US2379633A - Gas proportioning system - Google Patents

Description

lJly 3, 1945.

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GAS PROPORTIONING SYSTEM Filed May l, 1942 Patented duly 3, i945 A s'mrf;

GAS PROPORTIONING SYSTEM Owen Garretson, Phillips Petroleum Delaware Detroit, Mich., assignor to Company, a corporation oi Application May l, 1942, Serial No. 441,348

(ci. is- 184) 18 Claims.

My invention relates to a gas manufacturing plant control system.

More specifically, I herein disclose anfimproved control arrangement for a gas-air mixing unit which results in greater safety of operation, and also in improved perfomance with regard to production of a uniform air-gas ratio.

It has in recent years become common and well-known practice to use liquefied petroleum gases in air-diluted form for industrial furnace fuel, and also for distribution in mains to supply dwellings and business establishment in' small communities, Gas proportioning plants for this purpose are inexpensive to erect and maintain, and are often economically'justifled as` replacement or supplanting equipment where coke-oven or other gas manufacturing systems have previously been used. The U. S, Patent No. 2,021,271, to R. W. Thomas illustrates a complete gas manufacturing plant of the type referred to.

Several types of proportioning or gas-air machines are in everyday use, and these may be classified under two general groups. One type employs variable air and gas openings to control the proportloning,'while the other type employs xed gas and air orifices, depending upon control of the differential pressure across the xed orilces to obtain the desired proportioning. My invention relates to the fixed orifice type of systern.

My invention has for an object the provision of a positive means to prevent formation of an explosive mixture in a gas-air dilutor.

A further object is to provide improved and more positive means for shutting 01T the gas suD- ply Whenever the gas machine is shut down for any reason. 'f

Another object of my improvement is to attain the above desirable characteristics by the use of standard devices which are obtainable at low cost.

It is an object to provide for incorporation of my improvements in already Iexisting gas-air plants, without requiring extensive revision -or alteration of the original piping or electrical circuits.

pressor blower, which discharges a finished gas containing air and a liquefied petroleum gas vapor in denite proportions. The discharge is carried by conduit I I to a gas holder, a high pressure storage tank, or directly to a distribution main (not shown). The nished gas is formed by induction of air and raw gas through the intake lines I2 and i 3, respectively. Air is taken into line I 2 directly from the atmosphere, rst passing through an air cleaner or filter It. Raw liquefied petroleum gas vapor (hereinafter called LPG) is supplied under pressure to the inlet I5 from a storage tank or vaporizer (not shown). A zero regulator, indicated generally by numeral I6 and shown in diagrammatic section, reduces the gas pressure in line i3 substantially to atmospheric level. .'Proportioning of the air and gas induced or drawn into the blower ill is obtained by the use of calibrated xed orifices il and i8 in the lines IZand I3, respectively, The mixed air and gas enter the blower through the common line I9.

The zero regulator IS may be any one of several makes which are obtainable as standard items of manufacture. The important features of this unit are that it should have a large main diaphragm 20 separated from the valve 2l by a Other objects and advantages will be apparent v from the following specification in which Figure 1 is a schematic diagram, partly in section, of that portion of a gas-air dilutor system wherein my improvements are applied.

Figure 2 isa sample wiring. diagram which A illustrates the operation of certain elements c ontained in` Figure 1. u

Referring specifically to Figure 1, the numeral I0 is an impeller such as a centrifugal or comsmaller sealing diaphragm 22. The spring 2,3 is a long, soft, tension spring which urges the valve ZI toward the closed position, and is provided with an adjustment screw 24. The space under the main diaphragm 20 is subjected to the pressure at the inlet of orifice I8 in line I3 through the pressure registry tube 25. The pressure (slightly subatmospheric) in line I2 before the oiice I'I is transmitted by another pressure registry tube 26 to the upper side of diaphragm 20. This is for the purpose of compensating for variation of air inlet resistance due to air filter Ill.

The equipment and system so far described is old and well known in the art. In operation, running Aof the blower I 0 imposes a suction in line I9, through orices I1 and I8 and in lines I2 and I3. Suction registered in line 25 induces opening of the valve 2| against the spring 23 and also against the suction in line 26. It should be noted that, due to the restricting effect of valve 2I, the suction imposed in lines I3 and 25 will tend to be greater than that in line I2, whose intake end is relatively unrestricted. By proper adjustment of the spring 23 and by proper selecti-on of orifice sizes (I1 and I8) the desired mixture of gas and air is obtained at the discharge II as long as the blower I0 continues to run. Upon shutting down the system, as when a suiicient supply ample. y

immaterial, since no ilow of any consequence will y 2 of nished gas has reached the storage holder, the spring 23 must be relied upon to close the valve 2| and the trapped pressure under diaphragm 22 has been relied upon to aid in maintaining the valve tightly closed.

In continuing with the description of those parts of the system illustrated which comprise my invention, it will be seen that a great im.- provement over the above is obtained. In the line 25, I provide a solenoid-actuated valve 21, which valve is open when the solenoid is energized and is otherwise spring-loaded closed. Further, I provide a pressure line 2liV which is supplied with gas or air under pressure, irom a source not shown. This line contains a pressure regulator 29 and a second solenoid valve 30. The line 28 joins line 25 through a T connection 3l located between.

valve 21 and zero regulator It. The valve 3u is closed when the solenoid is energized, being otherwise spring-loaded open (the operation is converse to that of valve 21). Solenoid valves of the required style are at nominal cost. The pressure regulator 29 is any small regulator capable of delivering a low outlet pressure, as 5 inches water column for ex- The flow capacity of this regulator is occur in the line 28.

In operation, the solenoids of valves 21 and 30 are energized from the same power supply which serves the electric motorI (not shown) used to drive the blower I0. While the blower motor is running, valve 21 is open, valve 30 is closed, and the system operates as before described. Upon opening of the motor power circuit when shutting down, the valves 21 and 30 are de-energized; valve 21 closes, valve 30 opens, and a positive pressure is therebyadmitted under diaphragm from the source controlled by regulator 29. This positive pressure provides certain and complete closure of valve 2I. Since the spring 23 is no longer lrelied on for complete closure, the zero regulator may be adjusted more delicately. The spring 23 can be softer, and hence better suited for its primary function, which is pressure regulation.

Upon re-starting, the solenoid valves are energized by closing of the motor circuit. Valve 30 closes and 21 opens, allowing pressure under the diaphragm 20 'to bleed into line I3 and thus permitting the zero regulator to open.

available commercially the switch will oe actuated before the upper limit of explosive mixture is reached.

A modification which is of benefit in cases where the pressure downstream from the zero regulator tends to reduce excessivelyat high flow rates is also shown in Figure l, wherein 3d is a by-pass line around the orifice I8, and is a needle valve in the by-pass line.

In operation, this modification permits a restricted iiow in the line 3II, due to the diierential pressure which acts across the orifice and hence exists also across the respective ends of line 313 and also across valve 35. This flow of gas through the li'ne 3d, while small in magnitude, aids in keeping the zero governor open to a greater extent than would otherwise be obtained. Hence, the characteristics of the Zero governor at high ilow rates can be improved or modified to suit by adjustment of valve 35. The valve is opened wider at high flow to compensate for pressure drop in line I3.

In the wiring diagram, Figure 2, it is seen how the opening of'vacuum switch 32 coacts to stop the motor 33 and operate the valves 21 and 30. It is also seen how the valves 21 and 30 are actuated whether the motor is stopped by openingof switch 32, or by any other switch, such as the manual emergency cutoff 33 or the storage tank 'maximum pressure switch 31. These latter switches do not appear in Figure 1, but are ordinarily incorporated in all systems such as the one of which Figure 1 is a par For simplicity of illustration, the vacuum switch 32 (in Figure 2) has been shown as wired directly in the power circuit before the motor. It

is understood that a safety starting switch wouldin most cases be used and that such use would As a further precaution against explosion haz- I ard, I provide a vacuum-operated switch 32. The pressure element of this switch is connected to a point in line 25 between line I3 and valve 21. This switch is set to open when the pressure in line I3 falls below a predetermined value, such as 3, inches water column vacuum, for example. The electrical circuit is a series connection in one side of the motor (or motor-starter) circuit, so that opening ci the switch 32 will shut down the blower motor, and at the same time actuate valves 21 and 30 as before described.

The purpose of the above vacuum shut-off is to prevent formation of an explosive mixture in the system. The normal gas-air mixture formed by the system is well without the range of inflammability. Failure or even diminution of the gas supply at the inlet of the zero governor, however, could reduce the B. t. u. value of the mixture to an inflammable or explosive value. The vacuum shut-ofi, however, will be actuated in such event, since failure of the gas supply will result in formation of a subatmospheric pressure in line I3. The cutoff setting of switch 32 is selected so that be within the scope of the system here contemplated. Other obvious departures may be employed within the scope of my invention; for example the solenoid valves 21 and 30 could as well be of a low-voltage type, using transformers to reduce the voltage from or 220 to 6, l2, 24, or any suitable value. My invention resides in the system disclosed, rather than in any specific mechanical structure of valves, switches, regulators, or other devices. l

I claim:

1. In an air-gas proportioning machine of the blower-dilutor type, the combination of: an electrical prime mover selectively associated with a source of electrical energy for driving the said blower; a pair of fixed orifices respectively associated-with an air intake and a raw gas intake of the blower; a normally closed zero regulator controlling the inlet pressure to the gas orifice and arranged to be opened by operation of the blower; a separate pressure source adapted to load the zero governor to closed position; a pair of solenoidactuated valves selectively associated with said electrical energy source and operative to apply said pressure loading when de-energized, and pressure-actuated switching means operatively aS- sociated with the outlet of said zero regulator to de-energize said prime mover and said solenoid valves when the outlet pressure from the Zero regulator attains a predetermined minimum value.

2. In an air-gas proportioningmachine including a gas supply, an air supply and a blower, the combination of: an electrical prime mover selectively associated with a source of electrical energy for driving the said blower; a pair of fixed oriiices respectively associated with an air intake and a raw gas intake; a zero regulator having a diaphragm. controlling the inlet pressure to the gas estacas oriiice; a rst conduit placing one side of said diaa phragm of the regulator in communication withl the upstream side of said orice and a second conduit placing the rst conduit in restricted communication with the downstream side of said orice.

3. In a gas proportioning system including a gas supply, an air supply, means for effecting a minimum pressure comprising an impeller and a zero governor controlling the admission of gas to the impeller, a separate source of pressure fluid connecting with the zero governor and 'valve means operably connected with the impeller, normally closed to prevent flow of said pressure uid to the zero governor during operation of the impeller but opening during non-operation thereof.

4. In a gas proportioning system including a 'gas supply, an air supply, means for eecting a minimum pressure comprising an impeller and having an electric motor circuit, a zero governor controlling the admission of gas to the impeller, a separate source of pressure fluid connecting with the zero governor and valve means operably connected with the impeller normally closed to prevent ow of said pressure uid to the zero governor during operation of the impeller but opening during non-operation thereof, said valve means being under control of the electric motor circuit of the impeller.

5. In a gas proportioning system including a gas supply, an air supply,'means for effecting a minimum pressure comprising an impeller and a zero governor controlling the admission of gas to the impeller, a separate source of pressure uid communicating withthe zero governor, automatic means for admitting pressure from said source to the zero governor diaphragm during non-operation of the system, and automatic means for removing said pressure during operation of the system.

6. In a gas proportioning machine including a gas supply, an air supply, means for eiecting a, minimum pressure comprising a zero regulator and an impeller having electrical controlling means, an independent source of pressure adapted to load the Zero regulator to close the same, and solenoid valve means connected with said electrical controlling means'adapted to remove said pressure loading during energization of the .electrical controlling means.

7. A controlsystem for gas proportioning systems having a zero regulator governing the raw gas feed, an air supply, means for effecting a minimum pressure comprising the zero regulator and an impeller having an electrically driven prime mover, a source of independent pressure for loading the zero regulator in a closed position, valve means adapted to electrically apply or remove said pressure loading, and switching means operable by a predetermined minimum pressure in the outlet of said zero regulator to disconnect the prime mover from its source of electrical energy, whereby the prime mover is placed out of operation and the said valve means is actuated to positively close said valve regulator.

8. In an air-gas.proportioning machine or" the blower type, a gas supply, an air supply and a blower, the combination of an electric prime mover for the blower associated with a source of electrical energy for driving the said blower; a pair of fixed orifices respectively associated with the air intake and the raw gas intake; a zero regulator controlling the inlet pressure to the gas orifice; a separate pressure source adapted to-loadl the zero governor closed; a pair of solenoid actuated valves associated with said electrical energy source operative to apply said pressure loading when de-energized, and operative to remove said pressure loading when energized.

9. In a gas flow line comprising a rst gas conduit, a, zero regulator controlling iiow through said rst conduit, a diaphragm actuating the zero regulator to open and close said rst conduit to the flow of gas therethrough, a restricted oriiice in the conduit downstream of the zero regulator, and a second conduit transmitting gas under pressure from the first conduit at a point between the zero regulator and the orifice to one side of the zero regulator diaphragm to urge the dia-a phragm to close said first conduit and give zero regulation, the improvement comprising e iirst valve in said second conduit, a source of gas under pressure, a third conduit connecting said source 0f gas to said second conduit at a point between said first valve and said zero regulator, a second valve in said third conduit, and'means operable to open said first valve and close said second Valve when the zero regulator is to control the tiow in Athe iirst conduit and to open said second valve and close said iirst valve when the zero regulator is to be biased shut by said source of gas.

l0. In a gas flow line comprising a rst gas conduit, a zero regulator controlling flow through said rst conduit, a diaphragm actuating the zero regulator to open and close said rst conduit to the now of gas therethrough, a restricted orice in the conduit downstream of the zero regulator, and a second conduit transmitting gas under pressure from the rst conduit at a point between the zero regulator and the Iorifice to one sideof the zero regulator diaphragm to urge the diaphragm to close said first conduit and give zero regulation, the improvement comprising a third conduit connecting said second conduit with the first conduit downstream of said restricted orice,

and a variable restricting valve in said third conduit whereby the operation of the zero regulator is made more responsive to flow.

l1. In a gas flow line comprising a first gas conduit, a zero regulator controlling fio'w through said first conduit, a diaphragm actuating the zero regulator to open and close said rst conduit 1 to the flow of gas therethrough, a restricted ori- -duit connected ce in the conduit downstream of the zero regulator, and a second conduit transmitting gas under pressure from the first conduit at a point between the zero regulator and the orice to one side of the zero regulator diaphragm to urge the diaphragm to close said'rst conduit and give zero regulation, the improvement comprising a gas impeller connected to said first conduit downstream of said restricted orice, a motor driving.

said gas impeller, a power supply for said motor, a cut off for said power supply actuated by a predetermined minimum pressure and a third conto said second conduit and said cut od whereby upon said predetermined minimum pressure being reached in the third conduit the power supplied to said motor is cut off.

l2. In a gas ow line comprising a first gas conduit, a zero regulator controlling ow through and a second conduit said rst conduit, a diaphragmactuating the zero regulator to open and close said first conduit to the ow of gas therethrough, a restricted orifice in the conduit downstream of the zero regulator, transmitting gas under pressure from the rst conduit at a point between the zeroregulator and the orifice to one side of the zero regulator diaphragm to urge the da a second valve in said third conduit, a fourth conduit connecting said second conduit with the first conduit downstream of said restricted orifice, a variable restricting valve in said fourth conduit whereby the operation of the zero regulator is made more responsive to now..

i3. 'in a gas now conduit, a zero regulator controlling ow through said first conduit, a diaphragm actuating the zero regulator to open and close said first conduit to the flow of gas therethrough, a restricted orifice in the conduit downstream of the zero regulater, and a second conduit transmitting gas under pressure from the first conduit at a point between the zero regulator and the orifice to one side of the zero regulator diaphragm to urge the diaphragm to close said first. conduit and .give zero regulation, the improvement comprising a first valve in said second conduit, a source of gas under pressure, a third conduit connecting said source of gas to said second conduit at a point between said first valve and said zero regulator, a second valve in said third conduit, a gas impeller connected to said first conduit downstream `of said restricted orifice, an electric motor driving said gas impeller, an electric circuit supplying power for said motor, means operated by flow of electric current in said circuit to open said first valve and close said second valve and operated by failure of ow of electric current to close said rst valve and operi said second valve whereby the zero regulator is biased to close said first conduit when said electric circuit is open, a cut off to open said electric circuit actuated by a predetermined minimum pressure and a fourth conduit connected to said second conduit and said cut off whereby upon said predetermined minimum pressure being Ireached in the fourth conduit the electric circuit to the motor and said valves is opened. f

14. In a gas flow line comprising a rst gas conduit, a zero regulator controlling flow through said rst conduit, a diaphragm actuating the zero regulator to open and close said first conduit to the flow of gas therethrough, a restricted orifice in the conduit downstream of the zero regulator, and a second conduit transmitting gas under pressure from the rst conduit at a point between the zero regulator and lthe lorifice to one side of the zero regulator diaphragm to urge the diaphragm to close said first conduit and give zero regulation, the improvement comprising a first valve in said second conduit, a source of gas under pressure, a third conduit connecting said source of gas to said second conduit `at a point between said first valve and said zero regulator, a second valve in said third conduit, a4 gas impeller connected to said first conduit downstream of said restricted orifice, an electric motordriving said gas impeller, an electric circuit supplying power for said motor, means operated by iiow of electric current in said circuit to operi said first valve and close said second valve and operated by failure -of flow of electric current to close said first valve and open said second valve whereby the zero regulator is biased to close said first conduit when said electric circuit is open,

f a cut off to open said electric circuit actuated by a predetermined minimum pressures.

fourth line comprisingy a rst gas conduit connected to said second conduit and said cut on whereby upon said predetermined minimum pressure being reached in the fourth conduit the electricf circuit to the motor and said valves is opened, second conduit with the rst conduit downstream of said restricted orifice, and a variable restricting valve in said iifth conduit whereby the operation of the zero regulator is made more responsive to ow and said cut off more responsive to pressure.

l5, In a gas supply system in which an inflammable gas is mixed with air, a control system for preventing the formation of explosive mixtures of gas and air comprising in combination a gas line, an air line, thegas and air lines jo g to form a fuel line, an impeller in the fuel line impelling the fuel into a storage tank, 'a motor driving the impeller, electrically controlled means for positively closing the zero regulator independent of pressure in the gas, air and fuel lines, an electrical network including the motor windings, a source of electrical power and 'the electrically controlled means, and Vmeans for opening the circuit in the network comprising a switch responsive to a predetermined low pressure in the gas line, a manual switch and` a switch responsive to a predetermined high pressure in the storage tank, whereby when conditions under which an explosive mixture could form exist the gas line is closed.

i6. In a gas supply system in which an inflammable gas is mixed with air, a. control system for preventing the formation of explosive mixtures of gas and air comprising in combination a gas line, an air line, the gas and air lines joining to form a fuel line, an impeller in the fuel line impeiling the fuel, a motor driving the impeller,

electrically controlled means for positively closing the zero regulator independent of pressure in the gas, air and fuel lines, anelectrical network including the motor windings, a source of electrical power and the electrically controlled means, and means for opening-the circuit in the network comprising a switch responsive to a predetermined low pressure in the gas line, whereby when conditions under which'an explosive mixture could form exist the gas line is closed.

17. In a gas supply system in which an inflammable gas is mixed with air, a control system for preventing the formation of explosive mixtures of gas and air comprising in combination a gas line, an air line, the gas and air lines joining to form a fuel line, an impeller in the `fuel line impelling the fuel, a motor driving the impeller, an electrical network including the motor windings, and a source of electrical power, and means for opening the circuit in the network comprising a switch responsive to a predetermined low pressure in the gas line.

18. In a gas supply system in which an inammable gas is mixed with air, a control system for preventing the formation of explosive mixtures of gas and` air comprising in combination a gas line, an air line, the gas and air lines joining tc form a fuel line, an impeller in the fuel line impelling the -fuel into a storage tank, a motor driving ythe impeller, an electrical network including the motor windings, and a source of electrica power, and means for opening the circuit in thl network comprising a switch responsive to a pre ydetermined low pressure in the gas line, a man ual switch and a switch responsive to a prede a fifth conduit connecting said,

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