Patent Publication Number: US-2013240768-A1

Title: High Density Polyethylene Gate Valve

Description:
FIELD OF INVENTION 
     This invention relates to apparatus and methods for regulating fluid flow, and more particularly to a self sealing gate valve especially adapted and designed for use in challenging environments. 
     BACKGROUND 
     Landfills are often prolific contributors of green house gases, particularly methane (CH4) which according to the EPA is a greenhouse gas approximately 21 times more potent than carbon dioxide (C02), emissions. A common method of waste disposal and treatment, landfills produce these gases, among others, from the anaerobic digestion by microbes of organic matter. These gases, typically composed of mostly methane and carbon dioxide, may be collected and methane in particular may be utilized, with contemporary technology, to generate electricity by combustion, fuel industrial boilers, or be converted to pipeline quality High-BTU gas. In utilizing the methane from the landfill, greenhouse gas emissions are greatly reduced. 
     Landfills frequently have gas extraction systems to capture landfill gases. Gases are typically drawn out of a landfill with a low pressure vacuum via a wellfield collection system. The wellfield typically consists of multiple gas extraction wells that extend deep beneath the surface of the landfill to pull methane from a location near the bottom of the landfill. Each extraction well extends up to the surface of the landfill and there the extraction wells are manifolded together so that vacuum can be pulled with one centralized blower or compressor. 
     It is critical to regulate the vacuum draw on the landfill wellfield and flow of gas through the system and it will be appreciated that wellfield gas recovery and extraction systems employ numerous flow regulating devices, including a variety of valves. Regulating the vacuum or draw on the field regulates, to a degree, the type and rate of decomposition. Too much draw may pull oxygen into the wellfield enabling aerobic decomposition and causing underground fires thus requiring shutdown of the wellfield resulting in unrestricted release of greenhouse gases into the atmosphere. Too small of a draw will increase gas diffusion into surrounding soil and eventual release of methane into the atmosphere. Typically each extraction well utilizes a valve at the head of the well to adjust the vacuum pulled on the well. After monitoring the extraction well&#39;s gas flow and composition, an operator may adjust this valve to optimize gas recovery or limit oxygen pull into the landfill. 
     Landfill gas monitoring and recovery is referred to as a wet gas industry because the gases created in landfills are typically 100 percent saturated because water is produced throughout the wellfield in addition to oxygen, nitrogen, methane and carbon dioxide. The wet gas, the possibility of particulates, and low pressures associated with these systems present some significant challenges for gas flow regulating devices, particularly the valves used in the systems. Many existing valves can be damaged by the corrosive environment, and particulates in the gas often cause problems with proper sealing at the valve seat. 
     There is a need therefore for improved apparatus for regulating gas flow through landfill gas wellfield recovery systems, and in particular, valves that avoid the problems of know systems. 
     SUMMARY OF INVENTION 
     The subject invention is a gate or gate-type valve designed for use as a flow regulating device specifically for use in saturated gaseous, high particulate, high temperature, and low pressure environments such as in landfill gas wellfields and similar environments where particulate and water gathering can obstruct the operation of a typical gate valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood and its numerous objects and advantages will be apparent by reference to the following detailed description of the invention when taken in conjunction with the following drawings. 
         FIG. 1  is a side elevation view of a first illustrated embodiment of a valve assembly according to the present invention, showing the valve plunger and housing in an assembled condition. 
         FIG. 2  is an end elevation view of the valve assembly shown in  FIG. 1 . 
         FIG. 3  is an exploded view of the valve assembly shown in  FIG. 1  illustrating the components of the assembly. 
         FIG. 4  is a cross sectional view taken along the line  4 - 4  of  FIG. 1 , illustrating the valve assembly of the present invention with the plunger in the open position. 
         FIG. 5  is a cross sectional view similar to the view of  FIG. 4  except showing the plunger in the closed position. 
         FIG. 6  is a cross sectional view taken along the line  6 - 6  of  FIG. 1 , illustrating the valve assembly of the present invention with the plunger in the open position. 
         FIG. 7  is a cross sectional view similar to the view of  FIG. 6  except showing the plunger in the closed position. 
         FIG. 8  is a cross sectional view taken along the line  8 - 8  of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS 
     The valve assembly  10  according to the present invention is a gate valve that is defined by a valve body or housing  12  and a plunger assembly  50 . The plunger assembly  50  is in turn comprised of a plunger body  52  and a valve handle assembly  62 . The body  12  is defined generally by a T-shaped fitting having a linear length of tubing  14  that is plumbed inline in a wellfield gas line and a plunger assembly tube  16  that extends transverse to the linear tubing  14 . The housing  12  is preferably a one-piece unit that is fabricated from high density polyethylene (HDPE). The housing defines open conduits through the interior of the housing: the housing is plumbed in-line with appropriate connector fittings and the gas flow path extends through the linear tubing  14  and the plunger assembly fits into the plunger assembly tube  16 . As detailed below, the interior of the housing includes plunger seating structures to facilitate complete closure of the valve. It will be appreciated that the valve assembly  10  may be fabricated in any size appropriate for any particular installation—the nominal size of the tubing used for valve assembly  10  is sized to fit the tubing into which the valve assembly will be installed. 
     The outermost end  18  of plunger assembly tube  16  has external threads  20  and internal threads  22 , the purpose of which is detailed below. 
     With reference to  FIG. 3 , plunger assembly  50  comprises a plunger body  52  and a valve handle assembly  62 . Plunger body  52  is preferably defined by a one-piece elongate member that includes generally a distal end  54  and a proximal end  56 . An upper shaft portion  58  is adjacent the proximal end  56  and a lower shaft portion  60  that has an enlarged diameter relative to the upper shaft portion  58  is at the distal end  54 . Valve handle assembly  62  is the components shown in  FIG. 3  that are directly and removably attached to the end of upper shaft portion  58  at distal end  54  and allows an operator to axially rotate the plunger assembly  50  to open and close the valve assembly  10 . Valve handle assembly  62  comprises the following components: an internally threaded bonnet  64 , a first O-ring  80 , a second O-ring  82 , a cap  84 , a spring pin  86 , and a handle  86 . The bonnet  64  has a central opening  66 , and as seen in  FIG. 3 , the bonnet  64  is assembled with the plunger body  52  with upper shaft portion  58  extending through opening  66  of bonnet  64 . The opening  66  is sized to conform closely to upper shaft portion  58  and to form a seal against it and that seal is enhanced by second O-ring  82 , which resides in a circumferential groove in opening  66  so that the O-ring encircles upper shaft  58  and defines a seal between the bonnet  64  and the upper shaft  58 . The internal threads of bonnet  64  are identified with reference number  68 . 
     With reference now to  FIGS. 4 and 5  the assembled handle assembly  62  will be detailed. The first O-ring  80  is installed in a circumferential seat  90  in bonnet  64  and the second O-ring  82  is installed in a circumferential groove  92  in bonnet opening  66 . With the first and second O-rings thus installed, the shaft  58  is inserted through opening  66 . Cap  84 , which has an internal cylindrical blind opening  94  is installed over the end of shaft  58  and spring pin  86  is inserted through an opening  96  in cap  84  and into an aligned opening  98  in shaft  58  to thereby secure the cap to the shaft. The “upper” end of cap  84  has a square protrusion  100  that is sized to fit into a cooperatively shaped opening  102  in handle  88  and the handle is thus attached to the cap by inserting the protrusion  100  into the opening  102 . The handle is secured to the assembly with a screw  104  that threads into a threaded opening  105  in cap  84 ; a washer  106  is used to retain the handle on the cap. 
     The lower shaft portion  60  of plunger body  52  defines a sealing portion identified generally with reference number  70  and a threaded portion  72 . The sealing portion  70  includes at the distal end  114  of the plunger body a semi-hemispherically shaped bottom portion. That is, moving from the proximal to the distal ends, the vertical sidewalls of the sealing portion  70  transition to a smoothly radiused circumferential area that transitions to a generally flattened distal end  114 . 
     Valve  10  is assembled by attaching plunger assembly  50  with housing  12 . Specifically, and as best illustrated in the cross sectional images of  FIGS. 4 and 5 , distal end  54  of plunger body  52  is inserted into the opening of plunger assembly tube  16  and threaded portion  72  of the plunger body  52  is threaded into internal threads  22  of the plunger assembly tube  16 . As the plunger body is threaded into the plunger assembly tube, the sealing portion  70  of lower shaft portion  60  moves inwardly into the body  12 . Because the body is one-piece, the sealing portion  70  rotates as the body  52  is rotated to thread the body into the tube. At the point where the treaded portion  72  of the plunger body  52  are fully threaded into the internal threads  22  the bonnet  64  may be threaded onto the plunger assembly tube—that is, the internal threads  68  of the bonnet  64  may be threaded onto the external threads  20  of the assembly tube  16  and the bonnet is tightened in place to secure the plunger body  52  to the housing  12 . As the bonnet  64  is tightened onto the external threads  20  of the assembly tube  16 , first O-ring  80  is compressed between the upper circumferential rim  106  that is defined by the outer end  18  of assembly tube  16  and the seat  90  in the bonnet, thereby creating a leak-free seal between the interior of the valve  10  and the exterior of the valve. Moreover, it will be appreciated that the bonnet prevents disassembly of the plunger body  52  from the housing  12 . That is, with the bonnet installed and tightened as in  FIG. 4 , the plunger may not be threaded outwardly far enough to separate the plunger from the housing. 
     The valve  10  is shown in the open position in  FIGS. 4 and 6 , and in the closed position is  FIGS. 5 and 7 . From these figures it may be seen that the interior portion of the linear run of tubing  14  of housing  12  defines a valve seat  24  that is configured complimentary to the shape of sealing portion  70  of plunger body  52 . That is, the valve seat  24  is semi-hemispherically shaped to correspond to the semi-hemispherical shape of the distal end  114  of sealing portion  70 . More specifically, as shown in the drawings, the distal end  114  is defined by the substantially vertical sidewall of the sealing portion  70 , which transition to a radiused circumferential edge and a generally flattened bottom portion at distal end  114 . 
     It will be appreciated that as handle  88  is rotated axially to move plunger body  52  inwardly into housing  12  (with the threaded portion  72  of body  52  rotating in threads  22  of plunger assembly tube  16 ), the sealing portion  70  is driven into valve seat  24 . When the distal end  114  makes contact with the valve seat  24  and is tightened against the valve seat by continued rotation of handle  88 , the valve  10  is in the closed position, which of course closes the gas pathway through the valve. It will be appreciated that the valve assembly  10  is opened by axially rotating handle  88  in the opposite direction to move distal end  114  out of its sealing position against valve seat  24 . 
     With reference to  FIGS. 6 ,  7  and  8 , it may be seen that the valve seat  24  is defined essentially by a cylindrical bore that is cut into valve housing  12 , wherein the axis of the bore is coaxial with the axis extending through plunger assembly tube  16  and the bore extends into the tubing  14  immediately below the tube  16  to define the seat  24 . The threaded interconnection between the threaded portion  72  of body  52  rotating in threads  22  of plunger assembly tube  16  is a very close tolerance and defines an effective gas-tight seal between the passageway through tube  14  (through which gas flows) and the upper portion of the valve plunger assembly  50 —i.e., that portion of the valve plunger assembly outward of threaded portion  72 . The threaded interconnection of the bonnet  64  with external threads  20  also define a secondary or backup gas-tight seal, combined with O-ring  82 , which as noted previously, seals against shaft  58 . 
     The plunger assembly  50  may be used for regulating or limiting flow through the valve assembly by varying the position of the distal end  54  to thereby vary the size of the gas flow path through the valve. 
     The valve assembly  10  is a self sealing valve and defines two separate valve closing components. The first valve sealing component is defined by the gas flow opening and closing function of the distal end  54  and valve seat  24 . This first valve sealing component is used to open, close, and regulate the flow of gas through valve assembly  10 . The second valve sealing component comprises a primary and a secondary sealing functionality. The first is defined by threads  72  from the plunger body  52 , which seal off the valve and operational handle from the gas flow section of the valve assembly  10 . The second is defined by the bonnet  64 , which as noted previously seals against upper shaft portion  58 . 
     The plunger body  52  is a one piece system fabricated from HDPE. This may be contrasted with typical gate valves that utilize two or three piece plunger or gate systems. The one piece design does not allow vibration on the plunger during operation as with a typical two or three piece gate valve that can vibrate from the flow when not in the fully closed or fully open position. 
     Utilizing this one piece plunger design, valve assembly  10  has more rigidity when opening/closing the valve. This one piece plunger design is milled out of HDPE but is not limited to this material. 
     Other typical valves on the market have a separate female threaded plunger with a male threaded bonnet. In contrast, the valve assembly  10  utilizes a male threaded plunger and a female threaded bonnet. 
     The valve assembly  10  also utilizes a different style of sealing design in the throat as compared to a typical gate valve. Thus, typical gate valves seal using planar surfaces of the plunger against a complimentary shaped lip inside the valve body; this typically results in obstruction of flow and build-up of debris. The valve assembly  10  described and illustrated herein utilizes a semi-hemispherical shaped plunger that is received in a complimentary shaped seat at the bottom of the housing body; this ensures a solid seal around the plunger without obstructing flow. As shown in  FIG. 8 , the surface of the valve plunger that is presented to fluid flow in the linear tubing  14  is always a curved surface. 
     The valve assembly  10  is manufactured out of HDPE material (excluding handle  62  and the screws, pins used to attach the handle to the upper shaft  58 ). Because the entire valve is HDPE the valve may be fused into place permanently utilizing heat transfer welding techniques rather than bolted, threaded, or glued into place as with other gate valves. 
     The bonnet  64  also acts as a back up seal to threads  72  should the threads  72  wear and start to leak. 
     In one preferred embodiment, the housing body  12  utilizes a 2″ HDPE SDR-9 molded Tee. This tee is then custom milled inside the throat to receive the one piece threaded plunger. 
     The one piece threaded plunger rotates in a cylindrical motion throughout the entire travel area of the valve; with typical gate valves, the plunger does not travel in the horizontal direction, instead it only travels vertically while the plunger shaft rotates horizontally. 
     With typical valves, if the plunger travels linearly the plunger only comes in contact with the seat of the valve body when the valve is closed; if the plunger is a rotating plunger it is always in contact with the seat. The sealing portions of valve assembly  10 —specifically, sealing portion  70 , only comes in contact with the valve seat  24  when the valve is in the closed position, even though sealing portion  70  of course rotates axially as the handle  62  is rotated. 
     It will be appreciated that all of the components of the plunger assembly  50 , and the assembly itself, may be replaced in the field if the unit is damaged or leaking. In addition to the embodiments described above that illustrate the invention, those of skill in the art will appreciate that various substitutions and alterations may be made without departing from the scope of the invention. As a first example, the shape of the distal end  114  of the plunger body  52 , and the corresponding cooperative shape of the valve seat  24  may be varied. The shape shown in the drawings is described as being semi-hemispherical in geometry. The end  114  could just as well be a complete hemisphere, in which case the valve seat  24  would be cooperatively shaped as a hemisphere. As a second example, the bonnet  64  described above threads onto the external threads  20  of the plunger assembly tube  16 . The bonnet could just as well have external threads that thread into internal threads in the tube  16 . 
     While the present invention has been described in terms of preferred and illustrated embodiments, it will be appreciated by those of ordinary skill that the spirit and scope of the invention is not limited to those embodiments, but extend to the various modifications and equivalents as defined in the appended claims.