Carbon Seal Failure

[Abualnassr]

Hi.

We have a GE blower with the following specs:
dp = 0.5 Bar
Capacity = 7060 m^3/hr
Impeller material is SS403
Speed = 5800 rpm
Suction Temp = 138 C
Discharge Temp = 208 C
Brake Horsepower = 234 HP
Gas is Chlorine

But, the process is higher than the equipment specs where capacity is actually can go up to 8700 m^3/hr and suction temperature can go up to 200 C.

Now, the main problem we are facing as maintenance department is the failure of carbon seal rings.
We use 2 carbon rings (3-segmented design) and we almost replace the rings once every 2 month.

Any ideas regarding the failure and how we can prevent it.


Best Regards,

 

[bk19702]

Can you describe in more detail what the failure mode is??

 

[flexibox]

You do need better descriptions on what the failure looks like however i suggest that you check that the grade of carbon is suited to the application. You may have a compatability issue because I wouldn't think you have mechanical damage.

 

[JJPellin]

We have a Chlorinator blower in our CCR unit that may be similar in some ways. It also uses a segmented carbon ring seal with a Nitrogen purge between the rings. We have had very good reliability from the seal. Chlorine is an unusual product for us. It has material compatibility problems with many common materials. We had to replace all the mounting studs on our blower because they had used Stainless Steel and they cracked. I am not familiar with the metallurgy you indicated for your fan. But, the first thing I would do is verify the compatibility of the carbon grade and garter spring material with hot Chlorine gas. And, as noted above, more details would be helpful.

Johnny Pellin

 

[Abualnassr]

The failure is small fractures in the inside of the carbon ring, which lead to chlorine leak. And i noticed several times that when we replace the defected carbon rings that the color of the ring becomes greenish.

One told me that using 5-pieces rings might solve the problem, although it is about 4 times the price of the 3-pieces we are currently using. So, what do you think ?


P.S. as JJPellin plant, we use also N2 purging.

 

[rzrbk]

The stated speed of 5800 rpm seems very high for a contact seal like a carbon ring. (heat damage from friction?)

Is this speed comparable to other fans in your facility?

 

[bk19702]

Are you maintaining the N2 purge? Sounds as though the chlorine is attacking the carbons, which, based on what you've told us, would mean you don't have enough of a purge of N2 across the rings to keep the gas in the machine. The inner most carbon will always take the brunt of the abuse, especially in this service, but you shouldn't be getting chlorine out of the machine unless your purge has been compromised. I have chlorination blowers at my plant currently, using a three ring fan seal w/ N2 purge and we have not had issues. The metallurgy is key though: you really need to be cautious of the compatibility with the chlorine gas. For my application; metallurgy was all Alloy 600; Alloy C-276 for the carbon garter springs along with a elevated temperature rated carbon material for rings themselves. Properly maintained, I thing your 3 ring arrangement would work. Do you have a drawing or sketch of the design / support system?