US 2976950 A
Description (OCR text may contain errors)
March 28, 1961 o. c. SMITH METHOD AND APPARATUS FOR PREVENTING MOISTURE ACCUMULATION IN TANKS 2 Sheets-Sheet 1 Filed Jan. 17, 1958 INVENTOR: OSCAR C. SMITH BY +W ATTORNEYS March 28, 1961 o. c. SMITH 2,976,950
METHOD AND APPARATUS FOR PREVENTING MOISTURE ACCUMULATION IN TANKS Filed Jan. 17, 1958 2 Sheets-Sheet 2 OSCAR C, SMITH INVENTOR ATTORNEYS United States Patent METHOD AN D APPARATUS FOR PREVENTING MOISTURE ACCUMULATION IN TANKS This invention relates to a method and an apparatus for preventing moisture accumulation in a tank contain- 112g fluid, such as bulk transformer oil, fuel oil, gasoline, e c. a
As is well known, transformer oil is commonly used as an insulating medium in electrical transformers. It has been determined that the infiltration of moisture into the transformer oil acts as a detriment to itsinsulating properties. The problem of moisture contamination is accentuated because a tank containing this transformer oil is normally vented allowing it to breathe as a safety precaution. This breathing" of the tank prevents the build-up of excessive pressure within the tank such as might occur by the sun heating up the tank andcausing the oil therein to greatly expand. Conversely, it is also necessary to prevent the build-up of an excessive vacuum condition within the tank which could be caused by the cooling of the transformer oil carried therein and itsconsequent contraction. The breathing of the tank is accomplished by nothing more than providing vent means for it wherein'the pressure or lack of pressure within the tank will be adjusted to place the tank interior under a pressure in substantial equilibrium with the atmospheric pressure prevailing.
If breathing is allowed, whenever an excessive librium. Bulk transformer oil must, in most instances,
be transported or shipped from areas of supply to areas of demand.' In shipping such oil, a tank truck is commonly used as one mode of transportation. Whenever some form of long-range transportation must befused to deliver the bulk transformer oil 'to'whereit isneeded,
the breathing cycles of the receptacle containing the oil will be greatly multiplied owing. to the extreme changes I in temperature and atmospheric pressure encountered by thejtransportingvehicle as it travels from-one region to another. During thevacuum .stage of the fbreathing -cycle'of the tank, moist air from the atmosphere will be i drawn into the tank to. contaminate the transformer oil contained therein with-water formed from the. condensation of the moisture in the air andaccor'dingly impair its insulating properties. The degree of moisture contam nation isespeciallybad when the tank-containing the -transfor mer.o'il is transported through an areahavingahur'nidatmo'sphere.
' i In dispensing'transformer oil from the tank, pressure is lost from the tank in .theact of dispensing which again is likely to create a vacuum condition in the tank, result- Sing inrnoist air from the-atmosphere being drawnflinto 'the'tank dur'ingthis stageof the breathing cycle: to', con-1- taminat'e-the transformer oil. Y T 1 It is an object'of this invention to provide amethod ;-:and apparatus for maintaining a,;fluid su,ch.as bulk;t ransformer oil,- contained in a ventedfcank fr om; molstu ej" pressure relief valveassembly shown portion of Figure 2;
uid dispensing 2,976,950 Patented Mar. 28, 196 1 2 contamination. The apparatus and method contemplate the introduction of air under pressure through a line containing a drying chamber and into the interior of the tank, whereby the tank interior is at almost all times maintained under a predetermined pressurized condition in excess of atmospheric pressure, thereby substantially preventing the intake of moist air from the atmosphere to avert the introduction of moisture into the tank.
It is a further object of this invention to provide a method and apparatus for preventing moisture accumulation in a vented tank containing fluid, such as bulk transformer oil, regardless of whether the pressurecondition within the tank indicates an excessive pressure or a vacuum condition, in which a pair of air dehydrating units communicate with the interior of'the tank and act conjointly to prevent the introduction of moisture into the tank, one'such unit being effective when a pressure in excess of atmospheric pressure is to be maintained in the tank and the other unit being eflective when a vacuum condition is present in the tank.
It is a further object of this invention to provide a method of dispensing fluid from a vented tank while preventing the accumulation of moisture therein, wherein dry air isadmitted into the tank to preclude the occurrence of a. vacuum condition therein caused by the loss of pressure involved when the fluid is dispensed, thereby eliminating the intake of moist atmospheric air by the tank.
Other objects not specifically enumerated will become more readily apparent upon reading the description in connection with the accompanying drawings in which- Figure 1 shows a perspective view of a tank truck, in which the tank is equipped with the apparatus embodying the present invention; v
Figure 2 is anenlarged fragmentary view, partially schematic, of the tank shown in Figure 1, with parts thereof being shown in vertical section;
Figure 3 is an enlarged vertical sectional view of the vacuum valve assembly shown in the upper left-hand portion of Figure 2;
Figure 4 is an enlarged vertical sectional view of. the air filter component shown in the right-hand portion of Figure'Z;
Figure 5 is an enlarged vertical sectional view ofthe in the upper medial Figure 6 is' an enlarged transverse cross-sectional view of the drying chamber taken along line 6-6 in Figure 2.
Referring to the drawings more specifically,,.Figure 1 4 illustrates a truck 10 of the type carrying atank :11, ;suitable for transporting more particularly appropriate in thisinstance, bulk transformer oil. 1. The tank 11 is providedqwith the .usual apparatus '12 attachedtotits rear end 4 shown inFigure Z, When, transporting transformer 'oil in this manner, to be used as aninsulating medium in Ielectrical transformers, it is'important tomaintain the xtransforrner oil moisture-free, since the presenceglof moisture is detrimental, to the insulating properties of Thetank 11 is initiallpsubiected .to an extensive cleaning process in which all vestigesof moisturepresent in the tank areremoved. Following fluids, such as gasoline or as the transformer oil.
cleaning process, the transformer oil is introduced into} the tank ;1 1., It-is the usual, practice to vent' the tank 11, permitting, it: to fbreathe -should unequal pressure conditions prevail betweenj, the interior of thetank ;1- 1 an:d the atmosphere as.'a,safety precautionurShould f the tank- 11- become heated thereby causing the, trans former oil contained-therein} to expand, a greater presexist, in the. tank as compared to tl 1atof-,.a,t-' V .tm EPhQIQ- tQa ii l r-se yas ald. th ianls 1 t s im. 1
. sure will i 3 the transformer oil contained therein ,will contract to decrease the amount of pressure within the interior of the tank, again resulting in an unbalanced pressure condition between the interior of the tank and the atmosphere. When the pressure differential between the interior of the tank 11 and the atmosphere exceeds prescribed limits, a dangerous situation is created which could lead to either the exploding or collapsing of the tank 11 as the case may be. For this reason, the tank 11 is commonly allowed to breathe, thereby maintaining a sub stantially balanced pressure between its interior and the atmosphere at all times. While this breathing of the tank 11 is eminently successful as a safety precaution, it
creates an additional problem of moisture contamination of the contents within the tank. When the tank 11 contains transformer oil, for example, its contamination by moisture is highly undesirable, for reasons previously described.
The present invention concerns itself with providing an apparatus and method for maintaining the contents of a vented tank moisture-free. It has been found that if the interior of the tank 11 is maintained under a predetermined positive pressure in excess of atmospheric pressure, the likelihood of moist air from the atmosphere being sucked into the interior of the tank is slight.
Referring again to Figure 1, it will be seen that a pair of dehydrating units 13 and 14 are carried on the tank v11. The apparatus or unit designated by reference numeral 13 is utilized to permit the introduction of air under pressure greater than atmospheric pressure into the tank 11 to maintain a predetermined pressure dilferential between the interior of the tank 11 and the atmosphere.
The apparatus 13 is provided with means to relieve the compressed air of any moisture content prior to its introduction into the tank 11, as will be subsequently described.
A source of compressed air shown schematically in Figure 2 and designated by reference numeral 13a should be available in order to utilize the apparatus 13. This source of compressed air 13a may be mounted on the tank 11 in the form of a separate storage tankcontaining compressed air, but in most instances will comprise a compressor carried by the truck and suitable for compressing atmospheric air, since the use of a separate storage tank for containing compressed air would 'add considerable weight and bulk to the load carried by the truck 10. It should be apparent that the compressed air could also be obtained from a source 13a entirely apart from any apparatus mounted on the tank 11 or carried by the truck 10. For example, it is likely that suitable means serving as the source of compressed air 13a would be found at a location where the fluid in the tank is to be dispensed. When the source of compressed air 13a is not available,'tl e vacuum; valve assembly or unit designated by reference numeral 14 is effective to prevent the moisture pf the atmospheric air which may be drawn into the. nterior of the tank 11 from contaminating the contents therein. In the absence of the source of compressed air =13a, it is" to be noted that dispensing the fluid from the tank 11 by means of the usual pump and nozzle arrangement 12 shown in Figure 2 will create a Vacuum condition within the tank 11 as the fiuidis'withdrawn. Substantial pressure equilibrium between'the interior of the tank 11 and the atmosphere is maintainedby the vacuum valve assembly 14 which allows atmospheric air to be drawn into the "interior of the "tank 11, the
moisture in the atmospheric air being withdrawn in the f process, as is subsequently described. "In Figure), the vacuum valve assembly or unit 14 is as being mounted on the tank 11. The unit 14 "includes aconduit 15 leading from the atmosphere to the interior of thetank 1 1. Interposed in the conduit -15,-'there is a vacuum valve 16 havingi 'a separate conduit 17 leading away therefrom to the interior of the tank 11. In order to prevent the continuous presence of moist atmospheric air in the conduit 15 above the vacuum valve 16, a damper valve 18 is positioned in the end of conduit 15 adjacent to the atmosphere. The damper valve 18 remains closed until a vacuum condition of a predetermined extent is created in the interior of the tank 11 either by the cooling thereof or by the dispensing of some of its contents, whereupon the damper valve 18 and the vacuum valve 15 will be opened to permit the in gress of atmospheric air into the conduit 15.
The vacuum valve 16 is of conventional structure. being shown in greater detail in Figure 3, and comprising a valve housing 20 having a pressure-responsive flexible diaphragm 21 extending within its interior to divide it into a pair of chambers. Above the diaphragm 2.1, there is positioned a spring 22 which contacts the upper surface spring 22 for varying the degree'of vacuum condition required in the interior of the tank 11 to open the vacuum valve 16. Connected to the lower surface of the diaphragm 21 at its central portion, there is a rocker arm 23 for actuating a push rod 24 which extends through a valve seat 25. It will be noticed that the valve seat 25 is provided with a relatively wide bore therethrough with respect to the diameter of the push'rod 24 which penctrates it to provide a passageway 26 for permitting atmospheric air to pass through the vacuum valve 16 should a vacuum condition of a predetermined extent exist in the tank 11. Normally the passageway 25 through the valve seat 25 is closed by means of a valve closure 27 which is spring-pressed against the valve seat 25. Atmospheric pressure is communicated through the conduit 15 into the interior of the valve housing 20 below the diaphragm 21. The pressure present in the tank 11 is communicated through the conduit 17 to the interior of the valve housing 20 above the diaphragm 21. It will thus be seen that should a vacuum condition of a predetermined extent be present in the tank 11, the atmospheric pressure below the diaphragm 21 is sufficient to overcome the compressive force of the spring 22 mounted above the diaphragm 21 and normally urging the central portion of the diaphragm 21 downwardly. When this occurs, the central portion of the diaphragm 21 is ilexed upwardly, thereby moving the rocker arm 23 and the push rod 24 connected thereto, whereupon the push rod 24 unseats the valve closure 27 by moving it away from the valve seat 25 to permit the fiow of atmospheric air through the passageway 26 in the valve seat 25 and downwardly therefrom into the conduit 15 leading toward the tank '11.
Upon passing through the vacuum valve assembly 16, the atmospheric air is conducted through a drying chamber 30 interposed in conduit 15 for relieving it of the moisture contained therein. The drying chamber 30 contains a desiccant or drying agent, such as calcium chloride or silica gel, indicated at 31 whichetfectively extractsthe moisture content 'from the atmospheric air prior to its entrance into the'tank' 11. The drying chamber 30 preferably has wire mesh screens 31a installed above and below the drying agent 31 to retain it in'place within the chamber 30.
When the source of compressed air 13a is available, unit or apparatus 13 is employed to maintain a higher pressure within the tank 11 than that existing in'the atmosphere, whereby there will be little chance of atmospheric air being sucked through the unit or vacuum valve assembly 14 into the interior of the tank 11. Consequently the drying agent 31 in chamber 30 will he rarely called upon to extract moisture from'atmosphei'ic air passing' througli conduit 15 and will' remain unsaturated for long periods of time without the necessity of constant checking. Referring toFigu're' 2 in describing unit 13, there'is shown the source of compressed air 13a from which a conduit 32, Preferably flexible, leads to aL-rigid pipe 34, being connected thereto by a quick detachable connector33 of conventional design. The usual pressure regulator 35 is installed in the pipe 34 to insure that the proper amount of pressure is being introduced into the tank 11. A pressure gauge 36 may be provided in the pipe 34, thus giving a visual indication of the pressure therein. Following the pressure gauge 36, an air filter chamber 37 of conventional design may be installed in the pipe 34 to remove foreign matter and the bulk of the excessive water and moisture from-the compressed air prior to its entrance into a drying chamber 46 which removes the remaining vestiges of moisture from the compressed air. I 4
The air filter 37 is shown in greater detail in Figure 4 and comprises an outer cylindrical casing or shield 40 which may be of transparent material and upper and lower end members 40a, 40b. in the lower end member 40b of the air filter 37, there is provided a stop cock 41 for removing the excess water from the air filter37 when the compressed air is passed therethrough. It will be noted that as the compressed air enters the air filter 37 through pipe 34, it passes into outwardly diverging passageways 41a in the upper end member 40a of the air filter. The compressed air is thereby caused to swirl, allowing the bulk of the excessive water and moisture to be extracted therefrom, whereupon the excessive water falls to the lower end member 40b of the air filter 37 from which point it can subsequently be withdrawn by opening the stop cock 41. The swirling air then passes through an inner porous casing 42 spaced from the outer bular conduit 43 from where it is led out of the air filter 37 into a continuation of the pipe 34.
The pipe 34 is suitably connected to a conduit 45, preferably flexible, and leading to the dryingchamber 46. A cylindrical wire mesh enclosure or screen 47 is provided in the interior of the drying chamber 46 and contains a suitable desiccant or drying agent 50, such as calicum chloride or silica gel, which removes the remaining vestiges of moisture contained in the compressed air as it passes through the drying chamber 46 prior to its entrance into the tank 11. It will be noted thatthe drying agent 50 will be called upon to extract very small quantities of moisture, since the bulk of the same has already been removed from the compressed air by the air filter 37. Consequently, the drying agent 50 will remain effective to remove moisture from air passing therethrough for long periods of time without the necessity of constant checking.
From the drying chamber 46, the dry compressed air is led through conduit 51 into conduit 52 which leadsto the interior of tank 11. Conduits 51 and 52 are suitably joined together, as by a T-coupling 53. Thus, the
compressed air is permitted to enter into the interior Should a dangerous excess ofpressure be built-up in the tank 11, such as might occur from the heat of the sun expanding the fluid contained therein, a pressure relief a means 54 has been provided to allow the dangerous excess of pressure to be vented to the atmosphere. The pressure relief means 54 is mounted on the end of conduit 52 leading to the atmosphere and is shown in greater detail in.Figure 5.
' Referring to Figure 5 specifically, the pressure "relief means 54 is in the form of a valve comprising a housing 55 having a pressure-responsive flexible diaphragm 56 extending within its interior to divide it into a pair of chambers. Above the diaphragm 56, there is positioned a spring 57 which contacts the upper surface of the diaphragm 56. Suitable means are provided for adjustably regulating the degree of compression in the spring 5-7 for varying the degree of excessive pressure required in the interior of the tank 11 to open the pressure relief valve 54. A valve seat 60 is provided below the diaphragm 56, said valve seat 60 having a passageway 61 formed there'- through leading frornthe interior of valve 54 to the atmosphere. Normally the passageway 61 through the valve seat 60 is"closed by means of a closure plate 62 suitably connected to the lower surface of the central portion of diaphragm 56 and urged against the valve seat '60 by the spring 57. The pressure in the tank interior is communicated through the conduit 52 into the interior of the valve'housing 55 below the diaphragm 56. It will thus be seen that should an excessive pressure condition of a predetermined extent be present in the tank 1 1, this excessive pressure is sufficient to overcome the compressive force of the spring 57 mounted above the diaphragm 56. When this occurs, the centralportion of the diaphragm 56 is flexed upwardly, thereby moving the closure plate 62 connected thereto upwardly and away from the valve seat 60 to permit the dangerous excess of pressure in the tank 11 to pass through the passageway 61 into the atmosphere. When there is no longer any dangerous excess of pressure in the tank 11,
the closure plate 62 again seats itself on the valve seat 60 to close the passageway :61. a
It is to be understood that where the source of compressed air' 13a is carried by the truck 10 or otherwise readily available, the unit or apparatus 13 is employed while dispensing the fluid from the tank 11 to introduce additional pressure into the tank 11 toat least partially compensate for the pressure which is lost in dispensing the fluid, it being desirable to continuously maintain a predetermined pressure within the tank 11 in excess of atmospheric pressure. The unit or apparatus 14 is used when there is no' available source of compressed air to prevent the occurrence of a dangerous vacuum condition in the tank interior during the dispensing of the fluid by allowing atmospheric air from which the moisture hasbeen removed to be drawn into the tank 11. Although this invention has been described with particular reference to maintaining bulk transformer oil moisture-free, it is contemplated that it may be utilized with tanks containing various types of fluids from which it is desirable to eliminate moisture contamination.
Thus, there has been described and illustrated an apparatus and method for preventing moisture accumulation in a vented tank containing fluid regardless of whether the pressure condition within the tank indicates an ex cessive pressure or a vacuum condition.
In-the drawings and specification there has been set forth a preferred embodiment of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being defined in the claims.
I claim: I a
1. An apparatus for preventing the accumulation of moisture within a tank containing a fluid, said apparatus comprising a pair of dehydrating units, one of said units having a first conduit means for connection bethe compressed air before it enters the tank, the other' of said units having a. second'conduit means for com 7 mention to the interior of the tank and leading to the atmosphere, a vacuum valve assembly installed in said second conduit means, said vacuum valve assembly communicating with the interior of the tank and comprising normally closed valve means in said second conduit means operable in response to a predetermined vacuum condition within the tank to open,'whereby air from the atmosphere may pass through said valve means in said second 7 conduit means, and air drying means in said second conduit means for removing the moisture content from the atmospheric air before it enters the tank, whereby the tank will remain moisture-free regardless of whether an excessive pressure or a vacuum condition exists in its interior. 1 I a 2. Anapparatus. for preventing the accumulation of moistureiwithin a tank'containin a fiuid,said apparatus comprising a pair oi dehydrating units, one of said units communicating atone end with a source of compressed air and at the'other end with the interior of the tank, said, one unit comprising means for removing the moisture content from the'compressed air to permit it to enter into the, tank in a dry state, the other of said units communicating at one end with the atmosphere and at the other end with. the interior of the tank, said other unit comprising. vacuum valve means normally closing off communication between the atmosphere and the interior of, the tank and being operable in response to a predetermined vacuum condition within the tank to open for permitting the passage of air from the atmosphere therethrough, and means for removing the moisture content from the atmospheric air to permit it to enter into the tank in a dry state, whereby the tank will remain moisturefree regardless of whether an excessive pressure or a vacuum conditionexists in its interior.
3. The combination with a tank having a vent therein of, an apparatus for preventing moisture accumulation withinisaid tank, said apparatus comprising means serving as a source of compressed air, means for removing the moisture content from the compressed air, and means to direct the dry compressed air into the tank for pro- 8 viding a pressure therein at least substantially equal to atmospheric pressure, the intake of moisture-laden atmospheric air by said; tank; through the vent therein being eliminated upon the tank pressure being maintained at least substantially equal; to atmospheric pressure-.;
4. The combinatiorr'with a having a vent therein of an apparatus for preventing moisture accumulation within said tank, said apparatus comprising means; serving as a source of compressed air, means for filtering out the bulk of moisture content in the compressed air, additional means for removing the remaining vestiges of moisture from the compressed air, and meansto directthe dry compressed air into the tank for providing a pressure therein at least substantially equal to atmospheric pressure, the intakeof moisture-laden atmospheric air by saidtank through the vent therein being eliminated upon the tank pressure being maintained at least substantially equal to atmospheric pressure.
5. A method of preventingmoisture accumulation within a tank containinga fluid, comprising the steps of passing air through a line leading to-the tank, filtering out the bulk of moisture content in the air at a first station by swirling the air to separate the moisture therefrom through centrifugal force and drawingofi the centrifugally separated moisture from the air, extracting the remaining vestiges of moisture from the air at a second station prior to its entry into the tank, and directing the ,dry air into the tank to provide a pressure therein at least substantially equal to atmospheric pressure, whereby the intake of moisture-laden atmospheric air by the tank is eliminated.
References Cited in the tile of this patent UNITED STATES PATENTS 1,013,767 Hadley Jan. 2, 1912 2,273,344 Black et a1. Feb. 17, 1942 2,326,276 Avedikian Aug. 10, 1943 2,437,618 Schottgen Mar. 18, 1948 2,789,654 Zurit Apr. 23, 1957