Abstract:
A method involves inspecting/testing a refrigeration system. One or more conduits or other components cooperate with the compressor, heat rejection heat exchanger, expansion device, and heat absorption heat exchanger to define a refrigerant flowpath. The inspecting/testing method comprises placing a plurality of collars over respective joints along the refrigerant flowpath. The collars each define a space that may be exposed to one or more sensors. Based upon input from the sensors, the presence or absence of leaks at the joints is determined.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Benefit is claimed of U.S. Patent Application Ser. No. 61/078,367, filed Jul. 4, 2008, and entitled “REFRIGERATED TRANSPORT SYSTEM TESTING”, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length. 
     
    
     BACKGROUND 
       [0002]    The disclosure relates to refrigeration. More particularly, the disclosure relates to refrigeration system testing. 
         [0003]    An exemplary refrigeration system is a transport refrigeration system used to control enclosed areas, such as the box used on trucks, trailers, containers, or similar intermodal units, functions by absorbing heat from the enclosed area and releasing heat outside of the box into the environment. A number of transport refrigeration units employ a reciprocating compressor to pressurize refrigerant to enable the removal of heat from the box. Reciprocal compressors used in such applications commonly include a suction inlet and a discharge which are connected, respectively, to the evaporator and condenser of the transport refrigeration system. It is axiomatic that in order to ensure the reliability of the reciprocating compressor, the compressor should operate within the limits of the suction and discharge pressures for which it was designed. The ranges and ratios of suction and discharge pressures designed to be handled by a reciprocating compressor at various stages of operation is known as an operating envelope. The failure to operate within the compressor operating envelope will result in unnecessary wear and tear, and ultimately will bring about the premature failure of the compressor, thus creating unacceptable costs of money and time to the operator. 
         [0004]    Exemplary refrigerated transport systems use generators powered by internal combustion engines to power the compressors and any fans associated with the evaporator and condenser. U.S. Pat. No. 6,321,550, the disclosure of which is incorporated by reference in its entirety herein as if set forth at length, assigned to the assignee of the present application, discloses such a generator and associated control methods. 
         [0005]    There are many operational considerations for the units. Several considerations involve the temperature at which the enclosed area is to be kept. A given unit configuration may be made manufactured for multiple operators with different needs. Broadly, the temperature may be separated into two fields: frozen goods; and non-frozen perishables. An exemplary frozen goods temperature is about −10° F. or less an exemplary non-frozen perishable temperature is 34-38° F. 
       SUMMARY 
       [0006]    One aspect of the disclosure involves a method for inspecting/testing a refrigeration system. The system includes a compressor. A heat rejection heat exchanger is coupled to the compressor to receive compressed refrigerant from the compressor. Expansion device is coupled to the heat rejection heat exchanger to expand refrigerant received from the heat rejection heat exchanger. The heat absorption heat exchanger is coupled to the expansion device to receive refrigerant expanded by the expansion device and, in turn, coupled to the compressor to return refrigerant to the compressor. One or more conduits or other components (e.g., fittings, valves, sensors, and the like) cooperate with the compressor, heat rejection heat exchanger, expansion device, and heat absorption heat exchanger to define a refrigerant flowpath. The inspecting/testing method comprises placing a plurality of collars over respective joints along the refrigerant flowpath. The collars each define a space or chamber that may be exposed to one or more sensors. Based upon input from the sensors, the presence or absence of leaks at the joints is determined. 
         [0007]    In various implementations, the collars may be split collars. The placing may comprise assembling two halves of each split collar over the associated joint and clamping (e.g., self-sprung clamping) the halves together. The collars may include a port which may permit communication with a separate such sensor. The separate sensor may, sequentially, be exposed to the port of the various collars. The sensors may be chemical sensors. The system may be charged with a test fluid comprising at least 50% nitrogen, by weight, and less than 10% hydrogen by weight. The leak may be determined by chemical detection of the hydrogen leaking from the joint. After a successful test, the refrigeration system may be assembled to a refrigerated compartment positioned to be cooled by the heat absorption heat exchanger. 
         [0008]    The collar body may be spring biased/loaded toward a closed condition from an open condition. The body halves may be hinged and, opposite the hinge on the halves, the collar may include a pair of finger levers positioned to be compressed toward each other to open the body. The body may be resinous. 
         [0009]    The refrigeration system may be that of a refrigerated transport system and may be tested on an assembly line. The refrigeration system may be tested separately from or together with the container (e.g., a truck, trailer, or cargo container). At testing, the system may include a generator for powering the compressor. At least one first selected fan may be positioned to drive an airflow across the heat rejection heat exchanger and at least one second fan positioned to drive an airflow across the heat absorption heat exchanger. The first and second fans may be coupled to the generator to receive electric power from the generator. A controller may be coupled to the compressor and fans to control their operation and operation of the generator. 
         [0010]    The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a view of a refrigerated transport system. 
           [0012]      FIG. 2  is a schematic view of a refrigeration system of the transport system of  FIG. 1 . 
           [0013]      FIG. 3  is a first view of the refrigeration system of  FIG. 2   
           [0014]      FIG. 4  is a second view of the refrigeration system of  FIG. 2 . 
           [0015]      FIG. 5  is a third view of the refrigeration system of  FIG. 2 . 
           [0016]      FIG. 6  is a view of a collar for inspecting/testing a joint in the refrigeration system of  FIG. 2 . 
           [0017]      FIG. 7  is an open view of the collar of  FIG. 6 . 
           [0018]      FIG. 8  is a partial cutaway view of the collar of  FIG. 6  in a closed condition. 
           [0019]      FIG. 9  is a rear isometric view of the collar of  FIG. 6  in a closed condition. 
           [0020]      FIG. 10  is a top view of an alternate collar. 
       
    
    
       [0021]    Like reference numbers and designations in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0022]      FIG. 1  shows a refrigerated transport unit (system)  20  in the form of a refrigerated trailer. The trailer may be pulled by a tractor  22 . The exemplary trailer includes a container/box  24  defining an interior/compartment  26 . The container/box  24  may be a removable cargo container. An equipment housing  28  mounted to a front of the box  24  may contain an electric generator system including an engine  30  (e.g., diesel) and an electric generator  32  mechanically coupled to the engine to be driven thereby. A refrigeration system  34  may be electrically coupled to the generator  32  to receive electrical power. 
         [0023]      FIG. 2  shows further details of the exemplary refrigeration system  34 . The system  34  includes a control system  100 . The control system  100  may include: one or more user interface (e.g., input/output) devices  102 ; processors  104 ; memory  106 ; and hardware interface devices  108  (e.g., ports). An exemplary system  34  is illustrated based upon the system of PCT/US07/60220. Further details of such a system are shown in U.S. Pat. No. 6,321,550. 
         [0024]    The system  34  further includes a compressor  120  having a suction (inlet) port  122  and a discharge (outlet) port  124 . An exemplary compressor  120  is an electrically-powered reciprocating compressor having an integral electric motor. The compressor  120  may be coupled to the control system (controller)  100  to regulate its operation and to the generator  32  to receive power. A discharge line section/segment  126  extends from the discharge port  124  downstream along a refrigerant primary flowpath to an inlet of a heat rejection heat exchanger (condenser)  128 . A hot liquid refrigerant line section/segment  130  extends downstream from an outlet of the condenser  128  to an inlet of an exemplary receiver  132 . A hot liquid line section/segment  134  extends from an outlet of the receiver  132  to an inlet of a subcooler  136 . The subcooler  136  and condenser  128  may be positioned to receive an external airflow (e.g., driven by one or more fans  129 ). A liquid line section/segment segment  138  extends downstream from an outlet of the subcooler  136  to an inlet of a suction line heat exchanger (SLHX)  140 . A further liquid line section/segment  142  of the refrigerant line extends downstream from an outlet of the SLHX  140  to an inlet of an expansion device (e.g., an electronic expansion valve (EEV))  144 . A final liquid line section/segment  146  extends from an outlet of the electronic expansion valve  144  to an inlet of a heat absorption heat exchanger (evaporator)  148 . The evaporator  128  may be positioned to receive an external airflow (e.g., driven by one or more fans  149 ). A first section/segment  150  of a suction line extends downstream from the outlet of the evaporator  148  to the suction line heat exchanger  140 . A second section/segment  152  of the suction line extends within the suction line heat exchanger  140  to form a downstream leg in heat exchange relation with fluid in the upstream leg of the heat exchanger  140 . A final section/segment  154  of the suction line returns to the suction port  122 . A compressor suction modulation valve (CSMV)  156  may be located in the line  154   
         [0025]    The physical configuration of the system is merely illustrative and may schematically represent any of a number of existing or yet-developed constructions. The inventive methods described below may also be applicable to other constructions. 
         [0026]    The system  34  may include various additional components including valves, sensors, and the like. Of these, sufficient sensors for determining a characteristic evaporator superheat and a characteristic suction superheat are required and particular exemplary implementations are described below. An exemplary characteristic evaporator superheat is an evaporator outlet superheat (EVOSH) and may be determined responsive to measurements of an evaporator outlet temperature (EVOT) and an evaporator outlet pressure (EVOP). Accordingly, the exemplary system  34  includes an EVOP sensor  160  and an EVOT sensor  162  along the segment  150  and in signal communication with the control system  100 . The suction superheat (SSH) may similarly be determined responsive to measurements of compressor suction temperature (CST) and compressor suction pressure (CSP). Along the segment  154  downstream of the SLHX  140 , a pressure sensor  164  and a temperature sensor  166  are similarly positioned for measuring CSP and CST, respectively. 
         [0027]    In operation, a user will enter a temperature at which the compartment  26  is to be maintained. In one basic example, immediate entry may be by means of a simple two position switch wherein one position is associated with frozen goods and another position is associated with non-frozen perishable goods. The control system  100  may be pre-programmed (via software or hardware) with associated target compartment temperatures. For example, a frozen goods target temperature may typically be a particular temperature in a range of about −10° F. or below whereas a non-frozen perishable goods temperature may be a particular temperature in a range of about 34-38° F. The particular values may be pre-set according to the needs of the particular unit operator. 
         [0028]    Prior to use, it is desirable to inspect the joints to verify their integrity (i.e., that the joints are not leaking). Testing may occur in one or more of several stages, depending upon the manufacturing process. An exemplary manufacturing process involves pre-assembly of portions of the refrigeration system in discrete modules. This may be done away from a final assembly assembly line (e.g., offsite at different vendors). Assembly on the final assembly assembly line may thus involve forming a relatively small number of the total number of joints. These joints may comprise one or more fittings securing conduit segments to each other or may comprise additional components. Exemplary joining involves brazing of the fitting(s) to the conduit segments and, if appropriate, to each other. There may be braze defects allowing leaks. Efficient inspection of these particular joints  190  (the “final assembly joints”) may contribute to the efficiency of the final assembly assembly line. The other joints (within the respective modules) may have been already tested. 
         [0029]    In an exemplary inspection/testing process, the modules are assembled to each other. A test system  200  includes a plurality of collars  202  ( FIGS. 6&amp;7 ) and  203  ( FIG. 10 ) which may be placed over respective ones of the final assembly joints  190 .  FIGS. 3 and 5  schematically label these (with broken lines so as to not obscure the joints) and all with numeral  202  (although the specific collar configurations would vary). The joints  190  may take different forms (e.g., different sizes, and different configurations such as in-line, right angle, tee, and the like). The collars may be provided in a variety of configurations and sizes corresponding to the joints. As is discussed below, the exemplary collars  202  are shown for in-line joints while the collar  203  is otherwise similar but configured for a right angle joint. The system may be charged with refrigerant or with a test fluid. The exemplary collars  202  each include a port  204  for coupling to a sensor probe  206  for detecting leakage from the joint. With an exemplary test fluid as a gaseous mixture comprising, by majority weight, a relatively inert component (e.g., nitrogen) and a smaller amount of a relatively reactive component (e.g., hydrogen), exemplary sensors  208  are chemical sensors for detecting the reactive component. With a more inert fluid (e.g., pure helium), alternative sensors include pressure transducers. For detecting hydrogen, the exemplary sensor uses a transistor (e.g., MOSFET). Such detectors are available under the Adixen-Sensistor brand from Adixen Sensistor AB, Box  76 , SE-58102 Linköping, Sweden or Alcatel Vacuum Products, Hingham, Mass. 
         [0030]    The exemplary probe  206  and its sensor  208  are connected by wiring  210  to a monitoring system  212 . The exemplary monitoring system is a personal computer. The personal computer may be connected to a gateway controller  213  which also controls a programmable logic controller  214  controlling the assembly line and other stations therealong. The system  212  may include a monitor or display and various input devices (e.g., keyboard, integrated touch screen, and the like). 
         [0031]    The exemplary collars  202  are split collars wherein a body has a first piece  220  and a second piece  222 , permitting the pieces  220  and  222  to be assembled over the joint and secured to each other (e.g., via one or more clamps formed separately from the body or integral to the body). The body and conduit define a space/chamber  510  surrounding the associated joint when the body is assembled over the joint. An exemplary body material is an acetal resin (e.g., Delrin acetal resin from E.I. du Pont de Nemours and Company, Wilmington, Del.). The body halves may be machined from stock pieces of the resin. The resin may have lower chances of outgassing trapped hydrogen than does a typical aluminum alloy. The resin may also offer good self sealing characteristics to avoid the need for separate seals. Alternatively, the body may carry seals for sealing the space/chamber  510 . Exemplary clamping is a hinged clamping wherein the body pieces or halves  220  and  222  are coupled by a hinge  224 . The exemplary hinge  224  is spring-loaded by a spring  226  (e.g., torsion coil or metal or plastic/resin flex leaf) biasing the two halves towards a closed orientation about a hinge axis  520 . The exemplary collar includes a pair of finger levers  230  and  232  (e.g. which may be unitarily formed with halves of the hinge body or otherwise respectively secured to the two body pieces such as by screws—not shown). Exemplary levers  230  and  232  may be squeezed toward each other to open the body against spring bias. In the exemplary split body, ports  240  and  244  for accommodating and sealing with the portions of the refrigerant are on opposite sides of the joint and are each formed by a pair of semi-cylindrical surfaces  246  in the respective body halves. The exemplary body halves are square or, more broadly, approximately rectangular in planform and have flat perimeter rim surfaces  248  which mate/seal with each other in the closed condition and laterally surround the chamber. 
         [0032]    In the  FIG. 10  embodiment, the ports  240  and  242  are at right angles to each other for accommodating a right angle joint. 
         [0033]    In use, at the testing station along the final assembly line, the test technician may place a plurality of the collars  202  over the associated joints. The technician may also connect the source of the test fluid. Exemplary test fluid is at least 50% nitrogen (N 2 ) by weight and less than 10% hydrogen (e.g., 2-8% hydrogen, remainder nitrogen, with a particular example of 5-5.7% hydrogen, remainder nitrogen). The monitoring system may command an initial low pressure decay test (e.g., at 25 psi) where a sensed pressure decay will indicate a relatively large leak. This low pressure test may be performed before or after collar installation. If before, and the system passes the test, the collar may then be installed. In various implementations, there may also be a high pressure test after successful passing of the low pressure test (e.g., and before sniff testing). The monitoring system then commands a low pressure leak detection sniff test (e.g., at 100 psi). The monitoring system may instruct the technician to sequentially apply the probe to each specific collar and, when applied, check the sensor for evidence of leakage and may record results. After the test, the monitoring system may instruct disconnection of any fluid source and may display final results (e.g., binary leak/no leak or pass/fail or leak rates associated with each joint). Such results may similarly be displayed in real time during testing. 
         [0034]    If one or more of the joints is found to be leaking, the monitoring system may cause a halt in the progress of the leaking unit down the assembly line. The associated collar may be removed from that joint, the fluid may be fully or locally evacuated from the system, and the joint repaired/replaced. The collar (or a similar collar) may be replaced and the system may be retested. After testing, the collars may be removed and installed on a subsequent refrigeration system along the production line. Upon successful testing, the test fluid (if used) may be evacuated from the system and the system charged with refrigerant. 
         [0035]    One or more embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, the test methods and collars may be adapted to a variety of existing or yet-developed systems. Additionally, consideration of the test methods and collars may be made in designing or redesigning a system (e.g., to provide easier access to the joints). Accordingly, other embodiments are within the scope of the following claims.