Refinery Based Case Study of a Novel Gasket Designed for Use in Problematic Shell and Tube Heat Exchangers

CATEGORY: HEAT EXCHANGERS 
Refinery Based Case Study of a Novel Gasket Designed for Use in Problematic Shell and Tube Heat Exchangers

Type	Conference Paper
Author	Dene Halkyard
URL	Free Full Text Source:  http://www.flexitallic.eu/upload/case_study/refinery_based_case_study.pdf
Place	Stuttgart, Germany
Date	October 8-9, 2014
Conference Name	18th ISC-International Sealing Conference
Abstract	This paper provides a technical overview of a novel gasket design engineered to address sealing issues associated with the operation of shell and tube heat exchangers. It discusses field service experience using the gasket on a UK refinery. Shell and tube heat exchangers are commonly used items of process equipment in many industries. Depending on how they are operated heat exchangers can present significant technical challenges with regard to achieving leak free sealing performance. Fluctuations in axial load and radial shear effects brought about by thermal transients around the tube sheet girth flanges during start up or normal operation can a have a significant effect on seal performance. Additional factors such as available gasket load imposed by exchanger design; available space, the presence of stress raising nubbins and ease of access and installation can also have a bearing on gasket design. Refinery processes involving shell and tube heat exchangers can be particularly demanding, equipment is often old and can involve elevated temperatures, high pressures and cyclic operation. It is said that every refinery has its problem exchangers. Additional requirements for improved asset efficiency and emissions compliance place ever increasing demands on gasket performance. The novel gasket design offers benefits over traditional gasket styles more commonly used in shell and tube heat exchanger applications. It offers superior long term sealing performance, particularly in bolted connections subject to thermal transients. Refinery field service discussed in the paper reviews sealing performance in a number of problematic exchangers at the tube sheet to channel and tube sheet to shell connections. The heat exchangers, used to process heavy residual hydrocarbons are in excess of 30 years old with a history of managed leakage. High temperature, cyclic operation , seasonal fluctuations in product demand and the requirement for regular tube cleansing exacerbates the potential for seal failure.