SINGLE DRY MECHANICAL SEAL FAILURE OF AGITATOR.

[shyamshins]

Dear sir,

I need solution for single dry seal for agitator which failed at one of our site during operation.

Rotary carbon has came out of anti rotation pin, carbon got stuck to silicon carbide stationary face and drive pins rubbed on outer diameter of carbon removing its material.

I guess this is slipstick but unable to understand how I can solve this problem for which I need forum members help.

Process details are as follow:

PRODUCT: Cetirizine Dihydrochloride
OPERATING TEMP. 100 DEG.CELCIUS
RPM: 58
SP.GR.: 0.87
OPERATING PRESS.: Atmospheric and Under vacuum

About 20 % solid ( fine powder form ) added in Solvent,after addition of solids free flowing reaction mass available inside the reactor.

This is a dry seal and no lubrication is provided.

I am attaching photos of failed seal as well as of seal drawing.

Need your help to resolve this problem.

 

[shyamshins]

SINGLE DRY MECHANICAL SEAL FAILURE PHOTOS 1

 

[shyamshins]

SINGLE DRY MECHANICAL SEAL FAILURE PHOTO 2

 

[shyamshins]

SINGLE DRY MECHANICAL SEAL FAILURE PHOTOS 4

 

[shyamshins]

SINGLE DRY MECHANICAL SEAL PHOTOS 4

 

[HansBrinker]

Hi Shyamshins
You're best source of help will the engineering department - specifically a mixer seal product engineer - of any of the big 3 or 4 seal companies. You'll find it surprising the expected difference in performance of different face material combinations. Talk about humidity. Ask about different carbon grades and how they perform against reaction bonded silcon carbide, alpha sintered silicon carbide, tungsten carbide and ceramic. Some of the specifics may be proprietary and thus why you need to go right to the source for advice. Good luck, and put the questions to them

 

[Airsporter1st]

One problem I have experienced on more than one occasion with these seals is people misguidedly spraying them with leak detection fluid to check for leakage! The fluid migrates across the faces by capillary action and causes them to stick together.

I did not open all the photos because I am on a very slow connection, but the degree of damage is quite startling. I would definitely be ensuring that all the usual pre-installation checks are carried out and that they are within. required tolerance.

Neeedless to say the seal must be correctly set. Some fitters tend to overcompress it from the outset in the belief that it will leak less!

I would also be looking at the possibility of excessive axial and/or radial shaft movement, maybe at some point in the process cycle.

As has been said there are a variety of materials on offer from the various manufacturers. Dry running carbons have special properties. Are you sourcing faces from the seal OEM? having them made by a third party, from regular carbon, for instance is a no-no.