Seal Pot Showing Temperature

[smart2006]

We have two centrifugal pumps which we will be comissioning soon. One pump has tandem seal arrangement and one has dual seal arrangement. Both these pumps are using seal pots. For testing purposes, we used water to check the pumps. During testing both seals worked fine, water level in sea pot was good, however the seal pot saw a drastic increase in temperature. Please advice.

 

[bk19702]

Pressurized or Unpressurized? Dual seal and tandem seal cannot be used alone to describe the configuration. Tandem seals can be pressurized, so you need to clarify what piping plan you are using (Plan 52 or 53). Temperature in the seal pot will increase due to heat soak from the inboard seal plus face generated heat from the outboard. Do you have cooling coils on the pot? What buffer / barrier fluid are using in the pot??

 

[JJPellin]

We have a number of Tandem seal arrangements (API Plan 52) that generate a lot of heat that shows up as high temperature at the seal pot. We worked with our main seal supplier to understand why. I felt it was probably the design of the pumping ring. In the end, the seal manufacturer did the calculations and proved to us that the heat generated by the seal faces was the primary contributor to the hot seal pots. We only purchase seal pots with cooling coils. Adding cooling to the pot resolved the problem. I suggest you work with the seal manufacturer. Give them your process conditions and they should be able to determine the cause. They may recommend a larger pot or the addition of cooling to the pot. Depending on the seal design, they might be able to alter the face geometry or face loading to reduce the heat generated. It is also possible that a seal designed for a much lighter product than water would only experience excessive heat during testing with water.

Johnny Pellin

 

[Seal80]

Hi There

I work for a mechanical seal manufacturer.

It is normal for the seal pot to rise in temperature under normal operation. This means you are dumping heat from the mechanical seal. You should also notice that one of the two pipes is hotter. This will let you know that the system is "thermosyphoning" correctly.

In most cases we take the customers process information (seal size and type, pressures, process temp, ambient temp, barrier fluid etc). We use this to calculate the amount of energy (heat) that you need to remove from the system.

It could be that your system is running fine but it would be worth checking with your manufacturer. It could be that you require additional measures to remove more heat. This could be as simple as some finned tubing on the pipes to and from the seal. If you need to remove more heat you may need a vessel with a cooling coil.

If you would like me to run your process info through my software just let me know.

Thanks

S

 

[msouza]

Seal face heat generating is being transfered to the seal pot.
You can evaluate if there is any difference between the inlet and outlet port.
If the temperature is above of what is recommended by the seal mfg, you can cold de sealing fluid using a coil or something related.

Mario Souza
Application & Product Engineering
WMF Solutions Brazil

http://www.wmfsolutions.com

 

[flexibox]

small tip for you! Make sure that you use 3/4" tubing and sweeping bends as opposed to 90 degree elbows. if you have 1/2" tubing change it and you may notice significant change when considering all above comments. also check that the seal is vented correctly and that no air is present.

 

[smart2006]

Thanks for all the help guys.

 

[gyaneshwarp]

Temperature rise indicates thatheat is not being dissipated properly. Check if coolimg is adequate.

 

[bk19702]

Temperature rise in the reservoir means heat is being dissipated correctly. Heat is being transferred from the seal to the fluid in the reservoir. Whether or not the temperature rise is abnormal is beyond the scope of the information we've been given here.

 

[smart2006]

Dear Flexibox, you quoted

"Make sure that you use 3/4" tubing and sweeping bends as opposed to 90 degree elbows. if you have 1/2" tubing change it and you may notice significant change when considering all above comments."

Please explain why sweeping bends and 3/4" tubing are better.

 

[bk19702]

Sweeping bends are better than sharp elbows to help with the circulation of the fluid in the loop (i.e. use two 45's instead of one 90 to make a bend/turn). Personally I have used 1/2" tubing with no issues, although the 3/4" tubing would theoretically provide less resistance and would therefore further improve circulation rate.

 

[flexibox]

The barrier fluid or buffer fluid will need to circulate through the closed loop. You should avoid as many restrictions as possible by not using 90deg elbows in the tubing instead bend the tubing (hence the term Sweeping bends). Depending on seal size and application you can get away with 1/2" tubing too.

If you provide more information on shaft size and seal types we can eloborate further. trust this helps

 

[longeron]

Flexibox is right about the 3/4" tubing and sweeping bends- makes a huge difference.
In additon- be sure that the tubing runs are always rising from the seal to the reservoir without high points in between. High points will trap air and vapor lock the
circulation.
Another good thing to consider is radiant heat from nearby equipment. Reservoir placement should always be carefully considered around hot piping and equipment.