Achieving a Leak Free Start Up: Impossible Dream or Achievable Project?

Large petrochemical plants are shutdown periodically for maintenance and inspection. During the shutdowns a large number of gasketted joints are dismantled in order to gain access to the equipment, and subsequently remade at the end of the shutdown. In order to ensure the integrity of the pressure envelope, the plant systems are leak tested with high-pressure nitrogen prior to the introduction of hydrocarbons. If leaks from gasketted joints are discovered during this process, it becomes necessary to de-pressure the systems in order that the joints can be remade. During the 1990 Shutdown of the Huntsman Olefins6 plant at Wilton, approximately 200 gasketted joints were required to be remade during leak testing. This caused significant and costly delays to the start up of the plant. Later analysis showed that the leaks were the result of poor standards in the making and checking of the gasketted joints. A new joint making procedure was written for the 1993 and 1997 shutdowns, and this included a requirement for joints to be traceable by a tagging system to the technician who made the joint. The number of remakes reduced dramatically, to approximately 10 in each of the two shutdowns. In preparation for the 2002 shutdown engineers at Wilton set a target of achieving ZERO remakes during leak testing after the shutdown. This was a great challenge, especially given that approximately 7000 joints were to be remade by 400 technicians. The project was developed in partnership with Hedley Purvis Limited, who supplied design services for calculating residual bolt loads, and Klinger UK Limited, who supplied gaskets for use during the shutdown. The Olefins Joint Making procedure was further developed, requiring full traceability and the use of controlled tightening of joints to a pre-defined load. Great emphasis was placed on the role of people in effective joint making, and in ensuring that each technician was carefully briefed and validated in his understanding of the importance to the business of high standards in joint making. A training video was prepared to help in the process of gaining the understanding and involvement of the technicians and their supervisors. Hedley Purvis and Klinger supported Huntsman in the development of the video, and in the delivery of the training and validation exercise. The project was a great success, and resulted in the first “leak free” start up of the Olefins6 plant. The paper will described the project in detail, and will include a showing of the training video.