OTA Compression’s proprietary KS40 Compressor does not use rod packings, therefore is exempt from EPA’s Quad O rule 60.5385 (a), which requires the replacement of rod packings every 36 months or 26,000 hours. The KS40 compressor is a sealed compressor that does not allow vapors to escape to the atmosphere and does not require routine service to maintain the air tight seal. This compressor is utilized on the majority of our vapor recovery and wellhead units: GTO10, GTO20, GTO30, and GTO60.
The main engineering purposes of rod packings is to maintain alignment of the piston for stability and rigidity and to seal the open space between the cylinders to help prevent the loss of sales gas to the ambient. It is very important to monitor the seals for increasing vapor loss, especially in classified hazardous I and division I areas where gas concentrations are easily ignitable. Not to mention, any given air permit may require incremental monitoring of vapor loss or that the vapors be accounted for as fugitive losses.
Rod packings design vary among manufacturers but for this purpose can be thought of as a metal O ring attached to a piston rod. Rod packing is generally made from expensive materials such as ceramic, tungsten carbide, and chromium. These small parts can range in price anywhere from one dollar to a hundred dollars. Depending on the gap between the cylinders, the number of rod packings can vary.
The worst part about all of this is that the rod packing “change out” or replacement process will most likely occur in the field. As we all know, the field is far from a hermetically sealed environment. Any time you start tearing into pistons the last thing you need is dirt getting into your compressor. Dirt and debris create friction that ultimately mulch the packings. Dirt in or around rod packings is also one of the leading causes of leaks. Other reasons that packing can leak are worn rods, too much or too little lubrication, and even installing the packing backwards. Yes! This does happen, believe it or not!
All of this is just another reason one should try OTA Compression when looking for vapor recovery units or wellhead compressors.