Magnetic drive sealless internal gear0 vs Rotary external gear pump

[juanon]

Friends,

We are doing an evaluation on replacement of Rotary external gear pump with mechanical seals with a magnetic drive sealless internal gear pump.

The application is for Lubricating Oil recirculation ( continuous duty):
Flowrate of 26USGPM ,
Pressure of 25 psig
Temperature of 43.3 deg C. (the stream is cooled to 30 deg C in a heat exchanger in the circulation circuit).
Viscosity of the oil is 40SSU at 40 deg C ( Lowest operating temperature).
Particulates are eliminated through a 40micron filtration system at the discharge of the pump in the recirc circuit.


The pump required frequent seal replacement which led to this replacement proposal.

Can anyone please provide some guidance ( literature , journal articles to help in a meaning ful comparison) ?

Thanks

Samit

 

[micjk]

Pump and Systems pump handbook has some good info on comparisons between sealless pumps and mechanical seals. We use mag drive pumps at our facility to move hot "dowtherm" @ 245 deg C and "Baysilon" @ 35-150 deg C. They are really reliable pumps. Although ours are centrifugal and you are utilizing gear type, the drive principles are the same. We use both Klaus Union and Magnatex pumps.
Regards,
MICJK

 

[Lochie]

I am surprised that you are having seal problems in what is basically an ideal application with a relatively clean lubricating liquid at a moderate pressure. I would suspect that the pump has been incorerectly selected or there are some installation and operational issues that are contributing to the seal problems. I would think that mag drive on this application is not needed.

 

[juanon]

Gents,

Thanks for your help Pumping manual 9th edition TC Dickenson provides nice comparison.

Lochie,

I also believe the same; we are looking at the maintenance records to get a feel for the recurrence of the problem.

thanks for your input

 

[bhwtam]

Louchie & juannon,

I don't know what your lubricating oil is going to lubricate but I noted that the 40 micron filter is placed at the pump discharge, that means the mechanical seal is in contact with "dirty oil" which may have abrasive media contained.

Furthermore, do have a check whether the material of your mechanical seal is suitable for use with your lubricating oil. You are pumping oil does not mean it lubricates your mechanical seal.