Seal Type/Arrangement w/NO release to atmoshpere?

[kelleyh]

I need to find the BEST seal type/arrangement which will best keep process fluids contained and not released to the environment. We currently use a canned motor/pump, but the formation of aligomers fouls the motor cooling passages and we burn up the motors.

Looking at a standard API pump with probably a double mechanical seal. I'm looking for any advice or thoughts on exactly how to reduce to an absolute minimum the leakage of any process to the environment. Thanks.

 

[Milkboy]

Rotating Seat with Stationary Spring Design, in a Dual Seal arrangement is worth looking at.
(Rotating spring designs rarely pass emmisions testing)

Balanced inboard, Balanced Outboard,
Reversed Balanced design inboard (plus anti seat lift out design) to the seal can run as a single if the barrier fails.

The main factor, IMO, is you set up your pump, mech seal and system correctly you should not have any visble leakage.
i.e.
Shaft Run Out (typically 0.05mm)
End Play (float) (typically 0.05mm)
Concentricity of the Sleeve (if fitted) (typically 0.05mm TIR)
Concentricity of the Stuffing Box Bore (typically 0.1mm TIR)
Squareness of the Stuffing Box (typically 0.08mm TIR)

(or whatever you pump maker / seal maker rec's)


On a Dual seal (pressurised or unpressurised) you should be able to get SiC v Carbon faces on the outboard (and on the inboard ideally if chem compatible)
These faces are the best bet in a 'no visible leakage' scenario.

Consider a system with pressure switches / level switch which can give you a good feedback on how much level you have lost in your vessel/reservoir. If too much, it can stop the pump, say, so you can check it out futher.

Im sure there is more

HTH





-
Milkboy

 

[JJPellin]

If the pumpage forms a solid material that can plug up the cooling pasages in a canned motor, I would be reluctant to put that product between seal faces. I would suggest a double gas seal with nitrogen buffer. We have had very good luck with these in Amine, Caustic and other services with fluid that does not behave well between seal faces. If this is not practical, a pressurized double would be the next best choice. I would suggest use of a bias regulator to control the pressure in the barrier fluid to a fixed differential above process pressure. Our greatest problem with plan 53 is if the operators adjust the barrier pressure too high and fail the outer seal. If the process pressure changes a lot, a regulator to automatically adjust can save a lot of failures.