How does seal hydraulic balance work?
- There are two forces closing the seal faces:
①A spring forces caused by the spring, springs, or bellows pushing on the seal face.
②A hydraulic force caused by the pressure of the fluid acting on the closing area of the seal faces.
- There are three forces opening the mechanical seal:
①A hydraulic force caused by fluid or vapor trapped between the lapped faces.
②Centrifugal force that is causing the rotating portion of the seal to try and become perpendicular to the rotating shaft.
③Hydrodynamic forces generated between the seal faces because for all practical purposes liquids are not compressible.
- We balance these forces by reducing the closing area of the sale faces and thereby reduce the closing force. This is usually done by a small sleeve inserted into the seal or as stop machined into the shaft. Metal bellow seals have an effective diameter measured through the bellows to accomplish the same thing.