US3347286A

US3347286A - Loading or transfer systems for fluids

Info

Publication number: US3347286A
Authority: US
Inventors: Lawrence W Smith
Original assignee: Smith Precision Products Co
Current assignee: Smith Precision Products Co
Priority date: 1964-05-18
Filing date: 1964-05-18
Publication date: 1967-10-17
Anticipated expiration: 1984-10-17

Description

Oct. 17, 1967 w. lTH 3,347,286

LOADING OR TRANSFER SYSTEMS FOR FLUIDS Filed May 18, 1964 LAWRENCE w. SMITH,

, INVENTOR.

L/MTW ATTORNEY United States Patent Filed May 18, 1964, Ser. No. 368,032 8 Claims. (Cl. 141--39) This invention relates to loading or transfer systems for fluids, particularly vaporizable liquids such as liquefied peroleum gas (LPG).

A present conventional system will first be described and then the nature and advantages of the present invention will be set forth.

Present LPG delivery systems frequently involve the transportion of the LPG, which is customarily mixtures of butane, propane and associated hydrocarbons in liquefied form, to the delivery site by means of a tank truck. However, the system may involve the delivery of LPG from a stationary storage to a tank which is brought to the storage tank. The present invention is applicable to all such systems.

A typical delivery involves the driving of a tank truck as close as feasible to the tank of the consumer. Even under optimum conditions, however, this usually represents quite a distance, and as a result a considerable length of flexible delivery hose, piping, or other suitable conduit is required to connect between the truck tank and the consumers tank. In a typical operation the operators time and the amortized cost of the truck are as much a factor in the total economy of the procedure as is the cost of the LPG itself. Therefore, the quicker the delivery can be effected, the more effective and efiicient will be the entire operation. Because of the time factor, and also because operators desire to do no more manual labor than necessary, it is customary for the operator, after positioning his truck in delivery position, to start the delivery pump before carrying the delivery hose to the consumers tank. The pump has an input in communication with the truck tank and an output feeding a flexible hose, the other end of which is adapted to be connected to the consumers t-ank. At the output end of the hose there is a shutoff valve which is normally kept closed.

The operator, beforeleaving the site of the truck, starts the pump and drags the hose over to the consumers tank. He then connects the output end of the hose to the consumers tank and opens the valve at the output end of the hose. This starts the filling operation.

In the meantime, however, in the interval between the starting of the pump and the opening of the valve at the output of the hose, which is a considerable period of time depending on the distance and the difiiculty of stringing the hose from the truck to the tank, the pump has, of course, beenrunning continuously and building up pressure. Since LPG pumps are usually positive displacement pumps, some means must be provided to accommodate the pump output during this period. This is customarily done by a bypass pipe which leads from the output of the pump back to the truck tank. Interposed in the bypass pipe is a bypass valve which is usually a spring loaded type valve commonly set to open whenever the output pressure in the pump discharge line exceeds the pressure in the storage tank by a given amount, for example, 75 pounds per square inch. The bypass valve imposes a pressure differential of at least 75 pounds per square inch upon the pump.

sures are generally proportioned to As the pressure across the bypass valve builds up, the valve opens at around lbs., and thereafter operates so as to maintain a substantially constant pressure differential of 75 lbs., at all flow rates.

As a result the bypass activity of the pump during the time that the operator takes to connect the consumers tank represents a complete waste of energy and a considerable wear on the pump, since it is working against a maximum pressure while doing no useful work.

After the required quantity of LPG has been pumped into the consumers tank, the operator reverses his procedure. He closes the valve at the output end of the hose, reels the hose in as he returns to the truck, and then turns off the pump. This period also represents a complete waste of energy and a period during: which the pump is pumping futilely against maximum pressure.

Another shortcoming of present day filling apparatus is that the buildup of pressure in the consumers tank raises its pressure undesirably, with consequent limitation on the amount of filling possible. In the usual situation the consumers tank is relatively empty, that is, filled with a small amount of liquid and a large: amount of vapor. During the filling operation the liquid volume increases, compressing the vapor into a smaller and smaller volume. The resultant heat raises the temperature of the con sumers tank and hence increases its pressure. Tank presambient temperature. Consumer tanks have relief valves set to open at approximately 250 p.s.i. Except on very hot days, the pressure of the truck tank, added to the pressure differential setting of the bypass valve, does not come close to the 250 p.s.i. relief valve setting; yet, as soon as the pump discharge pressure exceeds the sum of truck tank pressure and bypass valve setting, the bypass valve opcns, delivery ceases, and the operator is forced to leave the consumers tank only partially filled, even though much more LPG could have been safely delivered without the relief valve opening. 0n the other hand, on hot days, the pressure in the consumers tank may, after some liquid is transferred, exceed the blow off pressure at which the relief valve opens, thereby spewing inflammable and/or explosive LPG throughout the area.

In the past it was customary to connect a vapor return line from the vapor space of the consumers tank back to the delivery tank, to prevent build up of excess pressure in the former. However, the LPG thus returned represented an unmetered loss to the consumer, and this practice has been barred in most states by various consumer-protective laws.

It is the object of the present invention to obviate certain shortcomings and disadvantages of the present day tank filling system and procedure.

It is a further and specific object to provide a system which allows the pump to work against the maximum safe total pressure.

Still more specifically, it is an object of this invention to relieve the load on the pump when the hose valve is closed by providing means for opening the bypass valve fully during the connecting and disconnecting interval, thereby relieving the pump from the heavy load against which it must otherwise work during these intervals.

It is a further object of this invention to provide a system in which the consumers tank may be filled up to a safe pressure even on hot days, without the danger of relief valve blow off. At the same time the system permits use of greater differential pressures where safe, and in cooler weather, with consequent greater filling capacity.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings wherein:

FIG. 1 is a diagram showing the principal elements involved in the tank truck filling of a consumers tank.

FIG. 2 is a schematic diagram showing in enlarged fashion a portion of the hookup betwen the truck tank and the consumers tank which employs a special type of valve constructed in accordance with principles of the present invention.

FIG. 3 is a detailed cross-sectional view of the s ecial bypass valve illustrated in FIGS. 1 and 2.

In the drawings there is illustrated a system for transferring fluid from a first container to a second container. Specifically there is illustrated as the first container a tank 11 which may or may not be mounted on a truck 12 that is to transfer LPG to a consumers tank 13. The vaporizable liquid, for example LPG, is drawn from the tank 11 by a pump 14 and thence directed to a flexible conduit or hose 16, the outlet 17 of which is connected to the tank 13. A bypass conduit or pipe 15 is connected from the output of the pump 14 to a special bypass valve 18 and thence back to the tank 11, as shown at 19.

The operator, after parking the truck 12 in loading position, prepares to unreel the hose 16 to the tank 13 and there connect it. Before doing so, however, he starts the pump 14, in order that he will not have to return to the truck after connetcing the hose 15 to the tank 13. At the outlet end 17 of the hose 16 is a manually operable valve which is in closed position. When the pump 14 starts, it rapidly builds up sufiicient pressure so that the pressure differential across the bypass valve 18 is sufficient to open the valve wide and permit the liquid to return directly to the tank through the pipes 1549, under very little more pressure that that in tank 11.

In accordance with the present invention, the bypass valve 18 in the bypass or recirculating pipe 15 is designed to respond to pressure in the tank 13 (or alternatively in the hose 16) in such a way as to move abruptly from fully closed position to fully open position when the pressure in the tank 13 or in hose 16 exceeds a predetermined value, and to move abruptly from fully open position to fully closed position when the pressure in 13 drops below a predetermined value. By this technique the pump 14 is not forced to work at high pressure through the bypass valve 18. Since the valve 18 opens completely in response to a pressure buildup in the hose 16 or tank 13, there is only insignificant pressure drop across the valve 18. Thus the pump 14 is able to work against a very low output pressure, only slightly higher than its input pressure (which is the pressure in the tank 11), thereby greatly lessening the deadweight load on the pump during the connecting and disconnecting operation.

In accordance with the present invention, this abrupt opening of the valve 18 is achieved by providing a pressure sensitive means which is independent of the bypass conduit 15. This pressure sensitive means actuates the valve 18. Means are provided for applying to this pressure sensitive means a pressure which is the function of the pressure in the tank 13 or hose 16. In a preferred embodiment of the present invention the means for applying this pressure takes the form of another flexible hose 21 and a cross conduit 22. Hose 21 is connected to the vapor space of the tank 13 above the liquid level therein. At the free end 20 of hose 21 is a manually operable valve. The pressure in the hose 21, or in line 22, is applied to a special pressure sensing chamber in the valve 18 which serves to initiate actuation of the valve member from open to closed position and vice versa.

Cross conduit 22 is provided between the output of the pump 14 and the connection or input 23 to the pressure sensitive compartment or chamber of the valve 18. Interposed between the output of the pump 14 and the cross connection 22 are a conventional check valve 24 which prevents back flow toward the pump 14 and a meter 26 which measures the amount of fuel passed into the transfer hose 16. The cross connection 22 also includes an orifice fitting 27 and a check valve 28 which permits fluid to flow (upwardly in FIG. 2) from the output of the pump 14 to the chamber input 23 but not in a reverse direction. A conventional relief valve 29 is provided near the input to the pressure sensing portion of valve 18. Valve 29 opens to allow escape of fluid should the pressure become dangerously high. The orifice 27 may consist of a partially closed valve, and thus be adjustable. The function of orifice 27 is to restrict appreciable flow of fluid from the line 16, so that when conduit 21 is opened to tank 13 at 241, the valve 18 will not open.

A form of valve 18 suitable for use in the present system is shown in FIG. 3. In this figure the valve casing 31 is provided with a number of chambers in communication with the valve member 32. There is an inlet chamber 33 to which the bypass pipe or conduit 15 is connected. As noted hereinbefore, the input end of the pipe 15 is connected to the output of the pump 14. There is an outlet chamber 34 to which the pipe 19, leading back to the tank 11, is connected. Passage of fluid from the chamber 33 to the chamber 34 is controlled by a valve 36 which seats at 37 to block passage between the two chambers. Fluid pressure in the inlet chamber 33 on the valve 36 is balanced by a piston 38, so that irrespective of the pressure in chamber 33 there will be no net effective force tending to move the valve member 32 in either direction.

Above the valve 36 is a balancing chamber 41 separated from the chamber 34 by an isolating piston 42. Above the chamber 41 and isolated therefrom by a transverse wall 43 is a pressure sensitive or actuating chamber 44. A valve stem 46 passes centrally upward in the valve casing 31 and to it is secured the

pistons

38, 42 and the valve 36. The stem 46 passes through a central opening in the transverse wall 43, an O ring 46' serving to maintain fluid isolation between chambers 41 and 44. On the rod 46 and closing the chamber 44 is a piston 47.

The entire valve member 32 is mechanically biased downward by a centrally disposed compression spring 48, the lower end of which bears against the piston 47, the upper end being adjustable through an adjusting screw 49 to adjust the downward bias on the valve member 32.

It will be noted that the pressure in the chamber 34 tends to move the valve member 32 upwardly, the latter being exposed to the chamber 34 not only in the annulus surrounding the valve 36 but also at the lower end of the valve stem 46 and the bottom portion of the piston 38. This upward force is substantially offset by the downward force exerted through the pressure in the chamber 41 which bears against the piston 42. The chamber 41 is connected by a pipe or other suitable conduit 51 back to the vapor space in the tank 11 above the level of the liquid contained therein. Since liquid and vapor pressures in the tank 11 are substantially equal, the pressures in chambers 34 and 41 are likewise substantially equal, and hence the net force on the valve member 32 is substantially zero, departing from Zero only by the slight difference in effective pressure area accessible to the chamber 41 in relation to the pressure sensitive area accessible to the chamber 34. Any net force tending to move the valve member 32 upward is more than offset by the adjustable spring 48, which tends to keep the valve closed, with the valve 36 seated on the seat 37. Actuation of the valve 18 is thus dependent upon the pressure in the chamber 44, which is connected to the pipe 23 leading to the vapor hose 21.

Operation The operation of the LPG transfer and loading system herein described is as follows:

After positioning the truck 12 the operator prepares to unreel the

hoses

16 and 21 over to the consumers tank '13. Before leaving the truck 12 he starts the pump 14, which is usually powered from the truck engine. Pressure at the otuput of the pump 14 promptly builds up to a pressure appreciably greater than that in the tank 11. This pressure is conveyed through the check valve 24, the meter 26, the orifice fitting 27, and the check valve 28, to the pipe 23 and thence to the chamber 44. When the pressure becomes large enough to overcome the bias of the spring 48, the force on the piston 47 moves the valve member 32 upward, opening the valve 36. With the opening of the valve 36 the output of the pump may fio-w freely through the bypass 15,

chambers

33 and 34 and pipe 19, back to the truck tank 11. This abrupt and full opening of the valve 36 allows the pressure at the output of the pump 14 to drop markedly and be only slightly greater than the input pressure to pump 14. Thus the load on the pump is greatly decreased. The drop in pressure at the output of the pump 14 does not affect the pressure in the chamber 44, however, because of the check valve 28.

The operator proceeds to unroll the

hoses

16 and 21 and connects them to the tank 13, the former being connected at 17 to the tank 13, the latter being connected to the vapor space of the tank 13 above the level of the LPG therein. The operator thereupon opens the manually

operable valves

17 and 20 located at the free ends of the

hoses

16 and 21, respectively. As soon as the hose 21 is exposed to the vapor pressure in the tank 13, the pressure in the hose 21 drops, thereby dropping the pressure in the chamber 44 and permitting spring 48 to close the valve 36. Thereupon the continued operation of the pump -14 forces LPG into the liquid hose 16 and thence into the consumers tank 13. As the pressure in the tank 13 builds up, it is transmitted through the vapor hose 21 to the chamber 44. When the point is finally reached where the tank 13 has maximumsafe pressure, the setting of the spring 4-8 is such as to permit the pressure in chamber 44 to again lift the valve 36, opening the bypass conduits 19 and again permitting the pump 14 to work at low loss through the bypass and back to the truck tank 11. The operator thereupon closes the valves at 17 and 20, disconnects the respective hoses, and reels them back to the truck. He then shuts off the pump 14, loads up his equipment and prepares ,to depart.

An alternative arrangement consists of connecting the end 2%) of hose 21 to the hose 16 adjacent its end 17. A valve is interposed at the end of hose 21 immediately before its connection to the hose 16 so that hose 21 may be selectively isolated from hose 16. This arrangement has the advantage of requiring that the operator make only a single pressure connection to the consumers tank 13, instead of two connections as in the previously de scribed embodiment.

This alternative embodiment of the invention is used substantially in the same way as the previously described embodiment. The operator connects the hose 16 to the consumers tank 13, opens the valve which places the hose 16 in communication with the tank 13 and then opens the valve at the end of hose 21 where it joins the hose 16. In this arrangement the pressure sensed in the vapor hose 21 is a few pounds higher than in the earlier embodiment because of the pressure drop across the fitting as the fluid flows from the hose 16 into the tank 13. This difference is small, and makes for a more conservative arrangement, for the pressure sensed by the hose 21 then tends to open the bypass valve 18 even sooner than before as the pressure in the tank 13 builds up. Thus there is even less.

danger of popping the release valve on the consumers tank 13. This arrangement of course is accompanied by the concomitant disadvantage that the tank 13 would not be filled quite as full as in the first embodiment.

While the instant invention has been shown and described herein in what is conceived to be the most practical and preferred embodiments, it is recognized that departures may be made therefrom within the scope of the invention which is therefore not to be limited to the details disclosed herein, but is to be afforded the full scope of the invention as hereinafter claimed.

What is claimed is:

1. In a system for transferring fluid from a first container to a second container and having a transfer conduit between said containers, a pump in said transfer conduit, and a recirculating bypass from the pump output to said first container, the combination comprising:

a bypass valve in said recirculating conduit, and

means directly connected and responsive to pressure in said second container for causing said bypass valve to move abruptly from fully closed to fully open position when the pressure in said second container exceeds a predetermined value, and to remain open during recirculation of fluid back to said first container.

2. In a system for transferring fluid from a first container to a second container and including a transfer conduit, a pump in said transfer conduit having its input connected to said first container and its output connected to said second container, a recirculating conduit connected from the output of said pump to said first container, and a bypass valve in said recirculating conduit, the combination comprising:

means independent of said transfer conduit for sensing the pressure in said second container, and

means responsive to said sensing means for opening said valve when the pressure in said second container exceeds a predetermined amount.

3. In a system for transferring vaporizable liquid from a truck tank to a consumers tank and including a transfer hose, a pump having its input connected to the truck tank and its output connected to the transfer hose, a recirculating pipe connected from the output of said pump to said truck tank, and a bypass valve in said recirculating pipe, the combination of:

means independent of said transfer hose for sensing the pressure in the consumers tank, and

means responsive to said pressure for placing and maintaining said valve in open position as long as the pressure in the consumers tank exceeds a predetermined amount.

4. In a system for transferring liquefied gas from a truck tank to a consumers tank and including a transfer hose, a pump having its input connected to the truck tank and its output connected to said transfer hose, a recirculating pipe connected from the output of said pump to the truck tank, and a bypass valve in said recirculating pipe, the combination comprising:

pressure responsive means for actuating said valve between open and closed positions,

a vapor hose having one end connected to sure responsive means, the other to being connected to the vapor sumers tank,

a shunt pipe connected between the output of said pump and said pressure responsive means, and a check valve in said shunt pipe for permitting passage of fluid from the output of said pump to said pressure responsive means while blocking passage in the reverse direction,

whereby upon operation of said pump with both of said hoses shut off, pressure will be applied from said pump to said pressure responsive means to open said valve and allow bypass circulation from the output of said pump back to said truck tank, and upon connecting of said hoses to the consumer's tank and opening of said hoses the drop in pressure in said vapor hose will cause said pressure responsive means to allow said valve to close, thereby pumping the output of said pump through said liquid hose into the consumers tank.

5. In a liquefied petroleum ing a tank truck having a transport tank thereon, a pump having its input connected to said truck tank, a transfer hose connected to the output of said pump, the other said presend being adapted space of the congas transfer system includend of said transfer hose being adapted to be connected to a consumers tank, a bypass pipe connected from the output of said pump back to said truck tank, and a bypass va'lve in said bypass pipe, said valve having a valve member for opening and closing fluid flow through said bypass pipe and an actuating member for actuating said valve member, the combination comprising:

pressure sensitive chamber means for applying an actuating force to said actuating member in response to pressure in said chamber,

a vapor hose having one end in communication with said chmaber, the other end of said vapor hose being adapted to communicate with the consumers tank,

a cross conduit connected between the output of said pump and said chamber and having therein a check valve for permitting fluid flow from said pump to said chamber but blocking flow in the reverse direction, and flow restricting means to effect pressure drop during fluid flow therethru,

whereby said valve is actuated in accordance with pressure in said chamber in order to bypass liquid back to the tank when the pressure in said chamber eX- ceeds a predetermined value and to close the bypass valve when the pressure in said chamber drops below a predetermined value.

6. In a system for transferring fluid from a first container to a second container, and having a transfer conduit between said containers, a pump in said transfer conduit, and a recirculating by-pass conduit around the pump, the combination comprising:

a by-pass valve having a valve member in said recirculating conduit movable between open and closed positions,

mechanical bias means urging said valve to closed position,

a first control chamber and a second control chamber, pressure in said first control chamber biasing said valve member to closed position, pressure in said second control chamber tending to cancel said mechanical bias means thereby biasing said valve member to open position,

conduit means for connecting said first control chamber with said first container, and

conduit means for connecting said second control chamber with said second container. 7. System in accordance with claim 6 wherein said valve has an inlet chamber connected to the output side of said pump and an outlet chamber connected to the input side of said pump, the pressure in said outlet chamber tending to move said valve member to open position and the pressure in said inlet chamber having no substantial net effect on said valve.

8. A control valve comprising: a balanced inlet chamber, an outlet chamber, a third chamber and a fourth chamber; a valve member movable between open and closed positions, interposed between said inlet and outlet chambers and adjacent to and in pressure communication with said third chamber thereby being responsive to pressure changes in said third chamber;

mechanical bias means urging said valve to closed position, adjacent to said fourth chamber and responsive to pressure changes therein;

the pressure in said outlet chamber tending to move said valve to open position, the pressure in said inlet chamber having no substantial net effect on said valve, the pressure in said third chamber tending to move said valve to closed position and the pressure in said fourth chamber tending to cancel said mechanical bias means thereby opening said valve.

References Cited UNITED STATES PATENTS 1,901,335 3/1933 Reynolds 14139 2,018,119 10/1935 Brouse 137115 X 2,421,325 5/1947 Griswold l37115 X 2,536,663 1/1951 SChaer 137-115 X 2,690,760 10/1954 Hughes 137484.2

FOREIGN PATENTS 1,298,300 5/1962 France 25162 SAMUEL ROTHBERG, Primary Examiner.

E. J. EARLS, Assistant Examiner.

Claims

1. IN A SYSTEM FOR TRANSFERRING FLUID FROM A FIRST CONTAINER TO A SECOND CONTAINER AND HAVING A TRANSFER CONDUIT BETWEEN SAID CONTAINERS, A PUMP IN SAID TRANSFER CONDUIT, AND A RECIRCULATING BYPASS FROM THE PUMP OUTPUT TO SAID FIRST CONTAINER, THE COMBINATION COMPRISING: A BYPASS VALVE IN SAID RECIRCULATING CONDUIT, AND MEANS DIRECTLY CONNECTED AND RESPONSIVE TO PRESSURE IN SAID SECOND CONTAINER FOR CAUSING SAID BYPASS VALVE TO MOVE ABRUPTLY FROM FULLY CLOSED TO FULLY OPEN POSITION WHEN THE PRESSURE IN SAID SECOND CONTAINER EXCEEDS A PREDETERMINED VALUE, AND TO REMAIN OPEN DURING RECIRCULATION OF FLUID BACK TO SAID FIRST CONTAINER.