Tandem Seal - Pressure for secondary seal

[DoraeS]

Hi,

If I have a tandem seal for pump and a tandem seal for gas compressor, what I understand is that the primary seal will be drawn from pump or compressor discharge to the stuffing box, and the secondary seal could be water for pump (API seal plan 52) and nitrogen for gas compressor. I would like to know if the above is correct? And if so, my question is, does the secondary seal pressure must be higher than the pump or compressor discharge pressure in order to prevent the primary seal from 'leaking'?
Also, does any one know which website can I find the relevant information?
Thanks a lot!

 

[ajs1972]

A tandem seal is two singles seals, normally put "back to back". In the space between the two seals exist a "barrier fluid" which must be under pressure, usually 1-2 bar above of the pressure of the process. With this excess of pressure avoids the leaks of the process fluid.

You can see the web page of seal suppliers (for instance, Burgmann) to know more about specific points.