Abstract:
A kit for constructing a de-aerator that includes a concentrator is adapted to be connected to a standard pipe coupling. The concentrator is inserted in the path of liquid conveyed through the pipe coupling for aggregating gas, and directing the gas to a cavity. The cavity is encased by the fitting which is a vertical, cylindrical sheath with one end adapted to be inserted into standard pipe couplings, and the other end adapted to be connected with the cap. The cap includes a vent adapted to open and shut in response to lowering and raising of the level of the liquid in the cavity below/above a threshold, respectively.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is the first application filed for the present invention. 
   MICROFICHE APPENDIX 
   Not Applicable. 
   TECHNICAL FIELD 
   This invention relates to gas removal from liquid distribution systems, and, in particular, to a de-aerator for removing gas suspended in liquids used for temperature control in closed-loop heating and cooling systems. 
   BACKGROUND OF THE INVENTION 
   A common problem with liquid heating and cooling systems, and liquid distribution systems in general, is the accumulation of gas pockets in distribution pipes. Dissolved or suspended gases separate from the liquid and naturally collect at various points in the system. Accumulations of gas may cause vapor lock that inhibits the effective distribution of the heated or cooled liquid, diminishing the efficiency of the heating or cooling system. Gas pockets may also induce noise and cause damaging cavitation in liquid distribution pumps. The introduction of gas into liquid distribution systems is therefore usually carefully controlled, but it cannot be completely avoided. Maintenance procedures, oxygen infiltration, and the injection of fresh liquid into the system all introduce some gas into the system. 
   Liquids that readily dissolve gasses at a temperature and pressure at which the liquids are injected into a system, and emit the gasses under operating temperatures and pressures in the system, are especially prone to the problems associated with gas accumulation. Such liquids include water, which readily absorbs oxygen and other gasses when cool, but emits the absorbed gases when heated. Because of its availability and heat transfer properties, water is commonly used in heating and cooling systems. Besides the undesirable affects of vapor locks, oxygen is a principal agent responsible for the corrosion of metal. Consequently, the removal of oxygen from heating and cooling systems is all the more desirable. 
   Gas removal from heating and cooling systems is well known. The gas is removed using venting devices referred to as de-aerators that are connected in various ways to the distribution pipes of the heating and cooling systems. The known de-aerators are generally expensive units that include a plurality of components encased in one or more metal housings connected to the distribution pipes. Inexpensive de-aerators are available, but they are generally much less effective at removing gas from the liquid. 
   An example of an expensive de-aerator is described in U.S. Pat. No. 5,490,874, entitled DE-AERATOR APPARATUS, which issued to Hans L. Kuster et al. on Feb. 13, 1996. The de-aerator includes a housing that forms an upright cylindrical chamber having fittings on opposite sides for the connection of the distribution pipes. The liquid flows through the distribution pipes into the chamber, and gas extracted from the liquid is exhausted through a valve controlled vent. The valve is opened and closed by the motion of a float that is buoyantly displaced by the rise and fall of the level of the liquid in the chamber. When the level of the liquid is below a certain point the valve is opened, permitting the accumulated gas to escape. When the liquid level is above the certain point the valve is closed, preventing the contents of the chamber from escaping. A concentrator that partially disrupts the flow of the liquid through the chamber extracts the gas bubbles and microbubbles from a liquid flowing through the chamber. The concentrator has a large surface area to volume ratio to facilitate the removal of gas from the liquid. 
   The less expensive de-aerators are typically adapted to be threadedly attached to a pipe fitting, such as a venting nozzle of a radiator, or other heating appliance. The less expensive de-aerators are constructed in a similar way with a float-based valve venting mechanism, but do not include a concentrator with a large surface area for removing gas from the liquid. The less expensive de-aerators are therefore adapted to remove large bubbles of gas from the liquid that rise under the force of buoyancy, but are inefficient at extracting finer bubbles and microbubbles from the liquid. 
   A disadvantage of all the known de-aerators is that they are expensive to construct and/or require special fittings that are time-consuming to install in a heating or cooling distribution system. 
   There therefore remains a need for a low-cost de-aerator that is easily installed without special fittings, and capable of efficiently extracting gas from a liquid conveyed through a distribution system. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide a low-cost kit for constructing a de-aerator adapted to extract gas from a liquid conveyed through a liquid distribution system. 
   It is a further object of the invention to provide a kit that can be installed in a standard pipe coupling to facilitate installation, reduce installation time and reduce component cost. 
   Accordingly, the invention provides a kit for a de-aerator for removing gas from a liquid distribution system comprising a cylindrical fitting having first and second ends, the first end being adapted to be inserted into a connector of a standard pipe coupling, and connected to the connector in a fluid-tight seal. The kit further includes a cap adapted to be connected to the second end of the fitting in a fluid-tight seal. A valve with a valve stem is connected to a float for selectively closing the valve when the liquid rises above a predetermined level in the fitting. The float opens the valve when the liquid in the fitting is displaced below the predetermined level by the gas. The kit also includes a gas concentrator adapted to extract gas from the liquid flowing through the pipe coupling, the gas concentrator being directly received in the coupling beneath the float. 
   The extraction of gas is facilitated by the gas concentrator, which is captively held in the flow of the liquid. The gas concentrator is constructed with a large surface area to mass ratio, so that the liquid flows through the pipe coupling without being significantly impeded by the gas concentrator. The gas concentrator causes microbubbles and bubbles of gas to merge to form larger bubbles. The larger bubbles rise under the force of buoyancy and accumulate inside the fitting. 
   The cap preferably supports the vent that releases the gas when the liquid level in the fitting falls below a predetermined level. As an alternative, the vent may be supported by the fitting. 
   The kit in accordance with the invention is simple to construct, easily and quickly installed, simple to maintain, and very cost effective because the body of the de-aerator is a standard T-coupling that is readily available at low cost. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which: 
     FIG.  1 . is an exploded perspective diagram of a de-aerator constructed using a kit in accordance with the invention, the kit being installed in a standard T-coupling oriented in a vertical-to-horizontal run of pipe in a fluid distribution system; 
     FIG.  2 . is a cross-sectional view taken along lines A—A of  FIG. 1 , showing the de-aerator in a non-venting state; and 
     FIG.  3 . is a cross-sectional view of a de-aerator constructed using a kit in accordance with the invention in a gas venting state, the kit being installed in a standard T-coupling in a horizontal run of pipe in a fluid distribution system. 
   

   It will be noted that throughout the appended drawings, like features are identified by like reference numerals. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The invention provides a simple and inexpensive kit for a de-aerator that is installed in a standard T-coupling in a fluid distribution system, such as a radiant heating system, for example. The kit, generally indicated by reference  10 , is installed in a standard T-coupling  12  having connectors  12   a ,  12   b  and  12   c  which receive standard fluid distribution pipes (not shown) that are secured to the coupling  12  by soldering, threaded joints, or the like. The kit  10  includes a fitting  14  that is extruded, cast and/or machined to a diameter of a pipe received in the connector  12   a  of the coupling  12 . The kit further includes a cap  16  that is connected to the fitting  14  in a fluid-tight seal, and a gas concentrator  17 , which in this example is a metal mesh, as will be explained below in more detail. The gas concentrator  17  is inserted directly into an unobstructed fluid flow path between an inlet, the connector  12   b , for example, and an outlet, the connector  12   c , for example, of the coupling  12 . 
   The fitting  14  is a cylinder preferably threaded at one end to permit connection of the cap  16 , which is correspondingly threaded. The fitting  14  may be soldered or glued inside the pipe coupling  12   a , in a manner well known in the art. The fitting  14  is hollow and forms a chamber  19  ( FIG. 2 ) when the cap  16  is connected thereto. 
   The cap  16  preferably supports a valve  18 . The valve  18  includes a valve cap  20  that is vented to permit gas to flow out of the de-aerator. A float  22  is connected to a lever arm  24 , which is connected to a pivot support  21  affixed to the underside of the cap  16 . A valve stem  26 , engaged by the lever arm  24 , is biased by the action of a compression spring  30  to seal a venting channel  28 . The weight of the float  22  overcomes the bias of the compression spring  30  when the level of the liquid in the chamber  19 , by which the float is supported, is displaced below a certain threshold by accumulated gas. The compression spring  30  is captured between a valve stem centralizer  32  and a spring seat  33  in the venting channel  28 . The valve stem centralizer  32  guides the valve stem as it is reciprocated within the venting channel  28 , but does not inhibit the escape of gas through the valve  18 . As shown in  FIG. 2 , the amount of gas accumulated in the chamber  19  is inadequate to open the valve  18 . In comparison,  FIG. 3  illustrates a condition in which the amount of gas accumulated in the chamber  19  is adequate to displace the level of the liquid to an extent that the lever arm  24  is pulled downwardly by the weight of the float  22 . This causes the valve stem  26  to be moved downwardly against the force of the compression spring  30 , which opens the venting channel  28 , releasing the accumulated gas. Such valve mechanisms are known in the art. 
   The gas concentrator  17  may be any one of various shapes and constructions known in the art. Preferably the surface area to volume ratio is maximized so that the flow is not overly restricted, but the interaction with gas bubbles suspended in the liquid is enhanced. Typical gas concentrators known in the art include cylindrical wire brushes, helicoidal metal structures and rows of combs or bristles. An alternative that is robust, efficient and inexpensive to construct, is a wire mesh fabric cut in a sheet, and loosely coiled to form a substantially cylindrical wire mesh coil with a spiral cross-section. The size of the sheet is chosen so that the wire mesh coil is easily inserted into the fixture, but the wire mesh coil is captively held in the stream of liquid beneath the float  22 . As an alternative, the gas concentrator  17  may be a brush structure as shown in  FIG. 3 , and may be constructed from a synthetic polymer, for example. 
   The de-aerator functions to release gas from a fluid distribution system. Bubbles and microbubbles of gas are trapped by surface tension around parts of the gas concentrator  17 . These bubbles and microbubbles aggregate to form larger bubbles of gas, which rise under their buoyancy to accumulate a layer of gas in the chamber  19  of the vertically oriented fitting  14 . The gas displaces the liquid causing the level of the liquid  34  to drop. The float  22 , falling with the level of the liquid  34  causes the lever arm  24  to pivot enough that the valve stem  26  is separated from a valve seat of the venting channel  28 . The channel is thereby opened and venting of gas occurs. Evacuation of the gas through the venting channel  28  causes the level of the liquid to rise in response to fluid pressure in the distribution system. The rise in fluid level raises the float which closes the valve after the liquid rises above a predetermined level. 
     FIG. 3  is a cross-sectional view of the kit  10  installed in a T-coupling  40 , which includes connectors  40   a ,  40   b , and  40   c , in a horizontal run of pipe (not shown). The installation of the de-aerator  10  begins with the selection of a point in the liquid distribution system at which the de-aerator  10  is to be installed. Preferably the installation point(s) is(are) located so that the gases, which are lighter than the liquid, will naturally collect there. After the point(s) of installation is(are) selected, an appropriately configured T-coupling  40  is installed at each point(s). The T-coupling(s)  40  is(are) installed so that the connector  40   a  for receiving the kit  10  is substantially vertically oriented. The fitting  14  is connected to the T-coupling using solder or glue, for example. The gas concentrator  17  is inserted into the coupling  40  via connector  40   a , and the cap  16  is secured to cover the fitting  14  in a fluid-tight seal. 
   The connectors  12   a ,  40   a  of T-couplings  12 ,  40  preferably have greater cross-sectional area than pipes (not shown) to which the T-couplings  12 ,  40  are connected. This has two advantages. First, the gas concentrator  17  can be larger and therefore more efficient. Second, the flow rate of the liquid through the gas concentrator is slower than the flow rate through the pipes. The slowing of the liquid helps release gas bubbles that are suspended in the liquid. 
   It will be appreciated by those skilled in the art that there are numerous operationally equivalent embodiments of the valve mechanism, and the gas concentrators that can be used in a kit  10  in accordance with the present invention. It should also be understood that although the valve mechanism is supported by the cap, it may likewise be supported by a sidewall of the fitting  14 . 
   The embodiments of the invention described above are therefore intended to be exemplary only. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.