Mechanical seals under vacuum

[flexibox]

I am interested in your comments on the topic of;

"Air entering a seal face under full vacuum".

Assume a single seal that is designed to handle full vacuum ie spring loads are designed to overcome full vacuum condition and seal.

Under this mode of operation, will air enter the seal face and flow into the seal chamber?

No silly answers like use a dual pressurized seal!

Look forward to reading your comments!

 

[IRstuff]

You're not allowing silly answers, but your question, as posed, is silly. If there were never any leakage, you wouldn't find leak detectors to buy for testing for it:

http://www.mksinst.com/docs/UR/PICOVacuumDS.pdf

TTFN

FAQ731-376

 

[flexibox]

Perhaps the question was not clear. This is on a centrifugal pump Injection water booster application. There is a single seal fitted and occasionally the seal chamber will see vacuum conditions. The question is will air ingress through the mechanical seal face during operation. Pump operates at 3000 rpm, seal chamber pressure normally 200Kpa.

 

[IRstuff]

I understood your question, the point is that ALL seals leak.

The only relevant question was whether or not it matters, which you seem to not want to answer. What amount of leakage is tolerable to your application?

TTFN

FAQ731-376

 

[ciddik]

No the seal will not allow the air to enter unless there is proper cooling for seal faces & seal is properly design to handle vaccum conditions, as self balanced seals do


siddik

 

[rzrbk]

If the seal chamber sees a vacuum, it will pull air thru the seal faces. If run this way for an extended time (i.e. more than just start-up), seal will overheat due to loss of lubrication, and flush may need adjusted to keep chamber pressurized.

 

[bk19702]

Under vacuum conditions, the seal will pull some air. As recommended, you may need to adjust the flush rate to pressurize the seal chamber at all times (a plan 32 for example). You can also run a startup quench of water on the atmospheric side so that the seal faces will remain lubricated during these conditions. In my experience I have seen seals experience vacuum conditions like you are describing recover and perform well, but ultimately some face damage occurs as a result.