Abstract:
A containment apparatus for protecting a surrounding environment from leaks originating from a stuffing box is provided. In some embodiments, the containment apparatus utilizes a float switch to switch off a pump associated with the stuffing box when the level of a liquid in the vessel exceeds a predetermined level. The switch can communicate ultrasonically with a receiver that relays a message to a user. In some embodiments, the vessel comprises two half vessels that are lined by a metal frame along there mating edges.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application incorporates by reference and claims the benefit of U.S. Provisional Application 62/138,253 filed on Mar. 25, 2015. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates to an apparatus for containing leaks from a stuffing box at a wellhead as well as methods for using the same. 
       BACKGROUND 
       [0003]    A common problem with wellhead production equipment is that many of the structures associated with a wellhead, such as a stuffing box and polished rod, are susceptible to leaking. As a result, the surrounding environment can be exposed to oil or other fluids which can have deleterious effects on local plants and wildlife. To solve this problem, devices are positioned around portions of the stuffing box and wellhead to contain the leaking material. However, prior containment devices suffer from one or more of the following problems: (1) tedious assembly of the device on the wellhead and tedious removal; (2) disassembly of the device to access the stuffing box; (3) disassembly of the device to visually inspect the stuffing box; (4) lack of a proper liquid seal; and (5) difficulty maintaining the device in a fixed position on the wellhead. As a result of these problems, wellhead operators are more reluctant to utilize containment devices ultimately leading to an increase in pollution. 
         [0004]    The present invention seeks to alleviate these problems by providing a containment apparatus that (1) is easily assembled on the wellhead, (2) provides a liquid tight seal around the stuffing box, (3) provides easy access to the stuffing box, and (4) allows for visual inspection or remote inspection of the stuffing box while the apparatus is in place. Such an invention promotes environmentally conscious behavior without the detriment of significant increases in cost and time. 
       SUMMARY 
       [0005]    As known to those skilled in the art, wellhead production equipment typically includes a stuffing box carried on the nipple of a pumping tee. The present invention provides a leak prevention apparatus or containment apparatus suitable for capturing leaks originating at the stuffing box. The apparatus includes a concave tub, a lid and a float switch. The concave tub comprises a wall having a first portion, which extends substantially vertically and terminates at an upper end in an upper rim, and a second portion, which extends substantially horizontally and terminates at an inner end in a lower rim. The wall extends from the upper rim to the lower rim. The lower rim defines a bottom aperture configured to receive a portion of a stuffing box therethrough in a fluid tight seal. 
         [0006]    The lid is positioned on the concave tub. The lid is dome-shaped and with an upper opening, which receives a polish rod therethrough in a water resistant seal. The lid also has a bottom rim, which mates with the upper rim of the concave tub. 
         [0007]    The float switch is mounted in the first portion of the wall such that the float switch is moved from an on-position to an off-position when a level of liquid in the concave tub exceeds a predetermined level. When moved to the off-position, the float switch wirelessly sends a signal to a monitor. 
         [0008]    The containment apparatus can further comprise an ultrasonic receiver configured to receive ultrasonic signals and send electromagnetic signals. The ultrasonic receiver is positioned remotely from the concave tub. When moved to the off-position, the float switch sends an ultrasonic signal to the receiver, and upon detection of the ultrasonic signal, the ultrasonic receiver sends an electromagnetic signal to the monitor. 
         [0009]    In another embodiment, there is provided a containment apparatus for protecting the environment from leaks originating from a stuffing box comprising a first half shell, a second half shell, and a lid. When the first half shell and the second half shell are joined together, they form a concave tub having a wall. The wall has a first portion, which extends substantially vertically and terminates at an upper end in an upper rim, and a second portion, which extends substantially horizontally and terminates at an inner end in a lower rim, so that the wall extends from the upper rim to the lower rim. The lower rim defines a bottom aperture configured to receive a portion of a stuffing box therethrough in a fluid tight seal. 
         [0010]    The first half shell can be made from metal or plastic and is defined around its periphery by a first portion of the upper rim, a first right edge, a first portion of the lower rim, and a first left edge. The first right edge and the first left edge each extend from the first portion of the upper rim to the first portion of the lower rim. The first right edge, the first portion of the lower rim and the first left edge are formed from a first metal frame attached to the first half shell. 
         [0011]    The second half shell can be made from metal or plastic and is defined around its periphery by a second portion of the upper rim, a second right edge, a second portion of the lower rim, and a second left edge. The second right edge and the second left edge each extend from the second portion of the upper rim to the second portion of the lower rim. The second right edge, the second portion of the lower rim and the second left edge are formed from a second metal frame attached to the second half shell. The second half shell is configured to join to the first half shell to form the concave tub; and, when joined, the first right edge mates with the second right edge to create a fluid tight seal, and the first left edge mates with the second left edge to create a fluid tight seal. 
         [0012]    The lid is positioned on the concave tub. The lid being dome-shaped and with an upper opening, which receives a polish rod therethrough in a water resistant seal. The lid also has a bottom rim, which mates with the upper rim of the concave tub. 
         [0013]    Other embodiments combined the features of the above two embodiments. In some embodiments, when the first half shell and second half shell are joined, a gasket can be positioned between the first half shell and second half shell so as to create the fluid tight seal. 
         [0014]    In some embodiments, the first frame comprises a lobe section defining a drain aperture located adjacent to the bottom aperture such that the liquids in the concave tub can be drained from the concave tub. The containment apparatus can further comprise a drain tube having a valve for controlling a flow of the liquids from the concave tub. 
         [0015]    In some embodiments, the first metal frame and second metal frame have a pivot-bolt connection. Also, embodiments can further comprise a grease zerk positioned in the wall. The grease zerk can include a hose extending from the grease zerk toward the bottom aperture such that grease can be applied to the portion of the stuffing box without opening the containment apparatus. 
         [0016]    Also, some embodiments utilize a lid comprising a first half portion and second half portion. The upper opening can be formed by a split gasket having a first half gasket mounted in the first half portion and a second half gasket mounted in the second half portion. The first half gasket and second half gasket interlock to form a water-resistant seal. The first half portion and the second half portion can each have a ridge adjacent to the upper opening 
         [0017]    In another embodiment, there is provided a method of monitoring a liquid level in a containment vessel comprising;
       (a) mounting the containment vessel on a stuffing box such that liquids leaked from the stuffing box collect in the containment vessel;   (b) detecting when the liquid level exceeds a predetermined level; and   (c) sending a signal when the liquid level exceeds the predetermined level, the signal resulting in an electronic message being received by a monitor.       
 
         [0021]    In the method, the signal can be an ultrasonic signal and the method can further comprise:
       (d) detecting the signal by an ultrasonic receiver positioned remotely from the stuffing box;   (e) converting the ultrasonic message into the electronic message; and   (f) sending the electronic message to the monitor.       
 
         [0025]    In the method, the ultrasonic receiver can be located from 5 to 200 feet from the stuffing box, 10 to 100 feet from the stuffing box, or can be 15 to 50 feet from the stuffing box. Also, the electronic message can be selected from the group consisting of text messages and email messages. Additionally, the method can further comprise shutting down the well when the liquid level exceeds the predetermined level. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1A  is a front view of a stuffing box assembly on a wellhead. 
           [0027]      FIG. 1B  is a perspective view of a stuffing box assembly on a wellhead. 
           [0028]      FIG. 2A  is a side perspective view of a containment apparatus with a lid in accordance with one embodiment. 
           [0029]      FIG. 2B  is a rear perspective view of the containment apparatus of  FIG. 2A . 
           [0030]      FIG. 3  is a perspective view of a containment apparatus with a partial lid shown. 
           [0031]      FIG. 4  is a perspective view of a float switch in accordance with one embodiment of the invention. 
           [0032]      FIG. 5  is a containment vessel having a metal frame in accordance with one embodiment. 
           [0033]      FIG. 6  is a front view of the containment vessel of  FIG. 5 . 
           [0034]      FIG. 7  is a sectional view of the containment vessel of  FIG. 5 . 
           [0035]      FIG. 8  is a top view of the containment vessel of  FIG. 5 . 
           [0036]      FIG. 9  is a perspective view of a first half portion of a lid for a containment vessel. 
           [0037]      FIG. 10  is a schematic representation of a well having a pump and a stuffing box utilizing a containment apparatus in accordance with one embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0038]    In the description that follows, like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of the invention. The terms “inwardly” and “outwardly” are directions toward and away from, respectively, the geometric center of a referenced object. Where components of relatively well-known designs are employed, their structure and operation will not be described in detail. 
         [0039]    Wellhead production equipment typically includes a stuffing box carried on the nipple of a pumping tee. The present disclosure provides a leak prevention apparatus suitable for capturing leaks originating at the stuffing box. As will be understood upon review of the drawings and description provided herein, the present disclosure describes improved structures and methods for the leak protection apparatus. The present disclosure also describes a method and apparatus for remotely monitoring the liquid levels in the containment apparatus. Additional improvements will be apparent upon review of the appended drawings and written description thereof. 
         [0040]    To provide a frame of reference for the present invention,  FIGS. 1A and 1B  depict a typical stuffing box  100  on a wellhead. In relevant part, the stuffing box can comprise a polished rod  102 , a stuffing box base  104 , a nipple  106 , a pumping tee  108 , a flange  110  and a lube cap  112 . Containment apparatus  200  shown in  FIGS. 2A and 2B  is suitable for mounting at various places on stuffing box  100 , including at flange  110  and at nipple  106 . 
         [0041]    Turning now to  FIGS. 2A and 2B , containment apparatus  200  of the present invention can be divided into essentially three primary components: (1) a containment vessel or tub  300 ; (2) a topper or lid  400 ; and (3) a liquid level monitoring system, which generally comprises at least a float switch  210 . 
         [0042]    As depicted in the figures and as best seen from  FIGS. 3-5 and 10 , a float switch  210  is mounted in the wall  302  of the tub  300 . The float switch has a float arm  212  within tub  300  that is moved by rising liquid levels in the tub from an on-position to an off-position. Generally, float switch  210  is connected to the well pump  214  ( FIG. 5 ) so as to be able to turn on or off the will pump based on the liquid levels within tub  300 . The connection can be a hardwire connection, wireless connection, pneumatic connection, or similar. That is, when float switch  210  is in its on-position, pump  214  can operate but, when float switch  210  is in it off position, pump  214  is prevented from operating. 
         [0043]    In some embodiments, housing  208  of float switch  210  contains a transmitter and a battery to supply power to the transmitter. The transmitter is configured to send a signal when the float switch moves to the off position. Additionally, housing  208  of float switch  210  will be sealed so as not to let liquids and/or gasses penetrate into the housing area where the transmitter and battery are located. 
         [0044]    In other embodiments, the transmitter can be wired into the pumping unit or well pump  214 . The transmitter is configured to send a signal when the float switch turns off the pump. 
         [0045]    In either embodiment, the transmitter can be configured to send any suitable signal such as an electromagnetic signal or an ultrasonic signal. The electromagnetic signal can send a message directly through a cellular network to a person monitoring the well operation, such as the operator of the well. Hereinafter, such a person is generally referred to as a monitor. 
         [0046]    Preferably, the transmitter is an ultrasonic transmitter, which sends out an ultrasonic signal. Such an ultrasonic signal reduces the need for antennas and reduces risk in the hazardous area around the stuffing box, which can sometimes be a class  1 , division  1  hazardous zone. In such hazardous zones, electrical components exposed to gasses present in the hazardous zone create a risk of fire or explosion. If an ultrasonic transmitter is used, then an ultrasonic receiver  216  ( FIG. 10 ) is typically used within range of the ultrasonic transmitter. Ultrasonic receiver  216  typically will be configured to transmit a signal over a cellular or satellite network. Thus, by using ultrasonic receiver  216 , antennas and other electrical components associated with sending an electromagnetic signal can be placed outside of any hazardous zone and, hence, reduce the risk of igniting flammable gases within the zone. For example, the ultrasonic receiver can be located from 5 to 200 feet from the stuffing box, 10 to 100 feet from the stuffing box, or can be 15 to 50 feet from the stuffing box. 
         [0047]    In operation, when little or no liquid is present in tub  300 , float arm  212  is in a lower position and float switch  210  is in its on-position such that well pump  214  can be run. Typically, in the on-position no signal is sent from float switch  210 . If the stuffing box is leaking, then liquid will collect in tub  300 . Eventually, the rising liquid levels in tub  300  will move float arm  212  from its lower position to a higher position such that float switch  210  is moved to its off-position. In the off-position, float switch  210  prevents well pump  214  from running thereby reducing or stopping leakage into tub  300  before the liquid capacity of tub  300  is exceeded. Also, in the off-position, the transmitter sends out a signal. 
         [0048]    If the signal is an electromagnetic signal, then float switch  210  sends a signal through a cellular network or satellite network to the monitor. The signal can be an electronic message, such as a text message, email message, pager message or similar, which the monitor can receive on a computer, smart phone or similar. In some embodiments, the electronic message can be sent to a website through a cellular network or through a satellite. The website receiving the message can then send out an email or test message to addresses that are listed on the account. Often there will be several pumps on the same system; that is, that send signals to the same website or to the same monitor of the wells. In such cases, the signal can contain a unique identifier such that the containment apparatus associated with the ultrasonic signal can be identified. For example, the electronic message can contain GPS information on the well&#39;s location or other information to identify the well or containment apparatus, such as a unique ID number. 
         [0049]    More typically, the signal will be an ultrasonic signal. A receiver positioned outside the hazardous zone receives the ultrasonic signal and in response sends out an electromagnetic signal, typically over a cellular network. The signal can be an electronic message, such as a text message, email message, pager message or similar, which the monitor can receive on a computer, smart phone or similar. In some embodiments, the electronic message can be sent to a website through a cellular network or through a satellite. The website receiving the message can then send out an email or test message to addresses that are listed on the account. 
         [0050]    Often there will be several pumps within ultrasonic transmission of the receiver. Each of the pumps can have a containment apparatus associated with its stuffing box. In such cases, the ultrasonic signal can contain a unique identifier such that the containment apparatus associated with the ultrasonic signal can be identified. The receiver in response to the ultrasonic signal then sends out an electronic message that identifies the containment apparatus. For example, the electronic message can contain GPS information on the well&#39;s location or other information to identify the well or containment apparatus, such as a unique ID number. 
         [0051]    The monitor of the well, such as the well owner or operator, receives the electronic message. The message typically shows the identification information for the well and that the well has been shut down. Because the message contains information to identify the well or containment apparatus, the monitor will know which well needs attention. 
         [0052]    Turning now to  FIGS. 5-9 , an improved version of the containment apparatus  200  is illustrated. The containment device has some common features with the device disclosed in co-pending application U.S. patent application Ser. No. 14/322,766, filed Jul. 2, 2014, and can be used either directly on a flange  110  or nipple  106  of the stuffing box  100  or can be used with an adapter ring as described in the previously mentioned patent documents. 
         [0053]    As best seen from  FIGS. 5-8 , tub  300  is a concave tub having a wall  302 . Wall  302  comprises a first portion  304 , which extends substantially vertically and terminates at an upper end  306  in an upper rim  308 , and a second portion  310 , which extends substantially horizontally and terminates at an inner end  312  in a lower rim  314 . Typically, first portion  304  and second portion  310  are connected by arcuate portion  316 . While described as separate portions, generally first portion  304 , second portion  310  and arcuate portion  316  are integral so as to form a seamless wall  302  extending from upper rim  308  to lower rim  314 . Upper rim  308  is configured to attach to lid  400 . Lower rim  314  defines a bottom aperture  318  and is configured to receive a portion of a stuffing box therethrough in a fluid tight seal, either directly or with the use of an adapter. The fluid tight connection with a stuffing box is further described in U.S. patent application Ser. No. 14/322,766. 
         [0054]    Tub  300  is composed of a first half shell  320  and a second half shell  340 , which when joined together form concave tub  300 . In describing tub  300  and its half shells the terms “left” and “right” are utilized to distinguish one side of tub  300  from the other side. For purposes of this description, the terms left and right are in relation to view looking towards face plate  301  in  FIG. 6 . It will be understood that the use of the terms “left” and “right” is for explanation purposes only and to ease understanding. 
         [0055]    First half shell  320  is made from plastic or a metal, such as aluminum, and is defined around its periphery by a first portion  322  of upper rim  308 , a first right edge  324 , a first portion  326  of lower rim  314 , and a first left edge  328 . First right edge  324  and first left edge  328  each extend from first portion  322  of upper rim  308  to first portion  326  of lower rim  314 . Further, first right edge  324 , first portion  326  of lower rim  314  and first left edge  328  are formed from a first metal frame  330  attached to first half shell  320 . As best seen in  FIG. 7 , inner end  312  of wall  302  interlocks into first metal frame  330  such that it is sandwiched between an upper frame member  332  and a lower frame member  334 . The interlock provides strength and guards against leaks by forming a fluid tight seal. Further, first half shell  320  can be attached to first metal frame  330  by glue and/or bolts  331 , see  FIG. 6 . 
         [0056]    Similar to first half shell  320 , second half shell  340  is made from plastic or a metal, such as aluminum, and is defined around its periphery by a second portion  342  of upper rim  308 , a second right edge  344 , a second portion  346  of lower rim  314 , and a second left edge  348 . Second right edge  344  and second left edge  348  each extend from second portion  342  of upper rim  308  to second portion  346  of lower rim  314 . Further, second right edge  344 , second portion  346  of lower rim  314  and second left edge  348  are formed from a second metal frame  350  attached to second half shell  340 . As best seen in  FIG. 7 , inner end  312  of wall  302  interlocks into second metal frame  350  such that it is sandwiched between an upper frame member  352  and a lower frame member  354 . The interlock provides strength and guards against leaks by forming a fluid tight seal. Further, second half shell  340  can be attached to second metal frame  350  by glue and/or bolts. 
         [0057]    First half shell  320  and second half shell  340  are configured to join to form tub  300 . When joined, first right edge  324  mates with second right edge  344  to form a first mating pair of frame edges. The first mating pair creates a fluid tight seal. Typically, at least one of first right edge  324  and second right edge  344  has a channel  362 . A gasket  364  is positioned in channel  362 , which allows gasket  364  to deform into channel  362  reducing the clamping pressure while still providing positive pressure on the gasket seal. Similarly, when joined, first left edge  328  mates with second left edge  348  to form a second mating pair of frame edges. The second mating pair creates a fluid tight seal. At least one of first left edge  328  and second left edge  348  have a channel  372  with a gasket  374  positioned therein, which allows gasket  374  to deform into channel  372  reducing the clamping pressure while still providing positive pressure on the gasket seal. 
         [0058]    First half shell  320  and second half shell  340  can each be connected by pivot-bolt connections or swing-bolt connections. A suitable swing-bolt connection can be best seen from  FIGS. 5 and 8  where swing bolts  376  attached to second left edge  348  and first right edge  324  with a barrel nut  378  mounted in lobes  380  on frames  330  and  350 , respectively. The barrel nut attachment allows swing bolt  376  to pivot about. When swing bolt  376  is pivoted into place on the first left edge  328  or second right edge  344 , it can be held in place by a roll pin  382 . Thus, when only one side of tub  300  has its swing-bolt held in place with roll pin  382 , the first half shell  320  and second half shell  340  can pivot about the swing-bolt connection to allow opening and closing of the two half shells without totally disconnecting them. Accordingly, tub  300  can be easily mounted on a stuffing box by hinging tub  300  open and closing it when tub  300  is correctly positioned. Upon positioning tub  300 , the swing bolts  376  on each side can be tightened to clamp together first half shell  320  and second half shell  340  in a liquid tight seal. This hinge and clamping system allows the two half shells to be parallel when being clamped together for better alignment and to eliminate gasket pinch on the hinge side. Additionally, it is desirable that gaskets  364  and  374  be sized so that the gaskets come into contact with both frames and forms a liquid tight seal before the frames are completely clamped together; i.e. touching This allows the two half shells to be fitted on a larger range of stuffing boxes because the halves do not need to be completely closed in order to seal. 
         [0059]    In some embodiments, first metal frame  330  and second metal frame  350  extend circumferentially around bottom aperture  318  as illustrated in  FIG. 8  and can have lobe sections  384  extending radially outward from bottom aperture  318 . At least one of lobe sections  384  can define a drain aperture  386 . As can be seen from  FIGS. 5-7 , drain aperture  386  can be connected to a drain tube  388  having a valve  390  for controlling the flow of liquids from tub  300 . Accordingly, bottom aperture  318  allows liquids in tub  300 to be drained from tub  300 . When tub  300  is made of plastic, the metal frame provides a stronger connection for drain tube  388  than the plastic portion of tub  300 , thus aperture  386  is less prone to deforming or cracking that could cause leaks and/or drain tube  388  to pull out from aperture  386 . 
         [0060]    In some embodiments, tub  300  includes a grease zerk  392  positioned in wall  302  such that grease can be applied to a portion of the stuffing box without opening the containment apparatus. Grease zerk  392  can include a hose (not shown) extending from grease zerk  392  toward bottom aperture  318 . 
         [0061]    With reference to  FIGS. 2, 3 and 9 , the topper or lid  400  will now be described. As can be seed from  FIG. 2 , lid  400  comprises a first half lid  402  and a second half lid  404 , which together form dome-shaped lid  400 . Both half lids are identical.  FIG. 9  shows first half lid  402  but the following description applies to second half lid  404 . Half lid  402  has an upper opening with a half gasket  406  such that when half lid  402  and half lid  404  are fastened together the two half gaskets  406  form a complete gasket  408  defining a center aperture  410 . Thus, the complete gasket has a bulging disk shape with a hole in the center. A polish rod can be received through center aperture  410  such that gasket  408  forms a water-resistant seal with the polished rod. Half gasket  406  is partially contained in an upper rim  412  of half panel  414  so as to retain half gasket  406  in place. 
         [0062]    A half panel  414  floatingly interacts with upper lid base  416  such that it can slide relative lid base  416  to accommodate polish rods that might be askew, at an angle, or off center from the containment apparatus. Thus, half panel  414  can slide laterally with respect to lid base  416  but is still confined so as not to slide out of relationship with lid base  416 . The half panels of first half lid  402  and second half lid  404  attach together by means of a clip  418  and tab  420  with clip  418  of one of the half panels securing over tab  420  of the other half panel. Typically, clip  418  and tab  420  will be formed on upper rim  412 . Also, ridge  422  can be formed on half panel  414  on or adjacent to upper rim  412 . Ridge  422  provides for a place to push when connecting two half panels together. 
         [0063]    As can best be seen from  FIG. 3 , bottom rim  424  of lid  400  mates with upper rim  308  of tub  300 . Lid  400  can be attached to containment vessel  300  in a number of different manners, which will be apparent to those skilled in the art. Preferably, bottom rim  424  carries one or more downwardly projecting tabs  426 . (Only the upper surface of tabs  426  is visible in  FIGS. 3 and 9 .) Downwardly projecting tabs  426  are configured to be received by one or more bayonet mount receiving slots  396  spaced accordingly on an upper rim  308  of the containment vessel  300  (see  FIG. 3 ). Bottom rim  424  of lid  400  is placed on upper rim  308  of tub  300  such that downwardly projecting tabs  426  are aligned with the bayonet mount receiving slots  396 . The lid  400  is locked in place by turning it clockwise to move tabs  426  into the proper position with the bayonet mount receiving slots  396 . Lid base  416  can have handgrips  428  to facilitate turning of lid  400 . Handgrips  428  can be “snap-on” handles that attach by pushing so that slots  430  and clips  432  engage in locking relation. Slots  430  can be either on the handles or the lid base with the other having clips  432 . 
         [0064]    The tub can be manufactured from metal, such as aluminum, or from any thermoplastic or thermosetting plastic material suitable for injection molding including, but not limited to polyurethane, polyamide, polyethylene, polypropylene, polystyrene, acrylonitrile butadiene styrene or polyvinyl chloride. The thermoplastic or thermosetting plastic can optionally include glass or carbon fibers. Polyethylene is currently preferred for use for the tub when the application will be at temperatures at or below about 120° F. Metal or a glass-filled polyamide, such as Nylon, is currently preferred for use for the tub when the application will be at temperature above 120° F. 
         [0065]    It is currently preferred that the frame be manufactured from a metal, such as aluminum for strength and corrosion resistance. 
         [0066]    The lid can be manufactured using any durable plastic material. Transparent polycarbonate is currently preferred. 
         [0067]    The gaskets can be formed from a rubber or a rubber like elastomer. Currently, polyurethane or a fluoropolymer elastomer is preferred, such as Viton™ synthetic rubber by DuPont Performance Elastomers L.L.C. Vitona. 
         [0068]    Although the invention has been described with reference to a specific embodiment, the foregoing description is not intended to be construed in a limiting sense. Various modifications as well as alternative applications will be suggested to persons skilled in the art by the foregoing specification and illustrations. It is therefore contemplated that the appended claims will cover any such modifications, applications or embodiments as followed in the true scope of this invention.