Patent Application
20100180962
The present invention is directed generally to vacuum relief assemblies for containment vessels. More particularly, it is directed to vacuum relief assemblies which protect against contamination by airborne contaminants.
Containment vessels may be used to store and/or transport a wide range of materials including chemicals, foodstuffs and the like. Common forms of containment vessels are railway tank cars or highway tank trucks. Such vessels are generally operated at an interior pressure that is neutral or slightly positive relative to outside atmospheric pressure. These vessels, however, are typically not well suited to withstand vacuum conditions wherein the pressure at the interior of the tank car drops significantly below exterior atmospheric pressure.
To address the avoidance of vacuum conditions within a tank car or other containment vessel, it is generally known to utilize vacuum relief valves that open selectively to deliver air from the atmosphere into the interior of the vessel when the internal pressure drops below a predetermined level. This introduction of air is carried out by opening a normally closed flow path between the atmosphere and the vessel interior. Upon opening the flow path, air is pulled from the atmosphere into the vessel interior until the pressure differential is substantially eliminated. The flow path is thereafter closed until vacuum conditions reoccur. An example of such a vacuum relief valve is a valve available from Salco Products, Inc., Lemont, Ill.
While such systems are quite effective, the opening of the flow path may present an opportunity for contamination of the lading within the vessel by insects or other airborne particulates.
A vacuum relief assembly for a containment vessel is provided. The vacuum relief assembly includes a pressure activated vacuum relief valve including a valve body defining a flow path. The valve is adapted to be selectively opened to provide fluid communication from the atmosphere to the interior of a containment vessel. A screen member is disposed upstream of the inlet opening of the flow path to block ingress of airborne debris.
The following drawings illustrate exemplary embodiments and constructions of the present invention and, together with the general description given above and the detailed description set forth below, serve to explain the principles of the invention wherein:
Reference will now be made to the drawings wherein, to the extent possible, like reference numerals are used to designate like elements throughout the various views.
The illustrated tank car 10 includes a flange plate 20 disposed across a surface of the containment shell 12. It includes a threaded opening into the interior chamber of the shell 12 adapted to accept a vacuum relief assembly 22.
The vacuum relief assembly 22 defines a flow path to allow air into the interior storage chamber in the event that vacuum conditions develop within the interior storage chamber. The path is otherwise closed when atmospheric pressure and the pressure within the chamber are balanced.
In the illustrated arrangement, the vacuum relief assembly 22 is secured to the flange plate 20 within the threaded opening. It is, however, contemplated that the vacuum relief assembly 22 may be disposed at an opening within the containment shell 12 or at the hatch structure 14 or other suitable portion of the tank car 10.
One exemplary construction of the vacuum relief assembly 22 is illustrated in
The valve body 26 includes a lower end defining a securement portion. It includes threads 29 adapted to engage threads in the opening within the flange plate 20. The threads are illustrated as pipe threads (NPT) a common method of attachment. It is contemplated, however, that valve body 26 may include a bolt flange rather than a threaded end. In that instance the flange plate 20 would include a hole, opening into the interior of the shell 12 of vessel 10 and threaded studs arranged about the hole to receive the bolt flange of the valve body 26.
In order to facilitate threaded engagement, the illustrated valve body 26 includes a hexagonally shaped flange 32 to accept a wrench. It would, however, have any other commonly used torque-acceptance configuration to receive a tool to tighten or loosen the valve body 26 relative to the flange plate 20.
As shown, a shoulder surface 36 faces upwardly away from the flange 32. As best illustrated in
In the illustrated construction, mounting posts 46 project upwardly from the upper edge surface 38 of the upper sidewall 34 and define the upper end of the valve body 26. Each has a top surface 47 provided with a threaded hole 48. The mounting posts 46 are preferably integral with the upper sidewall 34 although they may be formed separately if desired. The outboard surface of the mounting posts 46 is preferably generally aligned with the outer surface of the annular upper sidewall 34. The arcuate open spaces 42 between the posts 46 define an inlet opening 40 with access to the atmosphere surrounding the vacuum relief assembly 22. The flow inlet opening 40 provides an open fluid communication path to the atmosphere and interior passage 28 of the valve body 26.
As best understood through reference to
As illustrated in
Head 61 is connected to elongate valve stem 64 extending axially of the interior passage 28 and slidable within guide surface 72. Its free end is threaded and receives a nut 67 that limits the position of a valve bushing 68 disposed at an upper end of the stem 64 remote from the valve head 61. A compression spring member 69 is held in a compressed condition between the valve bushing 68 and the spring support shoulder 74. As will be appreciated, such an arrangement continuously urges the valve stem 64 and head 61 upwardly to a sealing position with conical seat 65 sealed against conical seat 31 of body 26 as shown. In this normally closed position, fluid communication through outlet opening 30 is blocked between the interior passage 28 and the interior of the tank car 10.
In the event that the valve 60 is subjected to a downward force due to the occurrence of a negative pressure at the face surface 62, the valve 60 overcomes the biasing force provided by the spring member 69 and moves away from the illustrated sealing relation with seat 31 thereby establishing fluid communication between the interior of the tank car 10 and the interior passage 28 of valve body 26. Since the interior passage 28 is open to the atmosphere at communication paths defined by inlet opening 40, fluid communication is established between the interior of the tank car 10 and the atmosphere. Accordingly, due to a low pressure condition within the tank car 10, air flows from the atmosphere, through the interior passage 28 and into the interior of the tank car 10. This flow path remains open until the vacuum condition within the tank car is reduced to a level permitting the valve 60 to return to the normally closed and sealed condition.
As illustrated in
The screen member 50 of cylindrical construction is characterized by an inner diameter that is slightly larger than the outer diameter of the upper sidewall 34 and the mounting posts 46 to permit sliding insertion of the upper sidewall 34 into the interior of the screen member 50. The outer diameter of the screen member 50 is also less than the outer diameter of shoulder surface 36 provided by the hexagonally shaped flange 32 disposed below the upper sidewall 34 such that the shoulder surface 36 provides a support platform for the screen member 50. The height of the screen member 50 is substantially the same as the distance between the shoulder surface 36 and the top surfaces 47 of the mounting posts 46 defining inlet opening 40. The screen member 50 resides around the upper sidewall 34 and the mounting posts 46 in covering relation to the open spaces 42 between the mounting posts 46. Thus, screen member 50 is positioned upstream of the flow inlet opening 40. That is, air passing through the spaces 42 defining inlet opening 40 must first pass through the mesh of screen member 50.
In the illustrated arrangement best seen in
In the illustrated arrangement, the cap 52 is secured to the mounting posts 46 by attachment bolts 59 extending through holes 56 in top wall 53 and into threaded holes 48 in top surfaces 47 of the mounting posts 46. The top wall 53 of the cap 52 is held substantially parallel to the shoulder surface 36 with the cylindrical side wall 58 outwardly beyond the outer diameter of the screen member 50. The screen member 50 is thereby held between the surface 36 and the interior generally planar surface 54 of cap 52. The cap 52 thus closes the upper end of the cylindrical screen 50.
As will be appreciated, in the illustrated configuration the cap 52 serves to close the open end of screen member 50 against entry of insects or other debris. Thus, the screen member 50 and the cap 52 cooperatively prevent airborne contaminants from entering the inlet opening 40 while permitting air flow into the interior passage 28.
Once the screen member 50 is in position, it provides an air permeable barrier, upstream of inlet opening 40, to insects or other debris that may otherwise pass through the spaces between the mounting posts 46 that define inlet opening 40. At the same time, the screen member 50 preferably provides sufficient air permeability such that it does not substantially restrict communication between the interior passage 28 and the outside atmosphere. In this regard, it may be beneficial for the screen member to have open voids occupying about thirty percent (30%) or greater of the total screen area. That is, the ratio of open to solid area is at least 0.30. However, higher or lower open void percentages may be used if desired. By way of example only, and not limitation, one potentially desirable material for forming the screen member 50 is steel mesh having an open area of fifty to sixty percent (50-60%).
As shown, in the assembled condition, the sidewall 58 of the cap 52 overlies a portion of the screen member 50 in opposing spaced relation. In this regard, the inner diameter of the wall 58 of cap 52 is in close proximity to a portion of the exterior of the valve body 26 while nonetheless maintaining a sufficient space to maintain air flow to the screen 50 without substantial obstruction.
During the period of air flow, that is when valve 60 is open, air is pulled from the atmosphere and into the inlet opening 40 through screen member 50. The air enters the inlet opening 40, free of insects and other airborne debris which would otherwise pass into the interior passage 28. Once the pressure within the interior of the tank car has been increased to a desired level, the valve 60 is urged back to the normally closed condition until vacuum conditions reoccur.
Importantly, it is to be understood that the illustrated and described operational features of the valve assembly are exemplary only, and any number of other operating configurations may be utilized if desired. Accordingly, it is to be understood that the use of any and all examples, or exemplary language provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed.
No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein.
