A plastics manufacturer installed a new cutting edge variable speed drive lubricant free compressor during their plant expansion. Rather than using a heatless desiccant dryer, the unit was purchased with an efficient heat of compression dryer estimated to save thousands of dollars in lost purge.
As part of the project, the power utility promised a significant financial incentive to help pay for the efficiency upgrades. As a requirement, the utility asked that a thermal mass flow meter be installed to track the compressor output flow.
Shortly after commissioning, the power utility installed data loggers to verify the new compressor was operating as expected. The readings showed that the 750-cfm compressor was only producing 400 cfm. This was communicated to the supplier who insisted the flow meter must be in error. Further tests were done, all pointing to reduced compressor capacity. Finally after a few weeks of negotiation the supplier agreed to come in and look at the compressor.
Once there, the service technician was surprised to find a large gasket had blown out and had developed a very large leak. The sound baffling of the compressor enclosure had masked the internal leakage so it couldn’t be easily detected without opening the access covers. Use of flow metering saved the day and the company avoided thousands in lost energy costs.
At another plant, a flow meter had been installed by the same power utility to track the output of a large variable speed drive compressor. For a time, this plant manually tracked the leakage flow on the weekend by having the security guards write down the readings when there was no production. Over the years, this practice was discontinued due to lack of communication. The plant flow was ignored until a compressed air auditor placed a data logger on the flow meter to do an efficiency check-up.
Once the data logger was downloaded after a week of monitoring, the plant superintendent was surprised to see some strange readings. The plant was operating on a 16-hour, two-shift schedule, 5 days per week — however, during the non-production times, the compressed air flow was quite high. In fact, when the auditor averaged the flow through all operating hours he found something startling.
More than 80% of all the compressed air that the very efficient variable speed drive compressor produced was lost to non-productive flow like leakage and machines left running during down times. The plant was very efficiently wasting thousands of dollars worth of compressed air. Needless to say, some immediate action was taken!
These two stories illustrate the value of flow metering the compressed air system and capturing the flow pattern with data loggers. Many meter types are available at reasonable cost these days, in ranges suitable for large systems and small. Metering is recommended for any system to assist in keeping the compressors and dryers running at peak efficiency.