Mechanical seals touch nearly every aspect of industrialized society. Wherever a rotating shaft moves fluid, mechanical seals play a key role in sealing process fluids in, keeping contaminants out, or both.
A few basic components and principles in mechanical seal design contribute to a working seal at the interface of the rotating shaft and stationary pump/mixer/seal-chamber housing. Mechanical seals are usually end-face seals or rotating-face seals, but in some designs they can be circumferential or even a hybrid of lip-type seals.
Dry containment seals provide enhanced safety and control of emissions. When coupled with the appropriate piping plans, they can provide early detection of sealing performance deterioration and trigger an alarm if the seal fails.
Many associations, societies and regulatory agencies have rewritten and redeveloped emissions and leakage standards and controls year after year. When the process rules are changed, manufacturers of seals, packing and gaskets are forced to implement changes as well. The manufacturers either produce seals that are better suited to handle the new regulations or they drop out of the market. These changes affect the way end users must look at the quality of flexible graphite and its ability to seal. Click here to read more.
Dual gas-lubricated seals use a pressurized, nitrogen gas barrier – usually at a higher pressure than the pumped fluid – combined with lift features to separate the seal faces to a small, controlled gap. Lift features – such as spiral grooves, waves, T-slots and hydropad grooves – create aerodynamic lift with the barrier gas pressure and shaft rotation, which generate a high film stiffness. This film keeps the seal faces separated, even during challenging conditions, such as vibration and cavitation.
This combination of features and design elements provides advantages not offered by other solutions. “Sealing Sense” articles in Pumps & Systems, November and December 2009, presented an overview of the basic principles of design and application of these seals.
Click here to read a “Sealing Sense” article that discusses the advantages that these unique seal designs offer when compared to other sealing solutions.