Pressure Vessels – Pressure Relief Devices, Corrosion Protection
Pressure Relief Devices
All pressure vessels should be equipped with one or more pressure safety valves (PSVs) to prevent overpressure. This is a requirement of both the ASME Code and API RP 14C (refer to Chapter 14). The PSV should be located upstream of the mist extractor. If the PSV is located downstream of the mist extractor, an overpressure situation could occur when the mist extractor becomes plugged isolating the PSV from the high pressure, or the mist extractor could be damaged when the relief valve opens, Rupture discs are sometimes used as a backup relief device for the PSV. The disc is designed to break when the internal pressure exceeds the set point. Unlike the PSV, which is self-closing, the rupture
disc must be replaced if it has been activated.
Pressure vessels handling salt water and fluids containing signficiant amounts of H2S and CO2 require corrosion protection. Common corrosion protection methods include internal coatings with synthetic polymeric materials and galvanic (sacrificial) anodes. All pressure vessels that handle corrosive fluids should be monitored periodically. Ultrasonic surveys can locate discontinuities in the metal structure, which will indicate corrosion damages.
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