LF Vent Pac

High-Performing, Long-Lasting Vent Seal

The Cook Compression LF Vent Pac® assembly employs patented* Low-Friction technology to create a high-performing, long-lasting vent seal.

For years, the Cook Compression “WAT” ring has set the standard for vent seals in environmentally sensitive packing cases. LF Vent Pac assemblies offer the high performance of previous designs, plus extended service life and simplified field maintenance.

Research on WAT ring performance led Cook Compression engineers to develop Low-Friction (LF) technology, which uses internal compression springs and a pressure plate to side-load a standard seal ring – without the increased heat generated by a wedge-type ring. By reducing rod temperatures, LF technology extends the seal and packing case life.

*US Patent #8,251,372

LF Vent Pac assembly illustration

Reduced Rod Temperatures

Field data and internal testing on instrumented Cook Compression test compressors demonstrate that LF technology reduces rod temperatures by 50°F (27.8°C) or more compared to the WAT ring.

Simplified Installation, Maintenance

The plate and springs are preassembled and bolted into the LF Vent Pac assembly at the factory to create a .375 inch (9.5 mm) cavity where a standard seal ring will fit. This design eliminates the need to handle individual springs and other internal components when rings are installed or replaced in the field.

Retrofit Capability

An LF Vent Pac assembly can be retrofit to most packing cases with at least 1.0 inch (25.4 mm) of axial space. If space is limited, the axial dimension can be reduced to 0.94 inches (23.9 mm) by substituting a thinner seal ring.

Compressor packing case


  • Extends seal ring and packing case life
  • Effectively seals vent
  • Retrofits to most packing cases
  • Accommodates standard size seal rings
  • Cartridge design for trouble-free field maintenance