*5.2. Maintenance*

During the interviews, increased maintenance was mentioned as a potential issue, particularly the need for both space and time to clean the heat exchangers. If the heat exchangers are not properly cleaned, pressure drops increase significantly, which can cause issues for operation of downstream process units. Heat exchangers that already experience problems with fouling are likely to be penalized by decreased reliability/availability if enlarged, due to the increased need for maintenance during operation. The decreased reliability/availability for tube-and-shell heat exchangers is caused by the need to lower the feed flowrate to the unit to enable cleaning on both tube and shell side of the heat exchanger. One solution stated by several interviewees for fouling issues is to remove existing shell-and-tube exchangers and replace them with parallel plate exchangers. In a number of interviews, it was stated that a simultaneous investment to improve current operability issues caused by fouling could increase the prospect of investing in an energy saving project. This is the case for the previously discussed retrofit proposal 1A. Combining an expansion of the heat exchanger with a replacement of the existing shell-and-tube heat exchanger would not only decrease utility usage but would also decrease fouling problems. This reasoning was confirmed in several of the interviews as well as at the validation seminar.
