Abstract:
A flushing unit for flushing vapor compressions systems with a flushing agent. The flushing unit includes a pressure relief member to ensure that the reservoir containing the flushing agent is not over-pressurized. In certain embodiments, the flushing unit is adapted to be in communication with a driving fluid or propellant, such as an inert gas or a flushing gas, and with a source of a flushing agent, such as a reservoir. The flushing unit includes a valve that, when opened, causes the driving fluid to flow into the reservoir containing the flushing agent and displace the flushing agent from the reservoir, causing it to ultimately flow into the system being flushed such as via a suitable hand-held injector. In the event the pressure in the reservoir exceeds a predetermined level, a pressure relief valve in the flushing unit is automatically actuated, thereby relieving pressure in the otherwise closed system.

Description:
BACKGROUND 
     The present disclosure relates to a flushing unit, and more particularly, to a flushing unit cap assembly particularly suited for flushing vapor compression systems, such as HVAC and refrigeration systems. 
     Air conditioning and other systems require periodic flushing of refrigerants and/or contaminants such as during retrofits, refrigerant conversions and compressor burnouts, as well as for periodic maintenance. Non-flammable flushing solvents are typically used, that are generally compatible with CFC and HFC refrigerants and compressor oils. Such solvents must comply with stringent EPA Significant New Alternatives (SNAP) standards, and are capable of removing particulates, sludge, residue oil, moisture and acid from line sets and other system components. 
     For example, replacement of an air conditioner or heat pump and the concominant upgrade from R-22 to R-410A refrigerant can cause compatibility problems, as the mineral oil used in R-22 systems is not compatible with the R-410A refrigerant and oil. R-22 is a hydrochlorofluorocarbon (HCFC), and the presence of chlorine results in the HCFC having an affinity for mineral oil. In contrast, R-410A is a hydrofluorocarbon (HFC) and has no affinity for mineral oil. Any mineral oil remaining in the system tends to hang up in the refrigerant lines and other system components. This reduces efficiency and can cause unwanted chemical reactions with R-410A refrigerant. It is also important to rid the system of moisture, since moisture can break down the synthetic oil used with R-410A and minimize or eliminate its lubrication properties, causing the compressor to fail. 
     Accordingly, systems have been developed that allow for the quick and easy flushing of HVAC and refrigeration system line sets and system components with flushing agents under pressure. However, safety concerns arise, as the cylinder containing the flushing agent can be inadvertently over-pressurized. This can result in explosion, causing personal and/or property damage. 
     SUMMARY 
     The problems of the prior art have been overcome by the assembly and apparatus set forth herein. In certain embodiments, a flushing unit includes a pressure relief member to ensure that the reservoir containing the flushing agent is not over-pressurized. In certain embodiments, the flushing unit is adapted to be in communication with a driving fluid or propellant, such as an inert gas or a flushing gas, and with a source of a flushing agent, such as a reservoir, which can be a refillable cylinder. The flushing unit includes a valve that, when opened, causes the driving fluid to flow into the reservoir containing the flushing agent and displace the flushing agent from the reservoir, causing it to ultimately flow into the system being flushed such as via a suitable hand-held injector. In the event the pressure in the reservoir exceeds a predetermined level, a pressure relief valve in the flushing unit is automatically actuated, thereby relieving pressure in the otherwise closed system. The flushing unit can be used with compression systems including but not limited to evaporators, condensers and line sets. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of a flushing unit attached to a flushing agent cylinder in accordance with certain embodiments; 
         FIG. 2  is a front view of a flushing unit shown with a dip tube attached in accordance with certain embodiments; 
         FIG. 3  is a top view, partially exploded, of a flushing unit in accordance with certain embodiments; 
         FIG. 4  is a side cross-sectional view of a cap for a flushing unit in accordance with certain embodiments; 
         FIG. 5  is a top view, partially in section, of a cap for a flushing unit in accordance with certain embodiments; 
         FIG. 6  is a side view of a hose connection for a flushing unit in accordance with certain embodiments; 
         FIG. 6A  is a front view of the hose connection of  FIG. 6  in accordance with certain embodiments; 
         FIG. 7  is a side view of a flare connector for a flushing unit in accordance with certain embodiments; 
         FIG. 7A  is a front view of the flare connector of  FIG. 7  in accordance with certain embodiments; 
         FIG. 8  is a cross-sectional view of a safety valve cap for a flushing unit in accordance with certain embodiments; 
         FIG. 9  is a side view, partially in section, of a ball valve for a flushing unit in accordance with certain embodiments; and 
         FIG. 10  is a side view of a biasing member seat holder in accordance with certain embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Suitable flushing agents are not particularly limited, and include commercially available solvents in which contaminants are soluble or miscible, such as terpenes, esters, polyalkylene glycols, polyol esters, polyvinyl ethers, etc. The flushing agent may include one or more cleaning agents. Suitable driving fluids or propellants for forcing the flushing agent out of the reservoir and into the vapor compression system include inert gases. A preferred driving fluid is compressed nitrogen, most preferably dry nitrogen. 
     Turning to the drawings, where like numerals indicate like elements,  FIG. 1  shows a flushing agent reservoir  10 , which in the embodiment shown is an aluminum cylinder. The reservoir  10  can be refillable, such as via an inlet in the reservoir  10 , or can be a single use reservoir that is disposed of when emptied. The reservoir  10  includes an opening  12 , providing access to the interior of the reservoir. In the embodiment illustrated, the opening  12  has internal threads (not shown), which can mate in sealing relationship with corresponding external threads  13  on connecting member  16  of the cap  20  of flush unit  15 . An O-ring  14  can be carried in the annular groove  18  of connecting member  16  to ensure an effective seal between the cap  20  of the flush unit  15  and the reservoir  10 . Those skilled in the art will appreciate that other means of sealingly attaching the flush unit  15  to the reservoir  10  can be used, and that the threaded connection illustrated is merely exemplary. 
     Turning now to  FIG. 4 , there is shown an embodiment of the cap  20 . In the embodiment shown, cap  20  includes a first radial bore  21  and a second opposing radial bore  22 . Preferably each radial bore  21 ,  22  is internally threaded, as shown. Bore  21  has an internal diameter configured to receive externally threaded hose connector  30  ( FIG. 6 ). Radial bore  21  is in fluid connection with axial bore  23  via axial passageway  24 . Passageway  24  preferably has an internal diameter slightly smaller than the internal diameter of axial bore  23 . Radial bore  22  has an internal diameter configured to receive externally threaded member  44  of ball valve  50  ( FIG. 9 ). Radial bore  22  is in fluid communication with axial bore  27  via axial passageway  28 . Passageway  28  preferably has an internal diameter slightly smaller than the internal diameter of axial bore  27 . 
       FIG. 5  illustrates a third radial bore  32  in cap  20  having a longitudinal axis X that is perpendicular to the plane defined by the longitudinal axes Y and Z of axial bores  23 ,  27  and is also perpendicular to the coaxial longitudinal axes of radial bores  21  and  22 . The radial bore  32  is preferably internally threaded and configured to receive pressure relief valve  35  ( FIG. 3 ) described in further detail below. The bore  32  tapers radially inwardly to narrow passageway  33 , which extends between radial bores  21 ,  22  and has an inlet in fluid communication with radial bore  22  at  34 . 
     Turning to  FIGS. 2 ,  6  and  6 A, hose connector  30  is shown. Connector  30  includes a hexagonal flare  31  for facilitating attachment of the connector to the radial bore  21  by rotation, such as with the aid of a wrench. Extending from the flare  31  is an externally threaded member  36  configured to receive a hose (not shown) that is in fluid communication with a dispensing or injecting device such as a blow gun (not shown). Also extending from the flare  31  coaxially with member  36  but in an opposite direction is an externally threaded member  37  configured to be received by radial bore  21  in cap  20 . The hose connector  30  has a central passageway  38  ( FIGS. 6 and 6A ) providing fluid communication between the connected hose and the radial bore  21  in cap  20 . 
     Ball valve  50  connects to cap  20  via externally threaded member  44 , which threads into radial bore  22  such as by rotation. As partially shown in phantom in  FIG. 9 , ball valve  50  has a longitudinal passageway  51 , preferably centrally located, that can be opened or closed by actuation of lever  52 , causing semi-spherical member  53  to enter the passageway  51 , thereby allowing or blocking fluid flow through the passageway  51 . Those skilled in the art will appreciate that although a ball valve is shown, other valve types allowing selective fluid communication therethrough are within the scope of this disclosure. The longitudinal passageway  51  expands to an internally threaded inlet  54  that is configured to receive externally threaded member  46  of flare connector  43  ( FIGS. 7 and 7A ). Opposite coaxial externally threaded member  46  is a larger diameter externally threaded member  49 , which is configured to be in fluid communication with a source of flushing fluid such as nitrogen via suitable hosing, for example. The flare connector  43  includes a longitudinal passageway  45 , shown in phantom in  FIG. 7 , allowing fluid flow therethrough. 
     As best seen in  FIGS. 1 and 2 , a dip stick  55  is coupled to axial bore  23  of cap  20 , such as by press fitting. The dip stick  55  is a generally cylindrical elongated hollow tube. The length of the dip stick  55  should be sufficient to extend into reservoir  10  and be immersed in the fluid contained therein when in the assembled state, providing fluid communication between the interior volume of reservoir  10  and hose connector  30  via axial passageway  24  and radial bore  21 . 
       FIG. 3  illustrates the pressure relief valve assembly  35  in accordance with certain embodiments. The assembly  35  includes a generally cylindrical relief cap  61 , also shown in  FIG. 8 . Relief cap  61  has a generally hollow interior  66 , and includes a head  62  having an aperture  63  that is preferably hexagonal so as to receive an Allen wrench for facilitating rotation thereof to secure the relief cap  61  in the axial bore  32  of cap  20 . The relief cap  61  also includes one or more ports  64  positioned on the side wall of the relief cap  61 . Preferably two diametrically opposed ports are present and are positioned so that when the relief cap  61  is coupled to the cap  20 , at least a portion of a port  64  is open to ambient. The port or ports  64  extend radially inwardly of externally threaded portion  65  as shown, and allow fluid communication between radial bore  22  and the ambient, via radial passageway  33  and radial bore  22  ( FIG. 5 ). The externally threaded portion  65  of relief cap  61  is configured to mate with the internal threads of radial bore  32  in cap  20 . 
     Relief valve assembly  35  also includes biasing member  70 , which is preferably a compression spring that is positioned during operation in the generally hollow interior  66  of the relief cap  60 . The biasing member  70  seats on seat holder  72 , best seen in  FIG. 10 . The seat holder  72  includes a generally cylindrical portion  73 , preferably chamfered at its top, that has an outer diameter slightly smaller than an inner diameter of the biasing member  70 . An annular flange  74  extends radially outwardly from the base of the portion  73 , and preferably has a diameter substantially the same as the outer diameter of the biasing member  70 . Accordingly, the biasing member is supported on the flange  74 , with the portion  73  extending into the interior of the biasing member  70  when in the assembled condition. Extending axially from the flange  74  is a tapered portion  75 . Portion  75  tapers radially outwardly towards its free end  76  a distance sufficient to carry sealing member  77 , which is preferably an O-ring. 
     When the relief valve assembly  35  is in its assembled condition in cap  20 , in its normal (closed) state biasing member  70  forces seat holder  72  (and sealing member  77 ) against the opening between axial passageway  33  and axial bore  32 , blocking flow out of the passageway  33 . However, if the pressure in radial bore  22  is sufficient to overcome the force of the biasing member  70 , that pressure forces the seat holder  72  radially outwardly, thereby opening the pressure relief valve and allowing fluid communication between the axial passageway  33 , the axial bore  32 , and out the one or more ports  64  in relief cap  61  to ambient. As a result, the reservoir  10  is protected from over-pressurization. Those skilled in the art will appreciate that the biasing member  70  is thus selected to have a spring constant such that over-pressurization is prevented. A suitable spring constant is one where a pressure of about 200-210 psi is sufficient to overcome the bias of the biasing member  70 . 
     In operation, a suitable driving fluid or propellant such as nitrogen is placed in fluid communication with the flush unit  15  such as with suitable refrigeration hosing connecting to the inlet side (flare connector  43 ) of the ball valve  50 . The driving fluid is generally provided in a pressure regulated compressed gas cylinder having a valve. The cap  20  of the flush unit  15  is coupled to the flushing agent reservoir containing flushing agent, with dip stick  55  extending into the interior of the reservoir a sufficient distance so that it&#39;s open end is immersed in the flushing agent. The hose connector  30  is coupled to suitable hosing, which feeds an injector such as a blow gun or the like configured to introduce flushing agent into the compression system to be flushed. The pressure regulator on the driving fluid cylinder is set to a suitable pressure, such as 50-60 psi, and the ball valve  50  is opened slowly to pressurize the reservoir  10 . Driving fluid thus flows through the ball valve  50  into cap  20  via radial bore  22 , and into the reservoir via axial passageway  28  and axial bore  27 . Once the reservoir  10  is properly pressurized, the ball valve  50  (and the valve on the driving fluid compressed cylinder) can be closed and the driving fluid connection can be disconnected from the ball valve inlet. The reservoir  10  is now pressurized for use. 
     In the event too much pressure (e.g., exceeding about 200-210 psi) is provided to the assembly, the excess pressure biases against biasing member  70  in the pressure relief assembly  35 , forcing the seat holder  72  radially outwardly and thereby relieving pressure through the ports  64  in the valve cap  61 .