US2050565A - Proportional fluid feeding device - Google Patents

Description

Aug. 11, 1936. E. E. EDWARDS ET AL PROPORTIONAL FLUID FEEDING DEVICE Filed Nov. 19, 1934 2 Sheets-Sheet l fnrjeniors f/ared f. EaWar 5 Joseph E Pu/nam Patented Aug. ill, rare L ATNT PRGPORTIONAL FLlUllD FEEDING DEVICE Application November 19, 1934, Serial No. 753,522

Claims.

This invention relates to fluid feeding devices, and particularly to those which are adapted to control the rate of flow of a liquid in proportion to the rate of flow of a fluid, 'such as a confined flowing stream of gas.

In the natural gas industry the problem has arisen of introducing an odorant material, usually a volatile liquid, into the normally odorless gas, so as to give the latter a distinct and easily recognizable odor, to reveal the presence of leaks, accidentally extinguished-burners, and the like. In order to accomplish this safely and econom ically, the ratio of odorant to gas volume should be kept at a constant value. The gas is usually confined in a pipe or conduit at a pressure which may range from substantially atmospheric pressure to one of several hundred pounds per square inch. Rates of flow may be extremely variable, ranging from a minimum early in the morning to several maxima, of various magnitudes, during different parts of the day.

Heretofore, apparatus for this purpose have involved intricate and complicated systems of dia== phragrns, linkages, throttle valves, pilot valves, pumps, overflow weirs and the like, all of which are more or less unreliable without constant attention and many of which are subject to corrosion by the liquid being handled. In addition many require the use of a supplementary power supply, which is not always available, and which constitutes a source of continued expense in addition to the high initial cost of such devices.

It is an object of this invention to provide a sensitive diiferential fluid pressure responsive device which is adapted to operate upon large or small pressure differentials, which has a minimum of moving parts and which is also adapted to magnify small changes in pressure differential to actuate directly 2. positive liquid flow control means, the latter adapted to introduce the said liquid into the fluid stream or to dispose of it in any other manner.

Another object is to provide a device of this type which is entirely self-contained and which requires no outside power supply for its continued operation.

Another object is to provide a device of this type which will automatically stop the liquid being 'fed upon the cessation of flow of the fluid producing the pressure difierential, and will resume operation upon a starting of the flow of the latter fluid.

Another object is to provide an automatic device that will introduce volatile odorant liquid into a confined moving stream of gas at a rate proportional to the rate of flow of the latter.

Another object is to provide an odorant feeding or metering device that will require substantially no alteration to the gas line to which it is attached, and which will ofier little or no restriction to the normal flow of gas in said line.

Another object is to provide an odorant feeding or metering device that may be easily altered to make changes in the desired proportion of odorant liquid to gas flow rates, or to changes in the characteristics of the gas ilow.

These and other objects and advantages will become apparent from the description which follows and from the accompanying drawings, which form a part of this specification and illustrate a preferred embodiment of the invention, as applied to an odorant feeding device for a natural gas line.

In the drawings- Figure 1 is a vertical sectional view on the lon= gitudinal axis of an odorant feeding device in place on a gas line.

Figure 2 is a horizontal sectional view on line II-H of the device shown in Figure 1, and

illustrates the float arm, hinge, float, and counterweight in place in the odorant tank.

Figure 3 is a vertical sectional view on line III-III of Figure 2, to an enlarged scale and illustrates one form of construction of the float arm hinge.

Figure 4 is a vertical sectional view on line IV-IV of Figure 1, also to an enlarged scale and illustrates a preferred construction of the float element in which the liquid feeding orifice is mounted.

Referring to the drawings and particularly to Figure l, the numeral it represents a tight steel tank in which the volatile odorant liquid H may be stored, and which also serves as an enclosure for the control mechanism. Tank i0 is preferably mounted upon any suitable support (not shown) above the gas pipe line i2 into which the odorant liquid is to be metered.

In order to obtain a. pressure diflerential proportional to the velocity and 'therefore the rate of gas flow in line it, two Pitot tubes generally designated i3 and it, are provided, each of which is composed of a closed tube l5-lti with a side opening lil8. Opening ll faces the gas flow in line l2, as indicated by the arrow, which flow causes a velocity head pressure to be imposed upon the normal line pressure or static pressure in Pitot tube l3. Opening i8 is illustrated as facing down stream and is thereby subject to static pressure minus the velocity head pressure. If desired, tube it could be made responsive only to static pressure by being made open ended.

Tubes l3 and it will hereafter be referred to as the high pressure and low pressure Pitot tubes,

respectively. They may be suitably mounted in the screwed nipples l9 Welded to line l2, and are provided with any conventional orienting means or indicia so that the position of the openings ill-48, with respect to the longitudinal axis oi connection 2| is also preferably provided with a flanged union 24 near its junction with the bottom of the shell of tank In. High pressure connection 20 leads to the top of tank l0, where it is connected to dome 25, on which cover plate 26 and gasket 21 may be secured by bolts 28. Dome 25 also forms a space into which the float mechanism, to be described below, may be accommodated, as shown by the dotted lines of Figure 1,

r as when the tank I is first filled with odorant liquid N. A gage glass 29 of the conventional type may be provided to indicate the liquid level in tank l0.

The juncture-between the low pressure con nection 2|, which leads from low pressure Pitot tube l4, and tank I0, is conveniently made by a nipple 30 which extends from flanged union 24 and is preferably welded into the tank shell Ill. Supported on the inner end of nipple 30 inside of tank l0 (Figure 3) is a hinge body 3|. Hinge pin 32 is pivotally secured in the latter between the seat 33 and the center pivot '34, which latter is urged into recess 35 in pin 32 by spring 35. A cap 31 secured by screws 38 provides for removal and dismantling of the hinge assembly. These parts are preferably made from corrosion resisting alloys, such as brass or stainless steel, and the particular arrangement shown in this example has proved to work with a minimum of friction.

It will be noted that the low pressure connection nipple 30 is threaded as at 39 into a passage 40 in hinge body 3|, which passage communicates through seat 33 with the passage 4| in hinge pin 32. Float arm 42 is threaded into hinge pin 32 at right angles to the axis of rotation of the latter and is also provided with a central bore 43 which communicates with passage 4| and leads to the float assembly generally designated 44. A counterweight 45 is threaded onto rod 46, which extends from hinge pin 32 in the opposite direction from float arm 42, and serves to balance the float assembly 44 as will be described below:

Float assembly 44 is best shown in Figures 1 and 4, and consists of an upright displacement cup 41, to the bottom of which is connected float arm 42, so that any liquid which may enter the cup will drain through bore 43 in arm 42 and thence through the hollow hinge assembly, low pressure connection 2|, and eventually into gas line l2. A limit stop 48 is preferably securedinside tank Hi to prevent float arm 42 from reaching a horizontal or downwardly inclined position relative to the axis ofthe hinge pin 32, so that liquid may always flow therethrough as just described.

Near the bottom of displacement cup 41 is mounted a flange 49, which may be soldered to the cup wall, and into which may be screwed a threaded plug 50, provided with an orifice Displacement cup 41 is also fltted with one or more vent openings 52 near its upper edge for a purpose which will be described below.

Surrounding cup 41, is a float or cover shell 53 which is open at the bottom. The closed top of shell 53 is preferably provided with centering clips 54 and the shell may be detachably secured to cup 4'|'by means of a. wire bail 55 which passes through holes 56 near the bottom of the skirt of 5 cover shell 53 and clamps over a clip 51 on the bottom of float arm 42 near its outer end. This provides an easy means for substituting another shell of difierent diameter, in case the characteristics of the device are to be altered, as will be dscribed below. 1

The design of float shell 53, cup 41 and the location and size of orifice opening 5| are obviously dependent upon the maximum velocity of gas flow in line l2, the flow characteristics of the odorant liquid and the ratio between the volume of gas and odorant material that it is desired to maintain. Factors bearing upon these values will be discussed below and a concrete example given, from which the design of other installations may readily be determined by one skilled in the art.

The velocity head pressure is imposed upon Pitot tube l3 and is carried through high pressure pipe connection 20 to tank ||l above the liquid level therein. The low pressure is communicated from line |2 through Pitot tube l4 and connection 2| hinge assembly and hollow float arm 42 tothe interior of cup 41, from which it communicates through vent 52 into the inside of float shell 53. The top or outer side of shell 53 is therefore subject to a higher pressure over its entire crosssectional area, than that inside the shell, causing the latter to sink in the liquid N, until the added displacement of cup 41 over its cross-sectional area, balances this downward force. Float assembly 44 is originally balanced by counterweight 45, so that it will float in the liquid N with orifice 5| just above the liquid level in the annular space between cup 41 and float shell 53.

It is obvious that the only force acting to depress float assembly 44 is the pressure differential communicated to the opposite sides thereof by Pitot tubes i 3 and I4 or their equivalent. This force will be proportional to the velocity and therefore the rate of gas flow, and will act directly upon the orifice 5| to move the latter below the surface of the liquid ii, causing proportional flow of the liquid through arm 42, hinge 3|, connection 2| and tube l6 into line 2, as outlined above. If desired, the liquid N may be trapped or diverted from line |2 to any other destination, if such were the object of the device.

If a considerable pressure differential is available, as would be the case of an orifice in a high pressure line, where a relatively high pressure drop would not be objectionable, there would'be a correspondingly greater force available to push the float assembly 44 downwardly into the liquid. In this case, to prevent too great submergence of 60 orifice 5|, or in effect, to decrease the sensitivity of the feeding means, the respective cross-sectional areas of float shell 53 and displacement cup 41 would be approximately the same, so that a strong downward force on the exposed area 01' 65 the top of shell 53 would be counterbalanced by a relatively strong buoyant force upwardly from the effective cross-sectional area of the displacement cup 41 in liquid N. If, however, there is only a slight differential pressure available, as in 7 the case of a large, low pressure gas line with Pitot tubes as shown in Figure 1, the cover shell 53 should be relatively much larger in cross-sec tional area than displacement cup 41, so that the latter would sink deeply with but a slight in- 7 crease in differential pressure in the exposed area of shell 53. Thus, the sensitivity of the liquid feeding means varies as the ratio of the crosssectional areas of the shell 58 and the cup 41.

Should the absolute pressure in conduit I! change due to varying load or for other reasons. the resulting change in density of gas in the con duit will cause a variation in the pressure diflerential which controls the submergence of orifice 5|. This will substantially compensate for the pressure-volume change in the 'gas and will tend to preserve the proportional rate of flow of liquid I I from tank It).

It has been found that for small liquid flows through orifice 5| there is a practical minimum diameter which should be maintained, for if too small an orifice is used the well-known Reynolds number" will be too small to give a reliable flow discharge coeflicient and unsteady flow will result. with an odorant material such as Calodorant, a. petroleum derivative having substantially the flow characteristics of a light gasoline, a minimum orifice diameter of 0.031 inch was found desirable. i

In practice, for an installation on a 10 inch gas line operating at 100 lbs. per sq. inch and having a maximum demandrate of 100,000 cubic feet per hour, to which odorant was to be added at the rate of 3 gallons per million cubic feet, the orifice diameter was determined to be 0.035 inch, with a maximum submergence of 2 inches. The displacement cup 41 was 3 inches in diameter, and the cover shell was 17 inches in diameter. The tank size is obviously immaterial, being determined by convenience and storage capacity desired.

It will be appreciated, that, from the foregoing description and example, one skilled in the art of hydraulics will be able to adapt this invention to any given set of conditions of gas flow, pressure,

and proportion of odorant to gas flow. The es-- sential feature of the invention appears to reside in the combination of a diiferential pressure actuated flpat, carrying flow control means responsive to the position of the said float in a liquid supply, to cause a flow of the latter in proportion to the fluid flow producing the said pressure differential. Although a specific construction embodying this invention has been described and illustrated, it is to be understood that the invention is not limited to that specific device, and all such modifications and changes as come within the scope of the appended claims are embraced thereby.

We claim:

1. ma liquid flow control apparatus, the combination of a conduit, means in said conduit for creating a pressure differential proportional to fluid flow therein, a closed liquid storage tank, a

being responsive to the pressure differential in said conduit to vary the flow of liquid through said orifice.

2. A liquid flow control apparatus according to claim 1, in which said float is carried by a hinged member, said member provided with a passage through which liquid entering said float through said orifice will flow out of said tank.

from said-tank into said gas line,'at a rate pro- 3. A liquid flow control apparatus according to claim 1, in which'said float is carried by a hinged 1 member, by means of which liquid entering said float through said orifice will flow to said static pressure connection, and thence into said conduit. 5

4. A liquid fiow control apparatus according to claim 1, inwhich said float is provided with an outer shell and an inner cup, the outer shell opening downwardly and the inner cup opening upwardly, the said orifice being in the wall of said inner cup, and adapted to be submerged below the liquid in the annular space between said cup and said shell.

5. In a liquid flow control apparatus of the type described, a movable float in a closed liquid storage tank, said float comprising a hollow chamber in communication with and sealed by the liquid in. said tank, saidtank and said float chamber being connected, respectively, to sources of high and low differential pressure, oi liquid flow control 20 means carried by said float and responsive to its position in the said liquid, and conduit means leading from said flow control means to conduct the said liquid to a point outside of said tank at a rate proportional to said pressure differential. 2 6. A liquid flow control apparatus according to claim 5, in which said liquid flow control means includes an orifice adapted to be submerged with said float by the difl'erential pressure acting thereon, to permit liquid to flow from said tank. 30 7. In an apparatus for introducing an odorant liquid into a confined flowing stream of gas in a conduit; the combination of a closed odorant storage tank mounted above said gas conduit, a Pitot tube in said conduit with its opening facing 35 the flow of gas therein, a second conduit connecting said Pitot tube with the space above the liquid in said tank, a float in said tank, said float comprising a hollow chamber in communication with and sealed by the liquid in said tank, a third conduit connecting the interior of said float with said gas conduit, and liquid flow control means carried by said float and communicating with said third named conduit to permit odorant to flow 45 portional to the gas flow therein.

8. A float for a liquid flow control apparatus of the type described, comprising an outer shell having a closed top and open at the bottom, an inner cup closed at the bottom and mounted in said outer shell, means forming a gas passage between said shell andsaid cup at their upper ends, means for fastening said shells together, and an orifice in said inner cup. a

9. In a liquid flow control apparatus, the combination of a conduit, means in said conduit for creating a pressure differential proportional to fluid flow therein, a closed liquid storage tank, a movable float in said tank, means forming a high pressure connection from said pressure difl'erential means to the tank above the liquid level therein, means forming a low pressure connection from said pressure differential means to said float, and flow control means carried by said float to conduct said liquid from said tank, the position of said 65 float with respect to the liquid level in said tank being responsive to the pressure differential in said conduit to vary the flow of liquid through said flow control means.

,10. A liquid flow control apparatus according to claim 9 in which said float comprises a hollow chamber in communication with and sealed by the liquid in said tank.

ELDRED E. EDWARDS.

JOSEPH F. PUTNAM. I5

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