tornado that flow elements are very different and have critical rules for the installation of other meters, elbows tees etc.

I prefer to install the most difficult one to reach first. Often the easy to reach sensors block access to that one pain in the a$$ sensor.