Abstract:
A smoke producing device for detecting leaks in a fluid system comprises a smoke producing chamber and a fluid reservoir for containing a smoke producing fluid. A heating element is provided within the smoke producing chamber. The chamber has a pressurized gas inlet for receiving a pressurized gas and an outlet port for conveying pressurized gas and/or smoke out of said chamber. A fluid transfer device has a first portion disposed within the fluid reservoir and a second portion which is adjacent and/or in contact with the heating element. The fluid transfer device is a capillary flow device which conveys smoke producing fluid from the fluid reservoir to the vicinity of the heating element primarily by capillary action. In order to detect a leak in a fluid system, the smoke exiting the outlet port is conveyed into the fluid system, for example through a conduit connected to the outlet port. The presence and location of a leak in the fluid system, if any, is quickly and easily found by visually detecting smoke escaping from the system through a leak. Conversely, if no smoke escapes, then the integrity of the fluid system is confirmed and no repairs should be needed.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to leak detection in fluid systems and more particularly to methods and devices for leak detection using smoke.  
       BACKGROUND OF THE INVENTION  
       [0002]     There are many useful systems which contain and/or operate using a fluid (gas, liquid or combination of both). For example, automobiles have several systems which contain and utilize a fluid in their operation including the fuel system, the exhaust system, the heating, cooling and ventilation (HVAC) system, and the hydraulic power steering and brake systems, to name a few. Moreover, numerous industrial machines, household HVAC systems, and other devices utilize a fluid to operate. Such fluids include, for example, gases such as air or evaporated system liquid, fuel, hydraulic fluids, manufactured gases and liquids, and many other fluids.  
         [0003]     In almost all circumstances, it is important, and in many cases crucial, that these fluid systems be properly sealed to prevent leakage of the system fluid. As an example, in an automobile fuel system, the gas tank and gas lines must be thoroughly sealed to prevent gasoline fumes from polluting the air and also to prevent leaking fuel from creating a fire hazard, not to mention the obvious benefit of conserving gasoline. In HVAC systems, it is important to seal the ducting which transports the conditioned air in order to maintain the efficiency of the systems. Air leaks tend to do nothing but heat or cool an attic, wall interior or other undesired space.  
         [0004]     In many cases, leaks in fluid systems are very difficult to detect and/or locate because the leak is small or in a location not easily accessible. Accordingly, a variety of methods and devices have been devised to detect leaks in fluid systems. The most common leak detectors utilize a visual indicator to locate a leak so that the leak may be repaired. Some of the visual indicators include liquid dyes. The visual indicator is dispensed into the fluid system and leaks are detected by locating places on the system where the visual indicator has escaped the system. For instance, a liquid dye will leave a trace of dye at the leak and smoke will billow out through the leak. The liquid dyes are most useful for detecting leaks in fluid systems which utilize a liquid and are not so useful for gas systems or systems which must seal vapors created by the system fluid. Still, liquid leaks are typically easier to detect than gas and vapor leaks because the liquid itself is usually visible.  
         [0005]     Vaporized dyes and smoke are most useful for detecting leaks in gas systems and systems which have vapors. In some cases, vaporized dye may be added to the smoke such that a trace of dye is left at the leak as the smoke flows through the leak. In general, devices for producing smoke for leak detection comprise a sealed chamber in which smoke is generated by vaporizing a smoke-producing fluid using a heating element. The smoke within the sealed chamber is forced out of the chamber through an outlet port by air pressure from a source of compressed air pumped into the sealed chamber. However, all of the previously disclosed smoke generating devices contact the smoke-producing fluid with the heating element to produce smoke by one of two methods. The first method is to locate the heating element within a reservoir of smoke-producing fluid. For example, U.S. Pat. No. 5,107,698, issued Apr. 28, 1992 to Gilliam, describes a smoke generating apparatus which has the heating element at least partially submerged within the smoke producing fluid in the fluid reservoir.  
         [0006]     The drawbacks to a device in which the heating element is submerged within the smoke producing fluid are numerous. First of all, the level of the fluid within the chamber must be accurately controlled. This requires frequent monitoring and adjustment of the fluid level. Because the heating element is located within the fluid, the temperature of the heating element and the smoke chamber must also be accurately monitored and controlled in order to prevent combustion or explosion of the smoke-producing fluid. Worse yet, the fluid in the reservoir is heated and cooled with every use of the device, which tends to break down integrity of the fluid (such as oil). Also, in such recirculating designs, the fluid is easily contaminated by particulate and smoke by-products created by the smoke-producing process. The contaminants fall directly into the fluid reservoir because the smoke producing site is located directly within the fluid reservoir. The degraded fluid can cause several problems including ignition of the fluid, toxicity of the produced smoke and a decrease in smoke producing efficiency. This creates a serious maintenance issue requiring the regular replacement of the degraded fluid in the reservoir. Accordingly, the degrading of the fluid reduces reliability, may create a risk of combustion or explosion within the fluid reservoir, and the smoke produced with the contaminated fluid may have toxic components.  
         [0007]     The second method of delivering the smoke-producing fluid to the heating element is to blow or spray the fluid onto the heating element. Examples of devices having this type of fluid delivery are described in U.S. Pat. No. 5,859,363, issued Jan. 12, 1999, to Gouge; U.S. Pat. No. 5,922,944, issued Jul. 13, 1999, to Pieroni et al.; U.S. Pat. No. 6,142,009, issued Nov. 7, 2000, issued to Loblick; U.S. Pat. No. 6,392,227, issued May 21, 2002, issued to Banyard et al.; U.S. Pat. No. 6,439,031, issued Aug. 27, 2002, to Pieroni et al.; and U.S. Pat. No. 6,526,808, issued Mar. 4, 2003, to Pieroni et al. In each of these devices, the smoke-producing fluid is blown, sprayed or atomized through a nozzle onto a heating element located above the fluid reservoir. Pressurized air is used to blow, spray or atomize the fluid through the nozzle. The heating element is purposely disposed above the fluid reservoir so that the blown, sprayed or atomized fluid which is not converted into smoke will return to the reservoir.  
         [0008]     Again, this type of fluid delivery system has many drawbacks. For one, there must be a minimum amount of air pressure and air flow in order to spray the fluid onto the heating element. This prevents the device from being able to vary the flow rate of smoke being fed to the system being leak checked. A flow valve on the smoke outlet usually cannot be used to reduce the pressure and flow rate because the pressure drop through such valves causes at least some of the smoke to condense thereby reducing the amount of smoke produced. Also, the minimum amount of air pressure required by the smoke machine may exceed the pressure capacity of some systems which it is desired to leak check (for example, some automobile systems can only hold 4 inches of water pressure). Moreover, these smoke machines which require air flow to draw fluid into the air stream and/or spray the fluid toward the heating element are rendered inoperative if the flow rate is reduced below the operating level. This reduction may be caused by the system not having a large enough leak or by the use of a flow control value at either the inlet or outlet of the machine.  
         [0009]     Furthermore, because the fluid is circulated back from the heating element to the fluid reservoir, this type of device suffers from the same contamination and degraded smoke producing fluid problems as described above.  
         [0010]     Accordingly, there is a need for an improved method and device for producing smoke for detecting leaks in fluid systems which overcomes the deficiencies of previous devices. The device should be safe, reliable, compact, easy to use and maintain, and have a relatively low manufacturing and retail cost, compared to previously known machines.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention provides methods and devices for detecting leaks in a fluid system using smoke. The smoke machine comprises a housing having a smoke producing chamber and a fluid reservoir for containing a smoke producing fluid. A heating element is provided within the smoke producing chamber. The chamber has a pressurized gas inlet for receiving a pressurized gas and an outlet port for conveying pressurized gas and/or smoke out of said chamber. A fluid transfer device has a first portion disposed within the fluid reservoir and a second portion which is adjacent and/or in contact with the heating element. The fluid transfer device is a capillary flow device which conveys smoke producing fluid from the fluid reservoir to the vicinity of the heating element primarily by capillary action.  
         [0012]     The smoke machine may also comprise a pressure gauge which measures the pressure within said chamber, a flow meter which measures the flow rate of a pressurized gas provided to the chamber, pressure regulator to regulate the pressure of pressurized gas and a valve to shut-off or vary the flow rate of pressurized gas being provided to the chamber.  
         [0013]     In operation of the smoke machine, the fluid reservoir is first filled with a smoke producing fluid, such as mineral oil. Then, a power source is connected to the heating element and pressurized gas, such as compressed air, is supplied to the chamber. The fluid transfer device conveys the smoke producing fluid from the reservoir to the vicinity of the heating element by capillary action. Advantageously, the fluid transfer device does not require any power source to properly operate. As smoke producing fluid comes near to, or in contact with, the heating element, it is vaporized into smoke. The pressurized gas then carries the smoke out of the chamber through the outlet port.  
         [0014]     In order to detect a leak in a fluid system, the smoke exiting the outlet port is conveyed into the fluid system, for example through a conduit connected to the outlet port. The presence and location of a leak in the fluid system, if any, is quickly and easily found by visually detecting smoke escaping from the system through a leak. Conversely, if no smoke escapes, then the integrity of the fluid system is confirmed and no repairs should be needed. In a further aspect of the present invention, the valve may be adjusted to vary the flow rate of pressurized gas being supplied to the chamber. In addition, the valve may be closed to isolate the fluid system from the pressurized gas and the pressure gauge may be monitored to detect any pressure decay which can indicate the presence and/or size of a leak in the fluid system.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a front perspective view of a smoke machine according to the present invention.  
         [0016]      FIG. 2  is a rear perspective view of the smoke machine of  FIG. 1 .  
         [0017]      FIG. 3  is a perspective exploded view of the smoke machine of  FIG. 1 .  
         [0018]      FIG. 4  is a perspective bottom view of the main body subassembly of the smoke machine of  FIG. 1 .  
         [0019]      FIG. 5  is a perspective side view of the main body of the smoke machine of the  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]     Turning to  FIGS. 1-4 , a smoke machine  10  according to the present invention comprises a housing  12 . The housing  12  has a top cap  14 , a main body  16  and a bottom cover  18 . The top cap  14  and the main body  16  form a smoke generating chamber  20 . The top cap  14 , main body  16  and bottom cover  18  may be made of aluminum which is strong and lightweight, or any other suitable material such as stainless steel or plastic. The top cap  14  has a flange  22  with four through-holes  24 . The top cap  14  is installed on the main body  16  with the flange  22  resting on the top surface of the main body  16  and four screws  26  secure the top cap  14  to the main body  16 . A seal or gasket (not shown) may be utilized to seal interface between the flange  22  and the top surface  23  of the main body  16 . A pressure gauge  15  is attached to the top cap  14  and measures the pressure in the chamber  20 . A hook  17  is attached to the top cap  14  for hanging the smoke machine  10  in a convenient location such as under the hood of an automobile. Also, the bottom of the bottom cover  18  has a plurality of non-slip feet  11  so that the smoke machine  10  can stably and securely rest on a flat surface.  
         [0021]     The bottom cover  18  slides over a lower portion  30  of the main body  16  and is held in place on the main body by four screws  28 . Again, a seal or gasket (not shown) may be provided to seal the interface between the inner surface of the bottom cover  18  and the lower portion  30  of the main body  16 .  
         [0022]     Turning to  FIG. 5 , the main body  16  is preferably a machined aluminum component, but may be manufactured by any other suitable process. The main body  16  is a generally cylindrical and disc-shaped and has two grooves  32  around its circumference. The lower portion  30  has a reduced diameter which forms a shoulder for receiving the bottom cover  18 . The bottom surface  25  of the main body  16  has a round recess  34  for receiving a fluid reservoir  36 . The top lip (not shown) of the fluid reservoir  36  slides into the recess  34 . A gasket or seal (not shown) may be used to seal the interface between the main body  16  and the lip of the fluid reservoir  36 .  
         [0023]     The fluid reservoir  36  is a container for holding smoke producing fluid. The fluid reservoir  36  may be made of aluminum or any other suitable material which is compatible with the particular smoke producing fluid(s) being used. The fluid reservoir  36  has a threaded hole  38  (the hole  38  does not protrude through the bottom of the fluid reservoir  36 ) in the bottom for receiving a bolt  40  which secures the fluid reservoir  36  to the main body  16 . The main body  16  has a through-hole  42  (see  FIG. 5 ) through which the bolt  40  inserts and the head of the bolt (not shown) bears on the top surface  23  of the main body  16 .  
         [0024]     A dipstick  48  is provided so that the level of fluid in the fluid reservoir  36  may be checked without removing any of the covers or even the fluid reservoir  36  itself. The dipstick  48  has a handle  50  with threads which mate with threads on the top of the top cap  14 . The shaft  52  of the dipstick  48  extends down through the chamber  20 , through a through-hole  54  in said main body  16  and into the fluid reservoir  36 . The bottom portion of the shaft  52  of the dipstick  48  may have graduations for indicating the level of fluid in the fluid reservoir  36 . In order to fill the fluid reservoir  36  with smoke producing fluid, the dipstick is simply removed and fluid is poured into the threaded hole on the top of the fop cap  14 .  
         [0025]     The smoke producing fluid is a fluid which when heated to a certain temperature will produce a dense, non-toxic smoke. Suitable fluids include non-toxic petroleum based oils, such as mineral oil (baby oil). While the term “smoke” generally refers to the vapor and particulate that is a byproduct of incomplete combustion, the term “smoke” as used herein includes any visible gas, vapor, and/or aerosol (particulate suspended in a gas) or any combination thereof. The term “vaporize” means to transform a fluid into smoke.  
         [0026]     A fluid transfer device  44  extends from within the chamber  20  down through a through-hole  46  in the main body  16  (see  FIG. 5 ) and into the fluid reservoir  36 . The bottom end of the fluid transfer device  44  preferably extends almost to the bottom of the fluid reservoir  36 . The fluid transfer device  44  may touch the bottom of the fluid reservoir  36 , but should not unduly restrict the fluid reservoir  36  from properly seating in the recess  34 . The fluid transfer device  44  uses primarily capillary action to convey smoke producing fluid from the fluid reservoir up into the smoke producing chamber  20  and into the vicinity of a heating element  46 . The term “primarily capillary action,” or other similar terms, means that the fluid is conveyed by this type of force more than any other force such as pumping, or pressure differentials caused by suction, but does not exclude that some force may be applied to the fluid by modes other than capillary action. Capillary action refers to the motive force on a fluid produced by the surface tension between the fluid and a surface, in this case the smoke producing fluid and the material of the fluid transfer device  44 . Capillary action as used herein is not limited to the movement of a fluid in a tube or vessel, but includes any movement of fluid caused primarily by the surface tension forces described above.  
         [0027]     The fluid transfer device  44  may comprise a woven fiberglass wick such as the wick material available from Fil-Tec Company located in Hagerstown, Md. The woven wick is one inch in diameter. The fluid transfer device  44  must be able to withstand very high temperatures while also producing enough capillary action to convey the fluid from fluid reservoir  36  to the heating element  46 . Woven fiberglass is an excellent transfer device because the fiberglass can withstand temperatures as high as 1000 degrees Fahrenheit and the woven fiberglass material can convey an adequate supply of fluid by capillary action to the heating element to produce an ample amount of smoke. Moreover, fiberglass is also an excellent thermal insulator so that any heating of the fluid in the fluid reservoir  36  by the heat produced by the heating element  46  is minimized. In this described embodiment, the fluid transfer device  44  comprising a woven fiberglass wick conveys the fluid from the fluid reservoir  36  to the heating element  44  substantially or solely by means of capillary action, although the present invention is limited to such a fluid transfer device  44 .  
         [0028]     Alternatively, the fluid transfer device  44  may be any other suitable device which can adequately convey fluid from the fluid reservoir  36  to the heating element  46  primarily by capillary action. For example, an array of small, straight tubes, capillaries or filaments may also be a suitable fluid transfer device  44 .  
         [0029]     The heating element  46  is a coil of resistive wire which generates heat when an electrical current is conducted through normally by placing an electrical voltage across the wire. The wire is coiled closely around the fluid transfer device  44  such that when the heating element  46  is energized and heated, the smoke producing fluid on the upper portion of the fluid transfer device  36  will be vaporized into smoke. One suitable wire for the heating element  46  is a 20 gauge alloy-52 wire (52% nickel, 48% iron) available from Strategic Aerospace Materials in Hicksville, N.Y. Of course, other suitable wire or resistive heating material may be used within the present invention.  
         [0030]     The heating element  46  is electrically connected to two electrical standoffs  47 . The electrical standoff  47  extend through holes  49  in the main body  16 . Each electrical standoff  47  comprises an electrically conducting core and an electrically insulating sheath which insulates the core from the main body  16 . The other end of the electrical standoffs  47  are electrically connected to a controller  80 . A pair of extension cables  45  electrically connect to a pair of electrical inputs  87  on the controller  80 . In order to power the smoke machine  10 , the extension cables  45  are connected to a power source such as a battery, a transformer or an electrical outlet.  
         [0031]     The controller  80  comprises a printed circuit board having a power switch. The controller  80  is configured such that it is capable of one or more of the following functions: measuring the temperature of the heating element  46 , turning on and off one or more indicator lights; detecting the polarity of and turning on and off the power to the heating element  46  based on temperature and/or cycle-time criteria. The power switch on the controller  80  is operably coupled to an on/off button or switch  81  located on the top surface  23  of the main body  16 . The controller  80  is also operably coupled to two indicator lights  83  and  85 . The indicator lights  83  and  85  may be different colors, such as red and green, respectively. The controller  80  is configured such that one indicator light, for example green light  83 , will be lit if a power source is connected to the extension cables with the correct polarity. The controller  80  is also configured to light the other indicator light, the red light  85 , when the on/off button  81  has been actuated to turn on the smoke machine  10 . Finally, the controller  80  controls the power being supplied to the heating element  46 . The controller may be programmed to energize the heating element  46  when the temperature of the heating element  46  is below a specified temperature and to de-energize the heating element  46  when the temperature of the heating element exceeds a specified temperature. Alternatively, in a more complex control scheme, the controller may be programmed to initially energize the heating element  46  for a specified period of time. A the end of the initial time period, the controller  80  de-energizes the heating element  46 . The controller then evaluates the temperature of the heating element and if the temperature of the heating element  46  is below a specified value, the controller  80  again energizes the heating element  46  for another specified period of time (which may be the same or a different length of time as the initial time period). This cycle continues until the heating element  46  reaches the prescribed operating temperature such that the controller  80  de-energizes the heating element  46 . Then, the heating element  46  is left de-energized for a specified period of time. After the specified period of time has expired, the controller  80  evaluates the temperature of the heating element and if the heating element  46  is above a specified temperature, the heating element remains de-energized. If the heating element  46  is below the specified temperature, the controller  80  energizes the heating element  46 . This cycle continues for as long as the smoke machine  10  is being used to produce smoke.  
         [0032]     In order to convey the smoke produced by the smoke machine  10  into a fluid system to check for leaks, a source of pressurized gas is supplied to the chamber  20  through a pressurized gas fluid path. The fluid path begins at an inlet conduit  60  which has a first end for connection to a source of pressurized gas such as an air compressor and a second end connected to a flow meter inlet port  62 . The inlet port  62  may comprise a barbed fitting for securely retaining the inlet conduit  60 . The flow meter  64  is shown as a simple graduated floating ball flow meter, but other meters capable of measuring fluid flow rates may also be utilized, including electronic flow meters which may be electrically connected to the controller  80 . The flow meter  64  is secured to the bottom cover  18  using a flow meter bracket  66  which is attached to both the flow meter  64  and the bottom cover  18 .  
         [0033]     A flow meter conduit  68  extends from a flow meter outlet port  70 , through a hole  72  in the bottom cover  18  and connects to an inlet of a pressure regulator  74 . The pressure regulator  74  may be set to reduce the incoming gas pressure to the desired pressure depending on the types of fluid system to be leak checked. For example, for fuel vapor recovery systems in automobiles the pressure regulator should be set to about 13 inches of water column. The outlet of the pressure regulator is connected to a flow valve  76 . The control knob  78  of the flow valve  76  extends through a hole in the side of the bottom cover so that the flow valve  76  may be adjusted during the operation of the smoke machine. Alternatively, the flow valve may be an electronic valve which is connected to the controller  80 .  
         [0034]     The outlet of the flow valve  76  is connected to an adapter fitting  82  which threads into a threaded hole  84  in the main body  16 . A pressurized gas flow regulator  86  is threaded into the other side of the threaded hole  84 . The gas flow regulator  86  is a fitting with one or more outlet orifices sized to control the flow rate of gas out of the orifices and into the chamber  20 . The orifices may have a total area of opening totaling approximately 0.0064 square inches. At a pressure of 13 inches of water column, the orifices will regulate the flow rate to about 15 liters per minute. Without this regulator  86 , the flow rate of pressurized gas is normally the maximum flow rate of the pressure regulator  74 . In many cases, it is easier to detect and pinpoint the location of a leak with a smaller flow rate because the leak is not completely shrouded by smoke. This completes the pressurized gas fluid path.  
         [0035]     A smoke outlet standoff  90  is threaded into a threaded through hole  92  of the main body  16 . A fitting  94  is threaded into the other side of the hole  92 . The fitting  94  has a barbed end for securely retaining a smoke supply conduit  96  which extends out of the bottom cover  18  through a hole in the bottom cover  18 . The other end of the smoke supply conduit  96  is used to convey smoke from the smoke machine  10  to the fluid system being leak checked.  
         [0036]     The operation of the smoke machine  10  to detect a leak in a fluid system is as follows. The dipstick  48  is removed to check the level of smoke producing fluid in the fluid reservoir  36 . If the fluid level is too low or too high, fluid is added or removed through the dip stick  48  hole until the proper fluid level is achieved. A supply of pressurized gas, such as an air compressor, is connected to the inlet conduit  60  or directly to the flow meter inlet port  62 . The extension cables  45  are connected to a power source such as a 12-volt automobile battery. If the cables  45  are connected to correct polarity, the controller  80  will light the green indicator light  83 . If the indicator light  83  does not illuminate, the user must reverse the connection of the cables  45 . The smoke outlet conduit  96  is connected to the fluid system to be leak checked. An adapter may be utilized to connect the conduit  96  to the fluid system. For example, in leak testing an automobile exhaust system, an exhaust cone adapter may be used. The exhaust cone adapter has one end which fits into a tailpipe and the other end has a fitting to receive the conduit  96 . The fluid system may require one or more plugs to be installed in order to close the system so that it can hold pressure.  
         [0037]     Once the smoke machine  10  is properly set-up and connected to the fluid system, the pressure gauge  15  may be checked to ensure that the proper pressure of compressed air is being supplied. Several types of leak tests may now be performed with the smoke machine  10 . With the smoke machine  10  in either the “on” mode in which it is producing smoke, or in the “off” mode in which it is not producing smoke, a leak test to determine whether there is a leak in the fluid system may be performed by allowing the compressed air to pressurize the fluid system for a period of time. As the fluid system is being pressurized by the compressed air, the flow meter  64  will indicate an amount of volumetric flow of compressed air into the smoke machine  10  and fluid system. As the fluid system is filled and pressurized, the pressure gauge  15  will indicate an increase in system pressure and the flow meter  64  will indicate that the flow rate is slowly decreasing. After a period of time depending on the volume of the fluid system being checked, the system will reach an equilibrium in which the pressure will stabilize at or near the pressure of compressed gas being supplied by the smoke machine  10  (the pressure set by the pressure regulator  74 ). If the system has a leak, the flow meter  64  will indicate an amount of flow equivalent to the amount of air leaking out of the system. If the flow meter  64  indicates zero flow rate, then there are no leaks in the fluid system (or at the least, no leaks larger than the sensitivity of the flow meter  64 ). The size of the leak(s) may be approximated by reference to a calibration table or formula which correlates the size of the area of a leak to the pressure and flow rate through the leak.  
         [0038]     Another leak test may be performed by pressurizing the fluid system as described above and then completing closing the flow valve  76 . The pressure gauge  15  is then monitored to determine if there is any pressure decay in the fluid system. If the pressure holds, then there is no leak in the fluid system. If the pressure decreases, then there is a leak in the system. The rate of pressure decay can be used to approximate the size of a leak similar to the method described above with respect to flow rate.  
         [0039]     To determine the location of a leak in the fluid system, the smoke machine  10  must be turned on. The on/off button  81  is depressed to turn on the smoke machine  10 . The controller  80  then energizes the heating element  46  and turns on the red indicator light ( 85 ). The controller  80  will energize the heating element  46  by any suitable process, including without limitation the processes described above. The heating element  46  vaporizes the fluid on the fluid transfer device  44  which is in the vicinity of the heating element  46 , thereby producing smoke. The smoke is conveyed into the fluid system and the user then inspects the fluid system for any escaping smoke. If smoke is detected, the flow valve  76  may be adjusted to decrease the flow of smoke to more easily pinpoint the location of the leak in the fluid system.  
         [0040]     While the present invention has been fully described above with particularity and detail in connection with what is presently deemed to be the invention, it will be apparent to those of ordinary skill in the art that many modifications thereof may be made without departing from the principles and concepts set forth herein. Hence, the proper scope of the present invention should be determined only by the broadest interpretation of the appended claims so as to encompass all such modifications and equivalents.