Chemical Process Safety (PSM/RMP)
During a recent design review, we encountered some questionable "normal breathing" designs. I have always used the simplest of tests to ensure the tank has ADEQUATE venting during filling and emptying. Although OSHA allows the designer to use API 2000 (1968) or "other accepted standards," the simplest test is that the VENTING capability MUST be as large as the filling or withdrawal connections, but in no case smaller than 1.25". However, unfortunately, designers fail to read ALL of .106(b)(2)(iv), which goes on to state: (emphasis by me) If any tank or pressure vessel has: Membership Content
Source: www.probrewer.com
The implosion happened due to a vacuum created inside the tank when the MEG was pumped out into a storage reservoir on the vessel during mobilization.
The following incident is a precautionary example of the potential hazards of improperly depressurizing piping to remove a hydrate. During production operations, a control room operator observed a decrease in gas lift pressure supplied through a pipeline to a remote well location. The control room operator notified the onboard platform operators of the pressure drop and the possibility of a hydrate forming inside the 3-inch gas lift piping. The control room operator and platform operators planned to isolate and bleed the pressure to remove the possible hydrate. The control room operator from his station closed the pipeline shutdown valve (SDV) upstream of the manual flow control valve. Additionally, the platform operators physically closed the manual isolation valve upstream of the SDV, assumed the hydrate location, and departed the pipeline. The platform operators then started to relieve the pressure downstream of the hydrate location to atmospheric pressure without properly isolating the pipeline from the bleed point through a ball valve assembly attached to the 3-inch gas lift piping. The ball valve assembly consisted of a threadolet, threaded steel pipe nipples, two 1-inch ball valves inline, and a 90-degree elbow that pointed upward. With approximately 900 psi trapped behind the valve, the assembly separated from the threadless, striking one of the platform operators under the left armpit area, and causing bruising and swelling. The injured offshore worker was sent for medical treatment and was later released to full duty. The valve assembly could not be found and is suspected to have fallen overboard after striking the worker.
The Emergency Planning and Community Right-to-Know Act (EPCRA) requires businesses that store and/or manufacture, process, or use certain chemicals to complete the Tier II (EPCRA 311 and 312) Report and/or the Toxics Release Inventory (EPCRA 313) Report, also called the Form R. Section 112(r) of the Clean Air Act focuses on risk management for accident prevention. While these three (3) programs have similar reporting elements, they have significant differences outlined in the following table.
And I will bet someone will suggest a closed-top/bung-style container. Keep in mind that this is NOT preventing the event/failure that makes a bung top drum a safety device, but it could be a protection layer and most certainly would be considered a mitigation layer should we have an eruption from the container. When using the bung style drum, remember to ALWAYS have it vented so as to not "launch" the drum, making it a hazard. We always used the 2" bung for our hose/sparger and the 0.5" bung for our "vent". These bung drums also slow the liberation of gas/vapors from our absorbent material (usually water or caustic). So give it some consideration; it may just be the ticket for those unexpected "surges" caused by improper energy isolation or blockage breaking free in the piping. The same application is used for 5-gallon containers such as "draining oil" from a refrigeration "oil pot" where sputtering is not uncommon. But remember, VENTING is critically important. We can lay a rag over the vent to reduce splash/sputter from the opening; it can also help reduce odors and off-gassing - BUT NEVER BLOCK the vent with any mechanical device or leave it plugged/closed.
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Partner Organizations I am proud to announce that The Chlorine Institute and SAFTENG have extended our"Partners in Safety" agreement for another year (2024) CI Members, send me an e-mail to request your FREE SAFTENG membership
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"We were doing some cleaning at the end of yesterday. I boiled some water in the HLT to pump through the heat exchanger. At the end of the day, there were 40-50 gal left in our 3bbl HLT. I turned off the heat and went home for the night. The next morning, I came into the brewery to find an imploded HLT. I had clamped the lid on to keep humidity down in the building, and the cooling air/water in the HLT caused the tank to implode."
An ISO container, partly filled with Monoethylene Glycol (MEG), imploded on the back deck of a ship, spilling around two cubic meters (528 gallons) of MEG onto the deck and to sea and causing unrepairable damage to the tank itself. There were no injuries. The tank was a 26-cubic-meter tank containing ten cubic meters (6600 gallons) of MEG.
I have written many articles discussing evacuating hazardous materials from a piping system. Over my career, I learned that using an open-top container can have disastrous results. It may sound silly or petty, but when something fails in the tasks and the hazardous material erupts from the open-top container, making contact with the worker(s), you will begin to ask... is there a better way? 
