In order to quantify the susceptibility of the aluminum and titanium alloys to hydrogen embrittlement, Texas A&M has fabricated a special test fixture identified as a Small Hole Punch assembly to be used with a standard Instron tensile test machine. The test apparatus will puncture a hole into a test specimen that measures 3 mm in diameter and 0.5 mm thick. The purpose of these tests is to determine the relative effects of hydrogen exposure on the metal matrix, and thus, determine if the metal strength has been compromised.

The complete hydrogen pipeline compressor package that integrates all of these major components is shown in Figure 5. The complete modular package, as shown, is 26 ft long x 10 ft tall x 6 ft wide (at the base) x 8 ft. wide at the control panel, approximately ½ the footprint of a piston-type, hydrogen compressor. The packaged module can be transported to the installation site as a pre-assembled package with a minimum of final alignment, water piping, and electrical power connections, instrumentation, and controls start-up.

Preliminary design details of the completed pipeline compressor module include:

  • Compressor design conditions confirmed by project collaborators
  • Pinlet= 350 psig, Poutlet=1,285 psig; Flow rate= 240,000 kg/day
  • 6-stage, 60,000 rpm, 3.56 pressure ratio compressor
  • Integral gearbox pinions driving individual, overhung impellers
  • Design of compressor’s major mechanical elements completed and satisfied by two manufacturers per component
  • KMC tilting pad radial and thrust bearings designs validated for use
  • FlowServe single, gas face-seals have been validated for use
  • Heat exchanger specifications met by two manufacturers to cool hydrogen gas to 100°F between stages
  • Tranter Plate-type Heat Exchanger Design
  • Heatric Heat Exchanger (compact, plate-fin surface core)

Conclusions and Future Directions

The preliminary engineering and design of an advanced pipeline compressor system has been completed that meets DOE’s performance goals for a reliable, hydrogen pipeline compressor system, with a footprint one-half the size of existing industrial systems and at a projected system cost of approximately 75% of DOE’s target and a maintenance cost that is less than the $0.005/kwh. The advanced centrifugal compressor-based system can provide 240,000 kg/day of hydrogen from 350 to 1,300 psig high for pipeline-grade service. This has been accomplished by utilizing state-of-the-art aerodynamic and structural analyses of the centrifugal compressor impeller to provide high pressure ratios under acceptable material stresses. The technical approach that has been successfully implemented to reduce the developmental risk and increase the system reliability while maintaining a competitive cost includes using commercially available, and thus proven, bearings and shaft seal technology, as well as acceptable practice in bearing and gear loading.

The resultant design provides a compressor that meets DOE’s Hydrogen Plan for future pipeline delivery, as well as for use by the industrial, hydrogen gas industry where there are presently 1,200 miles of pipelines providing 9 million tons per year of hydrogen gas for industrial process chemical applications. A collaborative team has been assembled consisting of Praxair, Texas A&M (a materials researcher), and HyGen Industries (a hydrogen refueling industry consultant).

Future efforts include:
•Phase II. Detailed Design (01/2010 to 08/2010)

  • Detailed subsystems modeling
  • Detailed integrated systems analysis
  • Critical components design, testing and development

•Phase III. System validation testing (09/2010 to 06/2011)

  • Component procurement
  • Two-stage centrifugal compressor system assembly and lab test

CN engineering personnel who have contributed to this article include Jamin Bitter, Kerry Oliphant, Sharon Wight, Glenn Derbyshire, Ken Heidelmeier, Ron Provencher, Fred Becker, Dr. Karl Wygant, and Dr. Louis Larosiliere.

You may contact Francis A. Di Bella, PE at This email address is being protected from spambots. You need JavaScript enabled to view it. and Dr. Colin Osborne at This email address is being protected from spambots. You need JavaScript enabled to view it..

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