US2993344A

US2993344A - Lpg transport loading

Info

Publication number: US2993344A
Application number: US772258A
Authority: US
Inventors: Edwin E Reed
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1958-11-06
Filing date: 1958-11-06
Publication date: 1961-07-25
Anticipated expiration: 1978-07-25

Description

July 25, 1961 E. E. REED 2,993,344

LPG TRANSPORT LOADING Filed Nov. 6, 1958 6 l I I l 4 LR GAS FROM 5 STORAGE i I5 I 2 e 3 I P v i i G O Wquzw xxxx'A /I\' /\"4\\- POSITIVE DISPLACEMENT METER INVENTOR.

E.E.REED

ATTORNEYS 2,993,344 LPG TRANSPGRT LOADING Edwin E. Reed, Bartlesville, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware Filed Nov. 6, 1958, Ser. No. 772,258 6 Claims. (Cl. 62-49) This invention relates to apparatus and a method for transferring a liquefied gas to a closed container. In one aspect it relates to apparatus and a method for loading transport trucks with a liquefied gas Without the use of an equalizing line and without the transport truck being equipped for spray loading.

In some instances transport trucks which are used in liquefied petroleum gas transport service are equipped for spray loading. By the term spray loading is meant the provision of a relatively large liquid spray device disposed in the top of the transport tank so that liquefied petroleum gas, when pumped into the tank, is pumped through the spray for cooling so as not to build up high pressures as the liquid volume increases and the vapor is compressed. Such pumping equipment involves pipes and pumps for pumping the liquefied petroleum gas at the rate of from about 300 to 400 liquid gallons per minute. When such transport trucks are not provided with spray equipment, a separate pipe is run from the top of the truck tank to the storage tank so that, as liquid is pumped into the bottom of the truck tank, vapors escape from the top of the truck tank and are transmitted through the pipe to the storage tank so that pressure does not build up in the truck tank and cause popping of the relief valve.

Trucks which are equipped with the top tank sprays are kept cool so as not to build up excessively high pressures in the tank, and such tanks do not require a pressure equalization line leading from the truck tank back to the storage tank. Many LPG transport truck tanks are not equipped with such spray apparatus.

An object of this invention is to provide apparatus and a method for loading liquefied petroleum gas into transport trucks.

Another object of this invention is to provide apparatus and a method for loading liquefied gas into transport truck tanks which are not equipped for spray loading and without need for use of a pressure equalization line from the truck tank to the LPG supply tank.

Still other advantages will be realized upon reading the following description which, taken with the attached drawing, forms a part of this specification.

The drawing illustrates diagrammatically one form of apparatus for carrying out the method of this invention.

I have devised apapratus and a method for loading truck tanks, which are not equipped for spray loading, with liquefied petroleum gas. With my loading apparatus, pressure equalization lines are not required.

One important disadvantage in a prior art method of loading transport tanks with liquefied petroleum gas when using a positive displacement meter for measuring the volume of liquid being loaded into the tank is that when a pressure equalization line is employed between the top of the transport tank and the storage tank, the amount of vapor passing from the truck tank to the storage tank is lost from the truck tank. In other words, the positive displacement meters indicate that a larger volume of liquid is transferred to the tank than is actually in the tank. This is because a portion of the liquid has been returned as vapor to the storage tank through the pressure equalization line. In such cases, when the reading of the positive displacement meter is used in the purchase and sale of a product, the amount of liquefied pe- Patented July 25, 1961 troleum gas actually delivered is less than that indicated by the meter.

To eliminate this inaccuray, meters have been installed in the vapor return line and the volume so recorded has been deducted from the amount delivered to the transport tank through the liquid meter. This system of metering obviously has many disadvantages. For example, a gas or Vapor volume cannot be deducted directly from a liquid volume, it first being necessary to compute the liquid equivalent of the metered vapor. Since pressure and temperature must be measured simultaneously before such calculation can be made, it is customary to use a pressure and temperature compensated meter to measure the volume of vapor. Such a meter is very costly and therefore undesirable.

According to my invention, I provide a transfer pipe leading from the storage tank to a bottom fill inlet of the truck tank. This pipe is provided with a pump for the transfer of liquid and a positive displacement meter for volume measurement. The meter is placed on the discharge side of the pump. Connected with the transfer pipe at some point between the meter and the truck tank is a branch pipe which discharges to the top of the truck tank. At the point of entry of this pipe into the top of the truck tank is provided a check valve so disposed that upon rupture of the pipe, outflow of either gas or liquid from the truck tank cannot occur. I provide a fiow control means in this branch pipe and also a flow control means in the transfer pipe between the bottom of the truck tank and the point at which the branch pipe communicates with the transfer pipe. By controlling the rate of flow of liquefied gas through the transfer pipe into the bottom of the truck tank, and controlling the rate of flow through the by-pass line into the top of the tank, I am able to regulate and control the temperature and, accordingly, the pressure within the transport tank while the tank is being filled.

When the transport truck is equipped for spray loading, that is, there is a large spray connection at the top of the transport tank, the transport may be loaded with out use of a pressure equalization line. Many presently used transport trucks are not equipped with these large sprays for spray loading.

In order to be able to use a positive displacement metor for measuring the liquid volume of liquefied petroleum gas being loaded into a transport truck, I use the main transfer pipe and the branch pipe as mentioned above. The major portion of the liquefied petroleum gas is passed through the transfer pipe into the bottom of the truck tank. As liquid enters the tank from the bottom, the volume occupied by gas becomes smaller and smaller with the result that pressure in the tank increases. I reduce this pressure by allowing a portion of the liquefied gas to pass through the by-pass line and through the check valve and enter the top of the transport tank as a small spray. This spray addition of a portion of the liquid loaded into the tank cools the vapor contents of the tank with the result that the pressure therein is decreased. The regulators in the two pipes are actually throttle valves. The truck tanks are always provided with pressure relief valves in order to maintain safe working pressures within the tanks. In the case of liquefied petroleum gas, the relief valve is frequently set at a pressure of about 250 p.s.i.g. I set the throttle valve in the by-pass line to the top of the truck tank to close at a few pounds pressure below the setting of the relief valve. When the relief valve is set at 250 p.s.i.g., I frequently set the throttle valve in the by-pass line to close at a pressure of from 240 to 245 p.s.i.g. The throttle valve on the main transfer pipe to the bottom of the tank is set to close at a somewhat lower pressure than the setting on the throttle valve to the top of the tank, for example, this lower throttle valve is set to close at pressure from about 220 to 225 p.s.i.g. In this manner, as long as the pressure in the transport truck tank is below about 220 to 225 p.s.i.g., liquid will flow into the tank from the top and from the bottom. As the pressure in the tank approaches the set value of the regulator valve in the transfer line, the flow to the bottom of the tank will be slowed or even stopped.- As the pressure in the tank approaches the set value of the regulator valve in the by-pass line, the flow to the top of the tank will be slowed or even stopped so that the relief valve will not need to open for relief of pressure. It is realized that during any relief of pressure through the relief valve, the vapors so released from the tank will represent a loss of fuel.

In the drawing, reference numeral 1 identifies the tank of an LPG transport truck. A pipe 2 leads from a source of liquefied petroleum gas, such as liquefied propane, not shown. A positive displacement meter 8 is provided in pipe 2 at a location downstream as regards the flow of liquefied petroleum gas in pipe 2 from a pump 15. Downstream as regards flow of LPG from meter 8 is connected a branch pipe 4 which communicates with the top of the truck tank 1 through pipe 4a or through pipe 4b and tube 10. Pipe 4a contains a valve 12 and a check valve 7, as indicated. Pipe 4b also is provided with a valve 13 and a check valve 16. A transfer pipe 3 leads from the point of juncture of pipe 4 with pipe 2 through a check valve 17 and a connection 11 into the bottom of the truck tank 1. Pipe 3 is provided with a throttle valve regulator assembly 5 while pipe 4 is provided with a throttle valve regulator assembly 6. These throttle valve regulator assemblies are provided with throttle valves of any suitable type commensurate with the liquid the flow of which is to be regulated. Throttle valve regulator assembly 5 is actuated in response to pressure in pipe 3 between its valve and the truck tank, that is, substantially the pressure within the truck tank. Throttle valve regulator assembly 6 is actuated in response to pressure between the throttle valve of assembly 6 and the tank by way of pipe 4a or pipe 4b, that is substantially tank pressure.

I find that when loading a liquefied petroleum gas truck tank with this assembly of apparatus, the large spray connection for passing large liquid volumes is not required and also a pressure equalization line leading from the top of the truck tank to the supply tank is also not required. A relief valve 14 is provided in the top of the tank for pressure relief.

As an example of the operation of my invention, many liquefied petroleum gas transport truck tanks are provided with pressure relief valves set normally at about 25 p.s.i.g. With the relief valve set at 250 p.s.i.g., I set the throttle valve of regulator assembly to close at a pressure of 220 p.s.i.g. Thus, when the pressure in the tank reaches a value of 220 p.s.i.g., throttle valve 5 closes and liquid then flows only through pipes 4- and 4b and through tube and is impinged against the top of the tank; or liquid flows from pipe 4 through pipe 4a into the top of the tank, and is thus sprayed into the tank thereby cooling the contents thereof wtih a reduction in pressure. With the relief valve set at 250 p.s.i.g., I set the throttle valve of assembly 6 so that this valve will close at a tank pressure of 240 p.s.i.g. This throttle valve is set at this pressure so that upon loading the tank the flow of liquid through pipe 4 into the tank will continue after the valve of assembly 5 is closed thereby reducing the temperature and the pressure within the tank. This flow continues either through pipe 4a or pipe 4b, depending upon which one is installed with the tank. However, if pressure continues to increase, the valve of assembly 6 closes at 240 p.s.i.g. thereby stopping all liquid flow into the tank before actuation of the relief valve, with the resultant loss in fuel gas. When the valve of assembly 6 closes, all liquid flow into the tank is stopped until the tank and its contents 4 cool sufiiciently to reduce pressure to a value below 240 p.s.i.g., at which pressure this valve opens and tank filling continues.

In most cases, the tank is filled to the outlet of the spray tube 10 without reaching such a pressure that throttle valve 6 becomes closed. However, if pressure in the tank is increased to a value of 240 p.s.i.g., the throttle valve of assembly 6 closes at a pressure before the relief valve 14 relieves pressure. In this manner, fuel is not lost and all liquid metered into the tank remains in the tank.

By using this method and apparatus, I am able to use a positive displacement flow meter 8 to indicate and record the number of gallons or barrels of liquefied petroleum gas actually loaded into the transport truck tank. Thus, the dealer actually receives the quantity of liquefied petroleum gas indicated by the meter 8. Any suitable type of positive displacement meter desired can be used.

By use of my invention truck tanks are usually loaded in at least the same length of time as when using prior art equipment and methods. In some instances, however, they are loaded in less time, even though there is some slowing down in loading rate when a tank is nearly full.

While certain embodiments of the invention have been described for illustrative purposes, the invention obviously is not limited thereto.

I claim:

1. An apparatus for transferring a liquefied gas to a closed container comprising, in combination, a closed container for receiving the liquefied gas, a source of said liquefied gas, a first inlet for liquefied gas in the lower portion of said closed container, a second inlet for liquefied gas in the upper portion of said closed container, said second inlet being adapted to spray liquefied gas into the upper portion of said closed container, a first conduit communicating said source with said first inlet, a second conduit communicating said first conduit with said second inlet, a first throttle valve disposed operatively in said first conduit intermediate the point of communication of said second conduit with said first conduit and said first inlet, a second throttle valve in said second conduit, and said throttle valves being operatively responsive to pressures within the respective conduits intermediate the respective throttle valves and the container.

2. An apparatus for transferring a liquefied gas to a closed container comprising, in combination, a closed container for receiving the liquefied gas, a source of said liquefied gas, a first inlet for liquefied gas in the lower portion of said closed container, a second inlet for liquefied gas in the upper portion of said closed container, said second inlet being adapted to spray liquefied gas into the upper portion of said closed container, a first conduit communicating said source with said first inlet, a second conduit communicating said first conduit with said second inlet, a first throttle valve disposed operatively in said first conduit intermediate the point of communication of said second conduit with said first conduit and said first inlet, a second throttle valve in said second conduit, said throttle valves being operatively responsive to pressures within the respective conduits intermediate the respective throttle valves and the container, a pump in said first conduit intermediate said point of communication of said second conduit and said source for transferring liquefied gas from said source, and a flow meter in said first conduit intermediate said point of communication of said second conduit with said first conduit and said pump for indicaton of liquid flow.

3. A method for minimizing pressure within a closed container while passing a liquefied gas into said container comprising dividing a stream of said liquefied gas into two portions, passing one portion into the lower portion of said container whereby pressure in said container increases and simultaneously spraying the other portion into the upper and normally gas containing portion of said container, minimizing pressure increase in said container by reducing the rate of passing of said one portion of the liquefied gas into the lower portion of said container in response to pressure of said one portion of the liquefied gas entering said container while continuing spraying said other portion into the upper portion of said container,

4. A method for minimizing pressure within a closed container while passing a liquefied gas into said container comprising dividing a stream of said liquefied gas into two portions, flowing one portion into the lower portion of said container whereby pressure in said container increases and simultaneously spraying the other portion into the upper and normally gas containing portion of container, minimizing pressure increase in said container by increasing the relative rate of spraying of said other portion into said gas containing portion of said container by reducing flow of said one portion in response to a predetermined pressure of said one portion flowing into said container.

5. A method for eliminating popping of a relief valve in operative communication with a container adapted for the storage of liquefied petroleum gas, said relief valve being set to pop at a predetermined maximum working pressure, comprising dividing a stream of said liquefied gas into two portions, one portion being a major portion of said stream and the other being the remainder, passing the major portion into the bottom of said container until the pressure within the container reaches a predetermined pressure below said maximum working pressure, then terminating the passage of said major portion into said container, simultaneously spraying the remainder into the upper and normally gas containing portion of said container until the pressure within said container reaches a pressure intermediate said maximum working pressure and said predetermined pressure below the maximum working pressure and then terminating said spraying.

6. A method for eliminating popping of a relief valve in operative communication with a container adapted for the storage of liquefied petroleum gas, said relief valve being set to pop at a predetermined maximum working pressure, comprising dividing a stream of said liquefied gas into two portions, one portion being a major porton of said stream and the other being the remainder, simultaneously passing the major portion into the bottom of said container and spraying the remaining portion into the upper and normally gas containing portion of said container until the pressure within the container reaches a first predetermined pressure below said maximum working pressure, terminating the passing of said major portion into said container and continuing the spraying into the upper and normally gas containing portion of said container until the pressure therein reaches a second predetermined pressure between said first predetermined pressure and said maximum working pressure and terminating said spraying.

References Cited in the file of this patent UNITED STATES PATENTS 2,480,472 Jackson Aug. 30, 1949 2,487,863 Garretson Nov. 15, 1949 2,670,605 Van Zandt et a1 Mar. 2, 1954 2,790,307 Ayres Apr. 30, 1957 2,908,145 Haumann Oct. 13, 1959