Field reliability of plate heat exchangers in oil and gas processes - a market perspective

Abstract: In the offshore industry, reliability of installed equipment is of paramount concern due to safety, environmental and economic consequences. The costs of unplanned shutdowns and maintenance have high economic implications and are of increasing importance with tighter profit margins. Reliability is therefore of significance when selecting equipment model and brand. This report presents a survey of the field reliability of Alfa Laval plate heat exchangers in offshore oil and gas processes with main focus on failure data. Because of the increasing attention paid to the relationship between optimised maintenance and the achievement of field reliability, preventive maintenance practices are also included in the survey. Whether a product is reliable or not is in the end determined by the users. The users attitudes regarding Alfa Laval reliability are therefore surveyed as well. The method chosen was a cross-sectional survey focusing on quantitative primary data. Data was collected by using self-administered questionnaires distributed by email to maintenance personnel and process engineers at offshore oil production platforms. Valid responses were received for a total of 174 installations, including 309 units at 60 platforms in nine countries. For 65% of the surveyed installations, respondents reported no failures, 25% one failure and only 10% two or more failures. A total of 104 failures were reported. The average failure rate based on reported failures was estimated to 6,14 failures/106 h. As a comparison, 114 failures/106 h correspond to one failure a year. There is a risk that all failures have not been reported and the estimated failure rate should therefore be seen as some kind of minimum value. It should be noticed that findings of previous and related research indicate that in offshore oil and gas processes the estimated failure rate of plate heat exchangers are lower than the failure rate including all heat exchanger types. Failure causes reported in the survey are generally the result of either none or incorrect maintenance, or unsuitable operating conditions which the survey have given many specific examples of. External leakage was the most commonly reported fault mode with 45% of the failures. This fault was generally due to gasket wear-out or gasket blow-out. Overall the most commonly reported corrective maintenance action was replacement of a few or all plates (including gaskets). Recurring failures appear to be due to a lack of identifying the root cause of the problem, which can lie outside of the plate heat exchanger, leading to inappropriate corrective maintenance actions. The majority of all reported failures, 56%, did not have any negative influence on the production process at the platform, only 16% of the failures were reported to have caused a process shutdown. Maintenance practices vary broadly between the oil and gas companies and platforms but generally no or little preventive maintenance is carried out on the heat exchangers on a regular basis. Opening the unit for inspection, manual cleaning and the replacement of parts are most often only carried out on units that currently have or recently had failures. Overall, the end users’ attitudes and perceptions of the reliability of Alfa Laval and its products and support are very positive reflecting the few reported failures. 88% of the respondents consider the Alfa Laval plate heat exchanger to be a reliable or very reliable product.