Hydrodynamic Seals, are they all they're cracked up to be?

[Foxtrap]

Howdy,

I am working on a mostly rotating but sometimes static application and, like engineers before and probably always will till the end of time, I am having sealing issues. Unfortunately this is a project I am stepping into therefore am trying to figure out the reasoning of the first designer.

The seals that we were using were a PTFE spring energized seal. We are looking at holding 4500 psi static and 1500 psi when rotating at 140 rpm. The seal would be required about a Ø10". The PTFE's were melting. This as far as I can tell was a design error in the fixed and rotating pieces and there was metal to metal contact. Since a design change was necessary anyway someone (the boss) suggested going to a hydrodynamic seal. Has anyone used them before? Any suggestions or remarks would be helpful.

 

[longeron]

I've heard of mixer applications with diameters approaching yours and at operating pressures above yours. I'm not sure about the ability to hold under the static conditions. But I'd bet that a phone call to Flowserve, John Crane, Eagle Burgmann, or Chesterton might give you a better idea of what those mechanical seal mfgs offer for applications like yours.

 

[JJPellin]

There was a good paper presented at the International Pump User's Symposium that could be relevant. This paper was related to a hydrodynamic seal (referred to as an upstream pumper) for sea water service. This paper talks about a seal design that was limited to 300 psi dynamic and 450 psi static. But there may be similar designs that can go higher. I have never heard of one for a service as large, low speed and high pressure as yours. A copy of the paper could be purchased from Texas A&M Turbomachinery Laboratory, if you were interested.