PT. Leuwijaya Utama adopted the SKF E2 bearings as part of an urgent cost-saving programme, which was triggered by a sharp rise in local energy costs.
The cost-saving programme began in July 2010, when Indonesian industry at large faced a government-enforced increase in electricity costs. For PT. Leuwijaya Utama, a textile company with 300 weaving machines and 176 twisting machines consuming 2,120MWh per month in its Bandung factory, this meant an increase in costs of approximately 18 percent. To reduce the negative effect on bottom line profitability, a speedy and effective reaction was required to identify and achieve energy savings.
The management set about searching for ways to reduce energy consumption throughout the entire factory. Having ensured that no unnecessary lighting was being used, or machinery left on standby when it could be switched off, the management took a detailed look at production.
First investigations showed that 30 percent of the factory’s energy consumption was consumed by the twisting machines, which are critical in ensuring fabric quality. So, as well as taking measures to correct electric motor energy losses and optimising frequency converters for the overall electricity supply, the energy consumption of the twisting machinery was discussed.
Inside the Leuwitex twisting machines, lines of high precision spindles are driven by two powerful motors. As these machines operate 24 hours per day, frictional losses (and ultimately energy losses) occur in the rotational motion dependent on the quality of the bearings fitted at the ends of each spindle. With 176 twisting machines incorporating 256 spindles, this clearly presented an opportunity for energy saving.
Leuwitex plant panager, Mr Zenzen, took a pragmatic approach to investigating the potential for reducing energy consumption. First, he selected the three most likely methods of optimising bearing cost and frictional losses; he then put these three methods to the test in his spindles.
The three potential ‘solutions’ were (a) to use new bearings from the supplier of those in the original spindles; (b) to install low cost bearings of local Chinese manufacture; and (c) to switch to SKF Energy Efficient bearings.
SKF E2 deep groove ball bearings reduce frictional losses in a bearing by 30 percent or more when compared with a standard SKF bearing. The performance increase is the result of optimised internal geometry, low friction grease and a special low-friction polyamide cage. Designed for grease lubricated, light-to-normal load applications, SKF E2 deep groove ball bearings also consume less lubricant than comparable SKF Explorer bearings and enable a longer bearing service life.
Mr Zenzen fitted the three alternative bearing solutions to three separate spindle lines and ran them for three months, monitoring specifically the energy consumption of those lines. The result confirmed that with SKF Energy Efficient bearings, around ten percent total energy savings was possible. Extrapolating this result to the expected lifetime of the spindles, it was clear that these bearings would save the most energy and deliver the lowest total cost of operation.
“Having satisfied myself on the energy savings issue,” said Mr Zenzen, “I also needed to be sure that the overall SKF bearing performance was equally reliable in terms of the final product quality.
The twisting machines have two contra spinning spindles rotating synchronously in opposite directions. To maintain product quality it is of the utmost importance that these two spindles are rotating exactly as expected through the entire and continuous spinning/twisting operation.”
Mr Zenzen’s next test was to fit SKF Energy Efficient bearings to ten twisting machines and begin a ‘production run’. “I was delighted to find that the product quality was exactly the same as before, with constant, uniform delivery of the various designs, material thickness and feel,” he said. “This was especially important because we were in the process of expanding and also replacing some machinery in readiness for a new fabric product, and we needed to be sure we could rely on the machinery.”
This initial test was extended by adding more lines of spindles while keeping the original ten operating. Regular product quality checks among all the machines convinced Mr Zenzen that he had indeed found the best possible bearings for his textile machines, both in terms of energy efficiency and performance.
“I was extremely happy with the outcome of this project,” said Mr Zenzen. “We took time to be sure we had chosen the best solution for our original short term energy cost problem, and at the same time came to agree that SKF Energy Efficient bearings were equally the best solution for our long term plans.”
The plant now has 25,600 SKF E2 bearings installed on its machinery and is reaping the on-going rewards of enhanced energy efficiency on a daily basis.