Forensic transient analyses of two pipeline failures

Details pertaining to two groups of preventable accidents, both caused by transient events, are presented. The accidents could have been avoided if there had been better coordination during the design process, during system construction and during operation. Moreover, a number of common beliefs, inherited from the period when computer simulations were rare, as well as ill-informed attempts to mimic "good solutions", influenced design decisions and contributed to the performance difficulties. The two examples illustrate transient analysis in complex systems and raise crucial issues about the lines of responsibility; although such problems also exist in small systems, the damage is typically proportionally smaller, and thus small systems have tended to receive less attention. The first case presented involves the Abattemarco pipeline in Italy. In this case, an unauthorized decision to marginally decrease capital costs by reducing the pipe's pressure class significantly compromised system reliability. In the second case, involving a desalination plant, it was erroneously believed that such a low-pressure system would not be susceptible to transients and that, in any case, a higher pressure class would invariably cover all contingencies. The operation of this second system was further complicated by a decision to oversize the pumps, a choice that increased both capital and running costs and simultaneously diminished the reliability of the already vulnerable system.