Cooling Water Pumps

[Lucym]

I'M having Mechanical Seal failure on my cooling water pumps. It's a closed system using De Min Water and Glycol. The Carbon faces are pitting, Springs are discolouring and a type of Lime Scale is appearing on the Stat face. The Seals are Cranne 109 CB Vs TC with NBR70 O Rings.
Regards,
Richard

 

[budwiezer]

the seal face is suitable in your application it is no problem.but why your spring have discoloring maybe they have a chemical mix into your cooling water check the PH of you water if they have chemicals.the appearing of lime scale maybe came from your cooling water it is a dirty water.

 

[JJPellin]

Are you using ethylene glycol, propylene glycol or automotive anti-freeze? We found some of our operators using automotive anti-freeze in some seal pots since it was readily available. But automotive anti-freeze has additives that are designed to plate out on metal surfaces to resist corrosion. We insisted that they go back to pure, industrial grade ethylene glycol and reliability improved considerably. Also, my experience with demineralized water is that it can be much more corrosive than boiler feed water (which has less dissolved oxygen) or even well water. Demin water is hungry for minerals and will corrode some metals more aggressively than other water streams. What is the metallurgy of the springs?

Johnny Pellin

 

[flexibox]

Check your seal circulation line if you have one. If you do not have Plan 11 then incorporate the correct circulation flush plan as I do not know pumps type. To me it sounds like to much heat. Increasing flow to the seal may help solve the problem

 

[Seal80]

Hi There

DeMin water and carbon do not get on. If you change to a hard faced combination you will remove the issue. I would try Silicon Carbide Vs Tungsten Carbide.

I would also avoid using a PTFE wedge seal. They fret the shaft and just increase your repair bill. If the application is not chemically aggressive then a standard o-ring seal will be fine. If you are changing, it would be worth going for a hydraulically balanced seal as the faces are less likely to open in the event of a pressure upset (the 109 is not balanced). I know the AESSEAL SAI would do the trick, but all the manufacturers would have something.

If i ever come across carbon being degraded by demin water i always put in hard faced. If i ever specify a Demin water job, i always go hard faced. It just removes the issue.

Regards

Seal80