To generate the high pressure air required for PET (polyethylene terephthalate) bottle blowing, reciprocating compressors must take air from atmospheric pressure to about 600 psi (40 bar), usually in just three stages and at a relatively high speed. As a result, these non-lubricated compressors tend to run extremely hot.
Furthermore, given the use of the end product as a beverage container, the facility must maintain the highest standards of cleanliness for the compressed air.
TruTechTM 3210 Seals
The high temperatures and often wet air in PET bottle blowing are especially hard on the seal parts. Moisture can wash away the low-friction PTFE transfer film. Cook Compression TruTech 3210, a polymer alloy material for rod packing, piston rings and riders, is uniquely suited to the demands. It disburses heat more effectively off the rod and provides exceptional wear resistance due to its self-lubricating properties.
Ultra-Low-Leakage Packing Rings
Cook rod ring designs also address rod temperatures and sealing effectiveness. Cook Compression has a patented gapless packing ring design that eliminates leak paths and reduces the frictional heat load, allowing packing assemblies to run cooler, which can directly correlate to extended seal life.
Steel and Thermoplastic Plate Valves
Cook Compression has a long history of supplying steel plate valves from its OptimaTM series to the PET air compression market. Cook engineers the valve to application-specific conditions and provides steel internals that can handle temperatures up to 662°F (350°C).
Optima series valves with thermoplastic rings may also be used in the first compressor stages to improve valve life and reduce risk of cylinder damage.