Selection of agitator seal

[86782522]

Hi all,

I am working with an extremely aggresive chemical in a G/L reactor above 100C. Now I have problem selecting a suitable agitator seal. We have tested almost all fluoroelastomers like Kalrez, Chemraz etc. used in mechanical seals. Vapors of this chemical attacks all of these elastomers.

I am wondering what are my options now. Can you suggest me any other elastomer that I should try? Also do you know if it is possible to use mag drive agitator (w/ vendor info), which doesn't have any elastomer? What other options I can use like gas seal or a seal with gas purge etc? Let me know if you have experience with any of these alternatives or if you have any other suggestions.

Thanks in advance for all the replies.

 

[ash9144]

Without knowing the chemicals in the vapor space it is impossible to specify a type of suitable seal material. Are you sure you are getting chemical attack? There are many mechanisms to lead to seal failure.
Vapor purged double mechanical seals can be used but you must be able to account for the purge vapors going into your process. Dry nitrogen is a common purge gas.

 

[MJCronin]

8678....

Since you have a GL reactor, I assume that you are dealing with some very aggressive chemicals.

EKATO (and others) make agitators with mag drive assemblies

http://www.ekato.eu/en/products/ekato-rmt/produkte/ekato-esm/

Please complete this thread and tell us about your final solution.

-MJC

 

[longeron]

There are two other options that I can think of for secondary sealing elements for a mechanical seal that may work in your application: Grafoil or PTFE.

A popular seal type before the advent of perfluoroelastomers was a PTFE wedge type seal like a John Crane Type 9.

Grafoil wedges have also been used in the seal type mentioned above. This material is currently more often associated with metal bellows seals. A metal bellows seal may be a good fit for this asset. Also note that if this is a pharma or food grade application that hydroformed bellows are out there with shapes that are much easier to clean and don't have as many crevases as other types of metal bellows.

I'm sure your vendor will be glad to dicsuss these or even other options with you.

 

[unclesyd]

Have you tested all the different compounds from each base materials?

We have a organic chemical that also doesn't like elastomers so when Kalrez first came on the market I installed several in some pumps. The results were catastrophic. Sample returned to Dupont were evaluated and a new compound was sent to be tried. The results with the different compound were excellent. The same thing happened with high temperature HNO3, a change in compound resulted changing the outcome 180*. The same with Chemraz.

Prior to advent Kalrez and Chemraz we used the aforementioned Crane Type 9 on our pumps.

We had some special seals for reactors made by Burgman (German). The seals were a double configuration with a bleed and flush incorporated in the package. The only thing I remember was that when one was dropped the supervisor almost fainted, the cost at the time was over $20,000 for the 2" shaft seal.
I don't know what happened to Burgman as I don't find a website.

 

[chief]

If you do not find a suitable seal , consider a labryinth seal with a low pressure dry air purge. Commonly used in steam turbine applications but with steam as the medium of course.

Offshore Engineering&Design