SEP-OCT 2018

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SYSTEM INTEGRATION INTECH SEPTEMBER/OCTOBER 2018 33 Case study: Steam generation, distribution, and efficiency Figure 5. HRSGs added to the exhaust stacks from the main cooking lines provide steam capacity, so conventionally fired boilers do not have to produce as much steam. A major North American snack food manufacturer was undertaking a project to improve energy efficiency and reduce its carbon footprint across its fleet of manufacturing facilities. In one location, built around three large-scale pro- duction lines, it was clear that an enormous amount of energy was being wasted, blown out of stacks from the main cook- ing units. Early research determined that exhaust volumes and temperatures were high enough to make adding HRSGs prac- tical (figure 5), and these units would be capable of creating much of the steam necessary for the plant. This installation would be part of a larger project to deter- mine the amount of energy used in the facility, divided by each production line on a British thermal unit per ton produced ba sis. Looking at the larger data picture would indicate to unit leaders how well each line was performing and if there were wasteful areas needing to be fixed within the context of a predictive maintenance program. Adding the HRSG units was a major step toward higher efficiency, because the steam they generated did not have to be produced by conventionally fired boilers. Building on this initial gain would have to include serious analysis of the plant's steam distribution system, since steam pro - duction was one of the most energy-intensive elements of manufacturing. To give an indication of the size of the steam system, the plant had about 400 steam traps distributed throughout the facility. At the beginning of the larger improvement program, none of the steam traps had any type of diagnostic sensor in- stalled. The only monitoring was an annual audit where techni- cians compared actual performance against ideal parameters. This was a largely manual and very time-consuming undertak- ing. Unfortunately, it was also inconsistent and inaccurate. To make matters worse, given the time interval involved, a steam trap that developed a problem shortly after the audit could malfunction for almost a year before being discovered. The larger efficiency program created a list of objectives to improve steam generation and distribution efficiency, including: n improve boiler efficiency n maximize condensate capture and return n maintain heat exchangers more consistently n repair and upgrade pipe insulation n reduce system upsets that cause releases through pressure- reducing valves n monitor and maintain steam traps by implementing a pre- dictive maintenance program The last point proved to be particularly critical. Implemen- tation began with purchase and installation of 50 acoustic transmitters on the most critical steam traps based on capacity, criticality to the process, and difficulty of inspecting by manual methods. Installation was not without its challenges. The facili- ties manager responsible for the project observed, "The bulk of our time was spent getting to the traps, since many of them were in hard-to-reach places. We discovered that proper instal- lation is crucial. We had to ensure proper pipe contact with each device to prevent false cold readings." The new monitors provided continuous data on those units, which maintenance technicians began to analyze using a specifically designed data collection and analysis software tool. Within the first two months of operation, they identified 12 malfunctioning steam traps—24 percent of those being monitored. With the ability to check steam traps daily, maintenance soon began to schedule service and repairs much more quickly, stopping leaks and problems before they wasted sig - nificant amounts of energy. The facilities manager calculated that fixing just those 12 steam traps resulted in annualized savings of $27,800 and a CO 2 reduction of 205 metric tons. Payback for the initial deployment was 20 months. More detailed analysis allows predictive maintenance by anticipat - ing the development of major problems, virtually eliminating complete failures of any of the monitored steam traps. The plant now monitors 100 steam traps using acoustic transmit - ters and plans to add 100 more as the savings that have been realized pay for the next group. n Adding the HRSG units was a major step toward higher efficiency, because the steam they generated did not have to be produced by conventionally fired boilers.

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