Unbalanced Mechanical Seals

Unbalanced mechanical seals are simple, widely used sealing solutions in rotating equipment (like pumps and mixers) that rely on a design where the closing force from both spring pressure and the process fluid pressure is applied entirely to the seal faces. This configuration makes them cost-effective and ideal for standard, low-to-moderate pressure applications.
Key Features and Benefits
Simple and Compact Design: The straightforward, unbalanced design is mechanically simple, often requiring minimal axial space for installation.
Cost-Effective: Due to their simple engineering and fewer components, unbalanced seals are the most economical choice for general-purpose sealing needs.
Versatility in General Use: Available in various materials (stainless steel, carbon, ceramics, etc.) and configurations to handle a wide range of common industrial fluids, temperatures, and pressures (typically below 15 bar or 200 PSI).
Ease of Installation: Many unbalanced designs are component seals that are easy to fit in standard pump gland areas.
Limitations
The primary limitation of unbalanced seals stems from the high pressure applied to the seal faces:
Pressure Limitations: At higher pressures, the excessive force on the seal faces can cause overheating, rapid wear, and fluid film breakdown, leading to seal failure.
Heat Generation: Higher face pressure generates more frictional heat, requiring efficient cooling or quenching systems in certain applications.
Compression Set Sensitivity: They are more sensitive to rapid pressure fluctuations than balanced designs.
Common Types and Construction
Unbalanced seals are generally pusher-type designs and are widely available in various configurations:
Component Seals: Installed piece by piece, these are the most basic form of unbalanced seals.
Cartridge Seals: Pre-assembled units that incorporate an unbalanced design for easier installation in standard applications.
Single Spring vs. Multi-Spring: Both single coil spring and multi-spring designs can be unbalanced, with multi-spring types offering more uniform face loading.
Applications
Unbalanced mechanical seals are ideal for general-purpose applications involving clean, non-hazardous fluids and standard operating conditions:
Water and Wastewater Treatment: Used in pumps handling clean water, treated sewage, and other non-abrasive fluids with moderate pressure.
HVAC Systems: Employed in pumps handling hot and cold water for heating and cooling circuits.
General Industrial Use: Found in pumps and mixers across various manufacturing processes for handling general oils, mild chemicals, and solvents under standard pressure requirements.