Thermic oil pump seal problem 2

[asifraza0]

All experts:
I'm having bit of a problem with my Thermic oil pump
It is a Dean model 4144 high temperature pump 3x4x8.5. The thermic oil is Therminol 72 with a maximum operating temperature of 380 Deg C and the pump has a John Crane mechanical seal model 609
There had been three cases when the seal totally crapped out completely and has to be replaced. Per John crane the seal was damaged by coking of thermic oil on the seal face which lead to its failure. This seems a little odd since the pump has been operating only for 2 months
I've tried to trouble the problem by operating the pump closer to BEP by maintaining proper differential pressure.
The pump was working fine with a thermic fluid temperature of 330 Deg C; I've tried to raise the temperature to 345 Deg C. The pump ran for a day without any issues and then started to leak very badly. The seal failed again
Any experiences with a similar and similar issues
Araza

Asif Raza

 

[ashtree]

Is your pump fitted with a water cooled seal chamber?

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[asifraza0]

yes, we are using cooling glycol


Asif Raza

 

[ashtree]

Are you confident that you have the right flow rate? Are you staying within the correct temperature range?
Is the seal the right one for that application?

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[ashtree]

The John Crane seal has a maximum temp rating of 425 degrees C so if your temperatures are right you should be okay that way. But has this caking been due to excessive temperatures (above 380 degrees)?
What about operating pressures? Are you within the limits of the seal?
Am i correct that the caking of the oil on the shaft was preventing the correct seating of the moving face, thus causing the failure to seal?


Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[asifraza0]

My operating temperature is only 340 deg C
My operating pressure is optimal the discharge is only 100 psig
The caking is not on the shaft but on the seal face

Asif Raza

 

[LittleInch]

I would start looking carefully at the water cooling system. How does it maintain flow? When does it stop and start. How do you make sure you have enough cooling flow?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[ashtree]

Would it be possible that the seal chamber is exceeding 400 degrees?

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[moltenmetal]

Hey Asif: if the pump is the thermal oil type like the link below:

http://www.mp-gps.com/products/proc...mps/ra-series-air-cooled-thermal-liquid-pumps

Make sure that the finned section between the pump body and the seal, which is intended to allow the seal to stay cool, has not been insulated...

You listed the make and model of the seal but not the seal plan. The Dean pump used for thermal fluids uses a single mech seal, without a seal buffer fluid, so I'm not sure what your glycol is doing. If it is a pump with a double mech seal and a seal buffer fluid, then glycol is probably the wrong material to use as a buffer fluid in high temperature thermal oil service.

Are you sure the coking is happening on the seal? Or is there another item (i.e. a heater) which is causing the oil to coke?

More information will help the community answer your question better.

 

[JJPellin]

The key is the seal flush plan. The seal can take this temperature. But, if the oil will coke at this temperature when exposed to atmospheric pressure, then coke will form from the small amount of normal leakage past the seal faces. A jacket cooled seal chamber (API Plan 2) is generally a waste of coolant. The flow of coolant is probably not capable of removing enough heat to keep the seal faces below the coking temperature of the oil. I would add a plan 11 flush to keep heat from building up in the seal and add a steam quench (API Plan 62) to prevent coking at the seal face ID. If you prefer, you could leave the Plan 2 in place and add the steam quench. But, I see no benefit in the Plan 2 jacket cooling.

Johnny Pellin

 

[asifraza0]

Great post J Pellin:
I do not have steam in the plant. I only have cooling glycol and the chilled glycol
The pump has single mechanical seal without barrier fluid
The seal chamber is not exceeding 400 deg C
Thanks

Asif Raza