Safety Engineering Technology Course SAChE（不知道安全工程技术课程）.pptVIP

Pressure Relief “Grace under pressure” – Ernest Hemingway What is the Hazard? Despite safety precautions … Equipment failures Human error, and External events, can sometimes lead to … Increases in process pressures beyond safe levels, potentially resulting in … OVERPRESSURE due to a RELIEF EVENT What are Relief Events? External fire Flow from high pressure source Heat input from associated equipment Pumps and compressors Ambient heat transfer Liquid expansion in pipes and surge Potential Lines of Defense Inherently Safe Design Passive Control Active Control What is a Relief System? A relief device, and Associated lines and process equipment to safely handle the material ejected Why Use a Relief System? Inherently Safe Design simply can’t eliminate every pressure hazard Passive designs can be exceedingly expensive and cumbersome Relief systems work! Pressure Terminology MAWP Design pressure Operating pressure Set pressure Overpressure Accumulation Blowdown Code Requirements General Code requirements include: ASME Boiler Pressure Vessel Codes ASME B31.3 / Petroleum Refinery Piping ASME B16.5 / Flanges Flanged Fittings Code Requirements Relieving pressure shall not exceed MAWP (accumulation) by more than: 3% for fired and unfired steam boilers 10% for vessels equipped with a single pressure relief device 16% for vessels equipped with multiple pressure relief devices 21% for fire contingency Relief Design Methodology Locating Reliefs – Where? All vessels Blocked in sections of cool liquid lines that are exposed to heat Discharge sides of positive displacement pumps, compressors, and turbines Vessel steam jackets Where PHA indicates the need Choosing Relief Types Spring-Operated Valves Rupture Devices Spring-Operated Valves Conventional Type Superimposed Back Pressure Pressure in discharge header before valve opens Can be constant or variable Built-up Back Pressure Pressure in discharge header due to frictional losses after valve opens Total = Su