Patent Publication Number: US-2023137594-A1

Title: Leak detection

Description:
BACKGROUND 
     Field 
     Embodiments of the present invention generally relate to a leak detection apparatus useful to detect leaks from sealable vessels, including sections of pipe or piping, and more particularly to a leak detection apparatus employing helium and a helium detector. 
     Description of the Related Art 
     A leak detector can be employed to evaluate the presence and rate or amount of leakage occurring through a weld connecting two sections of a tubing, for example stainless steel tubing&#39;s, welded together to form a unit under test having at least one weld and at least two sections of tubing connected at the at least one weld. To perform the test, a lower than the ambient pressure is formed within the interior volume of the unit under test, commonly by connecting the interior of the unit under test to a vacuum pump or a volume at a desired vacuum level (desired sub-ambient, surrounding the unit under test, pressure), and thereafter helium is dispensed around a location of the unit under test such as a weld to be evaluated for leakage. A helium detector in the lower than ambient pressure region to which the interior volume of the unit under test is fluidly connected supplies an indication of whether helium has been detected in the lower than ambient pressure environment within the unit under test, and in some cases the concentration or atomic count thereof. 
     Helium leak checking is performed regularly on welds used to connect together pipings, and other fluid conduit geometries surrounding an intended to be fluid tight environment, using a helium wand to dispense helium from a helium source, and determine the presence and in some cases amount, of helium passing through the weld. As the helium is a very small atom, it can pass through openings in a weld that larger gas atoms or molecules cannot, because of their size, pass through. The amount of helium detected passing through the weld is an indicator of the porosity of the weld. This helium leak testing is often a manual process, whereby a technician or other operator or user connects the internal volume of a unit under test, for example the internal volume of lengths of piping including fittings and welds therein, to a vacuum source, for example a piping or reinforced hose connected to a vacuum pump, or for example to a factory vacuum line. The operator or user then holds the helium wand, and using a trigger  210  thereon, activates helium flow therefrom while moving the helium dispensing end of the wand over the area of the unit under test being checked for leakage. For example when the portion of the unit under test being evaluated for leakage is a weld, if the helium detector in the vacuum line indicates the presence of helium in the vacuum line over a preset amount or concentration, then the operator or user determines that the weld has failed the test and has unacceptable leakage, and the unit under test is either reworked or scrapped. In this testing paradigm, a small quantity of helium passing through the weld, but below a threshold amount, does not indicate a defective weld but can be used by the operator to monitor the effectiveness of the welding process forming the weld(s) connecting the tubing(s). 
     This testing methodology suffers from a number of limitations. For example, any record of the information relating to the passing or failing of the unit under test must be kept manually, and thus seldom is there a one to one tracking of a weld to a specific time of testing, or to the source of the weld, such as a specific welding operator, a welding station, the raw materials used to weld the tubings, and the lots from which the welded together tubings were drawn, all useful for defect tracing for quality control purposes. Additionally, the test operator or user affects the testing of the unit under test, because the presence of the proper vacuum pressure in the unit under test, and the speed at which the helium wand is moved over an along a weld, can impact the validity of the test. This can lead to false “passing” of a defective weld. 
     SUMMARY 
     In one aspect, an apparatus for detecting a leak in a unit under test includes a helium dispenser connectable to a helium gas source having a motion detector connected thereto, the helium dispenser configured to selectively dispense helium therefrom, a vacuum source releasably connectable to the unit under test through a fitting, a helium detector fluidly coupled to the vacuum source, and a controller operatively coupled to the helium detector and the motion detector and configured to receive electrical signals indicative of the speed of motion of the helium dispenser as helium is dispensed from the helium dispenser. 
     In another aspect, a method for sensing a leak in a unit under test includes scanning a SKU on a unit under test, sending the SKU information to a compute, connecting the unit under test to a testing apparatus, removing gas from an interior volume of the unit under test, monitoring the vacuum pressure within the interior volume of the unit under test until the vacuum pressure reaches a test pressure, initiating delivery of helium to the exterior of the unit under test through a helium gun by pulling a trigger on the helium gun to dispense helium therefrom, positioning the helium supply gun so that helium is released over a weld of the unit under test, detecting the movement speed of the helium supply gun during the dispensing of helium therefrom, and displaying the helium content internal to the unit under test on a graphical user interface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, may admit to other equally effective embodiments. 
         FIG.  1    shows a schematic view of a circuit for a leak detection test. 
         FIG.  2    shows a graph with measurements of the interior pressure of the unit under test, the helium detected, and time. 
         FIG.  3    shows a flowchart for a method for a leak detection test. 
         FIGS.  4 - 6    show a user interface graphical display depicting different outcomes of a leak test. 
         FIG.  7    shows an alternative construct of an accelerometer in a leak test. 
     
    
    
     To facilitate understanding herein, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     DETAILED DESCRIPTION 
     Referring to  FIG.  1   , a leak detection system  100  is shown. Here the leak detection system  100  is configured to:
         a) Supply helium under the control of an operator to a to be leak checked location of a unit under test, such as a weld location thereof;   b) monitor the vacuum pressure in the unit under test so that the operator does not prematurely release the helium to the weld before the proper base vacuum pressure in the interior volume of the unit under test has been reached therein;   c) determine the presence and optionally an indication of the quantity of helium entering into the interior volume of the unit under test; and   d) provide a pass or fail indication of the unit under test.       

     In one aspect, a controller or programmable computer is provided, and is operatively connected to: 
     A vacuum pressure sensor capable of determining a vacuum pressure in the interior volume of the unit under test; 
     a flow controller to determine the flow rate of helium; and to 
     an indicia reader capable of determining the type and manufacturing lot of the unit under test. 
     The computer or controller is further configured to monitor the vacuum pressure within the unit under test and the helium flow controller to determine whether the vacuum pressure was properly reached before helium was dispensed to a leak check area of the unit under test and whether the operator has exceeded the speed or velocity of the dispense region of the helium dispenser during the release of the helium therefrom adjacent to the region of the unit under test being evaluated for leakage. The computer or controller is also configured to provide an indicia of passing or failing, and to provide a notification to the operator of an improper test requiring that the unit under test be retested. Further, the system  100  is useable to allow the operator, user, or other personnel to track the amount of helium detected within a unit under test by type of unit under teat, lot number, serial number or other indicia of identification, of a unit under test and multiple helium leak tests of multiple units under test and over time, to determine trends in the amount of helium detected and allow the manufacturer of the welds to have better visibility into process drift or process change indicated by trends in the change or drift of the amount of helium detected over multiple units under test and over time, for root cause analysis of the weld integrity purposes, and for preventive maintenance to reduce the number of defective welds produced by the manufacturing facility over theme. In the implementation of the system  100  described herein, a power supply  130  is provided, and all of the electrical power to operate the various electrically powered components of the system are supplied with power from the power supply. This allows components of the system  100  to be mounted into a rack or other such device for ease of use thereof, and to reduce clutter. 
     In the system  100  of  FIG.  1   , a helium supply  101 , for example a factory helium supply having an outlet fitting such as a quick connect-disconnect fitting located adjacent to a test table  103  on which a unit under test  114  can be placed for testing, is provided. Alternatively, the helium can be supplied in a portable or moveable bottle, such as a bottle on a wheeled cart, or by other mechanisms and or structures. The helium supply  101  is fluidly connected to the input port of a mass flow monitor  102 . The mass flow monitor  102  measures, and thereby is useful for monitoring, the flow rate, and thus the amount, of the helium flowing through the helium gun  108  to which it is connected. The output port of the mass flow monitor  102  is connected, by a fluid supply tubing, to a two way coupling  106 . The two way coupling  106  is comprised of a female fitting  104  and a male fitting  105 . The fittings are cylindrical hollow metal fixtures wherein the female fitting contains a check valve composed of a spring biasing a ball against a sealing seat that allows the male fitting to fasten into the female fitting with a leak free seal, allowing helium to flow through the connected female and male fittings  104 ,  105 . The male fitting  105  is connected to a fluid tubing  107 , such as a flexible reinforced hose, leading and connected to the base of a helium gun  108 . 
     The fluid tubing  107  supplies helium to the helium gun  108  through a connection thereto at the base thereof when the male and female fittings  105 ,  104  of the coupling  106  are connected together. The helium gun  108  is comprised of a body  113  shaped for ergonomic use by the hand of a user. Inside of the body  113  is a hollow flow conduit extending from the tubing  107  at the base of the helium gun  108  to the dispense nozzle  111 , the flow through which is controlled by a valve (not shown) which is opened by an operator or user of the helium gun  108  depressing the trigger  210  of the gun, and closed off by the release of pressure on the trigger  210 . The helium gun  108  (helium dispenser) can be moved around freely within the range of the length of the tubing  107  connected thereto, to allow the dispense nozzle  111  thereof to be moved over locations of a unit under test  114  where a helium leak check is be performed. 
     Internal to the body  113  is an accelerometer  109 , which is used to measure motion of or acceleration of the helium gun  108 . Here the accelerometer  109  is capable of discrimination acceleration in the x, y, and z axes. The accelerometer  109  is connected to an accelerometer cable  115  here wrapped around the tubing  107  and connected at a location, distal to the helium gun  108 , where it is connected to a first CPU line  142  which may include a pair of accelerometer bus wires isolated from one another and extending from the connection thereof with the accelerometer cable  115  to the CPU  110 . The first CPU line  142  communicates information to the CPU  110  in the form of an electrical signal output from the accelerometer in response to motion of the helium gun  108 , and indicative of the speed of motion of the helium gun  108  while helium is being dispensed therefrom. The first CPU  142  line is configured to communicate information about the acceleration of the helium gun  108  and thus its velocity. A second CPU line  144  connects between the mass flow monitor  102  and the CPU  110 , to carry a signal from the mass flow monitor to the CPU  110  indicative of the amount of helium flowing from the helium supply  101  and thus outwardly of the nozzle  111  of the helium gun  108 . The flow rate of helium through the nozzle  111  of the helium gun  108  is monitored by the mass flow monitor  102 , which outputs an electrical signal indicative of the helium flow therethrough, which is electrically communicated, to the CPU through the second CPU line  144 . The CPU  110  is connected to the user interface  112 . The user interface (UI) allows the user of the helium gun  108  to receive visual and auditory information about the operation of the system  100 . If, during a test and while the helium is being dispensed from the helium gun  108 , if the acceleration or movement speed of the helium gun  108  reaches a preset maximum threshold value, a signal is sent from the CPU  110  to the UI  112 , and the UI  112  will display a failed test value and also, optionally, sound an audio alarm, display a video alarm, or both. 
     The system  100  also includes the testing apparatus hardware and facilities. This includes a vacuum source  150  connected, using a fitting, to a second fluid tubing  129 . The vacuum source  150  is for example a “house” source, which is piped to multiple locations within the manufacturing, testing, or manufacturing and testing facility to be used in multiple locations within the facility, such as a facility preparing welded pipings or equipment using those welded pipings, or both, and here is accessible through a quick connect coupling located adjacent to the table  103  on which the helium leak test will be performed on a unit under test. This second fluid tubing  129  contains therein a Helium detector  128 . For example, the helium detector  128  is positioned to be in fluid communication with the interior of the second tubing  129  through a T connection fitting to the vacuum tubing  129 , for example by being threaded into the stem of the T connection fitting, the arms of the T-connection fitting connected in line within the second tubing  129 . Thus, here, one arm of the T-connection fitting is fluidly connected to the house vacuum  150 , the second arm is fluidly connected to a reinforced hose  230  leading to a coupling used to connect the vacuum  150  source to the unit under test  114 , and the helium detector  128  is fluidly connected to the third arm or stem of the T connection. If helium is, as a result of the vacuum within the unit under test, pulled into the unit under test through pores in a weld or other portion of the unit under test  114  being evaluated, it will migrate to the helium detector  128  and the presence of helium in the interior volume of the unit under test  114  will be detected thereby. The helium detector  128  transmits an electrical signal related to the quantity or concentration of helium detected to the CPU  110 , through a helium detector line  127  composed of one or more electrical conductors communicating electrical signals corresponding to helium detection by the helium detector  128 , to the CPU  110 . The helium detector  121  is powered by the power supply  130  and is connected to the power supply  130  through the helium detector power supply cable  218 . 
     The interior volume of the second tubing  126  is, at one end thereof, fluidly connected to the interior volume of the unit under test  114  through the reinforced hose  230 , which is selectively connectable to the unit under test  114  through a coupling  124 . The coupling  124  is comprised of a female fitting  120  and a male fitting  120 . The opposed end(s) of the unit under test  114  is sealed with a cap or other sealing device. The fittings are cylindrical hollow metal fixtures wherein the female fitting includes a check valve having a spring biasing a ball against a sealing seat that allows the male fitting to snap into and thereby fasten into the female fitting with a leak free seal, to connect the interior of the unit under test  114  to vacuum, and thereby reduce the pressure within the interior volume of the unit under test  114  down to a user specified base (vacuum) pressure at which the unit under test  114  is evaluated for leakage at the welds thereof. Additionally, the helium detector  128  is, as previously described, in fluid communication with the interior volume of the second tubing  129 , and thus helium leaking through a weld in the unit under test  114  will be communicated to the helium detector  128  through the interior volume of the reinforced hose  230  and the second tubing  129 . The female fitting  122  portion of the coupling  124  is welded or otherwise fluidly and sealingly connected to the end of the second tubing  129  and the male fitting  120  portion of the coupling  124  is sealingly connected to the unit under test  114 . When the unit under test  114  is engaged with the male fitting  120 , the open end of the piping of the unit under test  114  locks into a cylindrical recess in the male fitting  120  with a leak proof seal. When the male and female fitting  120 , 122  portions are fastened together, this creates a continuous leak free sealed line from the unit under test  114  to the vacuum source  150 , with the helium detector  128  in fluid communication with the interior of the second tubing  129  at a location between the unit under test  114  and the vacuum source  150 . 
     Although in some aspects hereof the vacuum source is a house or facility vacuum line to which the unit under test can be connected, in the example here, the vacuum source  150  is a vacuum pump connected to the power supply  130  through the power supply line  215  to supply electrical power to operate the vacuum source  150 . In other aspects, the vacuum source  150  can be the aforementioned house or facility vacuum supply. When the vacuum source  150  is a separate vacuum pump, it is powered by the power supply  130 . The vacuum source pumps gasses and vapors, typically air, water vapor, or both, from the interior volume of the unit under test  114 , to bring the pressure of the interior volume of the unit under test  114  down to the desired test pressure. When helium is released over a weld region of the unit under test  114 , if there are openings in and through the weld connection that are larger than a helium atom, the vacuum will pull the helium released near and along the weld through the weld, into the unit under test  114 . The helium will migrate, or be pumped by the vacuum source  150 , through the reinforced hose  230  and the second tubing  129  to the location of the helium detector  128  to be detected thereby. 
     Internal to the vacuum source  150 , or within the second tubing  129 , is a pressure sensor  121 , which is connected to the CPU through the vacuum sensor line  216 . The pressure sensor  121  emits an electric signal which is transmitted along the vacuum sensor line  216  which is indicative of the fluid pressure within the second tubing  129  and thus in the interior volume of the unit under test  114  connected thereto. When the unit under test  114  is initially connected, through the coupling  124  to the second tubing  129 , the pressure in the second tubing  129 , which had been pumped down to the base or test pressure and maintained thereat by being sealed with the check valve of the fitting  122 , rises as the gas within the interior volume of the unit under test  114  migrates into the second piping  129 . Then, the fluid (gas, water vapor or both) within the combined volume of the interior volume of the unit under test  114  and the interior volume of the second tubing  129 , will begin to fall. The pressure sensor  121  sends electrical signals continuously, or at a desired refresh rate, to the CPU  110 , and the CPU  110  generates a pressure based output to the UI  112 , which displays a visual indication of the pressure within the interior volume of the unit under test  114 , which should be the same or nearly the same pressure as that in the second tubing  129 . The UI  112  can display the pressure as a number on the UI  112  display monitor, as well as graphically show the change in pressure within the unit under test  114  over time graphically on an X-Y axis where X is time and Y is pressure, and include a horizontal line on the graph displaying the threshold pressure at which the inner volume of the unit under test  114  has been lowered and reached the helium leak test pressure. The operator of the helium leak test on the unit under test  114  uses this threshold pressure line, and the dropping of the pressure below that threshold pressure line, as the indicator that one can begin the helium leak test on the unit under test  114 . 
     The helium detector  128  is connected to the CPU  110  through the vacuum sensor line  216 . The helium detector  128  is configured to output a signal indicating the detection of helium thereby, and of the relative concentration or amount of helium in the second tubing  129  during the test, which entered the fourth tubing  129  as a result of having passed through a weld and into the interior of the unit under test  114 . Concentration information can also be raw detector information, indicating the interaction of individual helium atoms with the detector, the more atoms interacting with the helium detector  128 , the greater the amplitude of the signal, or the number of individual signals representative of detection of an individual helium atom by the helium detector  128 . The output of the helium detector  128  to the CPU  110  can be continuous, or based on the sum of the detections of helium during a discrete time period. This information sent to the CPU  110  is displayed on the UI  112  display as helium concentration information and is also plotted graphically on an X-Y axis, with the Y axis being the concentration and the x axis being time, along with the pressure information. A preset threshold helium concentration is defined by the operator for the amount of helium allowed to be detected by the helium detector  128  during a test thereof. Alternatively, the system  100  can be configured that the CPU  110  receives identity information of the unit under test  114 , such as a bar code attached to the unit under test  114  and readable by a reader, which includes the type of unit under test  114 . The information can also include the threshold helium detected at which the unit under test fails the helium leak test, or the CPU  110  can include therein a look up table comparing the identity of the unit under test  114  and the threshold of helium at which the unit under test  114  is considered to have failed the test. Additional information, such as the time at which the unit under test, or individual welds thereof, were fabricated, the work station(s) or equipment used to fabricate the unit under test  114 , and the operator or operators whom assembled and welded together the tubing&#39;s making up the nit under test  114 . As helium is the smallest atom that is inert, other gasses which may be passing through the unit under test  114  when it is installed in a piece of equipment will commonly have much larger atomic or molecular sizes, and cannot pass through an opening through the weld that is just at, or slightly larger than, the atomic diameter of helium. The CPU is configured to sound an alarm, or display a notice of failed test, if the threshold allowed amount of helium detected by the helium detector  128  is surpassed. This failure notification can be displayed visually on the UI  112  display as a failure signal through text, display of a red light, both or other indicia. The UI  112  can also transmit the failure signal as an audio alarm. Additionally, if the coupling  124  is not forming a proper sealed connection between the reinforced hose  230  and the unit under test  114 , or if one or more welds of components connected into the unit under test are not sufficiently airtight, the vacuum source  150  will be unable to bring the pressure within the connected reinforced hose  230  and the unit under test  114  down to the test pressure, and the CPU can be configured to display or sound an alarm that there is a gross leak somewhere among the unit under test  114 , the coupling  124  and the second tubing  129 . The CPU  110  can be configured to cause an alarm to be sounded, displayed on the UI  112  display, or both, after a certain amount of time has passed since the unit under test  114  has been connected to the reinforced hose  230  but has not reached a desired vacuum pressure. 
       FIG.  2    shows graphically some of this information.  FIG.  2    is a graph having the interior pressure of the unit under test  114  measured along the left hand side Y axis, the helium detected quantity displayed along the right hand Y axis, and time along the x-axis. Curve  136  is representative of the pressure in a unit under test  114 . Here, at to, the unit under test is initially at atmospheric pressure and is connected to the vacuum supply  150  by connecting together fittings  120 ,  122 , at which time the pressure within the unit under test  114 , as detected by the pressure sensor  121 , begins to fall. Over time curve  132  extends to a location below a test pressure, and at time t 1  the operator dispenses helium to the region of the unit under test  114  at a weld thereof. Curve  134 , which should be evaluated based on the left hand Y axis, shows the amount or counts of helium atoms detected over time, beginning from when the trigger  210  on the helium gun was depressed by an operator. Here, the helium is slowly rising. The user establishes a test time period over which to dispense helium. Here, the not passing level is depicted on the right hand Y axis. Over the specified test period of t 1  to t f , the cumulative helium detected is less than the not pass level, and the unit under test  114  is considered to have passed. In contrast, the curve for the helium detected  136  for a different unit under test  114  shows the cumulative helium detected is greater than the not pass level over the specified test period of t 1  to t f , and this unit under test is rejected. Curve  132   a  in dashed line format shows the result where there is a gross leak somewhere in a connection of the test set up, the unit under test  114 , or both, as the unit under test cannot reach the vacuum required to start testing. Here the operator will check all of the connections, and retest the unit under test. If the vacuum test pressure cannot be reached, the unit under test  114  is set aside, and a new unit under test  114  connected. If this second unit under test reaches the test pressure, the initial unit under test is rejected. If the second unit under test  114  cannot reach the test vacuum level, the operator needs to disassemble the vacuum components, check the vacuum pump to ensure it is operating correctly, and rebuild the test setup. Thereafter, the two units under test, which did not reach the vacuum test pressure, are retested. 
     Of the issues effecting the validity of the helium leak test results, one is human error. One human error occurring during testing is the test operator delivering or releasing the helium from the helium gun  108  over or adjacent to the portion of the unit under test  114  being evaluated for a helium leak before the interior pressure of the unit under test  114  has reached the desired test pressure, which is a vacuum pressure substantially below the surrounding ambient air pressure where testing is occurring. The likelihood of helium entering an opening in the unit under test  114  capable of having helium pass therethrough, and the amount of helium gas being pulled through the opening, is a function of helium availability at an opening it can pass through, and the difference in pressure between the interior volume and the exterior of the unit under test  114 . The amount of helium being dispensed by the helium gun is digital, as the helium gun is calibrated frequently by dipping the tip end of the helium gun into a liquid and determining the amount if gas released when the trigger  210  is pulled and adjusting the helium pressure or the helium gun  108  to maintain the desired volumetric flow per unit time. The internal valving of the helium gun  108  moves between a fully open and a fully closed state, so that the helium flow cannot be modulated between full flow and zero flow. Thus, the main variable effecting the validity of the test is the amount of helium likely to pass through openings or porosity in, for example a weld  140 , given a desired release of helium in the vicinity of the porosity or opening. The testing of the unit under test  114  is calibrated based on the helium flow rate from the helium gun and the difference in pressure between the interior of the unit under test  114  and the exterior thereof. If the helium gun  108  flow rate is properly calibrated, starting the testing before the interior volume of the unit under test  114  has reached the desired level of vacuum pressure therein will result in fewer helium atoms being pulled through an opening or porosity in the weld or piping of the unit under test  114 , resulting in a unit under test being termed a test passing unit when it should not be considered a test passing unit, The CPU  110  is configurable to prevent helium dispensing until the pressure within the unit under test has reached the desired test pressure, or to provide the alarm signal described previously therein if the vacuum pressure within the unit under test  114  had not reached the desired test pressure before testing was initiated by releasing helium from the helium gun  108 . 
     To prevent helium from flowing before the desired vacuum pressure is reached in the unit under test  114 , the CPU is optionally configured to send a control signal to a valve  123  in the helium supply line, to open the valve only once the proper vacuum pressure has been reached in the unit under test  114 . 
     Another operator induced error in helium leak testing involves the operator moving the helium gun tip too quickly past the area of the unit under test  114  being evaluated for a leak. Here, the CPU is configured to read the signal received from the accelerometer  109  in the helium gun to indicate that the helium gun was moved too quickly, and the operator must redo the test by pumping the interior volume of the unit under test to the desired vacuum pressure thereof, and redo the leak test. In this fashion the system  100  increases the user&#39;s confidence in the meaningfulness and accuracy of the helium leak test to find undesirable porosity of leak paths in the weld or tubing being checked. 
     A method for allowing repeatable helium leak testing of a unit under test is shown in  FIG.  3   . At Act  1000 , a SKU code on the unit under test  114 , uniquely identifying the unit under test, including information such as the part number, the time it was completed, and other information as desired by the operator, is scanned and the information read by the CPU  110  and the CPU  110  is configured to associate the SKU number of the unit under test with the resulting test responses indicating a passing or failing unit under test  114 . Then, the unit under test  114  is fastened securely to the male fitting  120  of the coupling  124 , and the male fitting  120  is inserted into the female fitting  122  of the coupling  124  at Act  1001 . This creates a leak free seal between interior volume of the unit under test  114  and the second tubing  129  with the vacuum source  150 . In one aspect, the vacuum source  150  may be started in Act  1003 . In other aspects, the vacuum source  150  remains on and operational, to maintain a sub-atmospheric pressure in the reinforced hose  230 . As the vacuum  150  is turned on and starts to apply pressure to the unit under test  114 , the UI  112  will display the pressure internal to the unit under test  114 . The operator monitors the change in the vacuum pressure internal to the unit under test  114  Act  1005 . A desired system pressure for a test to be performed to a unit under test is determined by the operator, based on the pressure of the internal volume of the unit under test  114  displayed on the user interface  112 , or the CPU may be programed with this set test pressure and display or audibly emit information the operator can use to visually, graphically, or audibly determine that the test pressure has been reached. This test pressure is a set pressure at which the unit under test  114  would most appropriately respond to application of helium at or adjacent to any possible microscopic leaks in the unit under test  114 , and at which the system as a whole maintain the set vacuum pressure without further intervention. At Act  1007  the operator allows the unit under test  114  to reach the desired pressure, the test pressure, by visually watching the pressure read out on the UI  112  or allowing the CPU to monitor the pressure and create an alert through the UI  112  when the unit under test  114  reaches the test pressure. At the point that the pressure reaches the desired testing pressure, the operator can initiate helium delivery using the helium gun  108  in Act  1010 . The operator will dispense helium through the nozzle  111  of the helium gun by pulling the trigger  210  external to the body  113  of the helium gun  108 . The trigger  210  being opens a valve internal to the helium gun to allow helium to escape the nozzle  111  at a desired and pre calibrated constant flow rate. The flow rate is determined by an output of the mass flow monitor  102  (MFM) fluidly connected to the helium supply  101 . The MFM signal is used by the CPU  110  to determine that helium is released only after the test pressure within the unit under test  114  is reached and if it is released when the pressure is above the test pressure, a failure signal is sent by the CPU  110  to the UI  112 . This signals the operator to re-do the test while waiting for the appropriate test pressure to be reached. Alternatively, the CPU  110  controls a fluid switch on the helium line such that helium cannot flow from the helium source until the test pressure is reached in the unit under test  114 . If the operator attempts to run a test when the CPU  110  has not received a pressure signal from the pressure sensor  121  that appropriately meet the pressure set to be the testing pressure, a failure signal will be displayed by the CPU. The CPU  110  ensures helium delivery rate is in proper range using the MFM signal in Act  1013 . 
     Once the helium flow rate is in proper range, the operator positions the helium gun  108  at points of interest of the unit under test  114 . Specifically, at Act  1016  the operator positions the helium gun  10  so that the nozzle  111  is adjacent to a weld  140  of the unit under test  114  to test for leaks in the welds. At Act  1019  the operator will apply the helium to these points of interest, such as the welds of the unit under test  114 , by pulling the trigger  210  to release the helium gas from the nozzle  111  of the helium gun  108 . If there is a leak in the unit under test  114 , the helium will pass through the physical openings allowing the leak and be pulled into the unit under test  114  and flow either through the pull of vacuum pressure or by dispersion to the helium detector  128 . When an atom of helium reaches the helium detector, a reaction will occur in which the helium detector is able to identify the helium atom and send a signal regarding the concentration of helium atoms detected to the CPU  110  through vacuum sensor line  216 . The concentration of helium internal to the unit under test  114  will be displayed on the UI  112  in Act  1022 . A threshold amount of helium at which a failure of the weld test is declared is set by the operator, or, is stored in a look up table in the CPU and used to set the threshold of helium detection at which a failed weld or unit under test  114  is declared. If the helium detector detects more than the threshold amount of helium, the UI will display a failure notice. The CPU  110  will add the helium concentration data, failure notice data, and SKU number data representing the actual unit under test  114  that has failed to a database that can be accessed by the operator or other personnel. This data base will allow the operator or other personnel to determine if there is a flaw in manufacturing and where this flaw began, using the SKU number to identify the equipment and materials used to create the unit under test, the times at which the various welds where made on the unit under test, and the technicians making those welds and making up the unit under test  114 . This allows the operator or others to make decisions regarding manufacturing before extending resources to create further leaking units under test  114 . Additionally, this same data is collected for passing units under test, and the amount of helium detected, and changes thereof from unit under test to unit under test can be used to identify issues in the equipment, raw materials, or individuals involved in the manufacture of the units under test, to enable preventive maintenance, identify problematic lots of raw material, including trends in the performance thereof over time, ad to train or retrain technicians fabricating the units under test. The data can also be used to reduce the variance in the manufacturing process, by identifying the who, where, what and when of the manufacturing process of the units under test and tracking it to variations in resulting test performance. 
     In addition, if the accelerometer  109  within the helium gun  108  detects that the helium gun  108  is being moved too quickly by the operator, the UI  112  will display a failure notice and this accelerometer data and failure data will be added to a database accessible by the operator or others. Receiving a failure notice will prompt the operator to redo the test at Act  1025 , moving the gun more slowly this time. This will allow proper residence time of the nozzle of the helium gun  108  at leak sites for helium to penetrate the unit under test if there is a leak. Based on the failure rate of the operator due to accelerometer based test failures, a determination can be made if further training is needed for the test operator. 
       FIGS.  4  through  6    show the UI  112  screen that the helium gun operator will see while performing the leak test. The UI screen  112  displays the SKU barcode of the unit under test  114  that has been scanned for a leak test. The UI  112  shows a series of information graphics about the unit under test  114 . A first rate graph displays an upper limit  909  for a leak reading and a lower limit  901  for a leak reading, along with the actual leak reading  905 . The threshold limits are defined by the operator and are based on the vacuum pressure in the unit under test as well as the rate of helium delivered from the gun. A second graph compares helium concentration  912  in the unit under test with helium being delivered from the helium gun. In the operator panel, the UI displays an interactive manual start and stop for the leak test, based on the vacuum pressure in the unit under test. The UI displays information about the status and speed of the test. The UI displays an auto start and auto stop interface as well. Vacuum pump time is displayed during active testing. The UI displays a lead rate and gives a status of testing or failure depending on the circumstances.  FIG.  3    shown a test during active testing.  FIG.  4    shows a leak test that has failed due to the leaks in the unit under test. This is shown by the test result information reading a failure signal, as well as the leak rate graphical displayed surpassing the upper leak limit. The information regarding the speed of the helium gun reads slow, indicating that the gun was not moved too quickly for effective testing.  FIG.  4    shows a leak test that has failed due to the helium gun moving too quickly during testing. This is indicated by the leak rate  905  resting within the upper and lower limits  909 ,  901  respectively but the speed indicating a fast reading. 
       FIG.  7    shows an alternative construct of the accelerometer layout of the test system. Here, a first accelerometer  152  and a second accelerometer  154 , each separately connectable to the First CPU line  142  via first and second accelerometer leads  156 ,  158  configured to carry signals output by the first and second accelerometers  152 ,  154 , are provided. First accelerometer  152  is configured to be particularly sensitive to movement of the output nozzle  111  in the centerline direction L thereof, and second accelerometer  154  is configured to be particularly sensitive to movement of the output nozzle  111  in the rotational direction Θ about the centerline direction thereof. The use of two accelerometers and the mounting of them on the nozzle  111  close to the gas output location thereof increases the accuracy of the speed detection of the helium gas releasing portion of the helium gun  108 . However, a single accelerometer, on or within the nozzle  111 , is also specifically contemplated herein.