Original Date: 10/18/1999
Revision Date: 01/18/2007
Best Practice : Moment Weight Measurement System
To properly balance a set of blades on a rotor, one must first measure the moment weight of each blade and then install the blades in a sequence which optimally distributes the weight over the rotor. Done correctly, the rotor will remain in balance when operated at a high velocity. Orenda Turbines previously used a time-consuming method to accomplish this task. Each blade was weighed using a calibrated moment weight index to determine the moment weight. This value was handwritten on the blade, and then all the blades were sequentially lined up on a work table from heaviest to lightest. Next, the blades were paired up and checked to ensure that the moment weight difference of each pair was less than 5.0 gram-inches. Based on a predefined way, the pairs were installed opposite each other into a fixture. Once the blades were set up, the technician manually filled out a build sheet to record the blade and rotor information such as sequence number, serial number, moment weight, and other data. After the build sheet was completed, the blades were removed from the fixture and installed into the rotor. This approach provided many opportunities for recording errors which might not be caught until after the build was completed, leading to teardown and rework operations.
In 1998, Orenda Turbines developed the Moment Weight Measurement system. This system automates most of the operations and error-proofs the data entry. Now, the required number of blades are selected and simply labeled 1,2,3, etc. The serial number of each blade is entered into the computer as the blade is placed in the moment weight index for weighing. The computer automatically enters the moment weight directly from the weight index instrument, and checks to make sure that the serial number is correct and not a duplicate. This feature guarantees that only unique serial numbers are used for each blade. When all of the blades have been entered, the operator checks the moment weight difference between each pair of blades which are optimally sequenced by the computer. The computer then produces an installation list showing the installation sequence, and automatically generates and prints a build sheet. The need to place the blades in an interim fixture is completely eliminated.
Compared to the previous method, the Moment Weight Measurement system has produced significant advantages and benefits for Orenda Turbines. The system eliminated tedious and manual steps which were prone to errors; reduced the cycle time for blade sequencing and installation by more than 50%; and produces an annual savings of about $40,000. Documents generated during the measuring process are always consistent, and the build sequence is the best possible match. In 1998, the developer of the Moment Weight Measurement system won first prize in Orenda Turbines’ Idea Recognition System annual competition.
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