This application relates to measurement and testing of alignment or angles of rotational axes of rotational shafts using photoelectric detection means.
When machinery with machine shafts is disassembled for maintenance, during reassembly, various shaft sections must be realigned to high precision.
The traditional method of measuring shaft alignment is to glue a dial indicator or one or more photodetectors onto a shaft coupling face or onto a fixed location on the circumference of the shaft. Various measurements are taken of the two shaft segments with respect to each other. The dial indicator is used to measure the radial distance between the couplings. Then gauge blocks are used to measure the gap at 0°, 90°, 180°, and 270°. Then oil lift pumps are turned on to allow the shaft to be rotated by 90°. Then the lift oil pumps are shut off to allow the shaft segments to settle into their journal bearings. Then, the dial indicator and four gauge block measurements are repeated at 90°. The dial indicator measurement is used as a control to account for change in the gauge block measurements between rotational locations. Then the shafts are rotated twice more, to 180° and 270°, and the measurements repeated. Thus, sixteen gauge block measurements are taken, four dial indicator measurements are taken, and the lift oil pumps are used four times. A fifth rotation is required to get to a full 360° rotation, to verify the measurement against the original dial indicator measurement at 0°.
From those measurements, linear displacements and angular offsets are computed, then position and/or angle of one or both of the shaft sections are adjusted, and the measurements are repeated until the shaft segments are aligned to within the necessary tolerance.
In general, in a first aspect, the invention features an apparatus for measuring alignment of two shafts. Two magnetic bases each have two linear contact edges designed to engage with a circumferential surface of a shaft at least 10 inches in diameter and to ensure alignment between the base and an axis of rotation of the shaft to within a tolerance compatible with alignment tolerances of the shaft. Each base has a switch to vary magnetic flux for affixation and release from the shaft surface. Brackets attached to the bases are designed to attach laser photoelectric devices, the photoelectric devices designed to measure shaft misalignment.
In general, in a second aspect, the invention features a method. To circular faces of two shaft segments each at least 10 inches in diameter, two devices are attached. Each device has a base surface designed to engage with a circumferential surface of a shaft at least 10 inches in diameter, and each base surface having features designed to affix and release from the shaft surface, and to align with the rotational axis of the shaft to a precision allowing measurements to within tolerances required by machinery driven by the shaft. Each of the two devices has laser photoelectric devices for ascertaining a dimension of displacement of the two shafts from a desired axis of rotation relative to each other. The attaching including moving the devices to allow the linear contact edges to bite the circumferential surfaces of the shaft segments to assure parallel mounting. The bases and brackets are used to take multiple measurements by the laser photoelectric devices, rather than by rotation of the shaft. (Rotation of the shafts is not altogether precluded; rather, the base and photoelectric devices reduce the need for rotations between measurements, perhaps to zero.)
Embodiments of the invention may include one or more of the following. The laser photoelectric devices may be a one-laser system or a two-laser system. The brackets may be adaptable to allow the measurements to be taken through bolt holes of shaft couplings. The brackets may be designed to allow the laser photoelectric devices to face each other. The bases may be magnetic, with on/off switches to apply or withdraw magnetic flux for affixation or release of the base from the shaft. A bottom surface of at least one of the two bases may be modified from its commercially-delivered condition to provide raised rails designed to improve tactile feedback of to a user of the alignment between the base and an axis of rotation of the shaft. At least one of the two bases may have affixed thereto two rails designed to improve tactile feedback of to a user of the alignment between the base and an axis of rotation of the shaft.
The above advantages and features are of representative embodiments only, and are presented only to assist in understanding the invention. It should be understood that they are not to be considered limitations on the invention as defined by the claims. Additional features and advantages of embodiments of the invention will become apparent in the following description, from the drawings, and from the claims.
The Description is organized as follows.
Referring to
In
In the example of
Referring to
In some cases, measuring optical photoelectronic devices such those from Prüftechnik of Germany, including Prüftechnik's Rotalign Touch system or Rotalign Ultra system may be used (the two web pages https://www.pruftechnik.com/us/products/alignment-systems-for-rotating-machinery/shaft-alignment-systems/rotalign-touch.html and https://www.pruftechnik.com/us/products/alignment-systems-for-rotating-machinery/shaft-alignment-systems/rotalign-ultra-is.html as of the filing date, and ROTALIGN touch brochure, ROTALIGN touch Whitepaper, and ROTALIGN Ultra iS brochure are incorporated by reference). Among other alternatives are laser shaft alignment systems made by FixturLaser of Sweden, or Easy-Laser of Sweden, both of which are two-laser systems, or the Stealth Series from Hamar Geolasers of Danbury, Conn.
In the single-laser system shown in
Referring to
Measurement at three positions may be mathematically sufficient to measure alignment, if the apparatus is known to be perfect. Taking more measurement points may improve accuracy, provide redundancy for detection and correction of methodological error or misalignment within the apparatus, and reduce the number of trial-and-error alignment adjustments. Eight to fourteen measurement points may be desirable.
In
After each measurement is taken, laser unit 102 and sensor unit 104 are moved around the circumference of the shaft, and the process is repeated: laser unit 102 and sensor unit 104 are lined up, and then another finger press captures the next measurement point. Computer 122 may display the total number of measurement points taken, and the angle subtended by the measurements.
II. Alternative Configuration
In such cases, rods and blocks 200 may be arranged to hold laser unit 102 and sensor unit 104 in front of mounting base 210, down close to the shaft surface. Brackets 200 may provide a rigid and reproducible affixation of the laser and sensor unit 104 as low as touching the surface of the shaft. Magnetic base 210 shown (shown in grey in
The brackets may be designed to provide a range of heights so as to hold laser unit 102 and sensor unit 104 several inches above the surface to which base 210 is attached, to allow the laser and sensor to “see over” an obstruction.
III. Components
Referring to
V-groove 220 provides two linear contacts against a curved machine surface. In other configurations, the bottom surface of base 210 may have two rails 242. As will be shown in
Other similar bases 210 are available from Noga and other manufacturers. The appropriate base 210 for use with a given shaft may be chosen based on the configuration of the shaft. Generally, longer is better, to improve precision of alignment for parallelism, up to the width of whatever face the base 210 is to be attached to, and subject to a human's ability to manage the weight and length of the device. For larger-diameter shafts, bases 210 of wider width may be preferred. For smaller diameter shafts, bases 210 with narrower widths may be preferred. For non-ferrous shafts/couplings or large diameters, a wider V-block may be used, or magnetic base 210 may be replaced with a chain or strap fastener.
Magnetic base 210 has a magnet that can be switched on and off. The on position is labeled with a “+,” and the off position is labeled with a “−,” which can be seen in
Referring to
In some uses, the Prüftechnik laser unit and sensor unit 104 may be mounted on these two rods 234.
In other cases, where it is desired to hold laser unit 102 and sensor unit 104 closer to the surface of the shaft (like
The multiple sets of holes 236 in the mounting block 232 allows for mounting laser unit 102 and sensor unit 104 in different places relative to magnetic base 210. Using the center set of holes (as in
Referring to
Magnetic base 210 with linear or rail contact, as shown in
Referring to
Referring to
A rail spacing of about 50 mm (2 inches) or a little more, and length of about 120 mm (4.8 inches) seems to be a “sweet spot.” At those dimensions, the length is long enough that the linear errors in affixation of base 210 to shaft 110 translate into sufficiently small angular errors. As dimensions get larger, mass and resilience of the device tend to damp the tactile feel as the magnet “bites” the surface of the shaft.
Alternative configurations for the contact points may be curved, semicircular, or rollers, to provide touches at tangent points between the shaft surface and the base contacts. These may be more applicable for smaller-diameter shafts. For shafts below 10 inches in diameter, point contacts may be adequate. As shaft diameters increase above 10 inches, to 15, 20, 25, 30, 35, 40, 45, and 50 inches, the advantage of linear contact increases.
Fixed linear contacts may provide friction with the shaft surface that improves stability of the mounting. Rollers and smaller-contract rounded contacts may lack this frictional contact to prevent the small perturbations or gravitational sag that would disturb readings.
Magnetic affixation may be desirable, because magnets have a continuous character. A tension mechanism that may be tightened with a threaded tension nut may also be desirable. In contrast, mechanical connections based on chains and gears have a character that varies over the length of each chain link or gear tooth. In an application where high precision is essential, it may be preferred to avoid such variability.
The components of base 210 and brackets 200 may be designed to reduce internal resilience and play, to provide rigidity and consistent orientation of laser unit 102 and sensor unit 104 as they are moved from position to position along the circumference of the shaft or coupling. The rods and rod holders should be stiff enough that the weight of laser unit 102 and sensor unit 104 introduce no measurable “sag” as the device is rotated. If laser unit 102 and/or sensor unit 104 is slightly non-parallel or non-perpendicular relative to its base, the user can identify bad points using software in computer 122 to subtract it out, so long as the error is stable and consistent. While high precision of angle and dimension may be desirable, they are less crucial than rigidity and consistency.
IV. An Operational Use Case
Referring to
Referring to
Because of this askew-and-adjust placement, it may be desirable to position the mounting rods to hold the emission lens of laser unit 102 and aperture lens of sensor unit 104 over the center of magnetic base 210. If the lenses are centered (or, as a proxy, if the entire laser unit 102 and sensor unit 104 are centered) over their respective mounting bases, then as each base is twisted and adjusted to “bite” and align with the shaft surface, then the relevant components only change angle, not location. This eases the tasks of trial-and-error alignment.
Referring to
Referring to
Referring to
Referring to
The process repeats: first, sensor unit 104 is moved, and placed against the shaft circumference slightly askew, then the base's locking magnet is turned on, then sensor unit 104 is turned until the human feels the linear contacts bite. Then, the human unlocks the laser unit's magnet, moves laser unit 102 into position (
Once everything is lined up, then (
Computer 122 will tell when each reading has been recorded, and how many degrees of arc of the shaft are covered by the measurements. The whole process is repeated over the whole exposed rim of the coupling, until further measurements are blocked by the turbine casing or the full 360° is covered.
Referring again to
The human may take a second set or several sets of measurements as a repeatability check to make sure the measurements are consistent.
When computer 122 and human are satisfied, then computer 122 may display a result screen to allow the human to review a computed misalignment result. Computer 122 may display a vertical offset, a horizontal offset, and horizontal and vertical angularity or gaps/diameter.
For the convenience of the reader, the above description has focused on a representative sample of all possible embodiments, a sample that teaches the principles of the invention and conveys the best mode contemplated for carrying it out. Throughout this application and its associated file history, when the term “invention” is used, it refers to the entire collection of ideas and principles described; in contrast, the formal definition of the exclusive protected property right is set forth in the claims, which exclusively control. The description has not attempted to exhaustively enumerate all possible variations. Other undescribed variations or modifications may be possible. Where multiple alternative embodiments are described, in many cases it will be possible to combine elements of different embodiments, or to combine elements of the embodiments described here with other modifications or variations that are not expressly described. A list of items does not imply that any or all of the items are mutually exclusive, nor that any or all of the items are comprehensive of any category, unless expressly specified otherwise. In many cases, one feature or group of features may be used separately from the entire apparatus or methods described. Many of those undescribed variations, modifications and variations are within the literal scope of the following claims, and others are equivalent.
This application is a continuation of U.S. application Ser. No. 16/658,072, filed Oct. 19, 2019, Alignment of Rotational Shafts, now issued as U.S. Pat. No. 11,300,404; which is a non-provisional of U.S. Provisional App. Ser. No. 62/748,464, filed Oct. 21, 2018. The '072 and '464 applications are incorporated by reference.
Number | Name | Date | Kind |
---|---|---|---|
4518855 | Malak | May 1985 | A |
4553335 | Woyton | Nov 1985 | A |
4709485 | Bowman | Dec 1987 | A |
5077905 | Murray | Jan 1992 | A |
5684578 | Nower | Nov 1997 | A |
5715609 | Nower | Feb 1998 | A |
6046799 | Lysen | Apr 2000 | A |
6098297 | Belfiore | Aug 2000 | A |
6411375 | Hinkle | Jun 2002 | B1 |
6784986 | Lysen | Aug 2004 | B2 |
6792688 | Busch | Sep 2004 | B2 |
6873931 | Nower | Mar 2005 | B1 |
6915582 | Engels | Jul 2005 | B1 |
6968625 | Segerstrom | Nov 2005 | B2 |
7174649 | Harris | Feb 2007 | B1 |
7301616 | Foley | Nov 2007 | B2 |
8209875 | Harris | Jul 2012 | B1 |
8689455 | Smith | Apr 2014 | B2 |
8955230 | Alexander | Feb 2015 | B2 |
8997365 | Alexander | Apr 2015 | B2 |
9080862 | Weihrauch | Jul 2015 | B2 |
9366527 | Weihrauch | Jun 2016 | B2 |
9605951 | Hblzl | Mar 2017 | B2 |
9964394 | Andersson | May 2018 | B2 |
11193760 | Strunk | Dec 2021 | B2 |
11200404 | Zhao et al. | Dec 2021 | B2 |
11300404 | Jozokos | Apr 2022 | B2 |
20110176145 | Edmonds | Jul 2011 | A1 |
20130269194 | Sansom | Oct 2013 | A1 |
20150042986 | Weihrauch | Feb 2015 | A1 |
20160003608 | Lenz | Jan 2016 | A1 |
20160223320 | Hblzl | Aug 2016 | A1 |
20160363432 | Andersson | Dec 2016 | A1 |
20170232605 | Morton | Aug 2017 | A1 |
20200124409 | Jozokos | Apr 2020 | A1 |
20220268575 | Jozokos | Aug 2022 | A1 |
Number | Date | Country |
---|---|---|
204007548 | Dec 2014 | CN |
105841674 | Aug 2016 | CN |
108204792 | Jun 2018 | CN |
108458673 | Aug 2018 | CN |
6-147826 | May 1994 | JP |
2013-517482 | May 2013 | JP |
20-2008-0004566 | Oct 2008 | KR |
2020070005773 | Oct 2008 | KR |
2352901 | Apr 2009 | RU |
WO2014092523 | Jun 2014 | WO |
Entry |
---|
PCT/IB2019/058932 ISA/201 and ISA/237 Search Report and Written Opinion dated Feb. 7, 2020. |
PCT/IB2019/058932 China Peer Search Report dated Jan. 7, 2020. |
PCT/IB2019/058932 EPO Peer Search Report dated Jan. 10, 2020. |
PCT/IB2019/058932 JP Peer Search Report dated Jan. 9, 2020. |
PCT/IB2019/058932 US Peer Search Report dated Jan. 9, 2020. |
Prüftechnik Condition Monitoring GmbH, Prüftechnik White Paper: Precision Meets Connectivity (Sep. 2015). |
Prüftechnik Condition Monitoring GmbH, Rotalign touch, Precision Meets Connectivity, DOC 50.400.EN (2015). |
Number | Date | Country | |
---|---|---|---|
20220268575 A1 | Aug 2022 | US |
Number | Date | Country | |
---|---|---|---|
62748464 | Oct 2018 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 16658072 | Oct 2019 | US |
Child | 17712389 | US |