US2049239A - System for dispensing and metering volatile liquids - Google Patents

Description

Julj 28, 1936-.

F. w. WILCO X SYSTEM FOR DISPENSING AND METERING VOLATILE LIQUIDS Filed Sept. 9, 1935 v FIG.

Fig.2

A77" NEV Patented July 1936 UNITED, STATES PATENT OFFICE SYSTEM FOR DISPENSING AND METERING VOLATILE LIQUIDS Francis W. Wilcox, Alhambra, Calif., assignor to Parkhill-Wade, Incorporated, Los Angeles,

Calif., a corporation of California Application September 9, 1935, Serial No. 39,812

3 Claims.

the liquid dispensed, due to the fact that such on account of their large heat capacity and, inv

the case of underground tanks, on account of the 20 heat insulation afiordedby the ,burial of the tanks,

maintain a more or less constant average temperature, which temperature is substantially lower than the temperature attained in the piping and other apparatus associated with the tanks 25 during exposure to sunlight. p On account of such exposure of the associated piping and equipment, it has been found necessary to take extreme precautions to prevent vaporization of theliquid in these parts of the 30 equipment. Obviously, if partial vaporization of [the liquid occurs before its delivery to the meter, the meter will operate partly on vapor and will give volume indications in excess of the true volume of liquid actually passed through the meter. 35 Since a liquid pump is ordinarily used in these systems for delivering such liquids from storage tanks to the receiving fuel or transport tranks on automotive equipment, one method of eliminating this difliculty and insuring true readings of the 40 metering device is to discharge the liquid through a relief or back pressure valve immediately ahead of the receivingrtank, such back pressure valve being set to maintain a back pressure on the system between itself and the pump in excess of the 45 maximum vapor pressure which it is possible for the liquid to reach in this part' of the system. This requires that the back pressure valve be set to hold and maintain a pressure somewhat great- .er than that corresponding to the vapor pressure 50 of the liquid under the most extreme conditions of sun exposure. This set pressure is greatly in 'excess of the back pressure which would be required under average operating conditions, and consequently a great deal of pumping power is wasted in forcing the delivered liquid through -making deliveries at the required rates.

the back pressure valve at this excessively high setting.

The present invention provides means for ensuring that no vaporization can occur in the delivery line entering the meter nor within the meter 5 itself, while the back pressure held on the system is only such as is momentarily required to prevent vaporization at the existing temperature. Thus the power required to pump the liquid against the high pressure necessary to prevent vaporization at high temperature is used only when the temperature is high, while advantage is taken of all periods of lower temperature to correspondingly reduce the pressure and the power consumption.

This result is produced by using a differential pressure regulator to control the back pressure in the system in place of the simple pressure regulator having a manually controlled setting.

The objects and advantage of the invention will be evident on inspection of the attached drawing,

in which Fig. 1 is a diagrammatic elevtion of the system as a whole, and

Fig. 2 is a. vertical section through a suggested typeof differential pressure regulator, as indicated at I 8 in Fig. 1.

Referring first to Fig. 1, 10 is a storage tank, indicated in this illustration as a vertical tank -mounted above ground, it being understood that the tank may be of any shape and may be located beneath the surface if desired. II is any pump of suitable volume and pressure capacity for i2 is a vapor trap for separating any fixed gas which may be disengaged in the pump. This trap is preferably provided with a vertical baflle l3 and has in its upper portion a release valve I 4 actuated by a float l5. This valve is opened by the float when the liquid level in the trap is depressed below a 40 predetermined point by the accumulation of gas, which is thus vented from the trap and returns to the top of tank I0 through pipe IS. The insertion of the trap at this point ensures a. liquid free from gas bubbles on the downstream side of the trap.

eijei'hor suited to this service is shown iri'more detailin Fig. 2, it being understood that these detailsare illustrative only. In this figure,

- I3, is'a diaphragmcase divided by a flexible diaphragm 20 into two chambers 2| and 22. To this diaphragm is attached the stem 23 of a valve 24 situated in a valve body 25 which is spaced from packing gland 3| and into' chamber 23 through av packing gland 32. A spring 33 bears against gland 3| and urges the stem downwardly; 1. e:',-l n a di:

rection to close valve 24, this spring being held by a washer 35 and a nut 36 which can be adjusted up and down on the stem to vary the tension of the spring.

Referring now to both Figs. 1 and 2, a pipe 31 connects chamber 2| with 'pipe i6 through it with the upper side of tank iii. A pipe 38 connects chamber 22 with pipe 39 and through it both with thedischargeside of meter H and withjvalve chamber 30. A' pipe 40 connects valve chamber 29 with} a hand valve 4| to which a hose may be connected for filling the tanks of vehicles or otherwise withdrawing liquid from the system.

It will be seen that theva'por pressure existing in tank Ill is transmitted through pipes l5 and 31 to chamber 2| and is thus exerted on the upper side of diaphragm 20, tending to move valve 24 into a closed position. At the same time the .pump discharge pressure is exerted through pipes 39 and 38 against the lower side of the diaphragm, tending to open valve 24 and to permit liquid to flow from chamber 30 into chamber 29 and thence through pipe 40 to .the' delivery point. To cause this valveto open the pressure beneath the diaphragm must exceed the pressure above the diaphragm, and the extent of this excess pressure will be fixed solely by adjustment of the tension of spring 33, which urges the valve into closed position. It follows that the pump pressure required to open the valve and permit delivery of liquid will be the momentary vapor pressure in tank i0 and chamber 2| plus the resistance offered by the spring, and will vary with the momentary vapor pressure. Thus, regardless of the vapor pressure existing in the system, no vaporization can take place because the back pressure against the pump is always in excess of the vapor pressure by aflxed and controllable amount. The amount of this excess may be as small as may be desired, but in practice I prefer .to so adjust the tension of the spring as to maintain an excess of M to l5 pounds per square'inch.

'11; is obvious'that with this arrangement, as as general temperature level rises or falls the vapor pressure of the liquid in the storage tank will weather the vapor pressure in the storage tank will naturally decline, with the result that the total pressure held on the meter will correspondpredetermined by the adjustment of the regulator.

correspondingly rise and fall, thereby changing 'ingly-decline, but will always be higher than the One ofthe important advantages of this system of control as compared with the use of a simple back pressure regulator lies in the fact that the excess pressure against which the pump must deliver in order to insure correct metering is limited to a definite and fixed amount; instead of varying according to general temperature conditions at the installation, and being an excessively high amount under average operating conditions.

I claim as my invention:

1. In a system for dispensingand metering highly volatile liquids, in combination: a liquid storage tank; a pump arranged to take suction from said tank; a gas trap arranged in the discharge of said pump and a gas channel connecting said trap with said tank; a liquid meter arranged to be fed by said trap, and a differential pressure governor disposed in the discharge-of said meter, said governor being arranged and connected to maintain a constant pressure differential between the discharge of said meter and the vapor space otsaid tank.

2. In a system for dispensing and metering highly volatile liquids, in combination: a liquid storage tank: a pumping means; a liquid meter; a gas trap between said pump and said meter, and pressure responsive means adapted to maintain a constant differential between the pressure in said meter and the vapor pressure in said tank,

3. In a system for dispensing and metering highly volatile liquids, in combination: a liquid meter, and pressure responsive means adapted to maintain a pressure on said meter exceeding by a constant quantity the vapor pressure of the liquid

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