Patent Application
20060180203
This invention relates generally to condensate removal devices in gas piping systems, and more particularly to a variable load steam trap that can be retrofitted into pre-existing steam traps.
Steam is an efficient and widely used heat transfer medium for transporting energy. An unavoidable by-product when using steam is liquid condensate (i.e., water) that forms when heat is transferred away from steam along pipes or at heat exchangers. When condensate collects inside pipes or other components, system efficiency is significantly degraded. Condensate also can cause a destructive water hammer, a shock wave that damages components and can cause serious injury to people nearby. Accordingly, condensate should be removed from steam systems as it forms.
A steam trap is a mechanical device used to drain condensate while retaining or “trapping” steam. Traps are typically positioned at natural low points in steam systems where condensate collects or ahead of control valves where condensate could impede proper valve operation. Most traps operate using the inherent difference in density between liquid and gas to separate the fluids. Ideally, each trap should be capable of draining a massflow, or load, of condensate that flows to its location in the steam system. Each trap should also be reliable in operation to avoid costly inefficiencies that arise when condensate collects or when live steam is released from a defective trap. Several types of steam traps are commonly available. Some are complex in design and subject to fail without frequent maintenance.
Many steam systems are of very old design and contain highly inefficient condensate traps. Moreover, these traps may have mechanical parts that are prone to failure. Accordingly, it is desirable to replace or augment these traps with steam restricters that are efficient and reliable.
One type of trap that is economical and reliable is a fixed orifice trap. A relatively small hole or tubular passageway in a trap permits condensate to drain through. These traps are comparatively inexpensive and there are no moving parts to corrode or fail. They are very effective in draining condensate while preventing release of live steam. The condensate flowing in a fixed orifice generally blocks entry of steam. An example of a steam restricter device having a fixed orifice configuration is shown in co-assigned U.S. Pat. No. 5,088,518, the disclosure of which is incorporated herein by reference. This device is particularly suited for retrofitting into existing steam traps because it is compact.
A drawback to fixed orifice traps is that they cannot accept large variations in condensate load. The diameter of the orifice is fixed, and therefore the capacity of the trap, which is proportional to area of the orifice and the flow velocity, is also substantially fixed. Orifices are sized to drain an expected load. The actual load, however, can increase by a factor of four or more if ambient temperature decreases and/or air is forced over a steam heat exchanger, causing heat transfer rates from the steam to increase and causing formation of a larger quantity of condensate. In the past, this has been partially compensated for by over-sizing the orifice for the particular application. An over-sized orifice not only passes more load, but possesses a valuable secondary benefit of a greater ability to pass solid debris. Small deposits of corrosion or other particulate matter may become mixed within the flow of condensate and can clog the trap. There is less tendency for solid particles to lodge in an orifice or passageway that is relatively larger. However, a trap having an orifice that is larger than needed for ordinary loads tends to permit release of live steam and is inefficient.
A second type of trap is a thermodynamic or disk type trap. An obstruction comprising a flat disk is captured within the trap but is movable in the trap between a closed position in which the disk blocks flow of fluid through the trap, and an open position in which the disk permits flow of fluid. The disk may cycle between open and closed positions, and when in the open position the trap is capable of handling a greater quantity of condensate load than a fixed orifice trap. Condensate flow initially raises the disk open as it flows in, effectively increasing the orifice size for larger volumes of condensate. When steam enters the volume around the disk, it changes the local pressure and lowers the disk, closing the trap, which stays closed as long as relatively higher pressure is maintained above the disk. An example of thermodynamic trap is shown in co-assigned U.S. Pat. No. 6,148,844, the disclosure of which is incorporated herein by reference.
Thermodynamic traps require some space in which to operate because of the movement of the disk and the size of the openings. Accordingly, thermodynamic traps are not retrofit into existing traps, but are added onto steam systems as separate and complete steam traps making no use of the existing structure, or are incorporated as part of new steam systems. Thus, conversion to a thermodynamic trap has heretofore required either a complete replacement of the existing trap, or replacement of the entire steam system.
In general, a steam restricter of the present invention is adapted to be retrofitted into an existing steam trap having a chamber, an inlet for admitting steam and condensate into the chamber and a drain for draining condensate from the chamber to a condensate return. The steam restricter generally comprises a body having an inlet passage positioned for opening to the chamber of the steam trap when installed in the steam trap and a cavity in the body, the inlet passage in the body extending to the cavity. A drain outlet passage extends from the cavity for passing condensate from the cavity to the drain of the steam trap when installed therein. A thermodynamic stop disk is disposed in the cavity for movement in the cavity relative to the body between an open position in which the stop disk permits fluid communication through the cavity from the inlet passage to the outlet passage and a closed position in which the stop disk blocks communication from the inlet passage to the outlet passage. A mating base is sized and shaped for connection to the drain of the steam trap so that passage of fluid in the steam trap to the drain is blocked except through the steam restricter when installed in the steam trap. The outlet passage extends through the mating base and opens into the steam trap drain when installed in the steam trap.
In another aspect of the invention, the steam restricter is capable of handling variable condensate loads and is compact for installation in small spaces. The steam restricter generally comprises a body having a central axis and an inlet passage including first and second inlet passage members for receiving steam and condensate into the body and a cavity in the body. The second inlet passage member extends parallel to the central axis of the body to a mouth where the second inlet passage member opens into the cavity. A drain outlet passage includes a drain passage member adapted for fluid communication with the cavity. The drain passage member extends parallel to the central axis of the body to a port. The cavity and port are at least partially in registration with each other along the central axis of the body. A thermodynamic stop disk is disposed in the cavity for movement relative to the body between an open position in which the stop disk permits fluid communication through the cavity from the second inlet passage member to the drain passage member and a closed position in which the stop disk blocks fluid communication from the second inlet passage member to the drain passage member.
Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
Referring now to the drawings, and in particular
As shown in
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The body 41 has an inlet passage, generally indicated 95, in the cylindrical portion 57 opening from the chamber 23 of the steam trap 3 to allow fluid to enter the body. In the illustrated embodiment, the inlet passage 95 comprises three first inlet passage members 99 (two of which are shown in
The inlet passage 95 includes a second inlet passage member, generally indicated 103, in the cylindrical portion 57 of the body 41 in fluid communication with the three first inlet passage members 99. In the illustrated embodiment, the second inlet passage member 103 is an axial bore in the cylindrical portion 57 of the body 41 that is coaxial with the central longitudinal axis L1 of the steam restricter 1. As shown in
Referring to
A drain outlet passage, generally indicated 135, is in fluid communication with the cavity 89 for passing condensate from the cavity to the drain 29 of the steam trap 3. The drain outlet passage 135 includes three cavity passage members 137 (two of which are shown in
The manifold 71 of the outlet passage 135 at the bottom of the cylindrical portion 57 is in fluid communication with the drain passage member 139 in the mating base 47 so that fluid can pass from the manifold to the drain 29 of the steam trap 3. In the illustrated embodiment, the drain passage member 139 extends parallel to the central axis L1 of the body 41 through the mating base 47 to a port 141 that opens into the drain 29 of the steam trap 3 to allow condensate to exit the steam restricter 1 and flow into the condensate return 15. The port 141 of the drain passage member 139 is in registration with the cavity 89 to allow condensate to flow from the cavity into the drain 29 via the drain outlet passage 135.
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A thermodynamic stop disk 175 is disposed in the cavity 89 and is supported by the top surface 59 of the cylindrical portion 57. As shown in
In one particular embodiment, the cylindrical portion 57 of the body 41 includes a condensate passage 181 comprising a fixed diameter orifice in the conical bottom wall 107 of the second inlet passage member 103. The condensate passage 181 is coaxial with second inlet passage member 103 and passes through the cylindrical portion 57 of the body 41 to the manifold 71. In the illustrated embodiment, the condensate passage 181 has a fixed diameter across the length of the passage. The diameter of the condensate passage 181 in the body 41 is selected based on the condensate load requirements of the specific application and should be sized to adequately drain an estimated ordinary quantity of condensate load. The condensate passage 181 is located in the conical bottom wall 107 at the low point of the inlet passage 95 in the steam restricter 1 whereby liquid that collects in the inlet passage will flow through the condensate passage to the drain outlet passage 135. Further, the position of the condensate passage 181 minimizes the occurrence of steam entering the passage because in normal operation liquid will collect on the conical bottom wall 107 of the second inlet passage member 103 and seal against the flow of steam through the condensate passage. In the event that steam enters the condensate passage 181, the steam will enter the manifold 71 which has a larger diameter than the condensate passageway. Once steam enters the manifold 71 from the condensate passage 181 it will expand and be more likely to condense into water prior to being released out the drain outlet passage 135.
The condensate passage 181 is sized for an expected constant load of condensate that enters the steam restricter 1. When the actual load is larger than the estimated load for which the condensate passage 181 is sized, condensate collects in the second inlet passage member 103 and begins to rise until the thermodynamic stop disk 175 is lifted. It is understood that the condensate passage 181 may be omitted from the steam restricter 1 of the present invention so that all liquid condensate passes through the second inlet passage member 103 and the three cavity passage members 137 of the drain outlet passage 135.
In use, the steam restricter 1 of the present invention allows condensate that collects in the steam trap 3 to drain to the outlet 29 of the trap and prevents steam from leaking from the steam system of the heater 7 through the steam restricter. As condensate collects in the steam trap 3, liquid will enter the first inlet passage members 99 and pass through the cylindrical portion 57 of the body 41 into the second inlet passage member 103. As liquid condensate fills the second inlet passage member 103 a small amount of liquid will pass through the condensate passage 181 in the conical bottom wall 107 of the second inlet passage. If a larger volume of liquid is received in the inlet passage 95 of the restricter, liquid will fill the second inlet passage member 103 and the thermodynamic forces in the body 41 cause the thermodynamic disk 175 to lift. When the thermodynamic disk 175 lifts, liquid will exit the second inlet passage member 103 and pass through the annular channel 129 forming the lower portion of the cavity 89 and into the cavity passage members 137. The condensate will flow through the cavity passage members 137 into the manifold 71 at the bottom of the cylindrical portion 57 of the body 41 and into the drain passage member 139 of the mating base 47. The mating base 47 is positioned in the drain 29 of the steam trap 3 so the condensate discharged from the steam restricter 1 enters the drain and the condensate return 15 attached thereto. In this way, condensate is allowed to exit the steam trap 3 through the steam restricter 1 while steam is prevented from passing through the restricter to the drain outlet 3. When the condensate has been drained through the drain outlet passage 135 of the restricter 1, steam will enter the cavity 89 which forces the thermodynamic disk 175 to close. It is understood that the disk 175 will cycle (raise and lower) based on the volume of condensate load received in the steam restricter 1.
The steam restricter 1 of the present invention is capable of operating efficiently over a wide range of load variations. A small constant load of condensate flows through the condensate passage 181 while larger fluctuations in condensate load pass through the inlet passage 95, cavity 89, and drain outlet passage 135 of the restricter 1. The modular design and interchangeability of the parts of the steam restricter 1 of the present invention allows the restricter to be modified to fit specific operating parameters. For example, the body 41 can be changed to increase or decrease the size of the condensate passage 181 if the constant condensate load of a specific application differs from what was expected for the application. Also, the mating base 47 can be changed to vary the diameter D of the lower portion 155 of the base to accommodate a variety of drain sizes. Further, the restricter 1 of the present invention with the first inlet passage members 99 being radial openings in the body 41 and the second inlet passage member 103 and three cavity passage members 137 being vertical openings, is compact so that the body has an overall size that may fit in a variety of existing steam traps 3.
The advantageous construction of the steam restricter 1 is illustrated by the method in which the device may be retrofitted to an existing steam trap 3. Prior to beginning the retrofitting operation, the particular steam system would be analyzed to determine the appropriate body 41 and mating base 47 for the particular operational characteristics (e.g., the expected condensate flow rates) of the steam system. The steam restricter 1 of the present invention requires less analysis of the existing steam system prior to the retrofitting operation because the steam restricter is capable of handling a range of condensate flow rates. To begin retrofitting the steam restricter 1, the cover 33 is unscrewed from the steam trap 3 and removed to expose the chamber 23. The existing steam restricter (not shown) is removed from the chamber 23. The steam restricter 1 is inserted into the chamber 23 with the lower portion 155 of the mating base 47 sliding into the drain 29. Insertion of the lower portion 155 into the drain 29 blocks communication from the chamber 23 to the condensate return 15 except through the steam restricter 1. The gasket 51 is positioned between the bottom surface 161 of the flange 157 of the mating base 155 and the drain 29 to seal the mating base in the drain. To secure the steam restricter 1 in the drain, a coil spring 53 of the type described above is selected from a plurality of coil springs having different relaxed lengths. The selected spring 53 will have a relaxed length greater than the vertical height between the top wall 77 of the cap 75 and the cover 33 of the steam trap 3. The lower end of the spring 53 is fitted on the cylindrical protrusion 91 of the cap 75 and the cover 33 is screwed back onto the bowl 21 of the steam trap 3. The spring 53 is then held in compression between the cover 33 and the cap 75 of the body 41 such that it exerts a force on the body of the steam restricter 1 that presses the outlet base 47 into sealing engagement with the gasket 51 mounted on the drain 29.
Maintenance of the steam restricter 1 consists of occasional cleaning of the annular filter 43 and condensate passage 181. The steam restricter 1 may be separated from the bowl 21 of the steam trap 3 by removing the cover 33 and lifting the steam restricter out of the chamber 23. After removing the gasket 51 and the mating base 47 from the body 41, the filter 43 may be slid off the body and blown clean. The condensate passage 181 as well as the first inlet passage members 99, second inlet passage member 103, and cavity passage members 137 of the cylindrical portion 57 of the body 41 may also be blown clean. The steam restricter 1 is reassembled and replaced in the chamber 23 by following the same steps described above for the initial retrofit of the restricter into the steam trap 3. Removal and replacement of the steam restricter 1 may be carried out without the use of any tools.
A steam restricter kit, generally indicated 189, for retrofitting a steam restricter is shown in
In operation, the steam restricter 251 of
When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
In view of the above, it will be seen that several objects of the invention are achieved and other advantageous results attained.
As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
