Abstract:
Converting a liquid ring pump which vents sealing liquid (compressant) from the working chamber of the pump to a liquid ring pump having a gas venting system by retasking a selected passage of the liquid ring pump. The passage is selected from a group of passages consisting of ( 1 ) a sealing liquid introduction passage and ( 2 ) a sealing liquid vent passage.

Description:
FIELD OF INVENTION 
       [0001]    The present invention generally relates to a liquid ring pump (“pump”) which vents sealing liquid (compressant) from the working chamber of the pump. More particularly, this invention relates to a method of converting liquid ring pumps using a sealing liquid venting system into a pump having a gas venting system in order to accommodate varying compression ratios. 
       BACKGROUND OF THE INVENTION 
       [0002]    Liquid ring pumps are well known. U.S. Pat. No. 4,498,844, Bissell discloses a liquid ring pump with a conical port member. The conical port member has a vent re-circulation port in addition to the conventional intake and discharge ports. U.S. Pat. No. 4,498,844 is incorporated herein in its entirety. 
         [0003]    The pump shown in  FIG. 1  is of a known configuration of a conical liquid ring pump.  FIG. 1  is a vertically oriented sectional view, taken along a plane parallel to the pump&#39;s shaft.  FIG. 1   a  shows that the cross-section is taken along line  100 . Cross section line  100  thus provides the perspective point for  FIG. 1 . 
         [0004]    The pump has a first head  20  and a second head  22 . Each head has a gas inlet  20   a,    22   a . Each head has a gas discharge  20   b,    22   b.  The heads  20 ,  22  are located at the axial ends of the liquid ring pump. Located axially between the pump heads  20 ,  22  is a body or housing  23 . Located within the housing is a rotor  25 . The rotor  25  has rotor blades  25   a.  The rotor blades  25   a  extend from a hub  25   b.    
         [0005]    The body or housing  23  provides a chamber (working chamber) in which the rotor  25  rotates to draw air or gas  26  through gas inlets  20   a,    22   a  into the working chamber. The gas  26  is then exhausted from the working chamber through gas discharge outlets  20   b,    22   b.    
         [0006]    As can be seen, the gas  26  is drawn into the working chamber through conical port members  27 ,  28 . The gas is also exhausted from the working chamber through conical port members  27 ,  28 . The chamber is divided into a first working chamber  23   a  and a second working chamber  23   b  by rotor shroud  25   c  and lobe shroud  23   c.    
         [0007]    Sealing liquid  29 , see  FIG. 2 , is in the working chamber. As the rotor  25  rotates, the sealing liquid  29  is formed into a liquid ring within the working chamber. The liquid ring takes an eccentric shape that diverges and converges in the radial direction relative to shaft  30  of the liquid ring pump. Where the sealing liquid  29  is diverging from the shaft  30 , the resulting reduced pressure in the spaces between adjacent rotor blades of the rotor assembly (buckets) constitutes a gas intake zone. Where the sealing liquid  29  is converging towards the shaft  30 , the resulting increased pressure in the spaces between the adjacent rotor blades (buckets) constitutes a gas compression zone. U.S. Pat. No. 4,850,808, Schultz, provides an example of a conical liquid ring pump. U.S. Pat. No. 4,850,808 is incorporated herein in its entirety. 
         [0008]    The liquid ring pump shown in  FIG. 1  has sealing liquid entry or introduction paths  31  which allow sealant  29  to enter the working chamber. The entering sealant  29  passes through the heads and conical port member. Although the sealing liquid  29  is shown entering only through head  20  and conical member  27 , it could enter through head  22  and conical member  28 . 
         [0009]    In addition to having sealing liquid introduction pathways  31 , the pump of  FIG. 1  also has liquid vent paths to allow liquid to exit the working chamber during operation of the pump. Prior art  FIG. 2  shows a schematic of sealing liquid  29  exiting the working chamber through sealing liquid vent path  33 . The existing heads  20 ,  22  are symmetrical about the vertical axis permitting one head design to be used on either axial end of the pump. Depending on the direction of rotation, passages in the head are currently used for either introducing or venting the sealing liquid  29 . 
         [0010]    The design compression ratio is a ratio of the design discharge pressure to the design suction pressure. The operating compression ratio is a ratio of the operating discharge pressure to the operating suction pressure. In practice the pressure at discharge remains constant and is usually the atmospheric pressure. The suction pressure will vary depending on application. 
         [0011]    It is known that a pump having a fixed discharge port and an operating compression ratio less than the design compression ratio will have increased pressure within the working chamber. Increased pressure requires the use of additional pump power. To minimize the need for increased pump power, the prior art, as shown in  FIGS. 1 and 2  has compressant (sealing liquid) vent paths or built in liquid leakage paths to allow for the sealing liquid to exit the working chamber and reduce the pressure within the working chamber and within the buckets. Accordingly, the venting of the sealing liquid accommodates varying compression ratios experienced by the pump during operation. 
         [0012]    The use of compressant or sealing liquid vent paths (liquid leakage paths) has several draw backs. Venting requires a balancing act of continually releasing and replenishing the seal liquid in order to achieve an appropriate pressure within the working chamber. If the seal liquid flow rate is increased over the normal flow rate, then the power control function of the liquid venting method is overcome and pump power can increase at low compression ratios where it can overload the drive system. Further a sudden drop in vacuum pressure from the design compression ratio to a low compression ratio results in a period in which the pump has more liquid in it than the steady state low compression ratio condition. The excess liquid can result in overloads to the drive equipment. Also, if the seal liquid to the pump is reduced, the flow out through the liquid vent paths results in diminished sealing within the pump and the gas volume pumped is reduced. 
       SUMMARY OF THE INVENTION 
       [0013]    The disclosure provides for the conversion of a liquid ring pump which utilizes sealing liquid venting, into a pump which utilizes gas venting. Gas venting avoids the pitfalls associated with sealing liquid venting because, in part, it eliminates the need to continually introduce and release sealing liquid. Instead, when the pump is operating at a compression ratio less than the design compression ratio, gas can be vented from the working chamber of the pump to reduce the over compression. In return, this also reduces the shaft power requirements. The conversion of existing liquid ring pumps can be done through only minimal changes to the pump parts. 
         [0014]    A sealing liquid pathway of a liquid ring pump, either used for sealing liquid venting or sealing liquid introduction, is retasked to form a portion of a gas vent. The present disclosure shows retasking a sealing liquid introduction path in a pump head to provide a portion of a gas vent path. The disclosure also provides for converting a sealing liquid vent path of an existing liquid ring pump into a sealing liquid introduction path. 
         [0015]    Converting the sealing liquid vent path to a sealing liquid introduction path requires providing a new cone which seals off a portion of the vent path extending through the pump head. The new cone also provides a new channel to allow for the entry of sealing liquid into the working chamber from a pathway in the pump head previously used to form a portion of the sealing liquid vent path. Of course the path retasked to be a sealing liquid introduction path would be repiped to receive sealant. 
         [0016]    To provide for the gas vent, the pump head passage previously used for sealing liquid introduction is retasked so that it forms a portion of an appropriately sized passage way to vent gas to the pump discharge. Additionally, the new cone is provided with a vent passage which aligns with an opening in the pump head which was previously an opening for sealing liquid introduction but is now retasked to form an opening into a gas vent in the pump head. The new cone gas passage has a gas port through the cone&#39;s conical surface. 
         [0017]    The retasked and converted pump permits operation with reduced seal flow to the pump because the pump no longer relies on sealing liquid venting to accommodate varying compression ratios. Additionally, the retasking allows the pump to operate with sealing volume flow rates greater than or equal to 200% of the pump prior to retasking over the entire operating vacuum range of the pump without increasing the power requirements above those of the prior pump. Accordingly, the retasked pump is insensitive to a doubling of seal rate and insensitive to quick drops in vacuum. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a vertical sectional view of a prior art liquid ring pump taken along a plane parallel to the shaft of the pump. 
           [0019]      FIG. 1   a  is an end view of a pump head of the type shown in  FIG. 1 . 
           [0020]      FIG. 2  is a rough schematic of a blown up portion of the pump shown in  FIG. 1  showing a sealing liquid vent path which allows discharge of sealing liquid around the rotor periphery. 
           [0021]      FIG. 3  is a stripped down horizontal sectional view of a pump of the type shown in  FIG. 1  taken along a plane parallel to the pumps shaft; the Figure includes a pump head interfaced with a conical member. 
           [0022]      FIG. 4  is a horizontal sectional view through a liquid ring pump taken in a manner similar to the section of  FIG. 3 ; the pump head and cone have been reconfigured in accordance with the present invention to allow gas to be vented in a channel previously used for sealing liquid introduction. 
           [0023]      FIG. 5  is an isometric view of the conical member shown in  FIG. 3 . 
           [0024]      FIG. 6  is an end view of the conical member shown in  FIG. 5  looking into the nose or small end of the cone. 
           [0025]      FIG. 7  is an isometric view of the cone shown in  FIG. 4 . 
           [0026]      FIG. 8  is an end view of the cone shown in  FIG. 7  looking into the nose or small end of the cone. 
           [0027]      FIG. 9  is an end view of a pump head of the type shown in  FIG. 3 . 
           [0028]      FIG. 10  is an end view of a reconfigured pump head of the type shown in  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    The present invention converts a pump, which relies on sealing liquid vent paths, also known as liquid leakage paths, into a pump which utilizes a gas vent path. The gas vent path is now used to accommodate varying compression ratios, instead of the sealing liquid vent path. Prior to conversion of the pump, the pump can have all of the features shown in  FIGS. 1 ,  2  and  3 . Prior to conversion,  FIG. 3  shows a pump head  40  which has a sealing liquid (compressant) vent passage. The vent path or passage is formed by a channel  41   a  extending through pump head  40  and an aperture  41   b  extending through a flange  44  of conical member  46 . The vent path allows unwanted sealing liquid  29  to exit the working chamber. 
         [0030]    Prior to conversion, the pump head  40  also has a sealing liquid introduction passage. The seal liquid introduction passage is formed by a channel passage  48   a  extending through pump head  40  and a channel  48   b  extending through conical member  46 . 
         [0031]    To convert the pump shown in  FIGS. 1 and 3  to a gas vented liquid ring pump, a new conical member  50 , as shown in  FIGS. 4 ,  7 ,  8  is provided. Additionally, the pump head  40  is reconfigured by possible machining and the like, such that the seal liquid introduction channel  48   a  is retasked to form a portion  448   a  of a gas vent passage. The new cone  50  forms another portion  448   b  of the gas vent passage. The cone passage  448   b  has a port  448   b ′ through which gas to be vented enters the cone passage  448   b.  As shown in  FIG. 10 , the gas vent passage could also include piping  55  to allow gas exiting the retasked pump head  440 , through passage  448   a,  to terminate at the pump discharge  56  or to terminate in a discharge piping system  58 . Accordingly, the gas vent is formed by cone port  448   b ′, cone gas channel  448   b,  head gas passage  448   a  and the piping  55 . As can be seen the pump in  FIG. 10  has a main discharge  73 . 
         [0032]    In providing a gas vent channel through a portion of the pump head  40  which was previously used as a portion of a sealing liquid introduction path, it is important to make sure the passageway provided has sufficient area for the release of gas from the working chamber. The smaller the passage, the greater the pressure required at the gas port  448   b ′ and the greater the power required by the vacuum pump to achieve that pressure at port  448   b.  The higher power represents increased operating cost to the end user. Tests have shown that a ratio of pump capacity to passage area of 490 to 1,160 CFM per square inch results in an adequate passage cross sectional area. Preferably, no portion of the passage should have a restricted area outside of the desired ratio range. 
         [0033]    As best seen in  FIG. 8 , for a cone  50  designed for operation at 20 inches of mercury vacuum that includes a single vent opening  448   b ′, the leading edge  448   b ″ of the opening in the cone should occur between 130 and 140 angular degrees before the point of closest approach of the rotor blade  25   a  to rotor body  23 . The point of closest approach of the rotor body is approximated by line  60 . The direction of rotation is shown by arrow  61 . The angle of the closing edge  448   b ″′ of the vent opening (port)  448   b ′ is preferably from 110 to 115 angular degrees before the closest approach of the rotor to the body. The included angle from the closing of the vent opening to the opening of the cone&#39;s final discharge port  70  is approximately the angular distance between two successive rotor blades to a tolerance of 7 angular degrees. The inlet port is shown at  71 . 
         [0034]    The new cone  50  is provided with a sealing liquid channel  441   b  which allows for sealing liquid  29  to now enter the working chamber through what was previously used as a compressant vent channel  41   a.  A portion of the compressant vent channel  41   a  is thus retasked to be a sealing liquid introduction path  441   a.  Also pump  40  is reconfigured so that the compressant vent passage  41   a  is partially sealed at  41   a ′. Cone  50  seals the portion  41   a ′ of vent passage  41   a  by providing a cone flange  444  that omits vent port  41   b.  The flange  444  thus seals vent portion  41   a  at  41   a ′. The path now retasked as the sealing liquid introduction path  441   a,  would be repiped as shown in  FIGS. 9 and 10 . 
         [0035]    The term gas used herein is broad enough to include air. 
         [0036]    Although an example of the invention has been disclosed, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the spirit and scope of the invention. 
         [0037]    All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. 
         [0038]    Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. 
         [0039]    The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.