Refinery Storage Tank Thermowells Immersion Lengths

[Weegie]

Gents,
I'm looking for an industry standard/guide for immersion lengths of thermowells directly mounted in storage tanks. We have tanks from 12ft to 57ft in diameter. Only info I've found is an old Shell standard for (process ?) 'vessels', stating an immersion length of 18 inches. Thanks.

 

[controlnovice]

Try this link:

thread698-186164

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This is normally the space where people post something insightful.

 

[Weegie]

Thanks.
Senility is a wonderful thing.
I even put my 10cents work in that already discussed topic !!

 

[Weegie]

I found the details in the API publication 'Manual of Petroleum Measurement Standards, Chapter 7 - Temperature Determination'. API recommend a minimum projection of 36" into the tank (from the side) if the rtd/thermocouple inside the well is being used for custody transfer. If it's a local bi-metallic dial thermometer, recommended minimum is 12".
Point to note though, the publication has a lot of detail on temperature monitoring especially in 'custody transfer service' where acuracy plays a big part with respect to liquid volume and expansion due to heat. Well worth the read !