An increase in pipe O.D. as internal pressure is applied (shortens pipe) or a decrease in diameter (Reverse Ballooning: lengthens pipe) as external pressure is applied
George E. King Engineering, 5000 Oilfield Terms: A Glossary of Petroleum Engineering Terms, Abbreviations and Acronyms, US 2010. http://gekengineering.com/Downloads/Free_Downloads /Glossary_of_Petroleum_Engineering_Terms_25_August _2010.pdf, (Oil - Amer) {593}