Synopsis: Unanticipated problems can ruin even the best laid plans for compressed air system improvement. This industrial customer updated their air compressors and dryers and made efforts to reduce their leakage load, only to find the savings were not as high as anticipated. Analysis of the data collected remote logging system allowed the customer to find a hidden waste and fix it, thereby achieving their savings by a goal.
Over the years a window manufacturer did everything right. They were one of the first factories to install the newly developed variable speed drive compressors in the early ‘90’s and, at the time, they also installed a sophisticated control system, low pressure differential air filters, very large storage, cycling dryers, and a pressure/flow controller. The power company was very interested in assisting with the project and provided a very substantial incentive for the reduced power consumption.
But nothing lasts forever, due to advanced age and high accumulated hours, it was time for an upgrade last year. The company starting to consider buying new compressors and wondered how they could pay for them. The system was still running very efficiently, so any compressor changeouts would not substantially change the system efficiency, therefore, the potential power company incentive was quite small. Fortunately for them they called in an experienced compressed air auditor to have a look.
The auditor found the system was indeed running very efficiently, but times had changed. New more efficient compressors had been developed by compressor suppliers, and if they chose their new equipment carefully they could reduce power costs even more. And the auditor also found some surprising results, the leakage level In the plant was very high, enough to keep a 75 kW compressor loaded even when there was no production in the plant, like on evenings or weekends. Because the plant had not been monitoring their system with flow meters they were unaware of the problem. Much of this wasted compressed air leakage flow could be reduced to produce a substantial reduction in energy cost, and a significant power utility incentive. The maintenance crew immediately got to work in attacking their many leaks.
Fast forward to one year later, the auditor was invited back to do verification data logging to capture the new baseline. Measuring instruments were placed on the newly commissioned compressors and flow meters were installed. The auditor found that the non-productive flow had reduced substantially, however, only one week later the flow returned to the old levels on a weekend. The auditor, who was monitoring the flow daily using a remote monitoring system, contacted the local system operators and asked them to do a plant walk-through looking for anything out of ordinary.
The operators found the problem less than 30 minutes later. A large air valve controlling a pulse blowing operation in processing machine had failed open, consuming 4.5 m3/min (160 cfm). This air demand was within the sound dampening enclosure of the machine and could barely be heard, even in very quiet non-production times. Subsequent repair would yield savings worth $24,000 per year, just for this one improvement.
Final numbers showed the anticipated savings for the system upgrade were achieved, with the power utility granting an excellent incentive to help pay part of the cost of the improvements. Installed permanent monitoring instrumentation still remains and will allow facility maintenance personnel to continuously track flows and energy so any problems can quickly be detected and corrected.
Ron Marshall