A block-and-bleed valve module

Abstract: In one aspect the invention provides a valve module (33) for a process analyzer. The module includes a first block valve (33b) having a first opening, a second block valve (33c) having a second opening and a bleed valve (33d) having a third opening. The first and second block valves are made so that both are closed or both open at the same time. The block valves and the bleed valve are made so that, in a first mode, the block valves are closed and the bleed valve is open; in a second mode, the block valves are open and the bleed valve is closed; and in a third mode, all of the valves are open, thereby ensuring that the module is completely purged. In a second aspect the invention provides a stream-selection valve manifold. The manifold (2a) is made by joining two or more valve modules (33) side by side to form a common outlet passageway (18) and a common vent passageway (17), thereby ensuring that the manifold is completely purged. In a third aspect the invention provides a single block-and-bleed valve module (79). The module includes a block valve, a sample-fluid compartment (52), a vent compartment (53), an internal pneumatic actuator (63), an actuator compartment (64), a sample-inlet first passageway (54), a sample-outlet second passageway (55), a third passageway (65) for introducing a compressed gas into the actuator compartment, a fluid-disposal fourth passageway (76), a spring (62) for closing the block valve, a compressed gas for opening the valve, and a body (51) for containing the modular components. The fluid-disposal passageway (76) provides fluid communication between the vent compartment (53) and an external area suitable for the safe disposal of sample fluids and compressed gas contained in the valve module. The pressure within the vent compartment and the disposal passageway is normally kept equal to or lower than that of the sample-inlet passageway, sample-outlet passageway, and actuator compartment, in order to prevent fugitive emission of the sample fluid or the compressed gas from the module into the external environment. The flat-face sealing structure (71) of each valve is very tolerant of scratching and/or irregularities in the sealing structure and of abrasive particulates which may be present in the sample fluid, and even of minor structural damage to the sealing structure.

Description: The present invention relates to stream selection, such as the selection of sample streams being routed to a process analyzer. It is common practice to utilize a single automated process analyzer for analyzing multiple sample streams. This signficantly reduces the cost of analyzing gas and liquid process streams in petrochemical plants, refineries and other process-related industries. The sample streams are generally transported near to an analyzer by tubing or piping. An automated valving manifold, usually electronically controlled, sequentially selects and diverts individual sample streams to the automated analyzer. This type of valving arrangement is generally referred to as a "stream-select manifold." It is extremely important that sample-stream cross-contamination does not occur; i.e., absence of contamination of one sample stream by another in the sample stream selected for analysis. The most likely source of cross-contamination is from leaking "stream-select valves" in the stream-selection valving manifold. Another common problem is the contamination of a stream selected for analysis by residual fluid from a previous sample stream. This is likely to occur in a common passageway between the valve manifold and the analyzer. Valve-manifold designs have either "dead volume," irregular passageways, or large internal volumes, which require longer period of sample flow (purging) before all residual fluid from a previously selected sample stream is removed. A common source of "difficult-to-purge" internal valve manifold volume is pipe fittings which provide an irregular internal surface. A common source of dead volume is the space between the block valve of a "non-selected" stream and the common sample fluid passage to an analyzer. When longer sample-stream purge periods are required, it reduces the number of analyses which can be performed by an analyzer in a given period of time. This can increase the cost for analysis by requiring additional analyzers or otherwise negatively impact process adjustments based on current analysis. Most important, however, is the increased volume of purged sample material which must be discarded. This also increases cost and presents a greater risk of contaminating the environment. Valves utilized in stream-select manifolds for the most part were designed for ordinary pneumatic and hydraulic fluid-handling applications. Designs have been altered to some degree to accommodate stream-select manifold requirements. But few are designed exclusively for that purpose. Those which are designed primarily for stream selection are of the single block valve design, and are therefore prone to cross-contamination problems when even a slight leak develops. Modular valve manifold arrangements are well known and in common service. These manifolds, however, are designed to facilitate the addition or removal of individual valves, and to reduce the number of tube and/or pipe fittings required. Their main purpose is to reduce space in pneumatic and hydraulic, not analytical, applications. Hence little consideration has been given to reducing internal volume and/or "dead" (unpurged) space, or the prevention of cross-contamination by residual fluids. Few if any provide double-block-and-bleed (DBB) protection from cross-contamination. Some manifold/valve designs even allow stacking of manifold modules to create a manifold of a desired length; however, the valves are a separate entity, and are attached to the manifold. Another common problem with stream-selection valves is "fugitive emission" of sample fluids. This typically occurs when a valve stem seal fails. A metal bellows or diaphragm is frequently employed to seal the external actuation linkage to a valve's internal sealing mechanism. This arrangement, particularly when used in combination with a secondary packing, is very effective in reducing fugitive emission from valves. However, embrittlement of metal bellows or diaphragms, particulaly in hydrogen-rich sample-stream service, and fatigue from repeated actuation, often causes premature stem-seal failures. Additionally, valves employing the bellows/diaphragm seal design are expensive, thus limiting their application. Furthermore, when the bellows or diaphragm fails, there can be an abrupt release of potentially flammable and/or toxic fluids to the surrounding environment. In summary, bellows/diaphragm valve stem seals are very effective during their normal service life, but have a severe and potentially unsafe failure mode. Pneumatic actuation is often preferred in lieu of electric actuation for valves used in hazardous or electrically-classified environments. Current valve designs generally employ discrete pneumatic actuators usually mounted external to the valve with mechanical linkage through a seal to the internal valving mechanism. This arrangement results in a bulky design which takes up large amounts of valuable panel space. This is a particularly important consideration when considering the cost of providing panel space in a typical analyzer housing or environment. The large bulk also precludes close coupling of valves to minimize internal valve-manifold volume. FR-A-2382636 discloses a block-and-bleed valve module of the preamble of claim 1. Its first and second block valves are disposed on separate faces of a two-part head of the valve poppet. The bleed valve is disposed at the free end of the stem of the poppet. According to a first aspect of the present invention, there is provided a block-and-bleed valve module, comprising: a first block valve having a first opening, a first passageway, first flat-face sealing means and a first flat sealing surface; a second block valve having a second opening, a second passageway, second flat-face sealing means and a second flat sealing surface; a bleed valve having a third opening, a third passageway, third sealing means and a third sealing surface, the bleed valve forming a junction with the first and second block valves and communicating therewith; wherein each valve is closed when its sealing means presses against its sealing surface and is open when its sealing means is spaced away from its sealing surface; a valve poppet having a head with first and second head faces which face in opposite directions, wherein the first and second block valves and the bleed valve are disposed on and adjacent to the poppet with the first block valve being disposed on and adjacent to the first head face, and wherein the poppet is movable linearly between (i) a first position in which the first and second block valves are closed and the bleed valve is open and (ii) a second position in which the first and second block valves are open and the bleed valve is closed, with the first and second block valves and the bleed valve being open during transition of the poppet between the first and second positions; first urging means for urging the poppet towards its first position; and second urging means for urging the poppet towards its second position; characterized in that: the third sealing surface is a flat surface and the third sealing means is a flat-face sealing means; the second block valve is disposed on and adjacent to the first head face; and the bleed valve is disposed on and adjacent to the second head face. Usually, the second urging means comprises an internal pneumatic actuator. Preferably, the first urging means comprises a compression spring. In many embodiments, the valve module further comprises a body having an inlet port, an outlet port and a vent port for the first block valve, second block valve and bleed valve, respectively, the body being constructed and arranged to house the pneumatic actuator and the poppet in a cavity within the body. According to a second aspect of the present invention, there is provided a stream-selection valve manifold comprising first and second valve modules each in accordance with the first aspect of the present invention; and means for holding the first and second valve modules in a fixed configuration wherein the first and second valve modules are side-by-side, the second passageways of the second block valves lead to a common outlet passageway of the manifold and the third passageways of the bleed valves lead to a common vent passageway of the manifold. Non-limiting embodiments of the invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a schematic representation of a second embodiment of a stream-selection valve manifold for a process analyzer, made in accordance with the principles of the present invention. Figure 2 is a schematic representation of a first embodiment of a stream-selection valve manifold for a process analyzer, made in accordance with the principles of the present invention. Figure 3 is an isometric view of the stream-selection valve manifold shown schematically in Figure 2. Figure 4 is an isometric view of the second embodiment of a steam-selection valve manifold for a process analyzer shown schematically in Figure 1. Figure 5 is a cross-sectional view of the valve manifold shown in Figure 3, taken along the cutting line 7-7. Figure 6 is a cross-sectional view of the valve manifold shown in Figure 3, taken along the cutting line 8-8. Figures 7 and 8 are portions of the cross-sectional view of the valve manifold shown in Figure 5. Figure 9 is a schematic representation showing the removal of a valve module from the stream-selection valve manifold shown in Figures 2 and 3. Figure 10 is a cross-sectional plan view of one of the valve modules of the manifold shown in Figure 3. The valve manifold of the first embodiment (Figure 2) includes two valve modules 33. Each module 33 comprises an internal pneumatic actuator, an inlet block valve 33b, an outlet block valve 33c, and a bleed valve 33d. The two block valves 33b, 33c are constructed and arranged so that both are closed or both are open simultaneously. The bleed valve 33d is constructed and arranged so that, when the block valves 33b , 33c are open, the bleed valve 33d is closed; when the block valves 33b, 33c are closed, the bleed valve 33d is open. The three valves 33b, 33c, 33d are contained and disposed in and by a body 16 having an inlet port 19, and outlet port 18a, and a vent port 17 for the inlet valve 33b, outlet valve 33c, and bleed valve 33d, respectively (Figures 5 - 8). The internal pneumatic actuator comprises a valve poppet 15 having a stem 15a and a flange 15b, first biasing means 3 to urge the poppet 15 downward, and second biasing means to force the poppet 15 upward (Figures 5, 7, and 8). The first biasing means 3 may be a spring 3, a compressed gas, or other means. Preferably, however, the first biasing means is a spring 3 housed in a chamber 32. The second biasing means is preferably a compressed gas; it is stronger than the first biasing means 3, and prevails when the two are in opposition. The three valves 33b, 33c, 33d and the pneumatic actuator are disposed within a cavity 26 in the body 16. (Figure 5.) When the poppet 15 is in its extreme lower position (Figure 7), in response to the first biasing means 3 and in the absence of the second biasing means, the sample inlet and outlet valves 33b, 33c are in a closed or blocked configuration, and the bleed valve 33d is open. When the poppet 15 is in its extreme upper position (Figure 7), in response to the second biasing means, the inlet and outlet valves 33b, 33c are open, and the bleed valve 33d is closed. During transition between these two extreme positions, which is momentary, all three valves 33b, 33c, 33d are open (Figure 8). It will be understood that the portion of the cavity 26 providing the second biasing means may be maintained at a pressure substantially above atmospheric, even "in the absence of the second biasing means." Such a condition may indeed be beneficial, in order to prevent fugitive fluid emission from the modular body 16. The valves 33b, 33c and 33d comprise flat-face sealing means. Preferably, the valves 33b, 33c, and 33d include O-rings (Figures 5, 7, and 8). More specifically, a seal-plug bottom part 13 is positioned on a shoulder 26a formed by a reduction of cross-sectional area at the lower end 26b of the cavity 26. (Figures 5, 7 and 8. ) An O-ring 10b seals the outer surface of the seal-plug bottom part 13 to the inner surface of the cavity 26. A seal-plug top part 11 is disposed over the seal-plug bottom part 13. An O-ring 10a seals the outer surface of the seal-plug top part 11 to the inner surface of the cavity 26. A snap ring 8 retains the seal-plug top part 11 and seal-plug bottom part 13 in a fixed position. The poppet 15, comprising a stem 15a and flange 15b, extends axially within the cavity 26. Grooves 29a and 29b in the lower surface of the poppet 15 retain O-rings 12a and 12b. An alignment pin 31 disposed in a passageway 30 maintains axial alignment of the O-ring 12a with a passageway 32 and of O-ring 12b with the passageway 30. A portion 12aa of the O-ring 12a which extends beyond its retaining groove 29a, when forced against the lower surface of a first compartment 24 and in axial alignment with the passageway 32, forms the sample inlet valve 33b which either blocks or permits fluid communication between a sample inlet passageway 19, the passageway 32, and the first compartment 24. In a similar manner, the O-ring 12b forms the sample outlet valve 33c which blocks or permits fluid communication between the outlet passageway 18a, the passageway 30, and the first compartment 24. An O-ring 14 axially disposed around the lower end 15aa of the poppet stem 15a, the upper surface of the poppet flange 15b, and the lower surface of the seal-plug bottom part 13 forms the bleed valve 33d which blocks or permits fluid communication between the first compartment 24 and passageways 28, 27, and 17. (Figures 5, 6 and 10 .) The width of the grooves 29a and 29b is from about seventy-five to about ninety-five percent of the width of the O-rings 12a and 12b, respectively. Preferably, the width of the grooves 29a and 29b is from about eighty to about ninety percent of the width of the O-rings 12a and 12b, respectively. Even more preferably, the O-rings 12a and 12b are made of an elastomer having a hardness of from about sixty-five to about seventy-five durometer units, as measured on a Shore "A" gauge, and the depth of the grooves 29a and 29b is from about eighty-seven to about ninety-one percent of the width of the 0-rings 12 and 12b, respectively. The valve poppet 15 is normally maintained in the extreme lower position (Figure 5 ) by the downward force of the compression return spring 3 applied to the poppet stem 15a via an actuator washer 5, actuator piston 9, and an E-ring 4b. A second compartment 39 comprises the middle portion of the cavity 26. The second compartment 39 is formed by the upper flat surface of the seal-plug top part 11 and the lower flat surface of the piston 9. When the second compartment 39 is pressurized by an external pneumatic source (not shown) of sufficient pressure via a passageway 23, an upward force resulting from the pneumatic pressure applied to the lower surface of the piston 9 overcomes the downward force applied by the compression return spring 3, and lifts the poppet 15 to its extreme upper position (Figure7 ). The poppet 15 is in the intermediate position shown in Figure 8 for only a very short period of time while in transit between the two extreme positions. O-rings 6b and 12c provide a dynamic seal between the plug-seal top part 11 and the poppet stem 15a, thereby ensuring fluid isolation at any position of the stem 15a between the passageway 28 and the second compartment 39. The piston 9 and washer 5 are axially disposed and retained on the upper portion 15ab of the poppet 15 by E-rings 4a and 4b. The O-ring 6a, retained by the washer 5 and axially disposed in a third compartment 26a formed by the upper surface of the piston 9 and the lower surface of the washer 5, provides fluid isolation between the second compartment 39 and a fourth compartment 32, in which the spring 3 is disposed, and which is referenced to (equilibrated with) the atmosphere. The fourth compartment 32 is formed by the lower surface of a cover 2 and the upper surface of the washer 5. An O-ring 7 provides a dynamic seal between the piston 9 and the inside wall of the cavity 26. The cover 2, held to the top 16a of the body 16 by screws la and 1b, retains compression spring 3 (Figure 5). In the first embodiment (Figures 2, 3 and 6), the stream-selection valve manifold 2a for a process analyzer includes: (a) a plurality of pneumatic valve modules 33 joined side-by-side, (b) first and second end plates 4c and 4d, and (c) first and second mounting brackets 40a and 40b. The passageway 18a in each valve module 33 is in alignment with the passageways 18a of adjacent valve modules 33 in the manifold 2a. The first and second end plates 4c and 4d, which are in fluid communication with the passageways 18a of adjacent modules 33, provide means for external fluid communication to a single common passageway 18 formed by the outlet passageways 18a of the individual modules 33. An O-ring 12d (Figure 6) in a gland 18aa at the end of each module's passageway 18a provides a fluid seal with the passageway 18a of adjacent modules 33 and/or the end plates 4c, 4d. The passageways 17 in the valve modules 33 are joined and sealed with an 0-ring 12e in a gland 17a to form a common vent passageway 36 which terminates as a threaded opening 50 in the end plate 4c. The passageway 17 is closed at the end plate 4d by an O-ring 17b in a gland 48b (Figures 2 and 6). Mounting is facilitated by the use of mounting brackets 40a and 40b (Figures 3 and 6). The entire manifold 2a is held together by threaded rods 41a and nuts 41b. By loosening a first nut 41b at one end of a first threaded rod 41a, a valve module 33 can be removed by rotating it along a path 100 from a first point 100a to to a second point 100b about the first threaded rod 41a disposed in a first slot 45. (Figure 9.) After the valve module 33 has been rotated sufficiently (100b) to clear a second slot 42 from a second threaded rod 41a disposed in second slot 42, the module 33 can be removed from the manifold 2a. (Figures 3 and 9.) When a module 33 is thus removed, the remaining modules 33 and the end plates 4c, 4d remain assembled. Thus the construction of the manifold 2a permits rapid replacement of one or more of the valve modules 33 in the field. The passageways 18a of the individual valve modules form a common passageway 18 (Figures 1 and 2) to an analyzer (not shown). This common passageway 18 occupies a very small volume, and is easy to purge out. The passageway 18 is straight and smooth, has a regular surface, and has no "dead volume" or empty space, thereby significantly reducing the time required for sample flow (purging) before all residual fluid from a previously-selected sample stream is displaced. In a preferred embodiment, the width of the passageway 18 is from about 1.524mm (0.06 inch) to about 2.032mm (0.08 inch). The volume of each passageway 18a in each valve module 33 is from about 0.06 to about 0.08 cubic centimeters; yet the passageways 18a and 18 are not restrictive of fluid flow. The valve module C v is 0.05. The passageways 18a are located in very close proximity to the outlet valves 33c. The passageway 30, which connects the outlet valve 33c to the passageway 18a, is preferably from about 1.143mm (0.045 inch) to about 1.397mm (0.055 inch) in length. (Figures 5, 7, and 8.) The passageway 18a has no "dead" or unpurged space; hence it purges out cleanly and quickly when serving as a conduit for fluid communication in the manifold 2a. (Figure 6.) Internal passageways 36 and 47 (Figure 6) of the end plates 4c and 4d, respectively, are also approximately 1.778mm (0.07 inch) in width, and are also constructed without "dead" or unpurged space. Hence the common passageway 18 servicing the entire manifold 2a has a very small volume and no dead space. When a valve module 33 is actuated and the block valves 33b, 33c are opened, sample fluid from that module flows into the common passageway 18 and out of both end plates 4c, 4d. (Figures 3 and 6.) The two flow paths may either be joined external to the manifold 2a, or they may remain divided, with fluid flowing from one of the end plates to vent or bypass, and fluid flowing from the other end plate routed to an analyzer. This pattern of fluid flow ensures that the entire common passageway 18 is adequately purged, thereby significantly reducing the number of fittings as well as the labor and time required for assembling the valve manifold 2a. In the second embodiment, the manifold 2c (Figures 1 and 4) has two valve modules 33 disposed side-by-side in a flow-through modular body 41, thereby eliminating the need for the end plates 4c, 4d and the mounting brackets 40a, 40b of the manifold 2a (Figures 3 and 6). The flat-face sealing structure of each valve is very tolerant of scratching of and/or irregularities in the sealing means, of abrasive particulates which may be present in the sample fluid, and even of minor structural damage to the sealing means.

Claims: A block-and-bleed valve module (33), comprising: a first block valve (33b) having a first opening, a first passageway (32), first flat-face sealing means (12a) and a first flat sealing surface; a second block valve (33c) having a second opening, a second passageway (30), second flat-face sealing means (12b) and a second flat sealing surface; a bleed valve (33d) having a third opening, a third passageway (28), third sealing means (14) and a third sealing surface, the bleed valve forming a junction with the first and second block valves (33b, 33c) and communicating therewith; wherein each valve (33b, 33c, 33d) is closed when its sealing means (12a, 12b, 14) presses against its sealing surface and is open when its sealing means is spaced away from its sealing surface; a valve poppet (15) having a head (15b) with first and second head faces which face in opposite directions, wherein the first and second block valves (33b, 33c) and the bleed valve (33d) are disposed on and adjacent to the poppet (15) with the first block valve (33b) being disposed on and adjacent to the first head face, and wherein the poppet (15) is movable linearly between (i) a first position in which the first and second block valves (33b, 33c) are closed and the bleed valve (33d) is open and (ii) a second position in which the first and second block valves (33b, 33c) are open and the bleed valve (33d) is closed, with the first and second block valves and the bleed valve being open during transition of the poppet between the first and second positions; first urging means (3) for urging the poppet (15) towards its first position; and second urging means (9) for urging the poppet (15) towards its second position; characterized in that: the third sealing surface is a flat surface and the third sealing means (14) is a flat-face sealing means; the second block valve (33c) is disposed on and adjacent to the first head face; and the bleed valve (33d) is disposed on and adjacent to the second head face. The valve module of claim 1, wherein the second urging means (9) comprises an internal pneumatic actuator. The valve module of claim 2, wherein the first urging means comprises a compression spring (3). The valve module of claim 2 or 3, further comprising: a body (16) having an inlet port (19), an outlet port (18a) and a vent port (17) for the first block valve (33b), second block valve (33c) and bleed valve (33d), respectively, the body (16) being constructed and arranged to house the pneumatic actuator (9) and the poppet (15) in a cavity (26) within the body. The valve module of claim 4, wherein the body cavity (26) comprises: a first portion (26b) extending from the lower end of the cavity to the lower surface of a seal-plug bottom part (13); a second portion extending from the lower surface of the seal-plug bottom part (13) to the lower surface of a seal-plug top part (11); a third portion extending from the upper surface of the seal-plug top part (11) to the lower surface of an actuator piston (9); and a fourth portion extending from the upper surface of the piston (9) to the lower surface of a cover (2); the head (15b) of the poppet (15) being disposed in the first portion (26b) of the cavity, the third passageway (28) being disposed in the second portion of the cavity, compressed gas being disposed in the third portion of the cavity, and the first urging means (3) being disposed in the fourth portion of the cavity. The valve module of claim 4, wherein the body cavity (26): has upper and lower ends; has a middle portion; has a shoulder (26a) formed by a reduction of cross-sectional area at the lower end (26b) of the cavity; includes a seal-plug bottom part (13) disposed on the shoulder (26a); includes a first O-ring (10b) which seals the outer surface of the seal-plug bottom part (13) to the inner surface of the cavity; includes a seal-plug top part (11) disposed above the seal-plug bottom part (13); includes a second O-ring (10a) which seals the outer surface of the seal-plug top part (11) to the inner surface of the cavity; includes retaining means (8) for retaining the seal-plug top part (11) and seal-plug bottom part (13) in a fixed configuration; with the poppet (15), comprising a stem (15a) and the head (15b), extending axially within the cavity, the stem having upper and lower ends (15aa, 15ab); includes alignment means (31), disposed in the second passageway (30), for preventing rotation of the poppet (15) in the cavity; with the head (15b) having first and second retaining grooves (29a, 29b) for the first and second sealing means (12a, 12b), respectively; with the third sealing means (14) being axially disposed around the lower end of the poppet stem (15a); includes a piston (9) of the pneumatic actuator axially disposed and retained on the upper end of the poppet stem (15a); includes third and fourth O-rings (6b, 12c) for providing a dynamic seal between the seal-plug top part (11) and the poppet stem (15a); and includes a fifth O-ring (7) for providing a dynamic seal between the piston (9) and the inside surface of the cavity. The valve module of claim 6, wherein each sealing means (12a, 12b, 14) is an O-ring and the width and depth of the first and second grooves (29a, 29b) are from about seventy-five to about ninety-five percent of the width of the first and second sealing means (12a, 12b), respectively. The valve module of claim 6, wherein each sealing means (12a, 12b, 14) is an O-ring and the width of the first and second grooves (29a, 29b) is from about eighty to about ninety percent of the width of the first and second sealing means (12a, 12b), respectively. The valve module of claim 6, wherein each sealing means (12a, 12b, 14) is an O-ring, the first and second sealing means (12a, 12b) are made of an elastomer having a hardness of from about sixty-five to about seventy-five durometer units, as measured on a Shore "A" gauge, and the depth of the first and second grooves (29a, 29b) is from about eighty-seven to about ninety-one percent of the width of the first and second sealing means (12a, 12b), respectively. A stream-selection valve manifold (2a, 2c), comprising: a first valve module (33) according to any one of claims 1 to 9; a second valve module (33) according to any one of claims 1 to 9; and means (4c, 4d, 40a, 40b, 41, 41a, 41b) for holding the first and second valve modules (33) in a fixed configuration wherein the first and second valve modules are side-by-side, the second passageways (30) of the second block valves (33c) lead to a common outlet passageway (18) of the manifold (2a, 2c) and the third passageways (28) of the bleed valves (33d) lead to a common vent passageway (36) of the manifold (2a, 2c). The stream-selection manifold (2a) of claim 10, wherein: the width of the common outlet passageway (18) is from about 1.524mm (0.06 inch) to about 2.032mm (0.08 inch); the volume of the part (18a) of the common outlet passageway (18) in each valve module (33) is from about 0.06 to about 0.08 cm 3 ; and the C v of the first and second valve modules (33) is from about 0.04 to about 0.06. The stream-selection manifold (2a) of claim 10 or 11, wherein the holding means (4c, 4d, 40a, 40b, 41a, 41b) comprises: first and second threaded rods (41a); first, second, third and fourth slots (42, 45); a first pivot point comprising the first rod (41a) disposed in the first slot (45) in the first valve module (33), about which the first valve module can be rotated until the third slot (42) in the first valve module is clear of the second threaded rod (41a), after which the first valve module can be removed from the manifold without removing the second valve module, the first rod or the second rod; and a second pivot point comprising the first rod (41a) disposed in the second slot (45) in the second valve module (33), about which the second valve module can be rotated until the fourth slot (42) in the second valve module is clear of the second threaded rod (41a), after which the second valve module can be removed from the manifold without removing the first valve module, the first rod or the second rod.

Inventors: MAYEAUX DONALD P, MAYEAUX, DONALD P.
Applicants: WHITEY CO, WHITEY CO.
Application year: 1993
Main classification: F16K3
IPC codes: F16K27, G01N35, G01N1, F16K11