Do we have to remove the throat bush for API Plan 02 1

[Sam993]

I would like to seek your experience about removing the throat bush or nick bush at the end of the stuffing box, when using API plan 02 in a high viscous material such asphalt. Some body claim it is good to do that and fully machine the stuffing box in order to have good venting and keep the fluid at low viscosity.

Best Regards

 

[flexibox]

That would be a good idea to remove the throat bush on this application. This may assist to get some circulation inside the stuffing box as well as venting. Make sure that you maintain temperatures in that area and permanent Plan 62 (LP Steam) should be used. I assume that you will be using a High Temp Metal Bellows seal with two hard faces. Do not turn the steam off when the pump is shut down to protect the seal faces. If you are using electrical tracing think twice!

good luck!

 

[bk19702]

Plan 02 works best with a wide open seal chamber throat; this allows more natural circulation of the product around the seal faces. Eliminating the restriction is highly recommended; the larger the throat, the better for this flush plan.

 

[gyaneshwarp]

Removing the throat bush is good idea. But by doing so the temperature in the stuffing box would be equal to pumping temperature. Which may cause premature seal failure.

Suggest that replace use rotating throat bush i.e. have a throat bush fixed to the sleeve or shaft with a clearance of about 0.6 to 1 mm betwee rotating throat bush and stuffing box.

This will isolate the stuffing box liquid and you will be able to reduce the temperature in the stuffing box.

 

[bk19702]

Having the mechanical seal immersed in the process fluid is the primary driving purpose of an API Plan 02. The seal generated heat is removed primarily by conduction / convection. Typically, you will see either jacketed seal chambers, seal glands or both in these applications. "Isolating" the seal chamber from the process when using a Plan 02 will gain you nothing but a premature seal failure. You require as much circulation around the seal as possible with this plan - plain and simple. Isolation is only necessary if exclusion from the process is vital for one reason or another - (I.E. Plan 32, 23, etc). Keep the throat bushing out on Plan 02.

 

[msouza]

First of all, for this sort of pumped fluid, it is necessary to keep the seal chamber environment warmed, even before pump start-up, this is the way to heat the pumped fluid and reduce its viscosity. Concerning the bottom of the seal chamber, it must be completely machined, open, for a better pumped fluid circulation, because this is the only way this fluid will have to reach the seal faces. High temperature rotating belows seal is highly recommended, to avoid rotating unit hang-up, to expel particles from the seal face area, thru the rotating belllows and work in high temperature environment.

Mario Souza
Application & Product Engineering
WMF Solutions Brazil

http://www.wmfsolutions.com