GB2040715A - Producing a calibration gas mixture - Google Patents

Abstract

A gas blending system for blending predetermined accurately measured quantities of gaseous components transferred from separate pressurized supply tanks (A, B, C, D), preferably on input signals received from a computer includes a mixing vessel, (20) a pressure transducer (19) associated with said vessel (20) for measuring the pressure of the gases, producing an output signal and transmitting same to the computer and a circulating pump (10) connected in series with the vessel 20 via conduits (11, 12, 13, 14, 13', 14'). Valves (15,---15N) respectively connect the component supply tanks into the system, the valves being a multi- component valve assembly operatively communicating the two ends of the conduits for flow of gas therethrough in providing the functions of purging gas from the system, admixing the gaseous components received from the pressurized supply tanks to form the gaseous blend, and producing a product output blend of the admixed gases. The system is also provided with means for venting gases (17) from the system in the event of over pressurization, or leakage. <IMAGE>

Description

SPECIFICATION Producing a calibration gas mixture It is the primary objective of the present invention to provide apparatus and method for blending gaseous components in accurately measured quantities to provide calibration gas mixtures, especially a static gas blending system which can be readily automated.

Another, and more specific object, is to provide such gas blending apparatus which is of relatively simple and inexpensive construction, particularly one wherein the gaseous components can be added in preselected quantities, and the inputs readily monitored and controlled.

Another object is to provide a method for the production of a calibration, or reference gas, suitable for use in analytical instrumentation.

These objects and others are achieved in accordance with the present invention, an apparatus embodiment of which is constituted generally of a system which includes: a pressure vessel, or gas mixing vessel, preferably one of large mass, or of massive weight as relates to the volume of gaseous components capable of being mixed therein, a pressure transducer for measuring the pressure of the gases in said gas mixing vessel, or system, and producing an output signal in response to the measured pressure, a circulating pump connected in series via conduits with said gas mixing vessel, for homogenizing, or admixing, the gases, and a plurality of valve components, preferably a multi-component valve assembly operatively communicating the two ends of the conduits to form a circuit for flow, or circulation of gas therethrough, and through said system to provide the functions of purging gas from the system, admitting gaseous components received separately from pressurized supply tanks, admixing the gases to form a product gas blend, transferring all or some increment of said product gas blend from the system, and venting gases from the system.

The multicomponent valve assembly per se forms another apparatus embodiment, a preferred embodiment which in fact lies at the very heart of the system embodied by the preferred apparatus combination. The multicomponent valve assembly is comprised generally of a housing, preferably one within which is provided one or more vent passageways through which gases can be exhausted from the system, a component gas manifold within which gases can be injected and circulated through the system, and valve seats over which valves are mounted, the stems or plungers thereof intersecting a vent passageway and said component gas manifold. A mix valve, a product output valve, a vent valve, and a plurality of component gas valves, each of which can be independently opened and closed, particularly by signals independently received in programmed sequence from a computer, are mounted on said housing. Gases from the system are passed through said valve assembly in providing the functions of purging gas from the system, admixing the gaseous components received from pressurized supply tanks to form the gaseous blend, producing a product output blend of the admixed gases, and venting gases in the event of worn valves, or upset condition wherein too much pressure is generated in the system.

A preferred housing is one constituted of an elongate block in which there is provided parallel oriented, spaced apart axial passageways, each extending longitudinally through the block from an inlet at the same end of said block; a central passageway comprising a component gas manifold within which component gases of the blend can be injected, and circulated for admixing said gases, and preferably a plurality of vent passageways, suitably a pair of vent passageways, one located on each side of said central passageway and on a common plane therewith so that valves can be mounted on alternate sides of the block over valve seat openings formed by lateral openings in the block which connect a vent passageway with the component gas manifold. A plurality of valves which can be opened and closed in sequence, preferably by signals received in programmed sequence from a computer, are each mounted on a valve seat opening. Preferably, the valves are electrical or pneumatic, but more preferably a valve is constituted of both an electrical component and a pneumatic component. Suitably a single mix valve is employed, the mix valve forming an open-close or on-off connection in the circuit between the component gas manifold and the mixing vessel. A single product valve is also employed, this valve being mounted on said block over a valve seat opening adjacent a conduit which communicates the valve seat opening of said valve with a gas receiving source, or demand source external to said system. A single vent valve is mounted on said block over a valve seat opening, this valve being employed on an end of the component gas manifold, to minimize dead volume. An outlet communicates the component gas manifold via the orifice within the valve seat opening with a vent passageway. The block is also provided with a plurality of component gas valves. These are mounted on the block, each over a valve seat opening, and a gas inlet connected to each provides means for communicating a pressurized component gas supply tank for supply of a component gas. In closed position, the plunger of a valve can seal an orifice leading from said valve seat opening into said component gas manifold to close off the flow of a component gas from a supply tank into the component gas manifold, but in open position a component gas can be supplied by a pressurized supply tank to the component gas manifold. In a sequence of operation, the system can be purged in a cycle which includes opening the vent valve, closing all other valves, and then starting the pump to exhaust gas from the system, after which time the vent valve can be closed, the pump stopped, and a component valve opened to fill the system with a component gas, this cycle of exhausting and filling the system with the component gas being repeated a number of times to purge the system of all contaminants. After the system is exhausted of gas on the last step of the purging operation, the vent valve can then again be closed and each component gas can then be serially injected into the system by sequentially opening and closing the respective component valve to inject the gases of the blend. And, on closing the component valve of the last gas to be added to the blend, the mix valve can be reopened, and the pump again turned on to circulate, mix and thoroughly homogenize the gaseous blend. The product output valve can then be opened to transfer the gas blend to the receiving source, or portions of the gas blend can be withdrawn as needed.

In a particularly preferred embodiment, the component gas valves are mounted on the housing, or block, in pairs, one valve of a pair being employed to inject a gaseous component at a rapid rate into the system, while the other valve of the pair is employed to inject additional increments of the same gaseous component into the system during blending. Generally, each valve of a pair is mounted on alternate sides of the housing, or block, and a pair of the component gas valves are employed for each component gas added to system during blending. This permits fast initial injection of a relatively large volume of gas during blending with a first valve of the pair up to a preselected maximum pressure set point. As the gas then cools, and pressure drops to, or below, a minimum preset pressure level, additional smaller volumes or increments of the gas are added with a second valve of the pair. Each increment is added up to the maximum preselected pressure set point, until such time that the last increment is sufficiently small that the pressure virtually approximates or equals the maximum preselected set point after cooling.

The characteristics of a preferred gas blending system, multi-component valve assembly, and their principle of operation, as well as a method for the production of calibration gases will be more fully understood by reference to the following detailed description, and to the attached drawings to which reference is made on the subsequent description.

Similar numbers are used in the different figures to represent similar components. Subscripts are used where there are a plurality of similar components, and where reference is made to a component without use of a subscript where a plurality of similar components are present, the reference is intended in the generic sense.

Referring to the drawings: Figure 1 shows an overview of a static gas blending system; Figure2 depicts a preferred multi-component valve assembly; Figure 3 depicts a lower end view of said preferred multi-component valve assembly; Figure 4 depicts a right side view of said preferred multi-component valve assembly; Figure 5 depicts in section, and in isometric form, a Section 5-5 taken from Figure 2; Figure 5-A depicts a component, in partial section, taken from Figure 5; and Figure 6further depicts the multi-component valve of Figures 2-5 in combination with the static gas blending system.

Referring to Figure 1 there is shown a digital static gas blending system which includes generally a pump 10, a vessel 20, suitably a massive spherical pressure vessel which is connected via line 11 to the pump 10, and communicating lines 12, 13, 14which closes the circuit and serially connects the vessel 20 to the pump 10. The system includes a plurality of component control valves 15 (1 5n-1 through 15n), each of which is connected to a different source of pressurized gas, for providing different gaseous components to the gas blending system. Thus, where four gaseous components are to be blended four component control valves are employed, e.g., component control valves 151,152,153,154 to each of which is connected an individual tank of pressurized gas (not shown) and the gas is fed through the respective valve to line 12 of the digital static gas blending system. Three additional valves are required in the circuit, these comprising a mix valve 16 in line 14, a vent valve 17 located in line 14' which is a take off line between lines 13,14, and a product output valve 18 located in line 12' which is a take off line between lines 12, 13. The system also includes an electrical absolute pressure transducer 19, or other suitable means, for accurately and continuously monitoring the absolute pressure within the vessel 20, the output of which is transmitted to a computer (not shown). It is preferably directly mounted within the body of the pressure vessel 20 to minimize the dead area between the pressure sensor of the transducer and the mixing chamber of said vessel 20. Suitable transducer for this usage are well known, and produced by various manufacturers in this country. Reference is made to U.S. Patents Nos.

3,195,028; 3,271,669; and 3,318,153 for disclosures on the operation of pressure transducers, these patents being hereby incorporated by reference.

Preferably, the output of the transducer which is in the preferred embodiment is a DC output voltage or current linear with pressure that is electrically communicated via electrical conduits to the computer.

Each valve of the system is controlled by input signals from the computer in response to a predetermined program.

The pressure vessel 20 is necessarily one which provides a heat sink, or heat stabilizing means for rapid dissipation of the heat produced during the gas blending operation. The vessel might thus be one provided with a jacket within which a fluid can be passed in heat exchange relationship to the blended gases, or the vessel might be provided with various other heat exchange devices well known to the art.

Suitably however, the vessel 20 is quite massive relative to the gaseous contents introduced therein to provide a sufficient heat sink to hold the gas temperature substantially stable during the gas blending operation. Generally, the mass of the vessel 20 is at least about 20 pounds, and preferably ranges from about 30 pounds to about 42 pounds, for a vessel having an internal volume of 20 liters, the weight increasing proportionately as the internal volume of the vessel is increased. Suitably, the vessel 20 is of spherical shape and constituted of metal, e.g., stainless steel. In this system the pump 10 provides the required stirring for admixing the gases during blending, the heat being dissipated through the walls of the vessel 20.

In a typical gas blending operation, a gaseous blend can be formed from a plurality of gaseous components, e.g., inputs of gaseous components A, B, C, and D (from individually loaded pressurized tanks, not shown). The desired percentage composition of each of Components A, B, C and D within the total gaseous mixture to be blended is punched onto a keyboard as input to a computer, or other means, the computer controlling the several inputs of the gases to be blended by opening a valve in response to a predetermined pressure output from pressure transducer 19, a component being introduced into the line 12, of the previously purged system when the pressure within spherical vessel 20 is below a certain preselected minimum set-point, and the valve closed when the pressure within spherical tank 20 reaches a certain preselected maximum set point pressure. The gaseous components are then sequentially introduced into the previously purged system.

In an operating cycle, the method is one generally comprising the steps of purging the system, evacuating the system, introducing the component gases to the system, and then admixing or homogenizing the gases, after which time the blend is ready for transfer to the user as needed, or to a secondary vessel. In purging the system, notably the pressure vessel 20 which constitutes a mixing chamber, a first component gas, generally the largest component of the blend, is introduced to eliminate gas contaminates from the chamber; and then the vessel is evacuated of the purging gas and the pressure thereby reduced in the mixing chamber to a predetermined minimum level. Afirst component gas is then added to the pressure vessel 20, or mixing chamber, preferably sequentially in the order of the majority component first. Thus, if the concentration of four components of an admixture is A > B > C > D in the final admixture, the gaseous components are introduced in the order A followed by B, B followed by C, and C followed by D; each addition of a gaseous component being completed before the next gaseous component is introduced. The first gaseous component is added in amount sufficient to increase the absolute pressure in the vessel, or mixing chamber, to a first predetermined level for the first gaseous component; the second gaseous component is then added to the vessel, or mixing chamber, in amount sufficient to increase the absolute pressure in the mixing cliamberto a second predetermined level; a third component gas is then added to the vessel 20, or mixing chamber, in amount sufficient to increase the absolute pressure in the mixing chamber to a third predetermined level; and this addition sequence is continued up to the time of addition of the last gas which is to form a part of the component gas blend. The contents of the system are then circulated and stirred by starting and operating the pump 10 to obtain a homogenous gas blend.

Atypical cycle of operation employed in blending gaseous components A, B, C and D, supra, beginning with the step of purging the system is described by reference to Figure 1 as follows: 1. With mixvalve 16, product output valve 18 and all of the component control valves 15 (i.e., 1 5a, 152, 153 and 154) closed, and vent valve 17 open, pump 10 is energized to exhaust the contents of shpericalvessel 20 via lines 11, 12, 13, 14' through the venting system. This done, and the pressure within spherical vessel 20 having reached a low preselected level, e.g., 5 pounds per square inch absolute (psia), or lower, vent valve 17 is then closed and pump 10 is cut off.

2. Mix valve 16 is again opened. Valve 15, to which is connected a pressurized tank (not shown) containing the gaseous component of the blend to be added in greatest concentration, is then opened.

Gaseous Component A is then added up to a preselected pressure level, e.g., 15 to 50 psia. The gas fills the system byflowthrough lines 12,13,14; the gas flowing into line 11 after filling the vessel 20.

Component control valve 151 and mix valve 16 are then closed, vent valve 17 is then again opened, pump 10 is turned on and the contents of the system, especially vessel 20 are again vented by pumping the gas through lines 11,12,14, 14'. Vent valve 17 is again closed and valves 16 and 151 are again opened to refill the system with gaseous component A. Mix valve 16 and component gas valve 151 are then again closed, vent valve 17 is then opened and the gaseous contents of the vessel 20, and in fact the entire system, are again vented. The cycle of filling the system, and vessel 20 with Component Gas A, and thereafter purging vessel 20 of Component Gas A is conducted a plurality of times, usually about four times, until essentially all traces of any gaseous component other than gaseous Component A has been eliminated from the system. The purge thus completed, the system at low pressure, e.g., 5 psia, or lower, is now ready to receive the first permanent component of the blend, viz. gaseous Component A.

3. With mix valve 16 open and valves 17, 18 and 152, 153, 154 closed, valve 151 is opened, and gaseous Component A flows through the system and into vessel 20 to fill same with Component Gas A up to a first preselected pressure set-point level, e.g., 50 psia. The gas warms up slightly, and the pressure falls below the set point as the gas within the vessel cools. Continuous increments of gaseous Component A are added, the increments of Component A becoming smaller each time the set point is reached until such time that the last increment of gas maintains the preselected pressure set point level after the gas has cooled. On injection of the last increment of gaseous Component A into the system, and after thermal equilibrium has been reached, valve 151 is closed.

4. Valve 152, with mix valve 16 open and valves 17, 18 and component gas valves 15" 153,154 closed, is opened and gaseous Component B is then added up to a second preselected pressure set-point level, e.g., 70 psi. On equilbration of the gas after the last increment of gaseous Component B is added, component gas valve 152 is closed.

5. With valves 17, 18 and component gas valves 1 so, 152 and 154 closed, and mix valve 16 open, valve 153 is opened and gaseous Component C is then added to the system up to a third preselected pressure set-point level, e.g., 80 psi. On equilibration of the gas after the last increment of gaseous Component C is added, component gas valve 153 is closed.

6. With valve 16 open, and valves 17, 18 and component gas valves 15q, 152 and 153 closed, valve 154 is then opened and gaseous Component D is then added to the system up to a fourth set-point level, e.g., 85 psi. On equilibration of the gas after the last increment of gaseous Component D is added, component gas valve 154 is then closed, pump 10 is turned on and the admixture of gaseous Components A, B, C and D is then circulated through the system until the stirred admixture is thoroughly homogenous. The vessel 20 can serve as a storage facility or the admixture can be transferred to a storage vessel for subsequent use.

7. Product valve 18, in the event transfer to a storage vessel is desired, is now opened and, with all of Component gas valves 15andvalves 16, 17 closed, the admixture of gases A, B, C and D is pumped from the system via lines 12, 12' as a product.

A liquid component, or components, can also be added to the vessel, or mixing chamber, in predetermined quantities as by injection of the liquid directly through a septum inlet (not shown) in the vessel; or directly injected through a component gas valve inlet. Within the mixing chamber the liquid is stirred and homogenized, or vaporized with the component gases. The liquid introduced into the mixing chamberforms a portion of the gaseous blend, and its volume can be related to the total volume of the gaseous blend by varying the pressure in the mixing chamber as described in Application Serial No.

698,883, supra.

These gas blending functions, and others, are best conducted by use of a multi-component valve, or valve assembly, which includes a plurality of component control valve units, a mixing valve, a vent valve and a product output valve mounted within a single housing. A preferred valve of this character, a major advantage of which is that it can be located remote from the pressure vessel 20 itself, is described by reference to Figures 2 through 6.

Referring initially to Figures 2 through 4 there is depicted a preferred multi-component valve assembly 100 capable of carrying out all of the functions, and more, described by reference to Figure 1. The multi-component valve assembly 100 is comprised generally of a unitary housing 110 on each alternate side of which is fitted two-way electro-mechanical valves which are controlled by inputs from a computes to open and close passageways within the housing 110 for carrying out the functions required in the aforesaid component gas blending operation.

A mix valve, product output valve and a series of component gas valves equal in number to the maximum number of gaseous components that are to be blended together in admixture are located on one side of the valve housing. A vent valve is located at an end on the opposite side of the housing, along with a second series of component gas valves equal in number to the component gas valves located on the opposite side of the valve housing. One series of the component gas valves is employed to introduce relatively large volumes of the several gaseous components into the system, while the other series of valves are employed to introduce additional smaller increments of the gaseous components into the system. A pair of component gas valves, one valve of a pair being located on each side of the housing, is required for the introduction of each gaseous component to the system.

The housing 110 is constituted of an elongate solid block through the central axis, or center of which is provided a central opening or passageway which serves as a component gas manifold 111. Vent passageways 1121, 1122, which traverse the length of the block, are located on each side of the component gas manifold 111, in line with, equidistans from and parallel to the gas manifold 111. A plurality of equidistantiy spaced lateral openings 113 (1131 through 1136 and 1137 through 1131a, respectively), similar in size and shape, provide valve plunger seating surfaces which extend inwardly from the outer surface on each side of the block 110 (left and right side of Figure 2) to intersect at a right angle with a vent passageway 1121, or 1122, respectively, each opening being cut through the wall, providing a narrow passageway or orifice leading into the component gas manifold 111 wherein it terminates. A supply manifold, constituted of com ponent gas inlet openings 1A, 2A, 3B, 4B, 5C, 6C, 7D, 8D, to which connection can be made for the introduction of component gases (e.g., component gases A, B, C, D of a blend, supra) from pressurized supply tanks into the component gas manifold 111, are located on the upper face of block 110 (Figure 2), these openings extending into said laterally spaced openings 1133,1134,1135,1136,1138,1139,11310, 1 1311, respectively, at locations near the narrow passageways leading into the component gas manifold 111 such that a component gas from a source can be introduced therethrough into the gas manifold 111, or its flow interrupted by operation of a valve plunger, as subsequently detailed. A mix gas inlet connection located in block 111 above passageway 1131A provides an inlet for input of gaseous components into the component gas manifold 111 when the plunger is raised for circulation of a gaseous component, or admixture of gaseous components to effect mixing, and a gas inlet connection located above passageway 1 132A provides an inlet into component gas manifold 111 for the removal of a gaseous product blend from the system. An oversized, or enlarged gas inlet connection located behind passageway 1137A, located near the end of passageway 111, provides an inlet from component gas manifold 111 into the vent passageway 1122for venting gas from the system.

The vent passageways 11 2a, 1122, in addition to their function in normal operations also provide a unique safety feature in the event of a system upset, or malfunction which may develop excess pressure.

Should, for any reason, too much pressure be developed for the system to handle, a rupture disk 120 is provided at the end of the block 110 (the upper end, Figure 2) which, on being ruptured or broken leads into an open space or passageway 124 provided by an annular opening closed on one side by end wall 119. The passageway 124 is in open communication with vent passageways 1121, 1122.

The rupture disk 120 is sombrero shaped, the peripheral edges thereof being fitted across the sholders of a seating surface formed by an internally threaded enlarged opening 121 concentric with the component gas manifold 111 which it closes. It is held in place by an open centered washer 122 the inner edges of which, in turn, are pressed against the peripheral edges of the rupture disk 120 via tightening down on an externally threaded nut 123 which is threadably engaged via internal threads located within the opening 121. The rounded center of the rupture disk 120 is bulged outwardly and, on rupture at a preselected pressure which may be developed in the system, will pass gas via passageway 124 into vent passageways 112i, 1122. The vent passageways 11 2i, 1122 also provide a safety gas by-pass feature in the event that worn o-rings on the plunger produce leakage. This feature is particularly important in blending noxious gases, or gases of hazardous nature. In accordance with this embodiment, gases are prevented from escaping into the ambient atmosphere by maintaining the vent passageways 1121, 1122 at atmospheric pressure; this providing an easy escape route, or free ascess passageway for channeling an escaped gas, or gases, out of a working area to a safe storage, or disposal facility. In some instances the gases may be vented through a high stack, or chimney to the atmosphere.

The preferred valve components of the multicomponent valve assembly 100 are each characterized as electro-mechanical valve units which can be activated in timed sequence by input signals received frorn the computer (not shown). The electrical valve component of an electro-mechanical valve unit permits a very rapid response to an electrical signal, the electrical valve component in turn being used to actuate a pneumatic valve component to provide a powered response for opening and closing a valve.

Two-way valves, each comprised of a single electrical and single pneumatic component, are employed as controls for regulating the mixing, venting and product output functions. Generally similar valves are also employed in pairs, or as paired units for control of the component gas blending functions. In other words, a single two-way electro-mechanical valve unit is provided to control the gas mixing function, a single two-way electro-mechanical valve unit is provided to control the venting function, a single two-way electro-mechanical valve unit is employed to control the product output function, and a pair of two-way electro-mechanical valve units are employed to control each of the gaseous components which are introduced into the gas blending system. One electro-mechanical valve of a pair is employed to introduce a relatively large continuous volume of a single component gas into the system, especially as represented by the charges of the gas added to purge the system, or initial charge of a gas into the blending system during blending, and the second of the pair is employed to introduce relatively small increments of the same gas into the system at relatively rapid intervals during blending.

The several valves are stacked, or mounted side by-side each atop a pressurized air, or gas manifold 125,126, respectively, located on each side of block 111. Each valve is held securely in place via Tsupports 127 (1271-12713) located at the terminal ends and in-between the pneumatic portion of an electro-mechanical valve unit (Figure 4), the Tsupports being bolted to the top of the gas manifolds 125, 126, respectively. The singly mounted two-way valves are identified as the pneumatic valve component thus positively forces the piston upwardly to uncover, or open an opening through which a component, is introduced, this action opening the valve. Conversely deenergizing the electrical valve component, or solenoid actuated valve can cut off the flow of air to the pneumatic valve component, let air escape from the valve via a suitable passageway to the atmosphere, and thereby permit the spring to return the pneumatic piston to a closed position. Electromechanical valve components of this type are well known and are available from various manufacturers.

The pressurized gas actuated pistons of the pneumatic valve components are affixed to valve stems, orto plungers, which are extended into the valve stem seats, or openings 113 of block 110 which, for convenience can be best illustrated by reference to Figures 5 and 5A. Figure 5 shows vent valve 130, comprised of an electrical valve component 1301 and a pneumatic valve component 1302 upon the piston 1303 of which is affixed a valve stem, or plunger 1304. Additionally, Figure 5 shows piston 1293 of the pneumatic valve component 1292 of product outlet valve 129 to which is affixed a plunger 1294. The valve stem, or plunger 1294, which is typical of all of the others, is shown in partial section in Figure 5A. In either embodiment, suitably the plungers 1294 and 1304, respectively, are affixed to the piston 1293 and 1303, respectively, via attachment to enlarged tubular shaped coupling members 1297, and 1307, respectively, within which the perforated ends of pistons 1293 and 1303, respectively, are projected, the coupling members being provided with openings 90 apart through which pins 1295, 1296 and 1305,1306, respectively, are projected to secure the plungers to each of the respective pistons.

A valve stem, or plunger, e.g., plunger 1294, is constituted of a relatively large perforated shank end through which a pin is passed to secure same to the tubular shaped coupling member 1297 and to piston 1293, and its middle and forward ends are provided with spaced apart concentrically projecting surfaces 1298, 1299 and 12910, 12911 between which seals, e.g., cup seals or o-rings, suitably o-rings 12912 and 12913 are mounted. The leading edge, or tip of the plunger is provided with a relatively small frustoconic shaped projection 12914 within the small inwardly faced necked portion of which is seated a third oversized o-ring 12915,or one whose crosssectional diameter is sufficient to provide a surface which extends or projects beyond the face of the member 12914. This design of the plunger permits the o-ring 1 2915 to be thrust downwardly tightly over a smaller diameter passageway,and seated to cover same and close, or prevent the passage of gas through said passageway. For example, when the plunger 1294 is activated and pressed inwardly toward component gas manifold 111, the o-ring 12915 is tig htly seated over the passageway 11 32A to prevent escape of a product gas blend component gas manifold 111 through an opening (not shown) immediately over the projecting surface 1291q, the diameter of which is restricted to cover only an area insideo-rings 12913, 129is. Conversely, when the plunger 1294 is lifted the o-ring 129its is unseated, and o-ring 12915 is moved aside to uncover passageway 1132A sufficiently to permit escape of gas through said opening (not shown), the gas flowing through passageway 11 32A from component gas manifold 111 to a source of use of the product gas blend. The o-ring 12913 located above o-ring 12915, on the other hand, prevents leakage and escape of gas which would introduce error into the system.

The o-ring 12913, however, provides a safety feature in combintion with vent passageway 1121 since gas which may by-pass o-ring 12913 enters passageway 1121 and is vented. The o-ring 12912, on the other hand, in view of its location, prevents escape of gas to the atmosphere, or valve exterior; the gas entering the vent passageway 1121. The design and function of all of the plungers of the valve assembly 100 are similar, inclusive of component gas valves CV-1A, CV-2A, CV-3A, CV-4A, CV-1 B, CV-2B, CV-3B, CV-4B and vent valve 130, although the function of the component gas valves is to inject a component gas from an external source into component gas manifold 111, and vent valve 130 is designed, in its normal function, to pass gases from component gas manifold 111 to vent passageway 1122.

The design of all of the component gas valves is, as suggested, similar to that of, e.g., product output valve 129. The operation of a component gas valve is also similar, e.g., as can be seen by reference to Figures 1 and 4, except that the lifting plunger on exposing opening 2A, which is communicated to a pressurized gas tank (not shown) containing gaseous Component A, the pressurized gas enters into the space between the two lowermost o-rings of the plunger of valve component CV-2A2 and flows through the uncovered passageway 1 133A to enter into component gas manifold 111. The operation of the pneumtic component valve CV-1A2 is similar in design and function to pneumatic component valve CV-2A2 except that the opening 1A in the supply manifold from the pressurized tank which leads into opening 1138, and passageway 11 38A leading to component gas manifold 111 is more restricted to limit the amount of gas flowing into component gas manifold 111 given a finite period of time.

Though the function of the vent valve 130, as suggested, is to pass gas from the component gas manifold 111 to vent passageway 1122 the design of plunger 1304 need be no different from that of the other valve plungers. the function can be changed to provide for the flow of gas from component gas manifold 111 to vent passageway 1122 by providing an enlarged opening 1138A (Figure 5) sufficient to span and overcome the sealing effect normally provided by the o-ring immediately adjacent o-ring 13015 which closes the passageway 1137A; or by both providing said enlarged opening 11 38A and eliminating said o-ring immediately adjacent o-ring 13015. In operation of the vent valve 130 therefore, in its closed position shaft 1304 of the vent valve 130 is thrust inwardly, the o-ring 13015 being pressed tightly over the passageway 1 1 a7A to close off flow between component gas manifold 111 and vent passageway 1122. On the lifting of the plunger 1304 the passageway 1137A is uncovered and gas is passed from component gas manifold 111 therethrough via the enlarged opening 1 138A to vent passageway 1122.

The operation and function of multi-component valve assembly 100 is further depicted, in schematic fashion, by reference to Figure 6. A typical cycle of operation stressing the function of said valve assembly 100 for the blending of gaseous components, beginning with the step of purging the system, is characterized as follows: 1. With vent valve 130 open and all other valves closed (i.e., component gas valves CV-2A, CV-4B, CV-6C, CV-8D, CV-1A, CV-3B, CV-SC, CV-7D, mix valve 128 and product output valve 129) pump 10' is started and gas is withdrawn from sphere 20' via line 11' and injected into the component gas manifold 111 via lines 12', 13' and then exhausted through the passageway 1 137A and vented through vent passageway 1122 (FigureS).

2. After the sphere 20' and entire system are exhausted, the vent valve 130 is then closed and mix valve 128 is opened. Component gas valve CV-1A is now opened, component gas A, the major gaseous component to be blended in the gaseous mixture, is then injected in relatively large amount per unit of time via opening 1A into component gas manifold 111, the gas passing through the mix valve 128 and line 14' to sphere 20'. Mix valve 128 is then again closed, vent valve 130 is then opened, pump 10' is started and the gaseous contents of the vessel 20', and system, are again vented. The cycle of filling vessel 20' with Component Gas A, and thereafter purging vessel 20 of Component Gas A is conducted several times until essentially all traces of a gaseous component other than Component A have been eliminated from the system. The purge thus completed, vent valve 130 is again closed. The system at low pressure, e.g., 5 psi, is now ready to receive the first component of the blend, viz. gaseous Compo nent A.

3. Mix valve 128 is again opened. Then valve CV-1A is opened and gaseous Component A is injected into component gas manifold 111, the gas flowing through mix valve 128 and line 14' into vessel 20' to fill same with Component Gas A up to the preselected pressure level, e.g., 50 psi. The gas warms up slightly and, on reaching the preselected preset pressure component gas valve CV-1A is closed. The gas cools, and the pressure in sphere 20' again drops below the preselected set-point.

Gaseous Component A is then again added to the component gas manifold 111 via valve CV-2A again raising the pressure to the said preselected pressure level, e.g., 50 psi. Valve CV-2A is then again closed, the pressure falling below the set point as the gas within the vessel cools. Continuous increments of gaseous Component A are added via valve CV-2A, the increments of Component A becoming smaller as the peselected pressure set point is reached, until such time that the last increment of gas maintains the preselected set point level after the gas has cooled. Component control valve CV-2A is then closed.

4-6. Component gases B, C and Dare then sequentiallv added to the svstem via operation of valves CV-3B and CV-4B; valves CV-SC and CV-6C; and valves CV-7D and CV-8D, in their respective sequence. On equilibration of the gas after the last increment of gaseous Component D is added, com ponent gas valve CV-8D is then closed, pump 10' is turned on, and the admixture of gaseous Compo nents A, B, C and D then circulated through the system and sphere 20' until the admixture is thoroughly homogenous; the admixture of gases being pumped by pump 10' via lines 12', 13' into the component gas manifold 111 of the valve assembly 100, the admixture passing through the open mix valve 128 via line 14' to sphere 20', and via line 11 back to pump 10' for recirculation. Pump 10, after complete homogenization of the gas blend, may then be shut off.

7. Product valve 129 can now be opened and, with mix valve 128 open and all other valves closed, pump 10 can again be turned on to pumpthe admixture of gases A, B, C and D as a product.

Claims (9)

1. Apparatus for producing a calibration gas mixture of known composition from a plurality of component gases separately introduced therein and blended together suitable for use in analytical instrumentation, the apparatus comprising a pressure vessel forming a gas mixing chamber sufficient to provide a heat sink for holding the gas temperature substantially stable during the blending of the gases, a pump connected via suitable conduit with said pressure vessel, a mix valve connected via suitable conduits in a series loop with said pump and said pressure vessel, the pump providing a means for circulating gas, and homogenizing the mixture of gases introduced into said chamber when the mix valve is open, a vent valve downstream of said chamber and mix valve being operatively communicated with said chamber for controlling flow from said gas mixing chamber, for substantially exhausting said gas mixing chamber by operation of said pump when said mix valve is closed, a pressure transducer means being provided for measuring the pressure of the gases in said mixing chamber and producing a usable output signal in response to the pressure present in said mixing chamber, a plurality of component gas inlet valves being provided, each of which is in fluid communication via said conduits with said mixing chamber and with a supply source of a component gas of the gas mixture for control ing the introduction of the desired component gases into said mixing chamber, and a product output valve for withdrawal of a product gas blend.

2. An apparatus as claimed in claim 1, comprising means for purging the mixing chamber with a first component gas to eliminate gas contaminates from the chamber; means for evacuating the mixing chamber of the purge gas by reducing the pressure in the mixing chamber to a predetermined low initial pressure, means for controlling the adding of a first component gas to the mixing chamber by way of the gas inlet valves to increase the pressure in the mixing chamber to a first predetermined level above said initial pressure for the first oas component means for controlling the adding of a second component to the mixing chamber by way of the gas inlet valves to further increase the pressure in the mixing chamber to a second predetermined level, and means for stirring the gases in the mixing chamber to obtain a homogeneous gas mixture of the gases in the mixing chamber.

3. An apparatus as claimed in claim 2, comprising means for controlling the adding of one or more additional component gases to the mixing chamber by way of the gas inlet valves, whereby each component gas is separately added to further increase the absolute pressure in the mixing chamber to a predetermined higher level, the stirring means being operable, when the last gaseous component has been added.

4. A multicomponent valve assembly for use in a system for blending accurately measured predetermined quantities of gaseous components received directly from separate pressurised supply tanks, as on input signals received from a computer, the system including a mixing vessel, a pressure transducer associated with said vessel for measuring the pressure of the gases in said pressure vessel, producing an output signal in response to the measured pressure and transmitting same to said computer, and a circulating pump connected in a closed series via conduits which form a circuit, the multi-component valve assembly operatively communicating the two ends of the conduits for flow of gas therethrough in providing the functions of purging contaminants from the system, admixing the gaseous components received from the supply tanks to form the gaseous blend, producing a product output blend of the admixed gases, and venting gases from the system, the valve assembly comprising a housing constituted by an elongate block within which is provided an axially oriented vent passageway extending longitudinally through the block to an inlet at the outer end of said block, through which gases can be vented from the system, a component gas manifold comprised of a passageway, axially oriented and parallel to said vent passageway, extending longitudinally from an inlet at the outer end of said block, within which component gases of the blend can be injected, and circulated for admixing said gases, a plurality of spaced apart valve seat openings, each extended from an inlet at the surface of said block laterally through said vent passageway to said component gas manifold to which it is communicated via an orifice leading into said component gas manifold, a mix valve which can be opened and closed as by signals received in programmed sequence from said computer, being mounted on said block over a valve seat opening, an end of the conduit from said mixing vessel being communicated with said valve seat opening, the valve being sufficient to open and close the orifice leading from said valve seat opening into said component gas manifold to open or cut off communication with said mixing vessel via said conduit extended therefrom, a product output valve which can be opened and closed as by signals received in programmed sequence from said computer, mounted on said block over a valve seat opening which is communicated via a conduit with a gas receiving source external to said system, the valve being sufficient to open and close the orifice leading from said valve seat opening to said component gas manifold so as to open or cut off communication between said component gas manifold and said receiving source conduit, a vent valve which can be opened and closed as by signals received in programmed sequence from said computer, mounted on said block over a valve seat opening, and an outlet communicating the component gas manifold via the orifice within the valve seat opening with said vent passageway, the valve being sufficlient to close the orifice of said valve seat opening to cut off communication between said component gas manifold and vent passageway or open said orifice and thereby open communication between said component gas manifold and vent passageway so that gas can be flowed freely through the component gas manifold, a plurality of component gas valves, each of which can be independently opened and closed as by signals received in programmed sequence from said computer, mounted on said block each over a valve seat opening, to each adjacent valve seat opening of which is connected a gas inlet which provides means for communicating a component gas supply tank for supply of a component gas, each valve being sufficient to close the orifice leading from said valve seat opening into said component gas manifold to cut off the flow of a component gas from a supply tank into the component gas manifold or open said valve seat orifice so that a component gas can be supplied by a supply tank to the component gas manifold, whereby the system can be purged in a cycle which includes opening the vent valve, closing all othervalves, and then starting the pump exhaust gas from the system, after which the pump can be stopped, the vent closed, and a component valve opened to provide the system with a component gas, this cycle being repeated a number of times to purge the system, and at the time the system is exhausted of gas on the last step of the cycle each component gas can be serially injected into the system by sequentially opening and closing the respective gas component valve to inject the gases of the blend and, on closing the component valve of the last gas to be added to the blend, the mix valve can be reopened, the pump again turned on to circulate, mix and thoroughly homogenize the gaseous blend, and the product output valve can then be opened to transfer the gas blend to a receiving source.

5. Avalve assebly as claimed in claim 4, wherein the housing is provided with a pair of parallel aligned axially oriented vent passageways which extend from a passageway at one end of the block closed by an end wall, the vent passageway extending longitudinally through the block to an inlet at the other end of said block, through which gases can be vented from the system, a component gas manifold comprising a passageway, axially oriented parallel to and located between said vent passageways, closed at the end leading into said passageway adjacent the closed end wall by a rupture disk through which gases can be vented to said vent passageways on rupture of the disk, the component gas manifold extending longitudinally to an inlet at the other end of said block, within which component gases of the blend can be injected, and circulated for admixing said gases, a plurality of spaced apart valve seat openings on alternate sides of said block, each extended from an inlet at the surface of said block laterally through a vent passageway to said component gas manifold to which it is communicated via an orifice leading into said component gas manifold, the mix valve is provided with a plunger sufficient to open and close the orifice leading from said valve seat opening into said component gas manifold to open or cut off communication with said mixing vessel via said conduit extended therefrom, the product output valve is provided with a plunger sufficient to open and close the orifice leading from said valve seat opening to said component gas manifold so as to open or cut off communication between said component gas manifold and said receiving source conduit, the vent valve is mounted on said block over a valve seat opening to said component gas manifold, provided with a plunger sufficient to close the orifice of said valve seat opening to cut off communication between said component gas manifold and vent passageway or open said orifice and thereby open communication between said component gas manifold and vent passageway so that gas can be flowed freely through the component gas manifold, and the plurality gas valves being constituted of a pair of alternate valves employed for each gas added, each mounted over a valve seat opening, one valve of the pair being employed for the introduction of an initial large volume of a given conmponent gas, the other being used for smaller additional increments of the gas during blending, each valve being provided with a plunger sufficient to close the orifice leading from said valve seat opening into said component gas manifold to cut off the flow of a component gas from a supply tank into the component gas manifold, or open said valve seat orifice so that a component gas can be supplied by a supply tank to the component gas manifold.

6. A valve assembly as claimed in claim 4, wherein the housing constituted by an elongate block comprises a multi-component valve assembly communicating two ends of a conduit constituting a circuit within which a calibration gas mixture of known composition can be produced from a plurality of component gases provided in the pressurized tanks from which the gases are separately introduced and blended together to form a blend suitable for use in analytical instrumentation, and in which circuit is further contained a pressure vessel which forms a gas mixing chamber sufficient to provide heat sink to hold the gas temperature substantially stable during the blending of the gases, a pressure transducer associated with said vessel for measur ing the pressure of the gases in said pressure vessel, and producing a usable output signal in response to the measured pressure, a circulating pump con nected via a conduit with said gas mixing vessel, the mix valve being connected via suitable conduits in line and in closed series with said pump and said pressure vessel, the pump providing a means for circulating gas, and homogenizing the mixture of gases introduced into said gas mixing chamber for substantially exhausting said gas mixing chamber when said mix valve is closed.

7. A valve assembly as claimed in claim 6, wherein the mass of the pressure vessel in the circuit within which the multi-component valve is contained is large relative to the mass of the gaseous contents introduced therein, and is at least 20 pounds for a vessel having an internal volume of 20 liters, the weight increasing proportionally for vessels having larger internal volumes.

8. A valve assembly as claimed in claim 4 or 5, wherein a vent passageway is provided on alternate sides of the elongate block, the component gas manifold being located between the two vent passageways, valves being located on alternative sides of the block, and wherein one each of a pair of the component gas valves is located on alternate side of the block for each component gas added, one valve of the pair being employed for the introduction of an initial large volume of a given component gas, the other being used for smaller volume additions of the gas.

9. A valve assembly as claimed in any one of claims 4,5,6,7 and 8 wherein an end of the component gas manifold of the block of the multicomponent valve is closed by a rupture disk which separates said component gas manifold from a passageway leading into said vent passageway, the rupture disk being one which ruptures at excessive pressure to vent gas from the component gas manifold into the vent passageway.