Abstract:
Disclosed is an attachable spacer applied to the front base plate of a hand-held and self-contained XRF testing device that holds the face plate at a forwards tilt towards a test sample, and ensures that only the top rim of the face plate ever touches a test sample. The resulting triangular gap minimizes contact between the front plate window and the test surface, prevents the transfer of heat to the XRF testing device&#39;s circuitry, and locks in a fixed distance between the face plate of the XRF testing device and the sample being tested.

Description:
FIELD OF THE INVENTION 
     This invention relates to X-Ray Fluorescence (XRF) portable instruments configured to inspect, test and analyzing elemental composition of a test object, more particularly to a spacer accessory to be attached to the instruments. 
     BACKGROUND OF THE INVENTION 
     There are many non-destructive testing and/or XRF analysis applications involving complex situations which require thickness measurement, corrosion inspection and chemical composition analysis on high temperature test objects. As an example, sulfide corrosion of oil pipes is a significant cause of leaks and issues for the refining industry that cause early replacements, unplanned outages, loss of property, and, in extreme cases, injury to workers. According to the American Petroleum Institute (API) Recommended Practice 939-C (Guidelines for Avoiding Sulfidation Corrosion Failures in Oil Refineries), ⅓ of all high temperature sulfidic corrosion failures are due to low silicon content in the piping. The inspection of a pipe&#39;s corrosion status, chemical composition would require conducting XRF analysis on high temperature pipes. 
     Elemental analysis of oil refinery pipes with handheld, self-contained X-Ray Fluorescence (XRF) devices is a preferred method to help predict and prevent pipe failures from occurring. These handheld devices typically have a front plate window whereby an X-ray is emitted out to a test object, and the responding energy returning from the test object enters back to a detector in the device. On regular test objects of which high temperature is not present, the devices are usually held by operators in such a way that the front plate touches the surface of the test object. 
     However when the test object is of high temperature during an XRF operation, existing XRF device designs present problems as to how the operator can hold the handheld so that the front plate window can be placed in relation to the test object in the desirable manner. First, if the front-plate window touches the surface of the test object being tested, the front plate window might sustain damage or too much heat is trapped between the front plate and the test object. And high temperature oil pipes might contaminate the window, invalidating the result. Therefore some gap between the front plate window and the testing surface is desirable. Second, if the gap between the front-plate and the sample is too great, not enough X-ray energized energy from the sample is captured during the test for the analyzer, and the result is too faint to be accurate. Lastly, if the gap between the front-plate window and the sample being tested wobbles and is inconsistent, the air from the varying gaps attenuates the X-Rays inconsistently (more so for lighter elements such as silicon), and distorts the test results of the sample. 
     U.S. Pat. No. 7,939,450 B2 discloses an apparatus and method for processing a substrate with silicon to control spaces between the layers, and eliminate damage to transistor structures. While this method optimally automates the placement of layer spacing (and prevents the transfer of heat from the material), the solution does not solve the risk of potential damage to a front plate window. 
     U.S. Pat. No. 2012/0294418 A1 discloses a method of using a goniometer in order to rotate a testing sample to a precise angular position for XRF analysis. This solution though does not minimize the risk of contamination of the front-plate, nor does it allow an air flow that creates a gap which prevents heat from being transferred from the sample to the XRF analyzer. 
     U.S. Pat No. 2014/0204377 A1 discloses an auto-calibration, auto-clean, and auto-focus functionality for spectroscopic instruments (including XRF test devices) from a controller that configures motors to move an optics stage and a laser, in order to protect a front plate window. However, this solution is heavily dependent on software operation, and does not have the practicality of a simpler mechanical solution. 
     An inexpensive, easy to set up solution that can save the display window of an XRF device from abrasion and contamination, yet maintain a close and steady distance from a sample being tested, would be of great economic and ergonomic value. It would speed up XRF testing, reduce equipment replacement on a portable XRF testing device, and retain a higher percentage of valid test samples. 
     SUMMARY OF THE INVENTION 
     Disclosed is an attachable and removable spacer applied to the front base plate of a hand-held and self-contained XRF testing device that holds the face plate at a forwards slight tilt towards a test sample. The usage of such spacer allows only the top rim of the face plate and the spacer touch a test sample. The resulting triangular gap minimizes contact between the front plate window and the test surface, prevents the transfer of heat from the test object to the analyzer, and maintains a fixed distance between the face plate of the XRF testing device and the sample being tested. 
    
    
     
       BRIEF DESCRIPTION OF THE OF THE DRAWINGS 
         FIG. 1  is a schematic of an XRF instrument with a removable spacer ready to be attached the base plate of the XRF instrument according to the present disclosure. 
         FIGS. 2 a  and 2 b    are schematics of the XRF instrument with the removable spacer attached on the base plate. 
         FIGS. 3 a  and 3 b    are flowcharts of the process for operating the XRF instrument accommodating the application of the spacer. 
         FIGS. 4 a , 4 b , and 4 c    are views of the spacer design in top and cross sectional views. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The preferred embodiment of an XRF instrument creating a consistent space between the front window and the test object is herein presented by referring to  FIGS. 1-4   d.    
     Referring to  FIG. 1 , a conceptual view of an XRF instrument  10  is configured to couple with a spacer  6 , one at a time during operation. The XRF instrument further optionally includes an X-ray source  12 , a detector  16 , a data processor and memory  8 , a display  14 , and a front plate window  5  largely in the same way as conventional XRF instruments. 
     A front base plate  4  is devised as in conventional XRF instruments. An important novel aspect of the solution herein presented includes the employment of spacer  6 , with which any number can be attached over front base plate  4  according to the present invention. 
     An immediate exemplary usage of such an embodiment is to affix spacer  6  to front base plate  4  in semi-removable fashion, such as using screws. During operation, the instrument is held by an operator at handle  20 , with one edge of the front plate  22  and part of spaces  6  come into contact with the surface of the test object. With spacer  6  attached to base plate  5 , a consistent distance between front plate window  5  and the testing sample is formed. This is particularly important for elements with lower atomic numbers such as samples of silicon. At the meanwhile, the gap between testing surface and front plate window  5  created by space  6  decrease the heat trapped under the front plate window  5  and front base plate  4 , creating a significant benefit avoiding excess heat to be transferred into the instrument. 
     Reference is still made to  FIG. 1 . Spacer  6  is preferably attached over front base plate  4  by using a removable attaching means. Accordingly, spacer  6  is shown to be configured to be attached to front base plate  4  using two screws. Alternatively, spacer  6  can be attached by removably attaching means, which should be within the scope of the present disclosure. 
     Alternatively, any number of spacers  6  can be used depending on the application. For low atomic numbers of test samples, large air attenuation is not desirable. Therefore, no additional spacer  6  is needed for such situation. It should be appreciated that the usage of any number of, and any combination of any kinds of spacers, collectively numerated as  6  in  FIGS. 1 and 2  should be determined by the testing specifics, and the usage of all such should be within the scope of the present disclosure. 
     Further as shown in  FIG. 1  and  FIG. 2 a   , in this preferred embodiment, the screw holes on spacer  6  are of the same size as, and aligned with, the existing screw holes of front base plate  4 . In this way, spacer  6  shares the same set of screws as the existing front base plate  4 . This is to simplify the design modification and the operation of adding and/or removing spacer  6 . 
     Referring to  FIG. 2 a   , XRF instrument  10  is conceptually shown when spacer  6  is attached onto front base plate  4 . 
     Referring to  FIG. 2 b   , with spacer  6  attached, the only contact points are A on the rim of instrument  10  and B on spacer  6 . The gap in a shape of triangle ABC creates a space to avoid direct contamination of window  5 . The minimum contacting surface helps avoid heat from test object  7  being directly conducted into instrument  10 . 
     Alternatively, any other removably attaching means of spacer  6  is within the scope of the present disclosure. Such attaching means may include the usage of latch, pressure fitting, etc. 
     It should be noted that the preferred material of space  6  would be of low thermal conductance so that heat from the test object is not easily conducted into the instrument. Materials suitable for spacer  6  include ceramic, which is a primary material of choice. 
     Reference is now primarily made to  FIG. 3 a    with continued reference to  FIG. 1 .  FIG. 3  is a flowchart showing an operational procedure related to the usage of the embodiment shown in  FIG. 1 . 
     In order to accommodate the usage of a plurality of removable spacers according to the present invention, XRF instrument  10  is preferably devised with a plurality of corresponding calibration modes, factory-preloaded onto data processor and memory  8 , according the factory calibration when corresponding spacer is used. 
     It should be noted that the different calibration modes for different types of removable spacers  6  can be either designed in a new XRF instrument, or achieved by modifying an existing calibration module or functional block residing on the processor of an existing XRF product. The modified calibration module is shown in  FIG. 1  as  8   a . It can also alternatively be calibrated in a field operation or in a manufacturing set up, all of which should be within the scope of the present invention. 
     Continuing with  FIG. 3 a   , the method of calibrating an XRF instrument for a specific spacer is commonly known. Different calibration modes can be achieved in manufacturing settings for different types of the spacers. 
     Alternatively, if the thickness of the spacers is substantially homogenous and standardized, one can populate the values of different calibration modes by calculating the energy-dependent effect on the spectrum caused by the corresponding spacer. One can conduct sufficient number of calibration runs for a specific spacer, which yields a calibration factor for the spacer by comparing to the energy reading of the same XRF instrument without the spacer applied on the same set of samples. 
     Another note on the calibration modes is that it is preferable to prepare all possible calibration modes with corresponding calibration values for all possible combinations of using, or without using, any and any number of spacers provided with the instrument. The calibration values are stored in data processor and memory  8 . 
     The calibration modes is preferably made in a form of an executable functional code associated with corresponding calibration values store in, and as a module herein named calibration module  8   a  shown in  FIG. 1 . The calibration procedure preferably includes steps as follows. 
     Continuing with  FIG. 3 a   , in step  302 , the user starts testing by starting a calibration check with a calibration mode mostly used for a previous session of testing, i.e. for a light element or heavy atomic element. “Cal check” is commonly referred in XRF as shooting a sample of a known elemental composition. 
     In step  304 , calibration module  8   a  checks from a calibration shot on a calibration sample to determine whether the spacer is applied, and to determine automatically what kind of spacer is applied on front base plate  4 . Alternatively, when the known kind of element for testing (example: Si) is provided to the instrument, module  8   a  can be configured to determine if spacer  6  is the right match for such testing, noting that a lower atomic number needs a thinner spacer. Alternative step  304  can be that calibration module  8   a  only checks if spacer  6  is applied or not, and prompts the user to check if spacer  6  is the intended kind of spacer to be attached. 
     It can be understood by those skilled in the art that after the calibration check is initiated at step  302 , the energy reading on the known sample can indicate if spacer  6  is applied. And by comparing the known calibration factors stored in the instrument, optionally the calibration module  8   a  can yield what kind of spacer is presently attached to the front base plate. 
     Continuing with  FIG. 3 a   , in step  306 , calibration module  8   a  prompts the user via display  14  whether spacer  6  is applied, what kind of spacer is applied on front base plate  4 , and whether to change or remove spacer  6 , or alternatively change the calibration mode. 
     In step  308 , module  8   a  further checks which spacer (or no spacer) is chosen by the user. If a specific spacer is chosen, the procedure moves onto step  312 . If no spacer is chosen, the procedure moves onto step  310 . In step  412 , a specific calibration mode suited for the chosen spacer is chosen by calibration module  8   a , and executed by XRF instrument  10 . Alternatively, the user can also choose the calibration mode via display  14 . 
     In step  310 , if the user determines not to use any spacer and remove the same, the existing calibration mode for front base plate  4  without spacer  6  is executed to calibrate instrument  10 . In step  312 , XRF instrument  10  is ready for testing, which occurs in step  314 . 
     Reference is now made to  FIG. 3 b    with continued reference to  FIG. 1 , where alternatively a user can calibrate XRF instrument  10  manually. In step  301 , the user starts a “cal check” test. In step  303 , if it is needed to choose a cal mode for spacer. If the user knows a spacer is attached, the user enters “yes”. Otherwise the user enters “No”, and the procedure moves onto step  305   a . Upon choosing “yes”, in step  305  the user enters a calibration mode corresponding to the specifically know spacer that is attached. In step  307 , the chosen cal mode corresponding to the spacer is executed. The instrument is then ready for testing with the specific spacer on in step  309 . 
     Reference is now made to  FIGS. 4 a , 4 b  and 4 c   , and continuously to  FIG. 1 , where more details of the preferred embodiment of spacer  6  are provided. Referring to  FIG. 4 a   , which is a top view of spacer  6 , screw holes  24  are preferably aligned with those of front base plate  4 . The size, contour and shape of spacer  6  should also be very close to the corresponding part of front base plate  4 . Cross-sectional views  FIGS. 4 b  and 4 c    also exhibit the screw holes and the design of spacer  6 . The thickness of spacer  6  exhibited in  FIGS. 4 b  and 4 c    is exemplary and variations in thickness are within the scope of the present disclosure. 
     In addition to screws used in  FIGS. 4 a , 4 b  and 4 c   , it should be understood by those skilled in the art that other means can be used instead to attach and re-attach spacer  6  onto front base plate  4  of XRF instrument  10  (as well as their associated usage of corresponding calibration modes), and should all be within the scope of the present disclosure.