Method and apparatus for detecting a soft foot condition of at least one machine and for correction thereof

A system and method for detecting a soft foot condition of one or more machines. Several measurements of a soft foot condition of a machine to be tested are made and the numerical output of the measuring device is stored in a memory of the device of the present invention. This information is used to systematically diagnose (or assist in diagnosing) possible causes of such soft foot condition and to provide general or numerical advice on possible corrective action. Such advice will be systematically derived by a computer and will relate to remedies considered to be most effective or important, and will be provided to the operator of such instrument either by a readout on a screen or a display of an instrument employed for this purpose.

BACKGROUND OF THE INVENTION 
The present invention relates to a method and apparatus for detecting a 
soft foot condition of one or more machines. The term "soft foot," as used 
throughout this text, relates to the usage as is common among engineers, 
technicians etc., and is not directly related to the usage of the same 
term, as used in the medical or related arts. For those persons not 
acquainted with this term it should be explained that normally nothing is 
"soft" with the feet under inspection. To the contrary, the feet are quite 
inelastic. However, once the feet tie a machine under test to the ground 
in a sturdy fashion, then the geometric constraints of the feet and/or 
shop floor ground will cause small, but intolerable mechanical deformation 
or distortion of such specific machine. 
It has long been recognized that setting up and installing rotating 
equipment and machinery requires careful layout and care in the 
installation. This is especially true for equipment of some size, which 
despite of its weight and apparent stable construction, nonetheless 
requires attention to maintain mechanical dimensionality within predefined 
tolerances, which may correspond to minute fractions of an inch or may be 
in the sub-millimeter range. Neglecting such prerequisites will yield 
slightly, but definitely distorted, machine dimensions and thus will 
frequently cause reduced service life. Also, suboptimum output or 
efficiency may result from such machines, which may be combustion engines, 
electric motors or generators, turbines, lathes or other machine tools, 
pumps, ventilators (fans), gearboxes, and many more machines of the like. 
As is well known, installing and mounting such machines on uneven or rough 
surfaces will result in a somewhat distorted shape of their housings or 
enclosures, with subsequent adverse effects on the bearings for shafts, 
spindles or the like present in such machines. Another negative effect is 
in obtaining and maintaining correct alignment of the spindles of machine 
trains such as, for example, pumps and their driving motors. In electric 
motors or generators, deformation of the machine induced by inadequate 
mounting may have effects on the shape of the magnetic airgaps, usually 
reducing output power, efficiency, or both with such machinery. 
There have been investigations that demonstrate the economic impact of 
badly mounted or aligned machine trains, in addition to the power losses. 
Machines in the 10 hp range may require additional maintenance cost in the 
range of more than U.S. $400 per horsepower per year. The importance of 
machines positioned correctly and aligned to stringent levels should be 
understood by all levels of management involved. However, considering 
quality terms for such machinery became more frequent just recently. An 
analysis of the technical aspects of the soft foot condition carried out 
by the present applicants discovered that contrary to common 
consideration, determination of the causes of a soft foot condition and 
advising on corrective measures are not systematically carried out. One 
reason for this is that there is not only one "soft foot" situation, but 
several classes of such, which require different corrective handling. 
Thus, it still may be possible for an engineer trying to eliminate a soft 
foot condition on a machine, to perform just the opposite and worsen 
conditions because of a lack of understanding or proper guidance on how to 
proceed to eliminate such adverse constraints on the machine. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to give the persons 
involved in the art access to an instrument that employs useful and 
specific methods not only to diagnose a soft foot condition, but discern 
different types of such condition and provide automated and reasoned 
information on how to eliminate such a condition in the least time 
possible. 
The invention is based on the principles and the measurement capabilities 
of a laser alignment instrument, but is not limited to using an instrument 
of this specific type. Measuring equipment of the laser alignment type is 
already able to generally indicate a soft foot condition on a machine 
train. At least, the Optalign and the Rotalign systems of German 
manufacturer Pruftechnik are able to carry out such measurements. However, 
only numeric values informing about the magnitude of a soft foot condition 
are indicated, without providing any information on how to resolve such 
condition. According to the present invention, it is possible to perform 
several measurements on the soft foot condition and then utilize the 
numerical output of the measuring device to systematically diagnose (or 
assist in diagnosing) possible causes of such encountered condition and to 
provide general or numerical advice on possible corrective action. Such 
advice will be systematically derived by a computer and will relate to 
remedies considered to be most effective or important, and will be 
provided to the operator of such instrument either by a readout (i.e. 
alphanumeric information or pictograms) on a screen or a display of an 
instrument employed for this purpose. In another embodiment, such 
instrument will have an acoustical output, i.e. will provide information 
in a common language. With acoustical output, it may be of additional 
benefit to also have an acoustic input, employing direct speech input via 
a microphone to a computer, in order to implement an additional channel of 
inputting information or commands to such instrument. It is preferred, to 
have such instruments be of the portable type. 
According to the present invention, several measurements regarding a soft 
foot condition will be carried out on a machine to be tested. This is done 
in a manner as already known--e.g. loosening screws or nuts that normally 
clamp down the feet of the machine to the shop floor. One after another of 
such nuts or screws will be loosened on the machine under test, and the 
relating deviation of the contacting surface of a specific foot in 
relation to an ideal plane, if any, will be indicated as a numerical value 
and registered in a memory of the device of the present invention. 
Specific to the invention, and depending on the magnitude and geometrical 
distribution of such registered values, the instrument will proceed 
according to the method of analysis of the invention to finally suggest 
the most feasible corrective action, or give ranked information on such 
useful actions, in case several seem appropriate. As indicated above, such 
suggestion can be presented to the user of the device via a display, a 
screen, an acoustical output, singly or in combination. 
The preferred way to utilize the invention is depicted in the drawings, and 
a preferred method to utilize the invention will be demonstrated in the 
following description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As shown in FIG. 1A, several mechanical defects are known that will cause a 
soft foot condition. A piece of rotating equipment 11, such as a machine 
tool or the like, may be fastened by its four feet to a shop floor 10. Of 
the feet 12 and 13 shown in FIG. 1A, a parallel air gap is present under 
foot 13. Upon clamping or tying foot 13 to the ground, this air gap may be 
eliminated, and the machine housing may be distorted creating a typical 
soft foot condition. A similar condition is shown in FIG. 1B. Instead of a 
parallel air gap, a slanted air gap 16 is present under the inclined 
bottom surface of bent foot 15. Clamping down foot 15 to the ground 10 
will give rise to a soft foot condition with a distorted machine housing 
or casing as well. Another situation of similar kind is depicted in FIG. 
1C, indicating what is also called a "squishy foot" condition, which is 
caused by shims 18 of inadequate quality, or foreign matter between foot 
17 and the floor or ground 10. A further situation of a similar kind is 
depicted in FIG. 1D, indicating what is called an "induced soft foot" 
condition, which is attributable to a distortion of the machine housing 11 
induced by an external load or force, which, for example, may be induced 
via a coupling flange 19 that is used to connect two (misaligned) shafts. 
Similar to FIGS. 1A-1D, FIG. 2 shows a top view of a piece of machinery 
with a rotatable shaft, spindle or the like. In order to distinguish 
between individual feet of the machine, reference numerals 21-24 are 
shown, above or below which are indicated calculated soft foot values. 
Such calculations of soft foot values are obtained by first obtaining 
alignment values of a machine train with all its basic fastening elements 
strapped down to the shop floor, then loosening such fastening elements 
singly and one after another, in an ordered fashion, and taking alignment 
measurements on the machine in a regular procedure. In FIG. 2, on each 
single foot 21-24, additional numerical values are shown that represent 
the values of clearances, measured manually with a feeler gage, with the 
basic fastening element of that specific machine foot loosened. 
As shown in FIGS. 3A and 3B, the apparatus according to the invention may 
comprise softkeys 30 for inputting or editing clearances that are observed 
under specific feet, as symbolized by reference numerals 21-24, 24, on a 
symbolized machine, the direction of which is symbolized by an indication 
of a coupling flange 19. It is possible to enter several values for each 
foot, that relate to measured clearances under a specific foot of a 
machine in case the related fastening element has been completely loosened 
or removed. Reference numerals 41-43 indicate input fields for such 
measured values, that are on the inboard side of the machine. By 
activating one of the softkeys 30 it is possible to select input fields 
for entering measured values on the outboard side of each single foot. 
Referring to FIG. 3B, once all measured values have been entered, the 
device, in a first step in accordance with the method of the present 
invention will display values as entered in fields 51-54, as well as 
calculated values indicating the magnitude of the soft foot condition for 
each foot of the machine, as depicted in fields 31-34. Softkey-line 40 is 
available for entering further commands or for performing further editing. 
One of the most important commands as mentioned above will be the 
systematic evaluation of such numerical values displayed on the display 
and simultaneously present in the memory of the device according to the 
invention, in order to perform a machine assisted evaluation on the most 
likely underlying cause of a noticed soft foot condition. 
As depicted in FIG. 4A, in a first step S11 according to the method of the 
invention, a conventional measurement with subsequent calculation of soft 
foot condition is performed on all four feet of a machine under test, 
preferably using a laser based aligning instrument. The calculated values 
of the soft foot condition will be kept in the memory of the device. 
Step S11 being completed, the next step to be performed is S12, in which 
the results of step S11 will be evaluated. If all soft foot conditions are 
calculated to be less than 2/1000 of an inch (2.0 mils), the procedure 
will branch to step S13. With all values within predefined limits, there 
is no soft foot condition to correct, and after signaling such information 
to the operator by means of the display of the device according to the 
invention, the routine may terminate, preferably after having logged all 
relevant data in the memory of the device or in a host computer optionally 
connected by signal transmitting means to such device. It is also possible 
to employ acoustical signaling means to indicate that no further actions 
are necessary. 
If at least one soft foot condition is calculated to be larger than 2.0 
mils, the process continues with step S19, in which it is decided whether 
or not the three largest calculated soft feet conditions are of comparable 
magnitude, i.e. do not exceed an upper or lower boundary relative to their 
mean value (arithmetic mean, for example), which boundary will not differ 
by more than 5% of that mean value, or by more than 5/10000 of an inch 
(0.5 mils) absolute value compared to that mean value. It will be 
appreciated, that it is advantageous to have such task carried out by a 
computer, rather than manually. If the mentioned three largest values do 
stay within the specified boundaries, step S20 will be performed, in which 
a message is forwarded to the operator to loosen all bolts or primary 
fasteners on the machine under test and fill all visible gaps under the 
feet of the machine, maybe additionally checking on the local sturdiness 
of the floor. Step S20 generally relates to the condition, or activity, 
that is called rough soft foot. This is a millwright procedure by which 
the machine base bolts are loosened, and efforts are carried out to have 
each foot of the machine support the same load, or the correct proportion 
of the load, as well as to have each foot in full co-planar contact with 
its shim pad, i.e. with even loading over the area under each foot. Step 
S20 being completed, the process will continue with step S21 and prompt 
the operator to return to step S11 (start) or will automatically do so by 
itself, so that the soft foot evaluation on all four feet can be carried 
out again. 
If the three largest values do not stay within the specified boundaries in 
step S19, step S30 will be performed, in which it is determined whether or 
not at least one soft foot condition has been calculated to be 2% larger 
than all others and, in an absolute value, simultaneously be 5/10000 of an 
inch (0.5 mils) larger than all others calculated. It will again be 
appreciated, that it is advantageous to have such task carried out by a 
computer, rather than manually. If a positive determination is made in 
step S30, i.e. the "larger" condition was determined, the process will 
branch to perform step S40. In this step the operator will be notified to 
loosen a specific foot, according to what has been calculated by the 
instrument, and to measure the dimension of the gap below that foot, at 
all four corners of the foot. It may suffice to measure the apparent gap 
at only three corners, which are the easiest to access. The measurement 
may be carried out manually. It also may be carried out using gauges with 
an electronic output, connected to the device according to the invention. 
After all required values for a specific single gap have been entered into 
the device, step S41 will be performed. In step S41 the device will 
decide, based upon a prior calculation performed by the device, whether or 
not the average measured gap value has been determined to be greater than 
70% of the formerly calculated, numerical value of the soft foot 
condition. Upon this decision, either step S42 or S45 will be carried out 
automatically. Step S42 relates to the negative outcome, if the average 
gap value is greater than 70% of the calculated soft foot condition. In 
this step of the inventive method, the operator will be messaged, either 
acoustically or optically, that the foot currently under inspection is 
likely to be of the "squishy" type, possibly caused by foreign matter 
under the foot, or other circumstances that offer a higher mechanical 
compliance to the foot than intended or specified. A message may be 
displayed, in addition, to inspect a shim pack, if already present under 
the foot, and to clean it, if necessary, while taking care not to employ 
more than three shims simultaneously. Once the operator acknowledges the 
presented information within step S43, the process will return to step 
S11, where input values are obtained and numerical values are calculated 
for a predicted soft foot condition. 
If the decision of step S41 is in the positive, the routine will branch to 
perform step S45. In step S45, numerical calculations and logical 
decisions are carried out to determine whether the following conditions 
are simultaneously true: a) if the maximal extension of a single gap is 
still smaller than 1.2 times the smallest extension determined under that 
specific foot, and b) if the difference between the extensions, 
represented by the term "max gap-min gap", is less than or equal to 4/1000 
of an inch (4 mils, equivalent to about 0.1 millimeter, or 100 microns). 
If both conditions are true, the process will continue with step S47, 
signaling (or messaging) that the found gap requires filling, which should 
be done in a manner preferred in the art, i.e. shimming with high quality 
shims, with several shims being completely one above the other. In the 
other case, the process will continue with step S46, also signaling to 
eliminate the gap found, but by step shimming, as is also an accepted 
method in the art. On completion of either steps S46 or S47, the process 
will continue with step S48, which is a branch to step S11, in order to be 
ready for performing another machine assisted investigation of a soft foot 
condition. 
If, on the other hand, the determination in step S30 is in the negative, 
step S50 will be performed. In this step, it is determined whether the two 
largest calculated soft foot predictions are diagonally opposite on the 
machine under test. If it is determined that they are diagonally opposite, 
the procedure will continue with step S60. This step relates to the 
situation where two calculated, or predicted, soft foot conditions are 
about the same size. During the performance of this step, the operator 
will be prompted to loosen both fastening elements (e.g. nuts) for the 
specific feet being tested. The operator will also be prompted to measure 
the specific dimensions of the gaps below those two feet, preferably at 
all four corners of each foot. The operator may do so using a feeler gage, 
or an instrument that will provide its readings in machine readable form, 
i.e. providing data in a data format that may be transmitted via a cable, 
or optically, or otherwise as is known in the art. Having furnished such 
requested readings to the device of the present invention, the process 
will continue with step S61 in order to perform calculations and determine 
whether the average gage value (for each foot measured) amounts to more 
than 70% of the predicted value of the soft foot condition. If the outcome 
of such investigation, as applied to a single foot of the two mentioned, 
is in the positive, then the process will continue with step S62, where 
the operator will be prompted to fill the gap found, or step shim such 
gap, if necessary, employing accepted methods of the art. If, 
alternatively, the outcome is in the negative, then the routine will 
branch to step S63, by which the operator is informed that a specific foot 
(of the two feet currently under test) is likely to be "squishy." The 
operator will also be informed or prompted to do the following: to inspect 
a shim pack, possibly present under such foot, to clean the gap and/or 
shim pack, and reinstall a shim pack, preferably an unused one, with less 
than four shims. On completion of either step S62 or S63 the routine will 
branch via step S64 to step S11, so that a new measurement on a soft foot 
condition may be carried out. 
If the outcome of step S50 is in the negative, then the routine according 
to the inventive method branches to step S70. This branch relates to the 
condition that the two largest predicted soft foot conditions are 
predicted to be found either on the inboard side, the outboard side, or 
one of the sidelines of the machine under test. In step S70 the operator 
will therefore be prompted to loosen the mentioned two feet that are 
predicted to exhibit the largest soft foot conditions. The operator will 
also be prompted to measure the gaps of such feet to be tested, in a 
similar fashion as has been set out above. After step S70 will have been 
completed, step S80 will be encountered, in which a calculation and 
decision is performed very similar to that of step S61. If the answer is 
in the negative, then, similarly, the routine will branch to step S81, 
prompting the operator in the same way as in step S63. With step S63 
completed, the routine will commence via step S82 to S11, so that a new 
standard prediction on a soft foot condition may be carried out, in order 
to check for any remaining corrective action. 
If, alternatively, the outcome of step S80 is in the positive, then it will 
be decided in accordance with the present invention in step S90 if the two 
largest soft foot conditions are predicted to be on either end of the 
machine (ends of the machine relating to the ends of the main shaft of 
such a machine). If the answer is in the positive, the routine will branch 
to step S91, where it is signaled to the operator that the observed soft 
foot condition may be due to an induced effect. Such induced effect may 
relate to the fact that a coupling strain is possibly present, which may 
be confirmed by opening the coupling on the shaft of the machine under 
test, or by checking the alignment of the machine under test with regard 
to its counterpart. 
If, on the other hand, the answer is in the negative, step S92 of the 
routine will be encountered. This step will display a message to the 
operator that the induced soft foot condition is very likely due to 
external strains. Therefore, the operator (for example, a millwright), may 
also receive a message to remove possible pipe strains and any other side 
loads that may be present on the machine under test. 
With either steps S91 or S92 completed, the routine will proceed with step 
S93, which will branch to step S11 for entering a renewed, possibly final 
check on a soft foot condition on the machine under test. 
An illustration of a displayed message and a softkey-menu 60 to choose from 
is depicted in FIG. 5A, which relates to Step S20. A text message 62 in 
plain language is displayed, which may be accompanied by an appropriate 
"grouchy" icon 62 (instead of a "smiley" icon). By activating key 63 the 
routine will be allowed to enter step S21, which will effectively transfer 
control to step S11 (Start). On activating key 64, it will be possible to 
display detailed information to the operator. Such detailed information 
may relate to the history of measurements recorded on the particular 
machine under test, for example pointing out that a soft-foot condition 
has been worked on before, and recalling former causes and remedies 
applied to correct such situation from the memory of the device according 
to the invention. 
Another kind of display of detailed information may relate to the progress 
of work performed on one or several machines under test, as depicted in 
FIG. 5B. Display screen 80 for example will show by line 81, that a 
squishy foot condition existed with feet 2 and 3, as measured on the 
indicated date and time. Line 82 will reveal the further history of work 
performed on such machine, indicating for example the detection of a rough 
soft foot condition at a somewhat later point of time. Array 70 of 
softkeys may be activated manually by the operator, in order to proceed 
according to his intentions. For example, activating cursor keys 66, 67 
will scroll the highlighted line, e.g. 81, 82. Furthermore, information on 
a highlighted or otherwise emphasized line of displayed screen 80 may be 
gained by pressing key 64. Activating key 65 may transfer control of the 
routine to a next step, as defined by the method of the invention and set 
out above, for example. 
Although the invention has been described with reference to specific 
embodiments, various modifications of the disclosed embodiments as well as 
other embodiments of the invention will become apparent to persons skilled 
in the art on reference to the detailed description of the invention 
contained herein. Accordingly, the claims of the present application 
should not be limited to the specific preferred embodiments described.