Described in this article are a series of cracks found in a vessel during a routine inspection. The welding methods and procedures used to address unique problems associated with the repair of these cracks are described. After the repairs were completed and inspected, an online Acoustic Emission (AE) system was installed to monitor the mechanical integrity of the vessel while in operation. The system. presents data locally for use by operations personnel as well as remotely, via the internet, for detailed analysis by engineers. A major benefit of online monitoring is that it car? show an association between defect growth and operating conditions should process information be recorded by the system. AE data, therefore, can help optimize the operating conditions to minimize or eliminate defect growth and equipment damage. Until recently, online A-E monitoring was confined to a few, specialized applications such as high energy piping in refineries and power plants. The advent of better computers and software, high speed internet connections, and more reliable instrumentation has made remote monitoring a reality. The AE specialist can now operate the AE system and evaluate online data remotely and report results by web site or e-mail. The AE system has also been of use as a process monitor in addition to the vessel integrity monitor. It provides an ongoing condition assessment of the vessel. Gasket leaks on start tip and valve leakage are some of the problems that have been identified with the online AE system. (C) 2009 American Institute of Chemical Engineers Process Saf Prog 29: 51-54, 2010