NASA-LLIS-0620

Abstract

<strong>Description of Driving Event:</strong> <br>Upon closing a Shuttle AC Motor Valve during a cycling test, the pressure force differential across the valve deformed the Teflon interface a1dapter for a butt joint at the valve outlet port. The valve slipped free at the inlet port and approximately 160 gallons of Freon 113 was sprayed into the room at 250 psig and 56 gpm. Employees there immediately evacuated the room and suffered no ill effects. There was no equipment damage, but the Freon and productivity losses were costly. <br>Flow benches and tooling for several components were supplied together by the original equipment manufacturer (OEM) to transfer repair operations of these components to WSTF. Safety reviews, subsequent modifications, and personnel training for the motor valve addressed only a valve using a slip joint upstream and a butt joint downstream to facility lines. No other configuration of this valve was known to the reviewers or specifically identified by the OEM to WSTF. <br>An engineer new to the project received a valve with a smaller diameter outlet port for which the OEM had used the adapter to make the butt joint with the facility line. Because the adapter was already available among the tooling, the new project engineer believed it had been included in the system reviews, when it had not been. The OEM, in addition, had recently changed the material from which the adapter was made, from stainless steel to Teflon, to avoid scratching the valve, but transferred ownership prior to using the Teflon adapter and realizing its potential for failure. <br>Losses and hazards were maximized because the supply valve to the Freon tank was inaccessible, being in the direction of spray, and there was no isolation valve on the supply tank. In addition, the emergency instructions did not explicitly address significant Freon leakage.