Instrument air system and method

An instrument air system relating to the reduction of hydrocarbon emissions of a process using a pneumatic process-control subsystem, the instrument air system comprising:

• a shaft-driven air compressor configured to generate instrument air by compressing atmospheric air;
• a power take off configured to derive drive torque from a driven rotary shaft of the process, the power take off including a concentrically-mounted clamping collar adapted to frictionally engage the driven rotary shaft;
• a torque-transfer assembly configured to transfer the drive torque derived by the power take off to the shaft-driven air compressor, the torque-transfer assembly comprising a set of interoperating gears including a ring gear mounted to the clamping collar;
• a support housing configured to supportively house the power take off and the torque-transfer assembly;
• a support bracket configured to support the shaft-driven air compressor from the support housing;
• at least one motion restraint to restrain motion of the support housing induced by torque coupling with the driven rotary shaft;
• at least one shaft bearing adapted to concentrically engage the driven rotary shaft;
• an air storage tank configured to store a volume of the instrument air generated by the shaft-driven air compressor;
• an instrument-air dryer configured to remove moisture from the instrument air generated by the shaft-driven air compressor;
• and
• an instrument-air pathway configured to supply the instrument air generated shaft-driven air compressor to the pneumatic process-control subsystem;
• wherein
• the support housing comprises an internal gear chamber configured to contain the set of interoperating gears of the torque-transfer assembly;
• the set of interoperating gears comprise toothed gears;
• the toothed gears are adapted to convert an output shaft speed of the driven rotary shaft to an input shaft speed required to operate the shaft-driven air compressor;
• the support housing comprises a rotary-shaft passage adapted to pass the driven rotary shaft through the support housing;
• the internal gear chamber contains a volume of lubrication fluid adapted to lubricate the interoperating gears during operation;
• the at least one shaft bearing is mounted to the support housing at the rotary-shaft passage;
• the at least one shaft bearing is configured provide reduced-friction positioning of the support housing relative to the driven rotary shaft;
• the shaft bearing comprises a split bearing assembly having multiple bearing sections engagable on the driven rotary shaft while the driven rotary shaft is operably coupled to the process;
• the support housing comprises a first housing section and a second housing section;
• a first line of separation between the first housing section and the second housing section is arranged to enable mounting of the support housing around the driven rotary shaft while the driven rotary shaft is operably coupled to the process;
• and
• the power take off is configured to engage the driven rotary shaft driving a cooling fan of a petroleum-gas compressor.