Often mistaken as some type of modified tank car, Procor built ‘Pressure Flow’ cars were in fact constructed to an AAR Tank Car Manual prescribed specification; AAR 207A. Per most pressure vessel guidelines, operation above atmospheric pressure (14.7 psi) is subject to an industry issued code or standard. As example, boilers are subject to ASME pressure vessel codes, while steam locomotives are subject to DOT 49 CFR Part 230. Procor built Pressure Flow cars had an design/operating pressure of either forty or forty-eight psi.
Over a thirty-year period, between 1965 and 1995, Procor Oakville constructed more than five hundred Pressure Flow cars. Predominantly used in powdered cement transport, the higher pressure rating provided for over packaging of more volatile materials such as calcium carbide. Calcium carbide is used in steel making and in the production of acetylene and reacts violently when exposed to moisture. While also manufactured to support it’s lease fleet, most Pressure Flow cars were built under contract for sale to others. Sale customers included British Columbia Railway with thirty, Canadian National Railways with more than three hundred and Canadian Pacific Railway with more than one hundred.
Today, only a handful of Pressure Flow cars remain in service. Cars constructed in the 1960’s and early 1970’s were subject to the AAR forty-year interchange life limit. Powdered material transport migrated to conventional Class LO covered hopper cars equipped with low pressure rated pneumatic off loading apparatus. The last Pressure Flow cars constructed by Procor (UTLX 800000 – 800007) were built for the Union Tank Car fleet for use in Phosphorous Pentasulfide transport.
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