Additional detail would be helpful. When I read this, I am picturing the oil seals on the bearing housing that are primarily intended to keep the oil from leaking out. Most of these seals on our steam turbines are simple aluminum labyrinth seals. And, many of them chronically leak oil. If you are talking about a more sophisticated seal, I would pictures something with a floating bushing that might be brass/bronze. A seal of this type would normally be ported to allow for the introduction of a purge gas to help keep the oil in and keep the steam out. We have a number of these designs, as well. Most of them use dry instrument air as the purge gas. If it was available, I would prefer to use pure nitrogen. If this is what you are referring to, I would recommend the use of the purge gas as this would reduce the chance of water getting into your oil system or oil leaking out to atmosphere. If I completely missed the mark and you are talking about something else, I apologize.

Johnny Pellin

In gas compressors and expanders, dynamic gas shaft seals are well proven in service. These use N2 or air as a buffer medium ( sometimes both N2 and air) to segregate the seal oil from the process medium. Talk to John Crane or Borg Warner. The description from JPellin matches the assembly configuration for these gas seals.

Dear JJPellin,

Thank you for your reply. Yes that's what i mean .we should ask them to include an instrument air connection.

So i should use N2 not instrument air?

I prefer nitrogen rather than air. If ther were any water present in the housing, actively feeding it oxygen could contribute to corrosion. If the installation is indoors, nitrogen could contribute to an oxygen deficient atmosphere for your employees. All of our turbines are outdoors.

Johnny Pellin

The oil seal - open space - steam seal design is the only one I am familar with on the steam turbines I have worked on.

This vender is trying to sell you an upgrade or a system enhancement. Fine. That is his business - literally. Anything or any system that keeps oil out of the condensate, condensate drains, and boiler is good. Anything that keeps water out of the oil system is good.

Now, make the vender provide you concrete measurements and in-plant references about his system that measure actual reductions in oil ppm in the water, and water ppm reductions (or purity improvements) in the oil. Weigh those improvements (if measureable!) against the cost of his system, and the cost of its future maintenance and servicing and cleaning and supplies. (Filters, absorbents, seals? Those may likely be more profitable in the long run to him than the initial installation. )