We are dealing with a SAGD project with high velocity, high temperature and high pressure process data. The process fluid is water + bitumen + gas. In order to meet ASME PTC 19.3, suggested frequency acceptable ratio of (fw/fn) 0.8, with the flanged process connection, the only solution was to use Supporting Rings, which reduces Insertion Length from 10" to 5". The ring is not circular but rather octagonal in shape. It is machined to (tightly) fit the nozzles.

We have a concern that process fluid may go through the space between the ring and the nozzle and build up in the nozzle in the upper thermowell part, thus creating an oven effect and causing failure at the root of the thermowell, where the stress is highest. We have extraordinary velocities here, ~100 ft/sec, and we couldn't possibly avoid the use of Supporting Rings. Yet, we don't know what to expect. The process itself is very nasty so to speak.

Any advice would be greatly appreciated.

vesna. somborovic at worleyparsonsmeg. com

Vesna S.

 

Vesna,

With such high velocities your thermowell should only need a short "U" length, no need to project far into the flow stream.

In our high pressure oil applications 2500# we use, we strap the thermocouple to the outside of pipe underneath the insulation. This works well and avoids possible leaks.

Regards,
Roy