Abstract:
The invention is directed to a valve for gas under pressure, for example at temperatures below −100° C., comprising a body with a gas inlet, a gas outlet and a passage connecting the inlet with the outlet; a shut-off device for closing the gas passage; a spindle designed for operating the shut-off device; and at least one gasket between the spindle and the body. The valve further comprises at least one cavity around the spindle for accumulating particles separated from the at least one gasket while operating the spindle and the shut-off device, for example at temperatures below −100° C.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present invention is the US national stage under 35 U.S.C. §371 of International Application No. PCT/EP2015/064885, which was filed on Jun. 30, 2015, and which claims the priority of application LU 92493 filed on Jul. 4, 2014, the content of which (text, drawings and claims) are incorporated here by reference in its entirety. 
     
    
     FIELD 
       [0002]    The invention is directed to a valve for pressurized gas, more particularly for pressurized gas operating at low temperature like liquefied natural gas (LNG). 
       BACKGROUND 
       [0003]    Prior art patent document published CN 202140576 U discloses a low-temperature shut-off valve comprising a body with a gas inlet, a gas outlet and gas passage between the inlet and outlet, a hand wheel and shut-off device in the valve body for closing the gas passage by operating the hand wheel. The shut-off device comprises a movable closure member that is in threaded engagement with the body. A spindle supporting the hand wheel rotatably engages with the movable closure member. The spindle comprises a shoulder abutting against a corresponding shoulder on a cap portion of the body. A first gasket is provided between the shoulder of the spindle and the corresponding shoulder of the cap portion. This first gasket is ring shaped with a L-shaped cross-section. A portion of the gasket extends between the external surface of the spindle and the internal surface of the body. A second gasket is arranged around the spindle at a location that is more distal from the shut-off device. This second gasket is housed in the cap portion and is pressed by a sleeve that is in contact with the hand wheel via a sliding washer. The hand wheel is able to slide along the spindle and a spring is arranged between a distal end of the spindle and the hand wheel so as to press it towards the valve body. This urging force is transmitted to the sleeve via the sliding washer. This force is then further transmitted to the second gasket for pressing it against the external surface of the spindle. 
         [0004]    During operation of the above valve at low temperature, e.g. at less than −100° C. and even less than −150° C., as is usual with LNG, the gaskets made of elastomer become hard and frictional movement against them can produce elastomer particles. These particles can accumulate inside the valve and increase the torque necessary for operating it. Such valves require already a relatively high torque for operating them due essentially to the low temperatures and the resulting high stiffness of the gaskets. Any sensible increase in the operating torque is to be avoided. 
       SUMMARY 
       [0005]    The invention has for a technical problem to provide a valve that overcomes at least one of the drawbacks of the above mentioned prior art. More particularly, the invention has for a technical problem to provide a valve that is suitable for gases at low temperatures, e.g. below −100° C., while keeping a reduced operating torque and being gas tight. 
         [0006]    The invention is directed to a valve for gas under pressure, for example at temperatures below −100° C., comprising: a body with a gas inlet, a gas outlet and a passage connecting the inlet with the outlet; a shut-off device for closing the gas passage; a spindle designed for operating the shut-off device; at least one gasket between the spindle and the body; wherein the valve further comprises at least one cavity around the spindle for accumulating particles separated from the at least one gasket while operating the spindle and the shut-off device, for example at temperatures below −100° C. 
         [0007]    According to various embodiments, the valve comprises a first gasket and a second gasket, and a first cavity at least one cavity being between the first and second gaskets. 
         [0008]    According to various embodiments, the first cavity is shaped as a groove on the external surface of the spindle. 
         [0009]    According to various embodiments, the cross-section of the first cavity is generally rectangular shaped with a width that is more than 5 times higher, n various instances 10 times higher, than the height. The width is meant to be measured parallel to the longitudinal axis of the spindle and the height is meant to be measures perpendicularly to the axial direction. 
         [0010]    According to various embodiments, the cross-section of the first cavity is generally rectangular shaped with a width that is comprised between 1 mm and 8 mm, in various instances between 1 mm and 5 mm, and/or a height that is comprised between 0.1 mm and 1 mm, in various instances between 0.1 mm and 0.5 mm. 
         [0011]    According to various embodiments, the first cavity is in front of a cylindrical internal surface of the body that supports the spindle. 
         [0012]    According to various embodiments, the spindle comprises a shoulder axially abutting against a corresponding shoulder of the valve body, the first gasket being positioned between the shoulder of the spindle and the shoulder of the body. 
         [0013]    In various instances the first gasket has an at least generally rectangular cross-section. 
         [0014]    According to various embodiments, the shut-off device comprises a movable closure member housed in the valve body, the member cooperating with a seat around the gas passage in the body, a second cavity of the valve being formed in the member, the spindle engaging with the second cavity for actuating the member. 
         [0015]    According to various embodiments, the second cavity widens towards the spindle so as to be able to collect the particles separated from the first gasket while operating the spindle and the shut-off device. 
         [0016]    According to various embodiments, the second cavity widens up to the maximum diameter of the shoulder of the spindle. 
         [0017]    According to various embodiments, the external surface of the shoulder of the spindle tapers towards the closure member, the internal surface of second cavity on the member being shaped to conform to the tapering external surface of the shoulder. 
         [0018]    According to various embodiments, the movable closure member is in threaded engagement with the body, and the engagement between the spindle and the second cavity is in rotation. The spindle and the second cavity can slide relative to each other. 
         [0019]    According to various embodiments, the second cavity extends opposite to the spindle, beyond a proximal end of the spindle in the cavity to create a space for accumulating the particles from the at least one gasket. 
         [0020]    According to various embodiments, the body comprises a main portion that houses and guides the movable closure member, and an auxiliary cap portion that is screwed on the main portion and that bears the spindle, the first gasket and/or the second gasket. 
         [0021]    According to various embodiments, the auxiliary cap portion comprises a bore portion surrounding the shoulder of the spindle and configured for receiving, when the shut-off device is in an open position, an end of the movable closure element corresponding to the opening of the second cavity. 
         [0022]    According to various embodiments, the shoulder of the spindle comprises a surface that extends radially and that contacts the first gasket, the surface being raised at its external portion, and/or the shoulder of the valve body comprises a surface that extends radially and that contacts the first gasket, the surface comprises at least one rib at its external portion that penetrates the gasket. 
         [0023]    According to various embodiments, the second gasket cooperates with the cylindrically shaped external surface of the spindle, at an axial position of the spindle that is more distant from the shut-off device than the first gasket. 
         [0024]    According to various embodiments, the valve further comprises: a hand wheel in rotational engagement with the spindle; a sleeve around the spindle between the hand wheel and the second gasket; and a resilient biasing means acting between a distal end of the spindle and the hand wheel so as to axially press the hand wheel against the sleeve and thereby press the second gasket. 
         [0025]    According to various embodiments, the second gasket is a ring with a generally trapezoid cross-section with the larger base in contact with the spindle and the smaller base in contact with the body. 
         [0026]    According to various embodiments, one leg of the trapezoid cross-section of the second gasket is against a corresponding bevelled surface of the body and the other opposite leg of the trapezoid is against a corresponding bevelled surface of the sleeve. 
         [0027]    According to various embodiments, the larger base of the trapezoid cross-section of the second gasket comprises a recess, for example at a middle portion. 
         [0028]    According to various embodiments, the resilient biasing means comprises stacked Belleville washers. 
         [0029]    According to various embodiments, the valve comprises a cage housing the resilient biasing means and limiting the compression of the means by the hand wheel. 
         [0030]    The invention is particularly interesting in that its features permit to limit the torque necessary for opening and closing the valve, for example when used with gases at low temperatures where the gaskets, usually made of elastomer materials, become hard and stiff. This is particularly true for valves which cannot contain any loose lubricant like lubricating oil or grease. 
     
    
     
       DRAWINGS 
         [0031]      FIG. 1  is a sectional view of a valve in accordance with various embodiments of the invention. 
           [0032]      FIG. 2  is a magnified view of the area II in  FIG. 1 , in accordance with various embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    The valve  2  illustrated in  FIG. 1  comprises essentially a body  4 , a gas inlet  6 , a gas outlet  8  and a gas passage  10  fluidly interconnecting the inlet  6  and outlet  8 . 
         [0034]    A shut-off device consisting essentially of a movable closure member  12  is provided in the body  4  for closing the gas passage  10 . The movable closure member  12  is operated by a spindle  14  extending through the valve body  4 . 
         [0035]    The valve body  4  is comprised of a main portion  16  and a cap  18  that is attached to the main portion  16 , for instance by screwing. The main portion comprises a bore that houses the movable closure member  12 , the spindle  14  and the cap  18 . The movable closure member  12  is generally cylindrically shaped and comprises at its external surface a male thread that engages a corresponding female thread on an internal surface of the bore of the main portion  16  of the body. It comprises a front surface with a recess housing an element  121  of softer material that cooperates in a tightly fashion with a valve seat  20  that is formed in the valve body  4  around the gas passage  10 . The element  121  can be made of plastic material. 
         [0036]    The movable closure member  12  comprises also a cavity  122  that opens in a direction that is opposite to the element  121  and the valve seat  20 . This cavity  122  comprises a cylindrical internal surface that receives and engages in rotation only with a proximal end  141  of the spindle  14 . The proximal end  142  of the spindle  14  and the internal surface of the cavity  122  of the closure member  12  can take various shapes which are as such well known from the skilled person, e.g. splines or any section that is not symmetrical in rotation. 
         [0037]    The spindle  14  comprises a shoulder  142  that cooperates with a corresponding shoulder  181  and bore  182  on the cap  18 . A generally ring shaped first gasket  22  is housed in the chamber delimited by these two shoulders  142  and  181  and the bore  182 . 
         [0038]    The external surface  143  of the shoulder  142  of the spindle  14  can be bevelled so as to taper towards the shut-off device  12 . The shoulder  142  of the spindle  14  at the maximum diameter of the tapering external surface  143  closes the chamber that houses the first gasket  22  while keeping a minimal surface of contact between the external surface  143  of the spindle and the corresponding surface of the bore  182  of the cap  18 . 
         [0039]    In addition, the cap  18  forms a second bore  183 , larger than the first one bore  182  and positioned in front of the tapering external surface  143  of the shoulder  142  of the spindle  14 . This bore  183  can receive the raised end  123  of the movable closure member  12  that is opposed to the valve seat  20 . 
         [0040]    The cavity  122  in the movable closure member  12  widens towards the spindle  14 , thereby forming the raised end  123 . When operating the spindle  14 , the frictional forces acting on the first gasket  22  are likely to produce particles of the elastomer material of the gasket. Under the condition that the valve is positioned upwardly as illustrated in  FIG. 1 , e.g., with the axis of the spindle generally vertical and with the distal end  144  of the spindle  14  oriented upwardly, the particles separating from the first gasket  22  can fall downwardly by gravity and be collected by the funnel-shaped upper internal surface of the cavity  122 . The particles can then pass through the mechanical play between the external surface of the proximal end  141  of the spindle  14  and the corresponding internal surface of the movable closure member  12 , and then accumulate at the bottom of the cavity  122 . 
         [0041]    As is visible in  FIG. 1 , a passage  124  can be foreseen at the bottom of the cavity  122 , interconnecting the cavity with the housing for the element  121  cooperating with the valve seat  20 . 
         [0042]    The valve  2  comprises a second gasket  24  that is ring-shaped and with a trapezoid cross-section. The larger base of the trapezoid cross-section is in contact with the external cylindrical surface of the spindle  14  whereas the smaller base is in contact with the internal surface of the cap  18 . A sleeve  26  is slidably provided around the spindle  14  for pressing the second gasket  24 . 
         [0043]    The spindle  14  comprises at its external surface a groove  28 , the groove being between the first gasket  22  and the second gasket  24 . The groove forms a cavity that can accumulate particles separated from the gaskets  22  and  24 , more particularly from the second gasket  24 , similarly to the cavity  122  in the movable closure member  12 . The groove  28  can have a generally rectangular cross shape with a width that is larger, in various instances at least 5 times larger, for example at least 10 times larger than the height. 
         [0044]    The valve  2  comprises a hand wheel  30  that is in rotatable engagement with the distal end  144  of the spindle  14 . The hand wheel  30  can slide along the spindle while being in rotatable engagement. To that end the spindle  14  can provide a cross-section with a non-circular outer surface, e.g. a square outer surface, that engages with a corresponding inner surface of the hand wheel  30 . A sliding or anti-friction washer  32  can be interposed between the lower surface of the hand wheel  30  and the upper surface of the sleeve  26 . A stack of Belleville spring washers  38  is provided around the distal end  144  of the spindle  14 , between a nut  34  that is engaged with the distal end, and the hand wheel  30 . The spring washers  38  can be housed in an opened housing  36  that is interposed between the nut  34  and the springs  38  and that extends at the lateral surface of the springs up to close to the surface of the hand wheel that is in contact with the spring washers. The spring washers exert a biasing force on the hand wheel that is oriented downward, e.g., in the direction of the valve body so as to transmit that force to the sleeve  26  and to the second gasket  24 . The second gasket  24  is thereby constantly under pressure so as to cooperate in a gas tight fashion with the spindle  14 . The biasing force of the springs is also transmitted to the spindle  14  by means of the nut  34 . The spindle  14  is then biased upwardly, e.g., in a direction opposite to the valve body and that presses the first gasket  22  between the shoulders  142  and  181 , so as to provide a first gas tight barrier between the spindle  14  and the body  4 . 
         [0045]    The use of the housing  36  for the resilient biasing means  38  is interesting for it permits to keep the washers in position so as to work properly. It permits also to facilitate the assembly of the valve. In various instances, when tightening the nut  34  in order to pre-stress both first and second gaskets  22  and  24 , the nut can be tighten until the housing  36  contacts the hand wheel  30 , so as to ensure a minimum and also an adequate pre-stress of the gaskets. Any wear or matting of one or both of the gaskets will be compensated by the biasing force of the pre-stressed resilient means  38 . 
         [0046]    During operation of the valve, for example at low and very low temperatures, e.g., less than −100° C., or even less than −150° C., which is typical for liquefied natural gas (LNG), the material of the gaskets  22  and  24  becomes hard and stiff. The contact pressure between the gaskets and the spindle resulting from the mechanical pre-stress and/or the fluid pressure has for effect that the material of the gaskets can be subject to mechanical wear during rotation of the spindle, the wear resulting in the separation of material in small particles or even powder. These particles can accumulate at some places in the valve, for example between moving parts and non-moving parts, leading to an increase of the operating torque or even a blocking of the valve. The cavity  28  formed on the outer surface of the spindle  14  can accumulate these particles and avoid a blocking of the spindle  14 . In case the valve is in an upright position as illustrated in the  FIG. 1 , the cavity  28  can collect the particles from the second gasket  24  moving down by gravity. In case the valve would be in another orientation, e.g. with the spindle horizontal or downward, the cavity  28  can collect the particles from the first gasket  22 . The cavity  122  formed in the movable closure member  12  permits also to collect the particles from the first gasket  22 , for example when the valve is in an upright position as illustrated in  FIG. 1 . The funnel-shaped opening  123  of the cavity  122  is particularly useful for collecting the particles and prevent them from reaching the threaded engagement between the movable closure member  12  and the body  16 . 
         [0047]      FIG. 2  is a magnified view of the area II in  FIG. 1 , corresponding to the two gas tight barriers of the valve. 
         [0048]    It is exemplarily illustrated in  FIG. 2  that the surface  145  of shoulder  142  of the spindle  14  that contacts the first gasket  22  is not flat but rather is slightly bevelled. That surface  145  is shaped so that its external portion is closer to the shoulder  181  of the body than its internal portion. The shoulder  181  of the body comprises also a circular rib  184  that is intended to penetrate into the first gasket  22 . This rib  184  is positioned at an external circumferential portion of the shoulder  181  in order to be at least approximately aligned with the raised external portion of the shoulder  142 . The gasket  22  is therefore more stressed at its external portion so to be properly penetrated by the rib  184  and provide an adequate first gas tight barrier. 
         [0049]    It is exemplarily illustrated in  FIG. 2  that a flared external surface  261  of the sleeve  26  that can abut against the corresponding external surface  184  of the plug before the front end  262  contacting the gasket  24  would reach the bottom of the cavity of the gasket. 
         [0050]    Still in  FIG. 2  it can be observed that the shape of the second gasket  24  can have a trapezoid cross-section. The larger base  241  is in contact with the external surface of the spindle  14  whereas the smaller base  242  is in contact with the internal surface of the plug  18 . The larger base  241  can comprise a groove  243  that provides some room for deformation of the gasket. The side or leg  244  is in contact with the corresponding surfaces  262  of the sleeve  26  and the other opposite side or leg  245  is in contact with the corresponding surfaces  185  of the sleeve plug  18 . The axial force exerted by the sleeve  26  via its contact surface  262  is converted into a radial force thanks to the inclination of the surfaces  262  and  185 . 
         [0051]    In various embodiments, the different elements of the valve  2 , like the main body  16 , the plug  18 , the spindle  14  and/or the movable closure element  12  can be made of brass, steel and/or stainless steel. In various embodiments, some elements, such as the movable closure element  12  and/or the spindle  14  can be coated with Teflon® so as to lower the frictional forces.