US3090038A - Hazardous atmosphere detecting and signalling system - Google Patents

Description

May 14, 1963 v. w. KLEIN ET Al.

HAZARDOUS ATMOSPHERE DETECTING AND SIGNALLING SYSTEM Filed June 8, 1959 United States Patent O 3,090,038 HAZARDOUS ATMOSPHERE DETECTING AND SIGNALLING SYSTEM Vernon W. Klein, Kansas City, Mo., and Edwin C. Jones, Jr., deceased, late oi verland Park, Kans., by Cleo iones, administratrix, verland Park, Kans., assignors to Great Lakes Pipe Line Company, Kansas City, Mo., a corporation of Delaware Filed June 8, 1959, Ser. No. 818,872 6 Claims. (Cl. 340-237) This invention relates to detection and warning as to the existence of a potentially combustible atmosphere in a selected location, and refers more particularly to a method and apparatus especially suited for this purpose.

While there are many other situations in which the invention is useable, the primary one we have found is in connection with small buildings which enclose the pumping apparatus on hydrocarbon pipe lines. As is known, these pumping stations are located at intervals along the line and include such pumping equip-ment as is necessary, along with automatic control systems. Leakage of liquids, gas vapors or gases yfrom the lines at these points is likely to cause such a concentration of the combustible material in the enclosure as to result in an explosion should there be some means of ignition resulting from operation of the pumping equipment or other cause. The problem is particularly important where the station is unmanned.

It has long been a problem in the pipe line industry as to how to provide for an eifective and reliable surveillance over conditions in such enclosures and to provide a system which will, when conditions appear dangerous, further operate to provide a -signal which can be conveyed over large distances to some remote control point. We are aware 'of devices which operate to detect a condition which has already become hazardous, but this does not ll the need that exists. Our particular desire is to afford a method, and equipment -for carrying out same, which is capable of detecting and signalling the existence of a condition which, while not immediately dangerous lfrom the standpoint of imminent explosion, nevertheless is potentially so. Stated otherwise, it is an object of the present invention to provide for detecting and signalling the presence in a vselected area of a certain proportion of combustible gasoline vapor or gas which is less than that which will produce an explosion in the yarea at that moment. By such `an approach it is possible, when a potentially `dangerous `condition is detected, to dispatch workmen to the trouble point and effect the necessary repairs in the line or pumping equipment or shut down the equipment automatically before the explosion condition in the area occurs.

Another important object of the invention is to pro-A vide a detection and warning system of the character described which includes an arrangement whereby `the system is self-checking as to operability. It is a -feature of the invention in this respect that in the event of a breakdown or of improper operation of the system, a signal is likewise immediately transmitted to the remote control station so that work-men can be 4'dispatched at once. In the preferred form of the invention, -the signal circuit which is operated as a result of the breakdown of the detecting system is differentiated and distinct from that which signals the warning of the existence of the potentially dangerous condition so that the remote control point will be advised at the outset as to what to expect.

A further object of the invention is to provide a detection and warning system which is extremely simple in operation and low in first cost and expense of maintenance. The system is made up of simple components ICC , which are readily available on the market, and in its iinal assembled condition is compact and occupies little space. y

Other and yfurther objects of the invention together with the features of novelty Iappurtenant thereto will appear in the course of the following description.

`In the laccompanying drawing which forms a part of the specification and is to be read in conjunction therewith, and in which like reference numerals indicate like parts in the various views;

The single FIGURE is a schematic representation of a typical system embodying and operating in accordance with the invention.

As has earlier been stated, one of the chief objects of the invention is to detect and signal the presence of combustible gasesrin a selected `area before enough is present to cause an explosion therein. To this end our invention comprises partially enriching the atmosphere taken from the area with a combustible gas of the general type being tested for, the enriching taking place prior to or at the time of passing the :atmosphere through the testing device. The degree of enrichment can be varied, `depending on the extent of the early warning desired, but in all cases it is less than that which will produce combustion when an igniting means is brought into icontact with the mixture. As will be evident, `so long las the atmosphere in the area remain-s `free of combustible matter, the proportion of combustible matter to air in the testing device will remain below the explosive range. However, should the yair become contaminated with combustible matter, this will serve to enrich the mixture in the testing device and rellect a higher concentration than is actually present in the :atmosphere being tested. Wlhen the enriched mixture reaches the explosive limit the testing device voperates tor produce the ydesire-d signal. The Ifact that the area itself is not yet in an explosive condition affords an yopportunity Ifor `trouble-shooters to be dispatched to the scene and the necessary repair work can be accomplished before danger tothe equipment and the line is established, or in the alternative, the equipment can be shut downxbyl an appropriatev control system operated 'responsive to the signal.

`In applying the method in actual practice' we have employed an explosion-type testing device which is equipped with means =for continuously ilowing atmospheric gas from the area through an explosion chamber. This chamber is equipped with a sparking or igniting-means which, as testing continues, is continuously iired. Also fed to the chamber is a continuo-uscow ata preselected rate of a known combustible gas. Since a -major application of the invention is in connection with s By the medium of a signal system the explosion causes -signals to be sent indicating the existence of trouble.

As will later be described in greater detail, we have also provided a means of periodically checkingtlhe operabilityof the testing device and of signalling abreakdown of the testing equipment if that should occur.

indicates a conventional air blower or pump which is driven by motor 11. The intake of the blower connects with the area to betested, for example, the inside of a pump house or station (not shown), and a conduit or pipe 12 leads from the discharge of the blower to a comv bustion chamber 13. The air pump is preferably continuously driven by the motor 11, which is connectedby conductors 15 and 16 with electrical supply lines 17 and 18. In the present example an alternating current potential of 115 volts is applied to these latter lines and a main control switch 14 is `provided in the line 18.

The combustion chamber 13 is a simple construction, being a simple hollow enclosure having four nipples 13a, 13b,.13c and 13d. Air line 12 is connected with nipple 13a through a suitable'ame arrester 12a and a conventional spark plug 19 is fitted into nipple 13b. Nipple 13e contains a pressure-operated, normally open switch 20 which has a pressure-sensitive mechanism exposed to the inside of the chamber. Switches of this type are well known, consequently the construction will not be detailed here. Suffice it to note that the switch includes a contact 21 which, as will later be explained, at times is operated to close an electrical circuit on the occurrence of an explosion within the chamber. An exhaust conduit 22 is connected with nipple 13d, this conduit being open at all times to permit continuous ow through the chamber from the air pump. YThe exhaust is sufficiently restricted, however, as to cause enough pressure build up within the chamber Iwhen an explosion occurs as to operate switch 20.

The air or atmospheric gases continuously passed through the combustion chamber from pump 10 are enriched with a combustible gas by means of a pressurized supply tank 23 and a conduit 24 which is coupled through another flame arrester 24a with the air conduit immediately ahead of the combustion chamber. To provide for control of the rate of gasow a pressure regulator Z5 may be intenposed in the gas line and a manometer 26 may be used to determine the flow rate. Under normal operating conditions we have found that the flow of the gas should be regulated to produce a concentration in the combustion chamber of from 40% to 50% of that necessary to'produce combustion upon ignition.

The ignition means for the device comprises nothing more than a simple and conventional arrangement which includes a motor 27, breaker 28 and spark coil 29. The motor is supplied with alternating current at line voltage through conductors 30 and 31 and is designed to produce from 20 to 30 sparks per minute. Direct current is supplied the Vignition system from a stepdown transformer and rectier 32 through a system of conductors and switches including conductors 33, 34, 34a normally closed contact 35, conductor 36. The ignition system is electrically connected with the spark plug 19 by means of conductors '37. Preferably the output of the transformerrecthier is 6 volt direct current.

During normal operation of the system the air and the combustible gas are intermixed and flowed continuously through the chamber 13 and subjected to substantially continuous sparking through the medium of plug 19 and the earlier described ignition syste-m. Since the mixture inside the chamber is ordinarily too lean to ignite under normal operating conditions contact 21 will remain open. Y

It will be observed that the pressure switch 20 is included in series in a direct current circuit which includes conductors 33, 34, 38, 39, normally closed contact 40, conductors 41 and 42, a switch 43, conductor 44, relay coil 45 and ground 46. The pressure switch 20 also governs a circuit extending from the juncture of 41 with 42 through conductor 47, a normally closed contact 48 and an incandescent lamp 49. The lamp 49 is preferably mounted on the control panel for the station (not shown) or other easily visible location at the station itself.

As is believed evident the relay coil 45 forms part of a multiple contact relay which includes besides normally closed contact 35, normally open contacts Sti, 51 and 52, more of which will be said later.

The operation of the system as thus far described, is

. as follows. If for yany reason the atmosphere in the area being tested becomes contaminated with gasoline vapor or other combustible gas this will be rellected in the sample that is continuously being withdrawn and passed through the combustion chamber. As the contamination increases, so the concentration in the combustion chamber will increase also, and when it has reached the level for which the testing device is regulated the spark plug will cause an explosion to take place within the chamber. `Immediately upon occurrence of the explosion, switch 2l) is actuated and closes contact 21.

The closing of the contact 21 has two immediate results. First it energizes the relay coil 45 to open contact 35 and close contacts Sti', 51 and 52. The closing of contact Si) serves the function of permanently energizing the relay through conductors 33, 34, 34a, branch Sila, 42, switch 43 and conductor 44, thus maintaining the relay locked in the condition initially caused by the explosion. At the same time the spark plug is deenergized by opening of contact 35 to prevent any further explosion.

The closing of contact 5-1 completes a circuit through conductors 33, 34, 53, normally closed contact 54, conductor 55, contact 51 and conductor 56 to the coil 57 of a signal relay which can be employed to close or open, as the choice may be, a circuit 58 which includes means (not shown) for transmitting a signal to a remote location such as a central control and observation center. Preferably the circuit 58 also controls the main power supply to the pumping station and upon actuation of the signal relay 57 shuts off the station. To indicate at the station itself that a hazardous condition exists and that the pumping apparatus has been shut down as a result thereof, the lamp `49' is illuminated to the closing of the circuit to that element through pressure switch 20, as earlier described.

It will be apparent that the circuits as thus far explained will remain inthe condition described until such time as they are. reset by a momentary opening of the reset switch `43. This is preferably a manually operated switch which is manipulated by the workmen after they have inspected the station and corrected the condition which prompted actuation of the detector apparatus. Incidentally, it may be helpful to note at this time that reset switch 43 also has another function under certain conditions later to be described. At any rate, in resetting the signalling circuit the opening of switch 43 between conductors 42 and 44 deenergizes relay coil 45 with the result that the contacts 35, S0, 51 and 52 return to their normal illustrated condition. This results in commencement again of the normal testing operation, the signal relay `57 being deenergized from the circuit to the ignition system again being closed so that a spark will be obtained in the chamber.

In order to maintain a surveillance over the testing device itself and provide means of conveying information as to whether or not it is operating properly, we have devised the timed checking system now to be described. The key to the checking system is a time switch 59 which controls a pair of contacts 60 and 61. A rotary cam 62, driven at four revolutions per hour, for example, by a motor 63, serves to periodically shift lthe switch arm from engagement rwith contact 60 to engagement with contact 61, as illustrated by the broken lines. The cam is so designed as to hold the arm in engagement with contact 61 for a period equivalent to live to ten sparks of the ignition system. It will be understood, of course, that star-shaped cams or other types of cams may be employed, the object being to obtain at selected intervals a closing of the contact 61.

Upon the closing of contact 61 it will be observed that one circuit is completed from conductor 33 through 34, 34b, contact 61 and conductor 64 to a branch conductor 65 which supplies a relay coil 66 of another multiple contact relay. A resistor 67 isin series with coil 66 and a condenser 68 is parallel with the coil, thus to provide a momentary time delay in complete energization of the coil. This is for the purpose of insuring that before no1'- mally closed contact 69 of this relay is opened current will be transmitted past the relay through conductors 70 and 71 to the coil 72 of still another relay.

lt is important to understand at this point that the latter relay is a dual relay with opposed coils, one of which (coil 72) can be considered as the operating coil and the other (coil 73) as the reset coil. In the case of this double-relay element the actual structure includes means (not shown) for holding the armature in the position it assumes upon energization of the particular coil involved even though the circuit may later be broken. Thus a momentary energization of coil 72 results in closing of contacts 74, 75 and 76 and yopening of contacts 4S and 54. The contacts will remain in this condition until such time as the second coil (coil 73) is energized, at which time they will be returned to their original condition and remain there until coil 72 is again energized. Relays of this type are readily available on the market.

Returning now to an` outline of the sequence of events occurring upon energization of coils 66 and 72 through the closing of contact 61, it will be observed that as full power builds up in coil 66 contacts 69' and 40 of that relay are opened and contact 77 is closed. The opening of contact 69 breaks the circuit to the coil 72 but this has no effect other than to deenergize the coil as earlier explained, the contacts upon which coil 72 acts having, as a result of the momentary energization of the latter, been acted upon. As to contact 40, by opening this contact fthe circuit from pressure switch 20 to relay 45 is broken. Thus in eiect the closing of contact 61 operates to disable the warning signal circuit so that even if an explosion subsequently occurs in the chamberI land contact 21 is closed no energization of the warning signal relay 57 will take place.v

It will be observed, however, that the opening of contacts 40 and 69 is accompanied by the closing of contact 77 which serves to put the reset coil 73 of the dual relay in series with the pressure switch 20 through conductor 39, contact 77 and conductors 77a and 7S. For the moment, however, this circuit remains open since the pressure switch is open.

Turning now -to the eiect obtained by energization of the operating coil 72 of the dual relay, immediately upon closing of contact 74 a circuit is completed in conductors 79 and 80 through a solenoid operated valve 81 interposed in the air line 12. This valve is arranged to restrict the air ow through line 12 so tha-t in the chamber the proportion of combustible gas to air will immediately rise to a value which will bring about combustion when subjected to a spark from plug 19. 4In other words, the purpose is to artificially create an explosive condition in the chamber. This condition is obtained while contact 61 remains closed.

Upon the occurrence of an explosion during the test cycle (the occurrence of which assures that the system is operating normally) a circuit will be closed from the direct current source conductor 34 through conductor 3S, contact 21, conductor 39, contact 77 and conductor 77a and 73 to the reset oil 73. This coil will then operate to restore the relay contacts 48, 54, 74, 75 and 76 to the condition illustrated. As a result valve 31 will again open to permit normal air flolw. And shortly thereafter switch arm 59 will again fall opening contact 61 and closing contact 60 with the consequence that relay coil 6 66 is deenergized and contacts l40, 77 and 69 restored to their original condition.

It will be evident therefore that if all goes well during the test cycle -there is no signal of any sort transmitted.

We turn now, however, to the consequence of the failure of an explosion to occur during the test cycle. In this event there will be no energization of the reset coil 73. Thus when the switch 59 again closes contact 60 'at the end of the test interval the contacts of the dual relay will be in the position they were set by relay 72 or opposite that illustrated. Consequently as contact l60 is closed the circuit is completed from conductor 34b (which always has the direct current potential imposed upon it) through contact 60, conductor `82, contact 75, conductors 47 and 42, reset switch 43 and conductor 44 to the relay coil 45. This causes contacts 50, 51 and 52 to close. Since contact 76 at the dual relay is closed this immediately results in a circuit being completed from conductor 34 through conductor 53, contact 76, conductor 83, contact 52 and conductor 84 to another signal operating relay 65 which controls a circuit 86. The circuit 86 is generally like circuit '5S but is independent thereof and is arranged to communicate a separate signal which in this case indicates that there is some failure in the testing equipment itself. It will be understood, of course, that the power lines for the pumping equipment at the station can be controlled by circuit 86 so that when relay 85 is energized the pumping equipment will be shut olf until workmen can arrive upon the scene.

When workmen arrive at the pumping station to eitect whatever repairs are necessary, the testing system can be reset for operative condition by switch 43. Manipulaltion of this switch in addition tot deenergizing relay 45, :as earlier described, also connects conductor 34b directly with with the reset coil 73 through conductors 87 and '78. As earlier explained, the energization of coil 73 resets the dual relay to the illustrated usual condition and thus prepares the system again for normal operation. Y

vIt should perhaps be explained lthat the switch 43 is preferably of the bias-type. In other words, pressure against the switch serves to break the contact between conductors 42 and 44 and v-at the same time establish contact between conductors 34h and 87. When the switch is released it will return to the illustrated position again connecting 42 and 43.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in `a limiting sense.

Having thus described our invention, we claim:

l. Apparatus for maintaining surveillance over and sensing the presence of a potentially explosive concentration of combustible gas in a selected area prior to the time that the concentration is suiiicient to produce combustion in the area comprising a combustion chamber, a pressure sensitive switch mechanism associated with said chamber and operated in response to the occurrence of an explosion within said chamber, a signalling circuit controlled by said switch and operable to transmit an electrical signal upon the occurrence of said explosion, means for owing atmosphere from the area into said chamber, means for adding a known quantity of combustible gas to the chamber, said chamber including ignition means therein, a checking mechanism associated with said signalling circuit and including means for artificially inducing a test explosion in said chamber at timed intervals, said checking mechanism including means for temporarily disabling the signalling circuit and operable to restore the signalling circuit to operative condition upon the occurrence of a test explosion.

2. Apparatus as in claim l including a second signalling circuit governed by said checking mechanism and operable upon the failure of a test explosion to occur to transmit a separate signal indicating failure of the apparatus to perform properly.

3. Apparatus for maintaining surveillance over and sensing the presence of a potentially explosive concentration of combustible gas in a selected area comprising a combustion chamber, 'a pressure sensitive switch mechanism associated with said chamber and operated in response to the occurrence of an explosion within said chamber, a signalling circuit controlled by said switch and pera'ble to transmit an electrical signal upon the occurrence of said explosion, means for ilowing atmosphere from the selected area into said chamber, said chamber including ignition means therein, a checking mechanism associated with said signalling circuit and including means for artificially inducing a test explosion in said chamber at timed intervals, said checking mechanism including means for temporarily disabling the signalling circuit and operable to restore the signalling circuit to operative condition upon the occurrence of a test explosion.

4. Apparatus for maintaining surveillance over and sensing the presence of a potentially explosive concentration of combustible gas in a selected area prior to the time that the concentration is suiicient to produce combustion in said area comprising a combustion chamber,`

ignition means continuously tired within the chamber, mechanism continuously iowing atmospheric gas from the selected area through the chamber, a source of combustible gas of known properties, means connected with said source and said chamber and operating to enrich said owing atmospheric gas With a controlled proportion of said combustible gas, the proportion being less than that which will produce combustion in the chamber in the absence of combustible gases in the selected area, signalling means operable responsive to the occurrence of an explosion in the chamber to produce a signal, means operable automatically at predetermined intervals to cause an articially formed combustible concentration to occur in said chamber, and disabling mechanism coupled with said last named means and operable to disable said signalling means during the time that said artificially VJformed combustible concentration is delivered to said chamber.

5. Apparatus for maintaining surveillance over and sensing the presence of a potentially explosive concentration of combustible gas in a Selected area prior to the time that the concentration is sufficient to produce combustion in the area, comprising a combustion chamberf a source of combustible gas of the type for which the area is being tested, means continually passing through said chamber a mixture of atmospheric gas from said area and combustible gas from said source, the mixture being such as to be normally noncombustible, ignition means providing igniting temperatures within said chamber and operable to explode the mixture within the chamber whenever a combustible mixture is attained, a pressuresensitive switch mechanism associated with said chamber and operated in response to the occurrence of an explosion within the chamber, a signalling circuit controlled by said switch mechanism and operable to transmit an electrical signal upon the occurrence of an explosion within the.

chamber, a timing mechanism operable at timed intervals to remove said signalling circuit from control .by said switch mechanism for a selected period, means controlled by said timing mechanism and operable, during said removal, to alter said mixture to a combustible state whereby to artilicially induce a test explosion in said chamber, and means including said switch mechanism and operable, in response to and upon the occurrence of a test explosion, to reestablish the association between said switch mechanisrn and signalling circuit.

6. Apparatus as in claim 5 including a fault signalling circuit operable to signal the failure of a test explosion to occur.

References Cited in the tile of this patent UNITED STATES PATENTS 1,150,505 Diehl Aug. 17, 1915 1,977,481 Jones Oct. 16, 1934 2,170,056 Keinath Aug. 22, 1939 2,673,339 Gray Mar. 23, 1954 2,727,225 Lorenzetto Dec. 13, 1955

Claims (1)

1. APPARATUS FOR MAINTAINING SURVEILLANCE OVER AND SENSING THE PRESENCE OF A POTENTIALLY EXPLOSIVE CONCENTRATION OF COMBUSTIBLE GAS IN A SELECTED AREA PRIOR TO THE TIME THAT THE CONCENTRATION IN SUFFICIENT TO PRODUCE COMBUSTION IN THE AREA COMPRISING A COMBUSTION CHAMBER, A PRESSURE SENSITIVE SWITCH MECHANISM ASSOCIATED WITH SAID CHAMBER AND OPERATED IN RESPONSE TO THE OCCURENCE OF AN EXPLOSION WITHIN SAID CHAMBER, A SIGNALLING CIRCUIT CONTROLLED BY SAID SWITCH AND OPERABLE TO TRANSMIT AN ELECTRICAL SIGNAL UPON THE OCCURRENCE OF SAID EXPLOSION, MEANS FOR FLOWING ATMOSPHERE FROM THE AREA INTO SAID CHAMBER, MEANS FOR ADDING A KNOWN QUANTITY OF COMBUSTIBLE GAS TO THE CHAMBER, SAID CHAMBER INCLUDING IGNITION MEANS THEREIN, A CHECKING MECHANISM ASSOCIATED WITH SAID SIGNALLING CIRCUIT AND INCLUDING MEANS FOR ARTIFICIALLY INDUCING A TEST EXPLOSION IN SAID CHAMBER AT TIMED INTERVALS, SAID CHECKING MECHANISM INCLUDING MEANS FOR TEMPORARILY DISABLING THE SIGNALLING CIRCUIT AND OPERABLE TO RESTORE THE SIGNALLING CIRCUIT TO OPERATIVE CONDITION UPON THE OCCURRENCE OF A TEST EXPLOSION.

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