Abstract:
A high purity water delivery system has a reservoir ( 40 ) of purified water. A distribution line ( 42 ) extends downstream from an outlet ( 44 ) of the reservoir to a return ( 46 ) of the reservoir. A plurality of delivery stations each include an outlet ( 54 ′) and a diverter ( 102; 102′; 102″; 102′″ ). The diverter has an upstream inlet port ( 104 ) along the distribution line and a downstream outlet port ( 106 ) along the distribution line. The diverter has a supply port ( 108 ) downstream of the inlet port and a return port ( 110 ) downstream of the supply port. The diverter has a flow restriction ( 112; 112′; 216 ) between the supply port and the return port. Each delivery station includes a flow control valve ( 56 ′) between the outlet on the one hand and the supply port and return port on the other hand.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation application of Ser. No. 12/738,456, national stage filed Apr. 16, 2010, which is the US national stage of PCT/IB2008/002949 and entitled “High Purity Water System”, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length, and benefit is claimed of U.S. patent application Ser. No. 60/986,168, filed Nov. 7, 2007, and entitled “High Purity Water System”, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to water systems. More particularly, the invention relates to high purity water systems for laboratory, medical, industrial, and similar uses. 
     An exemplary high purity water distribution system delivers water to a number of delivery or use points. One exemplary delivery/use point is a faucet. Another exemplary delivery/use point is a water-utilizing piece of laboratory, medical, or industrial equipment. 
     Despite initial purification, high purity water systems have contaminant growth problems. Stagnant water in a system may provide a hospitable location for any residual contaminant to grow to unacceptable concentration. For example, a typical laboratory faucet is fed by a branch off of a main distribution line. When the faucet is shut-off, there may be stagnant water in the branch even if there is constant flow through the main distribution line. For example, constant flow through the main distribution line may be achieved by providing the main distribution line as a recirculating system. 
       FIG. 1  shows a “serpentine” system  20  having an initial non-purified water supply  22  (e.g., municipal water or main water for an industrial facility). A purification system  24  may include: one or more filters  26 ; thermal, or radiological processing stations  28 ; and pumps  30 . The purification system  24  delivers purified water to a purified water reservoir  40  (e.g., a holding tank). An exemplary main distribution line  42  is a recirculating line from an outlet  44  of the tank  40  to a return  46  of the tank  40 . A pump  48  may be located along the main distribution line  42 . The distribution line  42  may serpentine through various locations in the laboratory to deliver purified water to various distribution/use points  50 . 
     An exemplary distribution/use point is a faucet  52  having an outlet  54  and a valve  56 . The faucet may be at the end of a branch line  58  from the leg of a tee  60  along the distribution line  42 . In the exemplary faucet, the branch line  58  connects to a port  62  of the faucet. The exemplary port  62  and valve  56  are along a faucet mounting base  64 . Depending upon faucet geometry, at least the distance from the tee  60  to the valve  56  may constitute a dead leg wherein there is little water circulation when the faucet is shut-off. To limit dead leg contaminant growth, one possibility is to leave a residual flow through the faucet. For example, the faucet may have a nominal shut-off condition in which a small flow is discharged (e.g., to waste). Also, or alternatively, limitations may be placed upon the length of the dead leg. For example, with a very short dead leg, residual communication at the tee  60  between the branch line  58  and the main distribution line  42  may sufficiently limit stagnation in the dead leg. 
     Recent design practices dictate that a dead leg in a hot water system, should not exceed a length greater than six pipe diameters; in a cold system it is any static area, although rule of thumb numbers of three or four diameters are commonly used. This length is often referred to as the “6d” rule and has traditionally been determined by measuring the distance from the centerline of the supplying conduit to the physical blockage on its associated branch. See, e.g., Genova T F, “Microbiological Aspects of Pharmaceutical Water Systems,” presented at the High Purity Water Seminar, Institute for International Research, Westin Resort, Miami Beach, Fla., February 1998. Some less conservative gooseneck faucet configurations violate this rule. 
     An alternative system involves the use of recirculating laboratory faucets (RLFs).  FIG. 2  shows a “supply/return” system  20 ′ wherein the distribution line  42 ′ is divided by a balancing valve  43  into a supply/outbound leg/line  42 - 1  and a return/inbound leg/line  42 - 2 . The balancing valve  43  maintains a pressure in the outbound line  42 - 1  above a pressure in the return line  42 - 2 . In each use point  50 ′, the faucet  52 ′ has a supply port  62 - 1  and a return port  62 - 2 . The supply port  62 - 1  is connected to the supply line  42 - 1  via a line  58 - 1  and a tee  60 - 1 . The return port  62 - 2  is connected to the return line  42 - 2  via a line  58 - 2  and a tee  60 - 2 . The faucet  52 ′ has an outlet  54 ′ and a valve  56 ′. With the valve  56 ′ shut-off, there is no discharge flow from the outlet  54 ′. However, there is a recirculating flow along a recirculating flowpath (faucet loop)  70  from the tee  60 - 1  through the line  58 - 1 , port  62 - 1 , port  62 - 2 , line  58 - 2 , and tee  60 - 2  to return to the return line  42 - 2  and therefrom to the holding tank. By providing this residual recirculating flow, the dead leg may be substantially internalized to the faucet (and reduced to essentially zero with a purpose-configured RLF). This provides a great deal of flexibility in locating the faucet relatively remote of the supply line and return line. When the faucet  52 ′ is open and flow discharging from the outlet  54 ′, there may still be a residual return flow through the line  58 - 2 . 
     SUMMARY OF THE INVENTION 
     One aspect of the invention involves a high purity water delivery system. The system has a reservoir of purified water. A distribution line extends downstream from an outlet of the reservoir to a return of the reservoir. A plurality of delivery stations each include an outlet and a diverter. The diverter has an upstream inlet port along the distribution line and a downstream outlet port along the distribution line. The diverter has a supply port downstream of the inlet port and a return port downstream of the supply port. The diverter has a flow restriction between the supply port and the return port. Each delivery station includes a flow control valve between the outlet on the one hand and the supply port and return port on the other hand. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a first prior art high purity water distribution system. 
         FIG. 2  is a schematic of a second prior art high purity water distribution system. 
         FIG. 3  is a schematic of an inventive high purity water distribution system. 
         FIG. 4  is a view of a distribution/use point for the system of  FIG. 3 . 
         FIG. 5  is an alternate distribution and use point for the system of  FIG. 3 . 
         FIG. 6  is a dual distribution and use point for the system of  FIG. 3 . 
         FIG. 7  is a view of a body of a diverter of the distribution and use point of  FIG. 5 . 
         FIG. 8  is a longitudinal sectional view of the body of  FIG. 7 . 
         FIG. 9  is a view of a diverter including the body of  FIGS. 7 and 8 . 
         FIG. 10  is a side view of the diverter of  FIG. 9 . 
         FIGS. 11-14  are flow charts for four fixed orifice diverters 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
       FIG. 3  shows a high purity water distribution system  100  which allows recirculating faucets  52 ′ to be used in a situation other than a supply/return system. This may reduce costs of an initial system construction (e.g., a single line rather than both a supply line and a return line need to be brought proximate each distribution location). It may also allow retrofitting of existing single line serpentine systems. 
     It is believed that there have been erroneous prior art attempts at retrofitting existing single line serpentine systems with recirculating laboratory faucets. These attempts have involved placing the tee  60 - 1  immediately upstream of the tee  60 - 2 . In such a situation, the lines  58 - 1  and  58 - 2  would effectively operate in parallel rather than as distinct supply and return branches. With the faucet off, the two branches would effectively define parallel dead leg branches. 
     In the system  100 , the tees  60  of the system  20  are replaced by diverters  102 . Along the line  42 , the diverters  102  have an inlet port  104  and an outlet port  106 . The diverters have a supply/take-off port  108  and a return port  110  with a flow restriction  112  therebetween. The supply branch line  58 - 1  is coupled to the port  108  and the return branch line  58 - 2  is coupled to the port  110 . A recirculating flowpath  120  thus extends: along a supply branch  120 - 1  from the main flowpath through the diverter supply port  108 , and supply branch  58 - 1  into the faucet to near the valve; and returns via a return branch  120 - 2  extending through the faucet from near the valve and then through return branch line  58 - 2  and diverter return port  110 . Depending upon the particular kind of RLF, supply and return branches within the faucet may have different extents. The restriction  112  provides a pressure difference across the diverter and thus, across the recirculating flowpath  120 . 
     As noted above, the system  100  may have one or more advantages relative to the system  20  and/or the system  20 ′. For example, relative to the system  20 , the system  100  may be implemented to provide reduced opportunity for contaminant growth. Alternatively or additionally, the system  100  may provide simplification (and cost reduction) of the main distribution line relative to the system  20 . For example, the main distribution line of the system  100  may be relatively straight and compact compared to that of the system  20 . Whereas the main distribution line of the system  20  may be circuitously routed to proximate the base of each faucet (e.g., extending up into cabinets, benches, or other stations to reduce dead leg length), the main distribution line in the system  100  may be further away from its associated faucets (e.g., remaining entirely in-floor, in-wall, or otherwise being compact and non-circuitous). 
     Relative to the system  20 ′, the system  100  may essentially cut the required length of main distribution line in half by eliminating the distinction between supply and return legs. This also may essentially halve the associated plumbing labor involved in bringing both the supply and return to desired location relative to each faucet. The restriction  112  is sufficient so that the pressure differential allows sufficient recirculating flow in the recirculating flowpath  120  to control contaminant growth even when the faucet valve is in a full shut-off condition. When the faucet valve is open, there may, advantageously, also be a flow along the flowpath  120 , with the flow on the supply branch exceeding the return branch flow by the net flow discharged from the faucet. 
     An exemplary degree of flow restriction is a 40-60% reduction in flow area (discussed further below). 
     In one family of examples, the diverter is formed as a modified throttling valve wherein the supply and return ports are added.  FIG. 4  shows an example of a diverter  102 ′ formed as a modified George Fischer Type 315 Spigot Diaphragm Valve. The diverter  102 ′ includes a body  130 . The exemplary restriction  112 ′ is formed by the combination of a weir  132  of the body and a diaphragm  134 . The diaphragm may be displaced toward or away from an end of the weir to control the size of a gap  136  therebetween. Exemplary diaphragm control is via an adjustment mechanism such as a manual adjustment knob  138 . As is discussed further below, other embodiments involve a fixed orifice. As is discussed further below, an adjustable restriction such as that provided by the diaphragm may be used to simulate performance of a fixed orifice diverter. In the simplified views of  FIGS. 4-6 , various separate pieces are shown integrated. 
     The exemplary faucet of  FIG. 4  has an angled neck  140  through which two respective branch flowpaths  120 - 1  and  120 - 2  extend from the lines  58 - 1  and  58 - 2 . The two branch flowpaths join at the valve  56 ′. The outlet  54 ′ is at the lower end of a nozzle/fitting  142  extending downward from the valve  56 ′. The exemplary valve  56 ′ is a manual valve having an adjustment knob  144 . Such a configuration is intended to minimize any dead leg within the faucet. For example, the two separate flowpaths through the neck  140  minimize dead leg between the valve and the main distribution line. The exemplary branch flowpaths are side-by-side, although concentric flowpaths of other faucets may be used. With a vertically downward path from the valve  56 ′ to the outlet  54 ′, water trapping and stagnation therebetween is also limited. 
       FIG. 5  shows a diverter  102 ″ having a fixed orifice restriction (orifice)  112 ″. The faucet and connection details may be similar to those of  FIG. 4 . 
       FIG. 6  shows a diverter  102 ′″ having two supply ports and two return ports for feeding two faucets. Other details may be similar to those of  FIGS. 4 and 5 . 
       FIGS. 7 and 8  show an exemplary body  200  of the diverter  102 ″. The exemplary body is formed as a single piece of a non-metallic (e.g., polymeric) material. An exemplary body is formed by machining from a stock piece of the material. An exemplary material is rod stock of polyvinylidene difluoride (PVDF). Alternatives may involve molding (e.g., to final form or to an intermediate form finished by machining). 
     The exemplary body has a main line flowpath portion  202  extending from a first end  204  to a second end  206  (e.g., rims). Tubular neck portions  208  and  210  extend respectively to the rims  204  and  206  from a main body  212 . Exemplary portions  208  and  210  have internal diameters D I1 . The body includes an orifice  216 . The exemplary orifice  216  is circular having a diameter D I2  smaller than D I1 .  FIG. 8  further shows an outer diameter D O1  along the portions  208  and  210 . Exemplary D O1  and D I1  are the same as corresponding diameters of the associated main flowpath piping to which the diverter is coupled. 
     Various relative and absolute diameters are discussed further below. However, if non-circular orifices are used, cross-sectional areas may correspond to those described for circular orifices. Two ports  218  and  220  are formed in the interior surface  214 . Extending outward from the respective ports  218  and  220  are first branch portions  222  which may have a diameter corresponding to the necessary branch line ID. Extending to an exterior  224  of the main body from the portions  222  are enlarged regions  226  (which define body ports  228  and  229 ) for receiving fittings (e.g., flare adapters  230  with nuts  232  shown in  FIGS. 9 and 10 ) for respectively forming the ports  108  and  110 .  FIGS. 9 and 10  also show sanitary clamp adapter fittings  240  secured at the main body ends  204  and  206  (e.g., via bead- and crevice-free (BCF) welding). The exemplary enlarged regions extend to a top facet/face  250  shown in exemplary orientation facing directly upward. The exemplary body  212  has a pair of lateral facets/faces  252  and  254  facing slightly upward. Port pairs can be formed in any or all of these three faces  250 ,  252 , and  254 . Port pairs in two of these faces can provide a two-faucet diverter such as that of  FIG. 6 . Ports in three of these faces can provide a three-faucet diverter. The at least slightly upward orientation of each of these faces (and the associated ports) prevents the localized water stagnation that might occur with a downward-directed port pair. 
     Table 1 shows examples of four nominal pipe outer diameters (OD) for the main piping of the system. Table 1 further shows exemplary pipe ID. The particular ID associated with the given nominal OD may vary based upon pipe material and performance standard or schedule. Exemplary pipe materials are PVDF. Alternative materials include polypropylene (PP). However, metal or other pipes may be used. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Ex. 1 
                 Ex. 2 
                 Ex. 3 
                 Ex. 4 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Pipe OD (mm) 
                 32 
                 40 
                 50 
                 63 
               
               
                   
                 Pipe ID (mm) 
                 28 
                 35 
                 44 
                 56 
               
               
                   
                 ID area (mm 2 ) 
                 616 
                 962 
                 1521 
                 2463 
               
               
                   
                 Orifice ID (mm) 
                 20 
                 25 
                 34 
                 38 
               
               
                   
                 Orifice area (mm 2 ) 
                 314 
                 491 
                 908 
                 1134 
               
               
                   
                 % Open 
                 0.51 
                 0.51 
                 0.60 
                 0.46 
               
               
                   
                   
               
             
          
         
       
     
     The exemplary orifice diameters of Table 1 were selected to provide a generally favorable balance between sufficiently high recirculating flow diverted from the diverter and sufficiently low pressure differential across the diverter (pressure loss) over a range of main distribution line flows through the diverter. A fuller optimization could involve consideration of factors including or influenced by the numbers of diverters used, the length of the main distribution line (as well as any other factors influencing loss along the main line) and the like. By way of example, with the nominal 50 mm OD pipe, a target flow through the recirculating flowpath  120  was selected as one foot per second (0.30 m/s). With a 34 millimeter orifice, an exemplary main line flow was set at forty gallons per minute (2.5 liter/s) or a velocity of 5.4 fps (1.65 m/s). A resulting flow through the flowpath  120  was one gallon per minute (0.06 liter/sec) or 1.5 fps (0.46 m/s) through nominal 0.625 inch (15.9 mm) OD, 0.50 inch (12.7 mm) ID branch lines. An exemplary faucet-off branch flow is 1.0-5.0 fps (0.30-1.5 m/s), more narrowly, 1.4-2.5 fps (0.43-0.76 m/s), and/or 1.5-5% of a main line flow. 
       FIGS. 11-14  respectively show curve fits of diverted flow  300  and pressure drop  302  data for the four examples of Table 1. The identified SI units are conversions of the English units of the parentheticals. 
     In configuring or optimizing a system, a variety of techniques may be used to choose appropriate orifice size. As noted above, a mock-up of an ultimate system may be made using adjustable valves in place of fixed orifice diverters. Adjustments may be made to optimize orifice sizes. The actual system may then be built using corresponding fixed orifices. Similarly, experimental diverter bodies configured to receive replaceable orifice disks may be used, with disks interchanged until the desired orifice size combinations are determined. 
     One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, the invention may be used with a variety of recirculating faucets or other dispensing/distribution devices. Additionally, various piping technologies may be used. Especially in retrofit situations, details of the existing system may influence details of any particular implementation. Accordingly, other embodiments are within the scope of the following claims.