Stress corrosion cracking failure of a geothermal steam piping rupture disc

Abstract

Rupture discs are typically installed on the high-pressure carbon steel geothermal steam piping as a safety overpressure protection device. In a geothermal power station, a rupture disc burst without any evidence of an overpressure event. The rupture disc was rated for 17 bar, well above the steam piping operating pressure of 12 bar. This paper presents failure analysis results of the burst event of this rupture disc. The results indicated that the primary damage mechanism was chloride stress corrosion cracking (Cl-SCC), which led to change in the stress distribution on score lines and compromised the disc integrity. This paper also discusses materials selection options for the rupture disc with better resistance to Cl-SCC.