Seal Faces and Scale 1

[Milkboy]

Hey Group

If you are sealing a fluid with a quantity of disolved solids and the Calcium Carbonate has a tendancy to scale, would you expect scale to form on the actual sliding area of the seal faces

OR

Is hang up more of concern when it comes to scaling?


TIA

-
Milkboy

 

[Artisi]

Depending on the seal configuration both scenarios are possible.
Contact a/the seal manufacturer for more specific advice.

 

[ApC2Kp]

Milkboy,

Typical hot service high speed mechanical seal has liquid film that is partially vaporizing on faces. As the liquid film progresses from inside to outside, there will be partial vapor film formed. Solids are left from the vaporized film.

A hard face seal is recommended for fluids with dissolved solids or slurries. Tungsten carbide or silicon carbide are two choices for seal faces. Alumina ceramic could be suitable for moderate corrosive fluid or soft crystal solid.

 

[Milkboy]

Is there any recommended (or personal) limits, say in mg/l, of Total Dissolved Solids where you would switch from Carbon face to Hard face?

-
Milkboy

 

[ClicketyClack]

Are we talking hard water or something worse?

I have not had success with two hard faces and calcium deposits. I have had success with a soft face / hard face combo, usually SiC / C.

I have also used a double seal with a clean water barrier fluid. This cools the faces of the first seal and reduces calcium precipitation.

 

[Milkboy]

Still await full water analysis but its not listed as being "Hard Water", I think it just has a lot of CaCo3 in there.
Temp is 68 to 86 deg F

I was hoping use C v SiC as I guess this would run cooler as the C had good lube properties, and there is a chance of dry running / partial dry running at start up.
(Double seals are out as there are no utilities or $ left!)

@ClicketyClack > What have you seen with 2 hard faces and calcium with regard to failure mode?
How did the C / SiC improve your app? No face scaling?
What ppm of Calcium did you have?


TIA

-
Milkboy

 

[ClicketyClack]

I had a lot of abrasion failures. The two hard faces and the precipitation of the calcium were a bad combination. The softer carbon face will "run in" shortly after suffering abrasion damage. I don't know what the concentration was.

As far as the budget is concerned, it's cheaper to buy one double seal a year with a seal pot than four single seals a year. The double seal is especially useful if there is a chance of dry run. What size shaft do you have?

 

[Milkboy]

Theres a school of though that says that scaling / grit / etc would become embedded in the soft carbon and grind away at the SiC.
Would you then say this is not the case with CaCo3 scale?
Is calcium cabonate scale or similar therefore softer than C faces?


Shaft is 4" !

I take onboard your point about double but I know there wont be a change.

Thnks



-
Milkboy