Use of thermowell for slurry services

R

Thread Starter

Riolyn_Francisco

I am writing to you and asking for your help with regards to temperature control in a nickel-mining plant. Our project is in the Philippines and is called Rio Tuba Nickel Mining Project. It is supposed to produce nickel out of the ores. In effect, almost all in-line services have
slurries. Is it appropriate to place wells with its sensor in these in-line slurry services? Because according to SNC-Lavalin Australia, a
nickel-mining plant licensor, avoidance of well installation should be done. If this is true, could you suggest any way in which we could
properly install our temperature measuring instruments, RTD and thermocouples.
Or does this mean we should avoid temperature measurement for slurry lines altogether or shall we consider other temperature measurement type
(not line-mounted?) for such service ?
If temperature measurement for slurry service shall be avoided, please advise which of the temperature instruments for slurry service in HPAL Area can be deleted.

Please also send us supporting facts or information about the use of thermowells in nickel mining industries.
We hope that you could help us on this matter. Thank you very much.

regards,

Riolyn C. Francisco
Instrument & Control Engineering Department
JGC Philippines Inc.
2109 Prime Street, Madrigal Business Park
Ayala Alabang, Muntinlupa City 1780
Trunk line: (632) 876-6000 local 15034
e-mail: [email protected]
 
V

Vince Dooley

You could use surface probes on the outside of the pipes. The area needs to be thermally insulated and the insulation needs to be sealed to prevent moisture ingress into the insulation. Proper insulation can bring the surface temperature up to within less than a degree of the fluid temperature. The disadvantages are less accuracy and slow response. The advantages are improved reliability and increased safety.

Vince Dooley
 
M

McGinnis, Patrick W

Riolyn,

If the Licensor (SNC-Lavalin) mandates: "No TW's in slurry flowlines;" then don't be too shy to ask them: "Just WHAT is YOUR preferred solution?" You are not showing ignorance by asking the Licensor for input about an unusual application. Especially if they have given a warning without completing their sentence (with their solution).

However, thinking of this technically - for non-intrusive temp-measurement in a closed flowline, I'd first investigate using welded-pad RTD. (I'd hope to forget TC's for slurry.)

Pad RTD's will not provide fast response to change. However, I doubt nickel slurry changes temp very rapidly.

Also, Infrared Detector aimed at the line might be satisfactory (but more costly & maintenance intensive). If the slurry is in an open flow trench, an IR detector may be aimed into the slurry itself.

Back to the main point... In this case, the licensor should be consulted. I suggest you don't try to guess what they are thinking and wasting time re-inventing it... (also, CYA)

Patrick W. McGinnis
 
R

Riolyn Francisco

Thank you for your suggestion. An agent from the Licensor has come to our office and one of his suggestions was the same as yours. We shall install the well at the surface of the pipe, having its tip just a little bit below the flow area so that it will not interfere to the velocity of the fluid. And it will cause a not so accurate reading...and one disadvantage we expect is that the well shall only last for a year especially if the service is at very high temp.
Another option was that to install RTD element that is skin type....this will prevent the use of a well, although the lastness of its material is still in question.

Could you give an opinion about this? Thank you.

regards,
 
R

Riolyn_Francisco

I have already tried to e-mail SNC-Lavalin about a specific solution on the problem, but it seems that they're not really that prompt when it comes to answering querries....that's why I seek your help....anyway, thanks for the reply.... we'll try to consider your suggestion.

regards,

Riolyn Francisco
 
First the problem could be forces on thermowell and possibility to brake, or in case of bigger pieces of slurry, the TW could plug the pipe.

First problem with forces on TW is solved by installing the thermowell in elbow so that the flow direction vector is hitting the tip of the thermowell. Second problem can be solved by making "U" dimension of the TW as small as possible (just the tip of 1 cm to be in the stream). Installing the TW in elbow and making the insertion length small will solve the problem

Regards
 
V

Vince Dooley

Riolyn

Either method should work if designed correctly. There is no reason why surface probes should not last. Surface probes are safer and more reliable if the response time is acceptable.

It would help to have a bit more information. What are the pipe sizes? (diameter and wall thickness) What is the pipe material? Is it lined? What is the operating temperature range?

Regards

Vince
 
R

Riolyn_Francisco

Currently, the kind of material we specify were titanium and super duplex stainless steel. Connection size is 2" for rubber and organic lined pipe. Temperature range is designed between 200 to 300 degree Celcius.
 
R

Riolyn_Francisco

Good day. I would just like to ask for some comments with regards to the design of thermowell attached below. The agent from SNC-Lavalin discouraged us to use titanium hard coating at the tip of the well. According to him, based from his experience, breakage of titanium coating occurred when changes of temperature happen. Could you make some evaluations of our design below.

(Embedded image moved to file: pic26308.pcx)

|----------+------------------------+-------------------------------------------|
| Line | Well Material | Hard Coating
| | | |
| | Class | |
|
|----------+------------------------+-------------------------------------------|
| TI | Ti. Gr. 12 | Thermal Spray Coating of
Titanium, | | | |
| | | |
thickness 0.5mm over |
|----------+------------------------+-------------------------------------------|
| DSS | Super DSS (UNS S32750) | Thermal Spray Coating of
Titanium, | | | |
| | | |
thickness 0.5mm over |
|----------+------------------------+-------------------------------------------|
| A31 | Alloy 31 (UNS N08031) | Thermal Spray Coating of
Titanium, | | | |
| | | |
thickness 0.5mm over |
|----------+------------------------+-------------------------------------------|
| A20 | Alloy 20 (UNS N08020) | Thermal Spray Coating of
Titanium, | | | |
| | | |
thickness 0.5mm over |
|----------+------------------------+-------------------------------------------|
| U4 & U6 | 316SS | Thermal Spray Coating of
Titanium, | | | |
| | | |
thickness 0.5mm over |
|----------+------------------------+-------------------------------------------|
| GRL | Super DSS (UNS S32750) | Thermal Spray Coating of
Titanium, | | | |
| | | |
thickness 0.5mm over |
|----------+------------------------+-------------------------------------------|
 
M

McGinnis, Patrick W

Riolyn,

On 21 Nov I commented about this issue, suggesting that you contact the licensor and inquire: "Just WHAT is YOUR preferred solution?"

It seems you are now talking with the licensor, yet are still only making a path in the grass around the tree...

I suggest you tell the licensor - in no uncertain terms - that you don't want to hear any more "what you shouldn't do", that you require them to provide THEIR SOLUTION to the process for which they have licensing responsibility.

What a world!

Patrick

********* The opinions expressed herein are mine, not necessarily in agreement with those of my employer. Caveat emptor. *********
 
had the original question had mentioned use of rubber lined pipe was used and the temperatures involved, up front...
 
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