Blending of hydrogen in natural gas distribution systems. Volume III. Gas blends leakage tests of selected distribution system components. Final report, June 1, 1976--April 30, 1978

Abstract

This report describes tests made using various types of joints and materials commonly installed in gas-distribution systems to determine the gas-leakage behavior when blends of hydrogen and natural gas are distributed. Twenty sample test joints, consisting of eleven cast-iron cement and jute joints, five steel joints, and four plastic joints, were tested using straight natural gas, varying blends of hydrogen with natural gas, and varying humidity levels of the gas mixture. In the case of the steel joints, the pressure level was also varied but the gas mixture was not humidified. Test results show: (1) cast-iron joints and steel joints that did not leak with natural gas did not leak with blends of up to 40% hydrogen in natural gas; (2) cast-iron joints and steel joints that had small leaks with natural gas did not leak at a higher rate with blends of up to 40% hydroge in natural gas; (3) cast-iron joints that had large leaks with natural gas showed a detectable increase in leakage as the hydrogen level in the gas blend increased; (4) efforts to determine if the permeability of polyethylene tubing increases with increasing concentrations of hydroge in natural gas, and with aging of the plastic, were inconclusive; and (5) there was no preferential leakage of hydrogen in any of the joints tested using blends with up to 40% hydrogen in natural gas.