Electricity: measuring and testing – Magnetic – Plural tests
Reexamination Certificate
2002-03-01
2004-05-25
Le, N. (Department: 2862)
Electricity: measuring and testing
Magnetic
Plural tests
C324S226000
Reexamination Certificate
active
06741074
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to manufacturing rotating equipment and, more specifically, to inspecting rotating parts.
Rotating equipment is utilized in many manufacturing applications. Rotating equipment failures can cause lost production time, injury to personnel, and loss of capital equipment, all of which can reduce profitability. One known cause of rotating equipment failure is due to vibrations. Accordingly, some rotating equipment is operated with at least one proximity probe continually monitoring vibrations (displacement of the rotating part) to protect the equipment from damage due to excessive vibration. However, proximity probes typically introduce an error in the displacement signal thus generated. For example, an eddy current probe will introduce displacement errors due to material variations in the rotating part.
More specifically, eddy current probes derive distances utilizing induced electrical currents in the material of the rotating part and, therefore, variations in electrical properties of the material results in errors in the derived distance. This error due to variations of electrical properties is called electrical runout. Additionally, the proximity probe will read all displacements as indicative of vibrations. For example, mechanical runout (concentricity, roundness, and flatness) also is read as a displacement and is interpreted as a vibration. A common test procedure to assess the suitability of the proximity probe signal is to allow the rotating equipment to coast at a speed much less than its normal operating speed. The rational for this is that at this lower speed, vibration is essentially zero.
This test procedure is commonly referred to as the “slow roll” test. The displacement signal that the proximity probe provides during the slow roll test is considered the error in the signal. The measured error is related to the degree of mechanical runout plus electrical runout and thus does not differentiate between the two. However, known methods for correcting mechanical runout are different than known methods for correcting electrical runout and it is costly and time consuming utilizing a mechanical method for an electrical problem. Likewise, it is costly and time consuming utilizing an electrical method when the problem is mechanical runout.
BRIEF DESCRIPTION OF THE INVENTION
In one aspect, a method for separating electrical runout from mechanical runout includes positioning at least one position probe against a rotating part, positioning at least one proximity probe adjacent the rotating part, and calculating an electrical runout based on measurements obtained from the position probe and the proximity probe.
In another aspect, a method for facilitating a reduction in slow roll test failures includes measuring at least one of a concentricity value, an out of roundness value for a proximity surface of a rotor, and an out of roundness value for a journal surface of the rotor prior to the rotor being assembled in the rotating equipment. The method further includes measuring electrical runout and determining a predicted slow roll runout value of the rotor. Additionally, the method includes comparing the predicted slow roll value to a predetermined value and re-working the rotor when the predicted slow roll value exceeds the predetermined value.
In yet another aspect, inspection apparatus for a rotating part includes a data collection system and a plurality of position probes electrically coupled to the data collection system, wherein the position probes are disposed adjacent the rotating part. The apparatus further includes at least one proximity probe electrically coupled to the data collection system, wherein the proximity probe is disposed adjacent the rotating part. A computer is electrically coupled to the data collection system and is configured to calculate an electrical runout.
In a further aspect, inspection apparatus for a rotating part includes a data collection system and a plurality of position probes electrically coupled to the data collection system, wherein the position probes are disposed adjacent the rotating part. The plurality of position probes include a first probe, a second probe, a third probe and a fourth probe, the first probe is substantially 180° from the second probe, and the third probe is substantially 180° from the fourth probe. The apparatus further includes at least one proximity probe electrically coupled to the data collection system, wherein the proximity probe is disposed adjacent the rotating part. A computer is electrically coupled to the data collection system and is configured to calculate an electrical runout. The computer is further configured to determine a predicted slow roll runout for a right probe by adding a series of vectors as described later. The computer is further configured to determine a predicted slow roll runout for a left probe by adding a series of vectors as described later.
In another aspect, apparatus for predicting a slow roll test failure utilizing a data collection system includes a computer programmed to receive a plurality of probe measurements and generate at least one slow roll runout value for at least one of a left probe and a right probe.
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DeBlock Mark John
Fife W. R. Hugh
Armstrong Teadale LLP
Aurora Reena
General Electric Company
Le N.
Vick, Esq. Karl A.
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