US2699175A - Cold check valve - Google Patents

Description

Jan. 1l, 1955 R, 1 MAYHEW 2,699,175

COLD CHECK VALVE Filed June 26, 1952 INVEN TOR.

BY/Taerf layeu/ United States Patent COLD CHECK VALVE Robert L. Mayhew, Great Neck, N. Y., assignor to Hydrocarbon Research, Inc., New York, N. Y., a corporation of New Jersey Application June 26, 1952, Serial No. 295,767

7 Claims. (Cl. 137-106) This invention relates to check valves for use with reversing heat exchangers. More particularly this invention is directed to the problem of providing automatically operated valves at the cold end of reversing heat exchangers.

Reversing heat exchangers, such as those of U. S. Patent 2,566,310, issued September 4, 1951, to Burns et al., are now commonly used in plants for the liquefaction and rectification of air to transmit the cold content in the separated gases to the incoming air. The cold end of such heat exchangers is at a temperature of about 280 F., while the warm end is substantially at room temperature. For the successful operation of these reversing heat exchangers suitable reversing valves at each end of the heat exchangers are necessary. While mechanically operated reversing valves have been used at the opposite ends of exchangers, it has been found preferable to employ the mechanically operated valves only at the warm end and to use at the cold end check valves which are automatically responsive to changes in gas iiows brought about by the mechanically operated valves.

It is a prime object of this invention to provide a twoway check valve assembly for positioning at the cold end of a reversing heat exchanger which is automatic, leakproof, simple to construct and, above all, operative at low temperatures of the order of 280 F.

It is a further object of this invention to provide a two-way check valve assembly operated solely by the opposing forces of gravity and gas pressure and adapted to direct high pressure cold air from a reversing heat exchanger iiow path into an air header and, upon reversal, to direct cold low pressure separated gas from another header into the same-iiow path of the reversing heat exchanger.

These and additional objects and advantages of this invention will be apparent from the description which follows.

In accordance with this invention, two spaced gas headers, preferably parallel to one another and with the higher pressure header elevated above the other header, are communicatively connected to a gas duct by a check valve assembly. The check valve assembly comprises a central chamber communicating with the gas duct and having in its upper part an upwardly opening check valve permitting ow up into the high pressure gas header and in its lower part a similar upwardly opening check valve permitting flow up from the low pressure gas header. The gas duct connects the central chamber of the check valve assembly with a flow path of a reversing heat exchanger. A second check valve assembly similarly connects the two spaced gas headers with another flow path of the same reversing heat exchanger. Thus, with the two check valve assemblies, it is possible in one period of operation to have high pressure gas pass from one flow path of the reversing exchanger through one valve assembly to the high pressure header and low pressure gas pass from the low pressure header through the other check valve assembly to the other ow path of the exchanger. In the succeeding period of operation, high pressure gas passes from the second-mentioned flow path of exchanger through the second-mentioned valve assembly while low pressure gas passes through the firstmentioned valve assembly to the first-mentioned flow path of the exchanger.

The placement of the headers and the check valves 1n the same vertical plane affords a compact arrangement which can advantageously be positioned close to the cold end of a reversing heat exchanger.

In the accompanying drawings forming a part of this disclosure and showing for purposes of exemplification a preferred form of the invention without limiting the claimed invention to the illustrative instance:

Figure 1 is a perspective view of two check valve assemblies with a schematic showing of their connection to two flow paths of a heat exchanger;

Figure 2 is a cross-sectional elevation of the valve arrangement of Figure l, taken in a plane normal to the topi and bottom gas headers and including the line 2--2; an

Figure 3 is an expanded partial view of the sealin engagement of the valve face with the valve seat in the lower half of the valve assembly of Figure 2.

Figure 1 shows the valve assembly 10 positioned between a lower nitrogen header 12 and an upper air header 13. Port 14 is the gas ow connection between a central chamber 16 of the valve assembly and the cold end of heat exchanger 15'. The central chamber 16 has a valve body which is a cylindrical tube 17 connected to the top of central chamber 16 and leading vertically up into air header 13. Projecting downwardly from air header 13 is an outer tube 18 radially spaced from and circumferentially surrounding valve body tube 17. Tube 18 is attached at its bottom to tube 17 by seal ring 19, which may be welded both to outer tube 18 and inner tube 17. A normally plugged drain hole 20 is provided in outer tube 18. Similarly, the bottom of central chamber 16 is provided with an outer tube 22 having a normally plugged drain hole 21. Outer tube 22 may extend up into chamber 16 and be provided with drain holes 23. An inner valve body tube 25 is attached to nitrogen header 12 and passes up into central chamber 16 inwardly of and radially spaced from tube 22. At the bottom of outer tube 22, a sealing member 26, similar to member 19, connects tubes 22 and 25 in gas tight sealing relationship.

A sleeve 27 is centrally suspended in tube 25 by a multiplicity of bars 28 arranged in spoke-like fashion which may be attached to the sleeve and the inner wall of tube 25 in any suitable manner, such as by Welding. At or near the ends of sleeve 27 are provided bushings 29. A rod-like or tubular valve stem 30 ts inside sleeve 27 and bushings 29 and is capable of axial movement therein. Bushings 29 have a close tit around valve stem 30 for preventing lateral movement while permitting the aforementioned axial movement. At the bottom of stem 30 is a stop made up of a nut 31 attached by threads or a cotter pin 32 or, as preferred, by both. Surmounting the nut 31 is a resilient shock-eliminating cushion 33. The materials known as Kell-F and Teflon are suitable as a cushion for low temperature operation.

Attached to the top of rod 30 is a valve head 34 which has a spherical top section 36 extending from a point above stem 36 to the outer edge of tube 25. The radius of the spherical section is preferably equal to the diameter of the valve. The bottom half of valve head 34, shown as member 35 on the drawing, is an imperforate surface of revolution extending from the periphery of top section 36 downwardly and inwardly in a smooth curve to valve stem 30. This curved bottom surface 35 channels gas passing up through valve body 25 in a relatively streamlined ow thereby reducing to a small amount the pressure drop inherent in a gas iiowing through a valve. The spherically curved top 36 offers valve head 34 greater structural strength than would a flat surface. Radial, spaced-apart supporting ribs or webs (not shown) extending between top 36 and bottom 35 are generally used to strengthen further valve head 34. The entire structure of valve head 34 is preferredly produced as an integral cast member. ln the center of top 36 is a nutlike plug 37 welded in place. The projecting portion of plug 37 may be of any suitable shape to fit a tool which may be used to rotate valve head 34 and/or lap in the valve face 38 and valve seat 39.

The valve face 38 on the outer edge of bottom 35 of valve head 34 comes into sealing engagement with cooperating valve seat 39 on top of tube 2S (Figure 3). The cooperating valve face and valve seat may be merely machined metal surfaces engaging at any desired angle. However, it is preferred to bevel tube 25 and provide a valve seat at a 45 angle and also to use a special hard material such as No. 6 Stellite for facing each of the two surfaces. The surfaces of the valve face is preferably a spherical sector, tangent to the surface of the valve seat at its mid-point.

The same structure is present inside upper tube 17 but its valve head 44 has not been shown in cross-section like head 34. At the top of air header 13 is a bellshaped cap 40 placed directly over the axial line of valve bodies 17 and 25, which when removed permits easy access into the valve structure during assembly or repairs. Cap 40 may be welded to header 13.

Figure 2 depicts the period of operation when high pressure air is entering valve chamber 16 through port 14 and forcing valve head 44 up while simultaneously maintaining valve head 34 closed to prevent any air leakage into nitrogen header 12. Due to the lower pressure in header 12, valve head 34 and tubes 22 and 25 are made larger than their corresponding members 44, 1S and 17 to permit the larger volumetric ilow of gas to take place with minimum pressure drop and to permit the low pressure gas in nitrogen header 12 to lift valve head 34 easily. The drain tubes 18 and 22 are optional and if used their positions and dimensions may be changed to alter the annular distance and the axial relationship between these drain tubes and their respective valve bodies. Omitting these drain tubes would necessitate minor structural changes readily apparent to workers in the art. For instance, valve body 17 may be attached directly to upper header 13 and valve body 25 directly to central chamber 16.

For the operation of the valve assembly, port 14 is connected to the cold end of ow path 45 of heat exchanger 15. During the period of operation when cooled air is llowing out of path 45 of heat exchanger 15, air at a pressure of say about 100 p. s. i. g. enters through port 14 into chamber 16. At all times there is a pressure in nitrogen header 12 of less than 10 p. s. i. g., usually below p. s. i. g. The pressure of the air in chamber 16 forces valve head 34 closed against its valve seat 39 and lifts valve head 44 and its associated stem until the cushioning member at the lower end of the valve stem comes into contact with the bottom of the supporting sleeve member. Air is thereby permitted to flow from path 45 of heat exchanger 15 through port 14 into central chamber 16 and thence through tube 17 past the open valve head 44 into air header 13. Figure 2 illustrates the position of the various members during air inilow. In the same period of operation, nitrogen flows from header 12 through a duplicate valve assembly S0 into ow path 46 of heat exchanger 15, the valve head in the lower half of assembly 50 being open and the valve head in the upper half being closed.

When a suitable reversing mechanism at the warm end of heat exchanger is operated to reverse the directions of flow in heat exchanger 15, air then ows out of path 46 (as shown by the dotted arrow) into the central chamber of valve assembly 50 and thence up into header 13. In the absence of a supply of air to path 45, the air pressure in header 13 forces valve head 44 closed and with loss of pressure in chamber 16, the low pressure inside nitrogen header 12 is sutlicient to raise valve head 34 and permit nitrogen to tlow from header 12 through valve assembly 10 to ow path 45 of heat exchanger 15. This flow continues until the reversal mechanism at the warm end of heat exchanger 15 is again operated to repeat the flows obtained in the first-mentioned period of operation. The solid arrows in Figure l show the gas flows in one period of operation and the dotted arrows show the flows after reversal.

The drain tubes 18 and 22 have been provided for use in starting up an oxygen plant. As the temperature of the equipment falls, some of the water vapor originally present in the air will condense out in chamber 16 and air header 13, and will collect in the annular passageways between tubes 17 and 18 and between tubes 22 and 25. The water is Withdrawn through drain holes 20 and 21 by removing plugs therefrom or by opening valved drain pipes connected thereto.

As previously indicated, pressure drops due to gas ow must be kept to a minimum. The large size gas conduits (usually over 6 inches diameter) and the stream* line shape of the valve heads cooperate to limit the gas pressure drop through the check valve assembly to about 1/2 p. s. i. or less.

It is a further advantage of this invention that with the exception of the valve heads, all the component parts of the check valve assembly may be made of ordinary, commercially available pipes, rods, plates, etc. This is particularly important in the light of the valve sizes, which are over 6 inches in diameter, and the high expense of casting large valve forms according to prior practice.

While a preferred form of the invention has been described, it is pointed out that modifications thereof are contemplated. For instance, the valve heads may be simplified by omitting the hard facing on each valve head where it meets the valve seat.

Since still dii-ferent embodiments of the invention can be made without departing from the spirit and scope or this invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A check valve comprising: a cylindrical chamber disposed with its axis substantially horizontal, said chamber being closed at one end and having an open port at the opposite end; a substantially vertical valve body tube extending from said chamber; a valve seat at one end of said tube; a sleeve axially suspended in said tube; a valve stem slidably mounted in said sleeve for axial movement therein; a valve head mounted on said valve stem, said valve head having thereon a valve face for sealing engagement with said valve seat when said valve head is pressed against said valve seat; an outer cylinder surrounding said tube in spaced relation thereto and forming an annular space therebetween into which may pass liquid that otherwise would enter said tube; und a drain hole near the bottom edge of said cylinder.

2. An apparatus as in claim l in which there are two such tubes and valves, one of said tubes extending vertically from the top of said chamber and leading to an upper high pressure header and the other of said tubes extending vertically from the bottom of said chamber and leading to a lower low pressure header, the valve in the lower tube opening upwardly into said chamber and the valve in the upper tube opening upwardly into said high pressure header, each of said tubes being surrounded by an outer cylinder as aforesaid.

3. An apparatus as in claim 2 in which there is a duplicate set of said tubes, valves and chamber similarly disposed between said high pressure header and said low pressure header, and the ports of the duplicate chambers are connected, respectively, to separate passes of a rcversing heat exchanger.

4. ln combination: an upper high pressure gas header; a lower low pressure gas header; and a check valve assembly, said valve assembly comprising a chamber with a port therein, a substantially vertical valve body tube extending from each of said headers to said chamber, a valve seat at the upper end of each of said tubes, a sleeve axially suspended in each of said tubes by radially extending bar-like members attached at their respective ends to the sleeve and its associated tube, a valve stem slidably mounted in each of said sleeves, and a valve head mounted on each of said valve stems, each of said valve heads having an imperforate hemispherically shaped top surface connected at its periphery to a uniform downwardly and inwardly extending imperforate bottom surface having near its outer edge a valve face for sealing engagement with its associated valve seat when the valve head is pressed down against its associated valve seat, whereby a relatively unobstructed and smooth passage is provided through each of said tubes when its associated valve head is raised.

5. An apparatus as in claim 4 in which a cushioned stop is mounted at the bottom of each of said valve stems for contact with its associated sleeve when its associated valve head is raised, and bushings are mounted at the opposite ends of each of said sleeves to prevent lateral movement of said valve stems in their respective sleeves.

6. An apparatus as in claim 4 in which the tube extending from the low pressure gas header and its associated valve head are, respectively, of greater diameter than the tube extending from the high pressure gas header and its associated valve head.

7. An apparatus as in claim 4 in which there is a duplicate check valve assembly similarly disposed between said high pressure header and sfr id low pressure header, and the ports of the duplicate chambers are connected, respectively, to separate passes of a reversing heat exchanger.

References Cited in the file of this patent UNITED STATES PATENTS Schuberth Feb. 11, 1890 Smith Feb. 7, 1899 Biedermann Mar. 24, 1925 MacLatche Dec. 16, 1930 Sharp et al. Feb. 25, 1941 Wright Jan. 10, 1950

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