Automatic liquid supply system

Abstract

 An automatic liquid supply system comprising one or more liquid storage vessels, one or more self-priming liquid transport pumps, conduits connecting said storage vessels via the pumps with one or more liquid delivery points, and means for controlling the liquid current. The delivery conduit of the transport pump is divided into a conduit 8, comprising a buffer vessel 6 and leading to the liquid delivery points, and a conduit 8' including a pressure control means 7 the arrangement being such as to ensure the uninterrupted flow of liquid to the delivery points when gas or vapour is temporarily pumped.

Description

[0001] This invention relates to an automatic liquid supply system comprising one or more storage vessels for the liquid, optionally venting to the atmosphere, and installed at a low or underground position, one or more self-priming transport pumps for the liquid, conduits connecting said storage vessels through said transport pumps to one or more liquid delivery points and means for the automated regulation, control and adjustment of the liquid current.

[0002] Such a liquid supply system is known in practice in various uses, for example, in association with processes requiring and processing large volumes of solvent or liquid fuel for heating purposes. In particular in cases in which the liquid must be withdrawn in metered quantities at the liquid delivery points, the switch Of the self-priming transport pump from an empty to a full storage vessel constitutes a critical moment, because the liquid current is interrupted and first vapour will be drawn and pumped before liquid is supplied from the full storage vessel. A similar situation is encountered when the pump being used must be put out of operation and a reserve pump used instead. A solution for the problem outlined above that is used in practice in order to ensure an uninterrupted supply of liquid during the switching from an empty to a full storage vessel involves the installation of the transport pump or pumps next to the storage vessels in a pump pit. As the storage vessels are normally installed outside of buildings, this solution has the disadvantage that maintenance of pumps becomes difficult, because this maintenance must be done in all sorts of weathers. Other disadvantages are that such a pump pit is an area of a high danger class, that it is difficult to keep the settlements of the storage vessels and the pump foundations equal, unless the punps are secured to the storage vessels; that in the case of pump leakage the cladding of the storage vessels is liable to be attacked by the leaking liquid, while there is also a risk of adversely affecting the cathodic protection that is often used. In addition, the control systems for the pumps must be extended to the location of the storage vessels, while observation of the pumps by means of a closed TV circuit from a central control room is also rendered more difficult.

[0003] It is an object of the present invention to provide an automated liquid supply system, in which the disadvantages inherent in the prior system have been eliminated, at least the effect thereof has been considerably mitigated.

[0004] For this purpose, according to the invention, there is provided an automated liquid supply system of the kind defined in the opening paragraph of this specification, and which is characterized in that the delivery conduit of the transport pump divides in a point of bifurcation into a transport conduit leading to the liquid delivery points and a conduit in which, as closely as possible downstream of the point of bifurcation a control means suitable for pressure control in the system is included; the supply conduit includes a buffer vessel, and the point of bifurcation is located at a level sufficient to install the buffer vessel under it and to enable the liquid available within the buffer vessel to flow to the liquid delivery points by gravity.

[0005] The automated liquid supply system according to the invention is suitable for all sorts of liquids, for example, liquid fuel, such as fuel oil, or solvents. The supply system according to the invention is also suitable for being constructed so as to produce a substantially fully closed system with which liquid can be delivered to one or more of the liquid delivery points and a separately determined quantity'can be withdrawn at each delivery point. In the case of zero withdrawal at all delivery points, all of the liquid pumped must accordingly be able to be passed via the above control means in the discharge conduit and be recycled to the storage vessel.

[0006] One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing, which shows a diagram of a supply system according to the present invention.

[0007] Referring to the drawing, two suction conduits ₂₁ and 22 are each connected to a different storage vessel, not shown. These storage vessels may, for example, be in open communication with the atmosphere, i.e., without being pressurized.

[0008] The self-priming transport pump 3 withdraws via one of the suction conduits 21 or 22, for example conduit 22, with the other conduits possibly being blocked, liquid from the storage vessel connected to it, and pumps the liquid through delivery conduit 4 to the highest level, at which level the delivery conduit divides at point of bifurcation 5 into two conduits, namely, conduits ₈ and ₈', respectively. The further course of the liquid will be described hereinafter. To further illustrate the system located under the level of point of bifurcation 5, the supply conduit 8 is connected to a buffer vessel 6, to which furthermore transport conduit 16 is connected which, dividing, ultimately leads to liquid delivery points ₄₂, ₄₃ and 44. Immediately downstream of, at any rate as closely as possible to, point of bifurcation 5, a known per _se overflow valve 7 is included in conduit 8, which can be used for the pressure control in the entire system. Downstream of overflow valve 7, conduit 8" is connected to return conduit 9, to which the separate return conduits 9', 9 and 9"' of the delivery points are also connected, and which return conduit 9, dividing into conduit 31 and 32, is again connected to the liquid storage vessels not shown.

[0009] Downstream of branch point 5, all conduits are placed under a slope.

[0010] So long as a storage vessel contains sufficient liquid, a continuous stream of liquid is pumped by means of pump 3 through delivery conduit 4, which at point of bifurcation 5 flows through conduit 8 and into buffer vessel 6, and thence further through transport conduit 16 to delivery points 42, 43 and 44.

[0011] The liquid supply system as shown in the drawing naturally comprises the required control means, not shown, whereby the ultimate supply of liquid to the delivery points 43, 43 and 44 takes place fully automatically. These control means, which cooperate with other control means within a complete control system, accordingly, for example, provide for the selection of the suction conduits 21 or 22 and switching over to the other suction conduit as soon as the storage vessel connected to the one selected is enpty,and for the selection of return conduits 31 or 32 for connection to the associated storage vessels in which they are included. These control means do not constitute part of the present invention.

[0012] As soon as a storage vessel is empty, the control system ensures automatic switch-over to another vessel, and transportpump 3 is in communication through the other of suction conduits 21 or 22 with the vessel connected thereto. In the initial phase after the switch-over, transport pump 3 will first draw a quantity of vapour and pump this through delivery conduit 4. The arrangement of overflow valve 7 is such that the vapour arriving at the point of bifurcation 5 is passed by overflow valve 7 and discharged through discharge conduit ₈" downstream of the overflow valve, the common return conduit 9 and one of return conduits 31 and 32 to a storage vessel. So long as vapour passes the point of bifurcation 5, the liquid supply to the liquid delivery points is maintained from the liquid available in buffer vessel 6.

[0013] Buffer vessel 6 may also have the form of an over-dimensioned conduit: care should only be taken that there is such a capacity that the amount of liquid available in the buffer vessel ensures the supply of liquid to the liquid delivery points. In this connection the volume is determined by the capacity of the suction conduit and the capacity of transport pump.3., the pressure whithin the vesel and the withdrawal at liquid delivery points 42, 43 and 44.

[0014] The superfluous liquid at liquid delivery points ₄₂, 43 and 44 flows through-conduits 9', 9" and 9"' and the ultimate discharge conduits 31 or 32 back to one of the storage vessels.

[0015] Parts 3, 4, 5, 6, 7, 8, 8', 11, 16 form the pressure section of the system, the rest forms the low- pressure portion. The necessary working pressures for the liquid are realized at the delivery points and may differ from one delivery point to another.

[0016] It should be noted that it is not necessary to mount foot valves either in the suction conduits or in the return conduit system to the storage vessels. What is necessary is a return valve 11 in the delivery conduit, in case transport pump 3 is of the rotary type.

[0017] The liquid supply system as shown in the drawing may be installed in a building with the storage vessels being installed outside the building at a greater or less great distance from it, for example, under the ground. Such a situation will particularly be preferred in the case of liquids constituting a fire hazard.

[0018] Naturally, the automated liquid supply system as described above and shown in the accompanying drawing may be modified without departing from the scope of the invention. Thus, for example, two or more transport pumps may be used, or a pump may be combined with a reserve pump: when the pump in operation gets out of order, the reserve pump can then be switched on automatically.

Claims

1. An automatic liquid supply system, comprising one or more storage vessels for the liquid, optionally venting to the atmosphere, and installed at a low or underground position, one or more self-priming transport pumps for the liquid, conduits connecting the storage vessels via the transport pumps to one or more liquid delivery points, and means for the automated regulation, control and adjustment of the liquid current, characterized in that the delivery conduit of the transport pump divides in a point of bifurcation into a supply conduit leading to the liquid delivery points and into a discharge conduit in which, as closely as possible downstream of said point of bifurcation, a control means is included suitable for pressure regulation in the system, said supply conduit including a buffer vessel, and said point of bifurcation being located at a level sufficient for placing the buffer vessel under it for permitting the liquid available in the buffer vessel to flow to the liquid delivery points by gravity.

2. A system as claimed in claim 1, characterized in that the discharge conduit is formed as a return conduit leading to the storage vessels.

3. A system as claimed in claim 1, characterized in that the liquid delivery points also include return conduits leading to the storage vessels.

4. A system as claimed in claims 2-3, characterized in that the return conduits are combined into a coherent and co-operating return conduit system.

Drawing