As fleets convert to compressed natural gas (CNG) as a more environmentally friendly fuel supply, filling stations encounter new challenges to longevity and performance.
CNG filling stations require small, often non-lubricated, compressors that run at high speeds and high pressures, with low emissions and effective oil control. A premium must therefore be placed on sealing effectiveness.
Solid Ring Technology
Cook Compression Solid Ring Technology is optimal for these small compressors. Each set of solid packing rings provides greater sealing capacity than traditional radial and tangent cut ring sets, reducing the number of cups and rings required, which reduces frictional heat generation. The technology also uses the compressive properties of the ring materials to seal in sequence through a compressor stroke, reducing ring wear and providing greater sealing effectiveness, especially at higher pressures.
Piston Rings and Riders
Cook piston rings and riders are engineered for maximum service life and reliability. Seal joints and multi-piece rings are used in higher stages to reduce blow-by, while side notches on riders prevent pressure loading under the ring.
Moreover, Cook applies its extensive materials development work to select filled PTFE or PEEK materials that provide reduced wear and can withstand and disburse the heat generated at the sealing surfaces.
RTV oil wiper packing uses a proprietary knife-edge geometry to remove the crankcase oil film wherever it contacts the rod, keeping oil from the fuel supply. The single-groove design of the RTV oil wiper improves gas sealing to reduce fugitive emissions, which is especially advantageous in short-frame CNG compressors that do not have a separate wiper housing.
Wiper packing geometry is combined with a material designed to improve oil-wiping efficiency. TruTech™ 3110 is a PTFE-based compound engineered to provide a sharp wiping edge over extended use. It also allows the wiper rings to conform tightly to the rod surface, eliminating potential leak paths.
Ring Damped Valve
The intermittent running of fueling compressors, combined with their high speeds and pressures, can cause valves to fail prematurely. The Cook Compression Ring Damped Valve can extend valve life by reducing impact forces at these high speeds and protecting against impact fatigue.
For smaller valve envelopes, particularly in the later compressor stages, Optima™ series plate valves provide an engineered solution.