Thermowell U-LENGTH Calculation | Thermowell Insertion Length (MOST SIMPLE EXPLANATION)

Why do we it call U-Length ?
The U standards for unsupported length in thermowell
The U Length of thermowell starts from the tip of the thermowell to the edge of connection ( i.e flange or threaded connection)
How to calculate the U-Length of Thermowell ?
No matter what engineering project you are executing in any part of the world, the basic design rule remains the same.
Thermowell U-Length is the summation of Standout and Immersion Length
a) Standout Calculation
b) Immersion length Calculation
Criteria 1 : Nozzle Standout calculation
First let us look at standout Criteria of Nozzle.
In usually petrochemical project usually the Pipes have Insulation (Hot/cold/acoustic etc)
In order to remove the thermowell nuts, it is recommended to have a clearance space of 100mm
Thus if we assume a standout of 150 mm then with 100 mm insulation the Standout might have to increased to 200mm
So 200 (standout) - 100 (insulation) mm = 100 mm (Clearance space)
Similary we for 150 mm insulation we will increase standout to 250 mm so we have clearnace of 100 mm to easily remove bolts without having to cut through the insulation.
Criteria 2 : Thermowell immersion length rule of thumb
The immersion length is the length of the thermowell that protrudes into the process fluid past the edge of the pipe or vessel
In simple words the length of thermowell that is in contact with process.
See below picture
Imersion length criteria varies from project to project and Standard to Standard.
The optimum immersion length is a tradeoff between accuracy and response time with mechanical strength requirements
API RP 551 recommends a minimum immersion length of 50 mm (2 in.).
The thermowell tip should not be inside the edge of the nozzle. The tip should always be in contact with the flow stream.

[@AsadPassionateEngineer]

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[@balajiarni]

@AsadShaikh 6:30 - Pipe is shown completely filled (BLUE Colour), what if pipe have HALF volume of its capacity? Should we consider increasing IMMERSION length?

[@abdessamedghettas7167]

Thanks, very useful

[@keertirajgajare3932]

Very informative 👍

[@AsadPassionateEngineer]

Thank you so much 😊

[@rhashmi1]

Very nice.

[@AsadPassionateEngineer]

Thank you so much, Glad you found it helpful 😊

[@gauravlambhate4439]

Amazing bro....

[@AsadPassionateEngineer]

Thank you so much Gaurav !! 😀

[@abhishekmurarka1984]

Good one bro

[@AsadPassionateEngineer]

Thank you so much, Glad you found it helpful Abhishek 😊

[@playingdancinghappylearnin3892]

Why pipe thick ness not considered

[@mohithmohan9810]

Please do a video about wake frequency calculation

[@instrumentationcontrolauto9981]

Dear Asad can you please prepare a video on the Datasheet for control valves.

[@AsadPassionateEngineer]

Thanks this is a very good suggestion 😊 I will start to work on this right way !!

[@vaijainathnamgode3149]

Do u need to take Thickness of pipe and Gasket to calculate U length

[@vaijainathnamgode3149]

Hi.. could you help me to understand above query

[@AsadPassionateEngineer]

This is really a very GOOD QUESTION .
I can tell you my understanding,
1) Point 1 : Should we consider gasket thickness :The spiral wound gasket thickness are typically between 3.2 mm to 6.5mm max so as per my understanding this can be ignored by keeping a little safety margin in our calculation
2) Point 2 : The Thickness of wall of pipe : In the projects and calculation that i have worked, this is basically few mm thus during U- length calculation we can consider a safety margin for this aspect.
So accordingly the U-Lengths are decided with safety margin.
In brief the answer as per my opinion is that since these are minimum values considering a safety margin should suffice for the effect of these values.
hope I was able answer this question. I am also a learner like you so if anyone else has some other understanding please share !!

[@ssenthilvelbe]

Nice Video Asad. Can u tell me about what is meant by Insulation length

[@AsadPassionateEngineer]

We have various type of insulation, Like Hot Insulation (For Line with High temperature) Cold insulation etc. So, in simple words it is a cover on pipe to protect heat transfer or for personal protection.