Runout electrical

Expander-compressor shafts are preferably designed to operate below the first lateral critical speed and torsional resonance. A flame-plated band of aluminum alloy or similarly suitable material is generally applied to the shaft in the area sensed by the vibration probes to preclude erroneous electrical runout readings. This technique has been used on hundreds of expanders, steam turbines, and other turbomachines with complete success. Unless integral with the shaft, expander wheels (disks) are often attached to the shaft on a special tapered profile, with dowel-type keys and keyways. The latter design attempts to avoid the stress concentrations occasionally associated with splines and conventional keyways. It also reduces the cost of manufacture. When used, wheels are sometimes secured to the tapered ends of the shaft by a common center stretch rod which is pre-stressed during assembly. This results in a constant preload on each wheel to ensure proper contact between wheels and shaft at the anticipated extremes of temperature and speed. 

Biggs, D. H., Electrical Runout in Rotating Machinery, Hydrocarbon Processing p. 87, Dec. (1972). 

Rotor mechanical and electrical runout for pumps designed to use noncontacting vibration probes. 

Vectorial subtraction of slow-roll (300-600 rpm) total electrical and mechanical runout is permitted by the API rules. Vectorial subtraction of bearing-housing motion may be Justified if it can be demonstrated to be of significance. 

Electrical and mechanical runout of the rotor surfaces to be observed by vibration probes shall be determined and recorded. The runout shall be determined by rolling the rotor supported by V-blocks positioned at the centerhne of the bearing journals while measuring runout with a noncontacting vibration probe and a dial indieator simultane-... 

When noncontacting vibration probes are furnished, accurate records of electrical and mechanical runout for the full 360 degrees at each probe location shall be included in the mechanical test report. 

If the vendor can demonstrate that there is electrical or mechanical runout of the rotor surfaees at the proximity probes (see 2.5.9), a maximum of 25 pereent of the measured value or 6 microns (0.25 mils), whichever is greater, may be vectorially subtracted from the vibration signal measured during the shop test. 

A variation of the FM runout combiner used a filter in place of the long runout Hne to provide the same electrical delay. However, this modification did not substantially improve the electrical performance of the system, and notch filtering has also been added to retrofit these systems. 

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