Rotating machinery energy loss due to misalignment

Tests were conducted to measure the energy loss that results from misalignment and unbalance of rotating machinery. Several articles have appeared in maintenance trade publications that warn of misalignment energy losses of up to 15%. However, the articles are all written by employees of companies that sell expensive instrumentation to detect and help correct these problems. Gross misalignment and unbalance is associated with indifferent or negligent maintenance practices. Energy losses of this great a magnitude would clearly dictate major machinery maintenance upgrading, and use of vibration and infrared diagnostics. The tests the authors conducted and report in this paper do not show a 15% loss. The test program has measured less than 3% energy losses from gross misalignment, while unbalance appears to cause losses of less than 1%. The tests were conducted with a 30-hp 3-phase motor driving a 20-kW generator connected to a resistive load bank. Power into the motor and from the generator to the load was measured with precision power measurement instrumentation. Several different popular couplings were tested. It was noted with misalignment great enough to cause the 2% energy losses, significant temperature rise of the couplings was measured. This finding supports the concept of using infrared thermography to identify gross misalignment. The paper describes the tests, presents data and comments on the economic ramifications.