Failure of a Freeze Dryer Slot Door
Freeze-drying is utilized in the biopharmaceutical industry to give higher stability, broader temperature tolerance, and longer shelf-life to formulations that are unstable in aqueous solution (Green and Perry, Perry’s Chemical Engineers’ Handbook, 1997). Freeze-drying equipment consists of a drying chamber, condensers, a cooling system, and a vacuum system. The drying chamber is where the product is placed to undergo the lyophilization process. The chamber has two access points: a maintenance door, located in a mechanical room, and a slot door, located in a sterile clean room. The maintenance door permits entry into the chamber. The slot door facilitates tray loading and unloading from the clean room using an automatic tray handling system. At 9:26 AM on March 2, 2008, a freeze-dryer failed during the steam-in-place (SIP) cycle. As a result of the failure, the slot door was plastically deformed. Several items in the proximity of the slot door sustained damage. Fortunately, no personnel were inside the clean room when the event occurred; there were no injuries or loss of life. The impact to production was severe. The event removed the freeze dryer from service for approximately 2 months, reducing bulk powder production capacity by 33% during the time it was down. The failure occurred because the slot door was not closed properly when the SIP cycle began. Instead of being completely restrained, it was allowed to become simply-supported, seriously compromising its pressure-containing ability.
KeywordsPlastic deformation Failure Pressure vessel Pharmaceutical
- 1.Green, D.W., Perry, R.H.: Perry’s Chemical Engineers’ Handbook, 7th edn. McGraw-Hill, New York (1997)Google Scholar
- 2.ASTM International. A 240/A 240 M – 05a: Standard Specification for Chromium and Chromium-Nickel Steel Plate, and Strip for Pressure Vessels and for General Applications. ASTM International, West Conshohocken, PA (2005)Google Scholar
- 3.Budynas, R.G., Young, W.C.: Roark’s Formulas for Stress and Strain, 7th edn. McGraw-Hill, New York (2002)Google Scholar
- 4.Gere, J.M., Timoshenko, S.P.: Mechanics of Materials, 3rd edn. PWS Publishing Company, Boston (1990)Google Scholar
- 5.Jones, D.R.H.: Engineering Materials 3: Materials Failure Analysis – Case Studies and Design Implications. Pergamon Press Ltd., Oxford (1993)Google Scholar