6 What is the difference between the normal vent & the emergency vent?
7 What are the differences? (between the normal & emergency vents) No blocking devices in ERS No flame arresters in ERS ERS usually bigger Normal vent also handles vacuum Pollution abatement for normal vent Normal vent opens first Manifolding for normal vent.
15 Upset Scenario... Series of events leading to high vessel pressure
16 What do we want the ERS to protect against?...
17 Concept Sciences 1999 Allentown, PA 5 fatalities hydroxylamine
18 Concept Sciences The plant was designed to concentrate hydroxylamine (HA) up to 50% HA is known to be explosive above 70% concentration Due to startup problems, the actual concentration was 86% HA.
28 Bhopal 1984 Relief valve on an MIC storage tank lifted in the middle of the night releasing 80,000 lbs >2,000 people died within a short period ~30,000 people were permanently or totally disabled MIC reacted with water, source of contamination uncertain Incident had long-term ramifications for Union Carbide and the chemical industry as a whole.
45 Sizing vents is straightforward but we do need kinetics data for reactive scenarios
46 Types of runaway reaction Vapor Pressure Gas Generating.
47 Vapor Pressure Runaway Reaction Pressure related to temperature Control temperature by evaporative cooling.
48 Emulsion Runaway 1995, one-shot emulsion process Water charging system failed New operator being trained, batch not stopped 2,000-gallon, 120-psig reactor Broke 35-psig, 18-inch rupture disk ~1200 lbs ethyl acrylate released.
97 Toll Incident Wisconsin - 2002 Leaky steam valve heated a completed batch from 40C to 150C in 3 hours Resulting decomposition (>200 psig) MSDS: “This material is considered stable” No fatalities or injuries.
114 Why document? Required by OSHA PSM (Process Safety Mgmt) Required by EHS 536 (Process Safety Mgmt) For future Management of Change (MOCs) For future HAZOPs Avoid reconstructing the design Information can be used on other systems.
115 Vent System Analysis Follow the ERS procedure for every vessel & every relief device Store the results in a safe place