Study of the behavior of gas distribution equipment in hydrogen service. Final report, April 1, 1976-December 31, 1978

The results of this 2-3/4 year program show that no special maintenance or safety constraints are necessary when dry, pure hydrogen is carried in modern, well-maintained piping systems composed of conventional natural gas distribution components. Volumetric flow metering requirements were identified as the only significant operational problem. When the normal condition of turbulent or partially turbulent flow exists, our model distribution loops showed energy delivery for hydrogen to be at least 80% that of natural gas under the same operating conditions. Several general and important conclusions are stated below. Natural gas (or methane) leak rates are roughly equivalent to hydrogen leak rates on an energy basis (e.g. Btu/hour). Hydrogen exposure at the moderate temperatures and pressures encountered in the experimental gas distribution models did not create materials problems or related safety problems. However, there was a measurable change in the physical properties of plastic pipe, some adhesives, and some lubricants. Due to the threefold increase in volumetric flow rate of hydrogen required for equivalent natural gas energy delivery rates, existing meters may be undersized due to mechanical limitations and affect metering accuracy and lifetime. Test data are inconclusive, but gas flow metering accuracy, even within rated meter capacity, may bemore » less with hydrogen than with natural gas when employing conventional metering equipment. Meters may have to be replaced for hydrogen service. Throttling of hydrogen at conventional pressure regulating stations or as a result of major leaks does not create conditions conducive to large temperature rises due to Joule-Thomson heating. Thus the potential safety hazard of autoignition of hydrogen, due to throttling does not exist under gas distribution operating conditions.« less