Abstract:
A process control valve is disclosed including a valve body assembly which includes process fluid input and output ports, an actuation pressure port and a vent port. The valve body includes a cylinder with two pistons longitudinally spaced and separated by a biasing means such as a spring. The pistons each have a rod which acts as a seal for a process fluid port when normally biased by the biasing spring. The actuation port of the body assembly communicates with the opposite faces of the pistons from the bias spring to open the process fluid input and output ports by overcoming the biasing port closing force. The two pistons include rods having process fluid passageways therethrough. The pistons also include a valve poppet &amp; seat combination which is closed whenever actuation force is applied to the process control valve sealing the process fluid path from the vent port. A reversible input/output valve is disclosed as well as a modular assembly of interchangeable valves is disclosed.

Description:
REFERENCE TO RELATED APPLICATION 
     This is a divisional application based upon non-provisional application Ser. No. 09/172,113 filed Oct. 13, 1998, now U.S. Pat. No. 6,125,884. Applicant requests benefit of the Oct. 13, 1998, filing date of application Ser. No. 09/172,113. 
     This is a non provisional application based upon provisional application Ser. No. 60/062,464 filed Oct. 15, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     In the field of chemical process sampling, there has been a divisional application based upon a long felt need for improved sampling valves. Either single or multiplex valves are needed to sample an ongoing chemical process by receiving gas or liquid and upon control actuation, extract a sample of a process stream to be introduced into a chemical process analyzer such as a gas or liquid chromatograph and after the sample is taken, the valve is closed to the process stream. 
     In multiplex applications a number of valves are each coupled to a different stream at their input and to a single process analyzer at their output. The valves are actuated at different times to provide sampling of each of the streams without intermixing or cross contamination of samples. At the close of the sampling cycle, any residual of the sample stream is discharged from the actuated valve via a common vent output. 
     Since the valves must be usable in a variety of industries, sampling of a variety of process streams is expected. It is therefore essential that the valves be chemically resistant and diffusion resistant to the sample streams, which they might encounter. More specifically, they must be chemically resistant to material such as strong oxidizers, reducing agents, petrochemicals, especially aromatics and any combinations of such compounds. 
     Since the valves may be sampling streams from a process which is conducted at elevated or refrigerated temperatures, the valves must operate reliably in a range of the least 0 degrees F. to 300 degrees F. 
     The valves need to have a high degree of external leak integrity to prevent fire or toxic hazard as well as to minimize what is termed, fugitive emissions. 
     From the structural standpoint, the valves need to be small in size, simple in design and preferably available for assembly into a variety of modular forms for multiplexing a number of valves together at the input of the single process monitor. 
     The selection of materials for the valve&#39;s structure, as well as its essential seals, must all meet the standard of chemical and diffusion resistance as well as freedom from abrasion or wear which could cause contamination of samples, wear, leaks and shortened operational life. For a truly acceptable valve, some minimum one million cycles of trouble-free operation is needed. 
     Internally, it is desired that the flow path from the input stream through the valve be as straight or clear is possible, of minimum volume, and without dead end passages which can retain sampled fluid after the sample procedure is completed. 
     Heretofore, single valves and multiplex valves have been developed but they have failed to meet all of the standards set forth above. Complexity of design, the requirement of numerous seals and presence of confined passage ways have been common. The need for many seals, the failure or abrasion of any one of which may cause leak or contamination of the sample has definitely been the major cause of shortened life of the valves. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Faced with the foregoing state-of-the-art, I have determined that it is possible to develop such compact reliable process stream sampling valves which may be using alone or in multiple valve assemblies and achieve an operational life of at least one million cycles of trouble-free operation and without cross contamination or unwanted discharge of the sample stream. 
     I have accomplished all the foregoing objectives in a valve which is basically a rectangular valve body which defines a two-part cylinder with two independent operating pistons, each with a piston rod carrying a valve seal. The two pistons are biased away from each other to provide the closure of the two valves or ports namely the input valve or port and the output valve or port. The pistons are biased away from each other by single spring to normally maintain both of the input and output ports closed. When actuated at an actuation port, the actuation pressure is in communication with the opposite sides of both pistons from the common bias force, namely the spring, whereby the actuation pressure simultaneously opens both valves or ports by moving the pistons toward each other and closes the vent port. 
     The pistons on their adjacent faces include a valve seat and a valve poppet aligned and positioned so that upon actuation of the sampling valve, actuation pressure opens the input and output valves or ports, a vent valve or port which is normally in communication with the vent port is closed and the passages within the two pistons define a process gas flow route through the valve body and their piston rods between the inlet port and the output port. The outlet port is normally coupled to suitable analytic apparatus such as a gas chromatograph. 
     Only two sliding seals on the piston rods, two poppet seat seals and one poppet of the inlet and outlet valve, and the seal of the vent valve are exposed to process gas or liquids. Any remaining seals are either static or travel in the valve in areas which are not normally exposed to the primary process gases or liquid. 
     The valves are exceedingly simple in design, few parts are required and unessential parts such as end plates and mounting brackets are eliminated while improving the performance and versatility and ease of selection and installation. The interior volume of the process sampling valve of this invention, exposed to the process fluids sampled, is held to a minimum. The valves may be tailored to different and extreme process environments merely by change of relatively few seals to match the requirements of the process stream to be monitored. 
     This invention may be characterized as a normally closed, pneumatically operated, double block and bleed valve, designed for stream selection in liquid or gas analytical systems. The double block and bleed type valve provides leak integrity to assure against cross contamination of sample streams in multiple stream configurations. The bleed feature minimizes the chance of the previous sample stream being trapped inside the valve during analytical cycles. 
     Each compact module is designed to handle one stream. Multiple module configurations are available to handle multiple streams. In a multiple module configuration, the outlet ports are common to eliminate dead volume. Each module(s) is mounted on a base that contains a common outlet and vent port. The inlet and air actuator ports are located on each individual valve module. An individual valve module may be removed without disturbing the sealing integrity of other modules. Modules are simple to disassemble for easy maintenance. 
     Tapered Kel-F seats are used to seal the inlet, outlet and vent valve ports to eliminate leakage and chemical attack in liquid and gas systems. The flow path through each valve is unrestricted to minimize pressure drops. Internal volume is also minimized to 0.48 cc. 
     Operating pressure ranges of 300 PSIG (21 bar) and 500 PSIG (35 bar) and operating temperatures up to 300° F. (150° C.) allows for a variety of system designs. The minimum 40 PSIG actuating pressure is ideal for systems where there may be fluctuations in air pressure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     This invention may be more clearly understood with the following detailed description and by reference to the drawings in which: 
     FIG. 1 is a front elevation view of a stack mounted assembly of a number of process stream selector valves each in position for input of a process stream to be sampled from the top and with rear side outlet and venting ports; 
     FIG. 2 is a side elevational view of the stack of process stream selector valves of FIG. 1 showing a common base plate on the rear side of the stack of valves with stream outlet and vent outlets for the entire stack located at one end of the base plate; 
     FIG. 3 is a longitudinal sectional view through one of the process stream selector valves of FIG. 1; 
     FIG. 4 is a transverse sectional view through a full valve of FIG. 1 taken along the line A—A of FIG. 3; 
     FIG. 5 is a longitudinal sectional view of a valve of FIG. 1 similar to the sectional view of FIG. 3 but in a normally closed position; 
     FIG. 6 is a sectional view of a full valve taken along line B—B of FIG. 5; 
     FIG. 7 is a top plan view of a single valve of FIG. 1 showing the inlet port as well as the mounting holes, the latter of which are shown in dashed lines; 
     FIG. 8 is a longitudinal sectional view of another embodiment of this invention designed for in-line mounting with operational symmetry in which either end valve may be used as inlet or outlet port and with the process sampling valve assembly shown in the closed or process flow gas isolation or non-sampling condition; and 
     FIG. 9 is a longitudinal sectional view of the embodiment of FIG. 8 shown in a process fluid sampling or actuated condition. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Now referring to FIG. 1 in combination with FIGS. 2 and 7, a typical installation of a series of three process stream selector valves  10 ,  11 , and  12  can be seen in which three separate lines of fluid samples may be introduced into inlet ports  10   i,    11   i  and  12   i,  respectively, by operation of a remote control to introduce valve actuating pressure to any of the valves  10 - 12  at their respective actuating port  10   a,    11   a  or  12   a.    
     The actuating pressure is typically in the form of pressurized air is introduced to operate each of the valves upon command from external controller which is unshown in the drawing but is well known in the process stream sampling art. The process stream from any one of the normally closed inlet ports  10   i - 12   i  may be passed through the actuated valve to the respective outlet port  10   o - 12   o  of each individual valve as is shown and described below in connection with FIGS. 3 and 5. 
     The process stream sample from such individual outlet port is transferred to common outlet port  13  of FIG. 2 which is located in a single common base  15  which also is preferably designed to mount all the valves  10 - 12  and provides not only a common output port  13  but a common vent port  14 , as well. The base then acts as an output manifold. The valves  10 - 12  are all secured to the base  15  by fasteners  17  such as machine bolts and each may be removed separately and replaced by a blank which seals the output port  10   o - 12   o  and the vent port  10   v - 12   v  opening in the base  15  appearing in FIGS. 3 and 5. A blank plate with suitable  0  ring groove will suffice. 
     Whenever any of the valves  10 - 12  are not actuated, all non-actuated or closed valves block the flow of process gas at their respective inlets  10   i - 12   i  but their vent ports  10   v - 12   v  are all in communication with the common vent port  14  of FIG.  2 . 
     Now referring specifically to FIGS. 3-5 which are longitudinal sectional drawings of a valve  10  or its identical counterparts  11  and  12  of FIG. 1 to show its internal operating elements. FIG. 3 shows the valve  10  in an actuated or operated condition with flow lines showing the path of a process stream sample from inlet port  10   i  to the outlet port  10   o  as is described in more detail below. 
     Valve  10  may be seen as including a body  20  having its inlet port  10   i  located in an inlet plug  16  which is secured to the inlet end to the body  20  by a threaded cap  22  and sealed to the body  20  by a composite static seal 16 SS in the preferred form of a U shaped ring of Teflon, Kel-F or other polymer with an internal annular spring or an O ring or other type of seal suitable for the particular application. Spring ring seals of Polymer Concepts Technologies, Inc. have been found satisfactory for such use. Further experience has now concluded that simple  0 -ring seals are preferred. The body  20  defines the actuation port  10   a,  the vent port  10   v  and the outlet port  10   o.  The body  20  also defines a stepped diameter cylinder  24  with an end wall  25 , a smaller diameter cylinder wall  24   s  and a larger diameter cylinder wall  24   l. The inlet plug  16  defines the opposite end wall  30  from cylinder end wall  25 . 
     Contained within the cylinder  24  are a pair of pistons  31  and  32  with piston  31  of smaller diameter than piston  32  and located in the smaller section  24   s  of cylinder  24 . The larger diameter piston  32  is located within the cylinder  24  in its larger diameter section  24   l.  The pistons  31  and  32  move in opposite directions responsive to an actuating force, namely toward each other, upon actuation by pressure at the actuation inlet  10   a.  Upon the release of actuating pressure at inlet  10   a,  both pistons are returned to their outermost and process stream blocking positions by a central spring  50  which bears upon the inner faces of the two pistons  31  and  32 . Piston  31  mounts an appropriate sliding seal  31   s  within the smaller diameter section  24   s  while piston  32  mounts its similar sliding seal  32   s  in sealing engagement with the larger diameter section  24   l  of the cylinder  24 . 
     The pistons  31  and  32  each include integral piston rods  31   r  and  32   r,  respectively, which are in sealed sliding engagement with the walls of axial cylinder  24  extensions  24   se  and  24   le.  The pistons  31  and  32  and their respective rods  31   r  and  32   r  are hollow and terminate in radial ports  31   p  and  32   p  which allow communication between the inner faces of the pistons  31  and  32  and the cylinder extensions  24   se  and  24   le,  beyond the seals  31   rs  and  32   rs  of the piston rods  31   r  and  32   r.    
     The piston rod  32   r  of piston  32  carries its rod tip or seal  43  at its end to engage a valve seat  44  which is located on the inlet plug  16 . The rod tip  43  and valve seat  44  serve to form internal valve I and to close the inlet port  10   i,  whenever the valve  10  is not actuated. 
     The body  20  defines a conical tapered outlet port valve seat  35  of the outlet valve II which is in fluid communication between the central passage  31   cp  of piston  31  and the outlet port  10   o  and an extension passage  36  at the center of the end wall  25 . The rod  31   r  of piston  31  carries the actual rod tip or seal  41  which mates with seat  35  to form the output valve II and to close the outlet port  10   o  whenever the piston  31  is in its left most position in the drawing FIG. 3, i.e., the valve  10  is not actuated. 
     The pistons  31  and  32  each also include a respective inner extensions  31   e  and  32   e.  The extension  31   e  carries an annular vent valve seal  45  and the extension  32   e  defines a vent valve seat  46 . Therefore, the valve  10  in actuality contain three internal valves one at the inlet designated I, one at the outlet designated II, and the third valve between the pistons  31  and  32  designated III. The valve III controls the flow of internal residual process gas to the vent  10   v.    
     The pistons  31  and  32  are normally maintained in their extended positions away from each other as shown in FIG. 5 by the spring  50 . The vent port  10   v  is therefore normally opened to the atmosphere or to any gas collection and disposal device beyond the vent port  10   v.    
     Both the pistons  31  and  32  and their rods or extensions  31   r  and  32   r  are hollow and each includes a respective central passage  31   cp  and  32   cp  as well as ports  31   p  and  32   p  in their side wall to allow communication between the inlet and outlet ports whenever the pistons  31  and  32  are actuated and move toward each other by actuation pressure as is explained below. 
     The actuation port  10   a  is in communication at all times with the outer faces  31   fo  and  32   fo  of both pistons  31  and  32  via passages  51  and  52 , respectively. Actuation pressure at port  10   a  drives the pistons  31  and  32  toward each other against the returning force of spring  50 , opening the valve I and the valve II at the inlet and outlets of the valve  10  and closing the vent valve III, this last valve communicating with the vent port  10   v.  In the actuated condition, flow is open between the inlet port  10   i  and the outlet port  10   o  through valves I and II, the pistons  31  and  32  and their piston rods  31   r  and  32   r.    
     Upon cessation of actuation pressure at port  10   a,  spring  50  returns pistons  31  and  32  to their normal extended conditions closing the valves I and II while opening valve III to the vent port  10   v.  It should be noted that the only residual gas present anytime which might be considered trapped within the valve is the small quantity in this central passage of the piston rods  31   r  and  32   r.  This gas is purged through the vent as the inlet and outlet ports are closed by the actuation gas as the valve III closes last. Therefore, cross contamination between sequential process samples is effectively eliminated. 
     When a series of valves  10 - 12  is assembled as shown in FIG.  1  and each is supplied with its own particular source of process gas and each with its own actuation pressure source, in the absence of any actuation pressure, the inlet ports  10   i,    11   i  and  12   i  as well as the outlet ports  10   o,    11   o  and  12   o  of all valves  10 - 12  are closed and all of the vent ports  10   a - 12   a  are open and in full communication with the common vent port  14  of the block or base  15 . Therefore, there is virtually no residual gas in any of the valves  10 - 12  of the stack assembly. When any of the valves  10 - 12  is actuated, closing its vent valve III, the remaining unactuated valves remain isolated from the actuated valve and each are fully vented via port  10   v.    
     Valves used for process stream selection often are used for sampling highly corrosive gases. In such cases, the few parts which come into contact with the sampled gases, in this invention, namely, the body  20 , the input plug  16 , spring  50 , and pistons  31  and  32  need to be fabricated from materials which are unaffected by the gases to be sampled. This can be accomplished, typically, by fabricating these parts from type 316 stainless steel. Also, the seals required and exposed to such gases must not suffer deterioration and reduced reliability and operating life of the valves. Seals manufactured from such materials as the fluorocarbon resin of the Du Pont de Nemours Co. of Wilmington, Del. sold under the trademark TEFLON or the same company perfluoroelastomer sold under the trademark KALREZ, fluorocarbon elastomer sold under the trademark Viton or the polymer of the Monsanto Company of St. Louis, Mo. sold under the trademark Kel-F, fill nearly all such needs. 
     In this case, the design of the process sampling valve minimizes the total number of seals required, and in particular, reduces the number of seals which are exposed to the sampled gases or liquids thereby reducing the need for many seals of highest corrosive immunity. 
     There is one static seal  16   ss  between the valve body  20  and the inlet plug  16 . There are two piston rod sliding seals  31   rs  and  32   rs  in communication with the actually sampled fluid. 
     The rod tip seals  35  and  44  of the valves I and II and the annular vent seal  45  are the only other seals in contact with the sampled fluid. Therefore, this design process sampling valve has a minimum number of seals and only five of them are exposed to the sampled fluid. 
     There are two larger sliding seals piston seals  31   s  and  32   s  which are located on the rear or actuation gas side of the pistons  31  and  32  and not in direct contact with the sampled fluid. These seals  31   s  and  32   s  have only contact with the actuating gas. Access to all seals for inspection or replacement may be had after securing the input, output and actuation lines followed by removal of the inlet cap  22  and removal of the inlet plug  16  and the two pistons  31  and  32 . All seals are then visible for easy inspection or replacement, if ever necessary. 
     Each of the planar surfaces which contain a port is typically sealed by an O ring in an annular groove surrounding the port. All in accordance with well established hydraulic practice. The half annular recesses for these O rings are shown in each of the drawings, FIGS. 3-5,  8  and  9  and identified by the references RO. 
     ALTERNATE EMBODIMENT 
     In the case where one or more of the valves of this invention are intended to be mounted individually and not on the backing plate  15  of FIG. 2, or in any case where the valve is desired be mounted with the inlet and outlet ports in line or, for that matter, in any reversible inlet for outlet application, the embodiment of FIGS. 8 and 9 is preferred. 
     The embodiment of FIGS. 8 and 9 is the free standing or in line version of this invention. This valve, generally designated  60 , includes a rectangular body  61  which defines three of the four ports of the valve namely the actuation port  60   a,  the vent port  60   v  and one inlet/outlet port  60   o.  The second inlet/outlet port  60   i  is located on the end closure  62  secured to the end of the body  61  opposite from the first inlet/outlet port  60   o.  One clear feature this embodiment is that the inlet/outlet ports  60   o  and  60   i  are interchangeable without any modification of the valve, whatsoever. 
     The body  61 , similar to the embodiment of FIGS. 1-7 defines a dual diameter cylinder  63  with a piston  64  located in the small diameter section  63   s  of the cylinder  63  and a larger diameter piston  65  located in the larger diameter section  63   l  of cylinder  63 . Piston  64  also includes an integral rod section  64   r  which extends into a cylinder extension  63   ex   1  and piston  65  includes a piston rod extension  65   r  which extends into a second cylinder extension  63   ex   2 . The ends of both piston rod extensions  64   r  and  65   r  include end seals or rod tips  68  and  69 , which mate with valve seats  70  and  71 , one of which seat  70  is integral with the body  61  and the other, seat  71 , is integral with the end closure  62  to define the internal valves I and II. 
     The pistons  64  and  65  also include inward extensions, a seal extension  64   s  and a valve seat extension  65   vse  which together define the vent valve III, similar to the valve III of the earlier embodiment. 
     Similar to the previous embodiment, the pistons  64  and  65  are urged outwardly away from each other by a spring  50  normally closing valves I and II while opening the valve III which is formed by extensions  64   s  and  65   vse  of the pistons  64  and  65 , respectively. The valve III, as in the earlier embodiment, is normally open allowing communication between the interior of the process sampling valve  10  and the vent port  60   v.    
     Of importance to this invention is the fact that the two inlet/outlet ports  64  and  65  are in line so that this valve  60  may be located at any desired location merely by insertion in an existing sample or other line. The actuation pressure line to the actuation port  60   a  and the discharge line from the vent port  60   v  are located on opposite sides of the valve for ease of connection. 
     Another major advantage of this embodiment is a reversibility of inlets and outlets. In both embodiments, the small number of seals which are exposed to the process fluid insures reliability and long life of these valves. The fact that so few seals are required in valves of this invention allows the process engineer with extremely chemically reactive process streams to specify the most effective and expensive seal materials be used without incurring exorbitant costs. Similar to the embodiment of FIGS. 1-7 is the fact in minimum seals are necessary in the design and operation of this valve and only two moving seals and three valve seats are exposed to process gas flow. Also, the seals which are directly exposed to the process sample are the smallest seals in the valve and consequently less expensive. 
     The above described embodiments of the present invention are merely descriptive of its principles and are not to be considered limiting.