US 2362724 A
Description (OCR text may contain errors)
Nov. 14, 1944. Y T. v. SHEA 2,362,724.
LIQUEFIED PETROLEUM GAS DISPENSING SYSTEM Filed March 8, 1941 FIG? INVENTOR THOMAS SHEA Patented Nov. 14, 1944 LIQUEFIED PETROLEUM GAS msrnnsm SYSTEM Thomas V. Shea, Chicago, 111., assignor to Phillips Petroleum Company, a corporation of Delaware Application March- 8, 1941, Serial No. 382,421
This invention relates to improvements in systems for dispensing volatile liquids and liquefied gases.
Liquefied gases and volatile liquids, such as propane, butane and mixtures thereof or including one or both, are marketed extensively for use as motor or domestic fuels. The volatile liquids are stored under their own vapor pressure in suitable storage tanks, either aboveground or underground, from which they are transferred to fuel tanks or containers. In those systems in which the transfer of the volatile liquid from the storage container to a service container is effected by pumping the liquid, considerable difficulty is often experienced in making and maintaining prime on the pump. During periods in which the pump'is not in operation, vaporization taking place in the pump and associated piping causes the pump to lose its prime. When the pump is again started it must be .purged of the vapors and allowed to fill-with liquid before it will develop sufficient discharge pressure to effect the transfer of liquid. Because of the hazard of allowing highly combustiblevapors to escape to the atmosphere, they are preferably returned to the vapor space of the storage tank. The present. invention provides means for automatically purging the pump and discharge piping of vapors during the pump priming period and allowing the vapors to return to the storage tank. An object of this invention is to provide an improved system for transferring volatile liquids and liquefied gases.
Another object of this invention is to provide such a system with means for automatically re ducing the pressure. differential across the pump whenever the pump is unable to develop therequired operating pressure differential.
A further object of this invention is to provide such a system with means for eliminating vapor from the liquid transfer apparatus. -A still further object of, this invention is to provide means whereby a pumpused in such a system may be readily primed from. its regular supply of liquid.
A still further object of this invention is to provide such a system with means for establishing communication between the discharge of the 7 pump and the source of liquid, supply to the pump to facilitate the elimination of vapor and gas from the pump during the pump priming period. Figure 1 is a diagrammatic elevational view,
partly in vertical cross section, of apparatus suitable for carrying out the present invention.
Figure 2 i a cross sectional view of an excess flow valve suitable for use in this invention.
With reference to the drawing, the numeral 5 designates a storage tank, which may be either aboveground or underground, containing the liquid to be dispensed. A liquid eduction pipe 6 extending to the lower portion of the storage tank 5 provides an outlet for the liquid to be dispensed from the tank. The pump 1 of suitable type and capacity takes suction from the liquid eduction pipe and discharges fluid into the dischar e pipe 8. During normal operation liquid discharged from the pump flows through the pipe 8 to a meter 9. After metering it passes through the control valve [0 and pipe II to the container or fuel tank to which it is to be transferred.
.The pump 1 may be by-passed through the pipe I! in which the valve I3 is provided to control the quantity of liquid by-passed. In communication with the discharge pipe 8 is a differential pressure regulator M or relief valve of conventional design which opens to allow iiuidto pass when the pressure in the discharge pipe reaches a predetermined maximum. Fluid.passing the regulator I4 may be returned to the storage'tank through the pipe l5 which connects to the vapor space of the storage tank. The pipe l6 interconnects the discharge pipe 8 and the pipe l5. Interposed in the pipe IB is an excess flow valve II which allows free flow of vapor through the pipe IE, but which closes when the rate of liquid flow through the pipe it reaches a predetermined maximum.
With reference to Figure 2 of the drawing, an excess flow valve of suitable construction .for use in the present invention is shown for illustrative purposes. Excess flow valves of various types are known and available to the liquefied gas industry;
among these is the valve here shown and described.
It will be understood that in this invention no claim is made to the novelty of the excess flow valve per. se but to its use in a novel manner. The excess flow valve is shown in open position. In this position, the fluid from pipe l6 enters the coupling member 20 through the inlet passageway 2 I, flows through the valve and exits through the outlet passage 22 in the valve body 23 to the pipe IS. The interior of the valve body 23 comprises'an enlarged cylinder bore 24 forming a shoulder or valve seat 25 surrounding the outlet passageway. Within the cylinderbore 24 is a piston 26 with ports 21 and 28 to allow passage of fluid therethrough. The central portion of the piston is larger in diameter than the diameter of the end portion 29 nearest the outlet 22. This provides a seat for the spring 30 which tends to hold the piston in the position shown in the drawing. In passing through the excess flow valve, the fluid must pass through the ports 21 and 28 of the ported piston.
The frictional resistance to flow offered by the ported piston exerts a force on the piston tending to move it in the direction of flow. The pistonand the spring resisting'movement of the piston are so designed that when the ,fluid flow reaches a predetermined maximum, the end portion 29 of the piston cooperates with the valve seat 25 to close the exit passage 22 and prevent flow of fluid through the valve. When the valve is closed in this manner, there is set up across the piston a pressure differential which tends to maintain the valve in closed position against the action of liquid is flowing through the valve.
The operation of the system is as follows. When liquid is to be transferred from the storage period by action of the pressure difierential across :the valve as described with reference to Figure 2 of the drawing. The relief valve l4 prevents damage to the dispensing equipment from excessive pressure when valves Ill and I1 restrict the flow of liquid to less than the pump capacity.
It is seen that the excess flow valve acts as an automatic valve to reduce the discharge pressure on the pump during the pump priming period and to allow vapors from the pump and discharge piping to return to the storage tank. When the pump is filled with'liquid and is able to operate at its normal output, the excess fiow valve closes and is held in closed position as long as the normal discharge pressure of the pump is maintained.
conduit connecting the tank near its top to the dispensing conduit between the meter and the pump by two branch conduits connected in partank 5 to another container, the valves associated with the storage tank are opened and the pump 1 is started. .Prior to starting of the pump! there is substantially no differential in pressure between the discharge pipe 8 and the pipe l5, and the excess flow valve l'l isopen. The vapors .displaced by the pump during the priming period,
i. e., while the pump and piping are filling with liquid, is passed through the pipe l6 and the excess flow valve I1 and is returned to the storage tank through the pipe l5.' The excess flow valve is designed to pass the vapors from the discharge pipe 8 to the pipe l5 freely and without closing. When thepump and discharge piping are filled with liquid, some of the liquid passes through the pipe I 6 to the excess .flow valve.
the meter 9 and control valve "to the pipe H which directs it to a second container. The valve I1 is held in closed position during the pumping The excess flow valve allows liquids to pass 'a dispensing conduit connecting the tank near its bottom to a dispensing point, a pump in the dispensing conduit for pumping the liquid and vapor from the liquid to the dispensing point, a return conduit connecting the tank near its top to the dispensing conduit between the dispensing point and the pump by two branch conduits connected in parallel, an automatic pressure relief valve in one of the branch conduits opening for flow of fluids from the dispensing conduit to the return conduit whenever a predetermined maximum pressure is attained in the dispensing conduit and otherwise closing, and an automatic excess flow valve in the other branch conduit adapted to remain open as long as the material flowing therethrough is gaseous and to close when the material becomes liquid.
THOMAS v. SHEA.