Pat Douglas
Kirby Risk-Mechanical Solutions and Service
Motor repair businesses rely upon the quality of their company’s employees and equipment. Documentation is required more often by customers to satisfy their reliability engineers. Supplying erroneous data, even if it is unintentional, can be very disappointing to a customer.
Instrumentation that is not providing correct information can result in inaccurate diagnosis. This could mean returning a motor that still needs work, or putting unnecessary labor into a customer’s product. Neither of these is desirable and could result in customer dissatisfaction. With more of today’s equipment designed to run at full current and many times into the service factor, the margin for error is drastically reduced.
Calibrate equipment regularly
A bearing fit that measures borderline on the chart could really be out of specification if your micrometer is not calibrated. For example, a bearing fit is measured and it’s on the low side of the specification using the same micrometer that has been used for the last 20 years. It is checked with the standard at either end of its travel and all appears to be good. But, the threads could be worn in the area where the micrometer is commonly used, causing erroneous readings. This is why it is important to calibrate equipment regularly.
The expense of getting equipment calibrated can be balanced by the catastrophes it prevents. How much does it cost when you get a large 2-pole motor reassembled and on the test stand, only to find out it has a 1-time vibration due to imbalance? If a surge tester or hi-potential tester has never been calibrated, how do you know that the proper voltages are being use to conduct testing? What if a motor ships to the customer with an amperage problem that was not caught in-house because the test stand is producing inaccurate data? When data is sent with a motor back to the customer, these inaccuracies become embarrassments.
Calibration ensures correct data
Calibration is a necessary process to ensure the customer is provided accurate data. Each piece of equipment needs to have a unique identification (ID) number permanently attached or etched on the main body and the calibration date and due date on a tag attached to the tool. Calibration can be tracked with a simple spreadsheet using the ID number and a brief description of each piece of equipment. The spreadsheet can be set up to do the calculation for a due date – usually every 12 months. Some items like ring gauges may be moved to a longer cycle after history is established. A micrometer should be checked to a standard before each use to ensure accuracy.
When making a list of equipment to be calibrated, think of anything that takes a final measurement, or a measurement that could adversely affect quality of the product.
ANSI/EASA AR100
More information on this topic can be found in ANSI/EASA AR100
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