GB2026891A

GB2026891A - Degassing liquids under reduced pressure

Info

Publication number: GB2026891A
Application number: GB7926831A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-08-02
Filing date: 1979-08-01
Publication date: 1980-02-13
Also published as: FR2432705B1; DE2931003A1; GB2026891B; NL187322C; FR2432705A1; NL7808147A; BE878035A; NL187322B

Abstract

In a method and apparatus for degassing a confined volume of liquid, e.g. milk, to be measured during the transportation of the liquid from a first vessel (not shown) to a second vessel 8 via a gas separation vessel 1 and a volumeter 7, degassing is promoted by regulating the supply to, and discharge from, the degassing vessel dependent on a subatmospheric pressure to be maintained therein. A liquid level sensor 13 causes valve 11 to open and valve 6 to close if the liquid level falls, thereby drawing air out of the space 15 via pump 7 and drawing more liquid through pipe 3; then closes valve 11 and opens valve 6 to allow the liquid to be transferred via pump 7 to tank 8. Special arrangements using time switches are utilised at the beginning and end of a run. <IMAGE>

Description

SPECIFICATION Method and apparatus for degasing, during transportation, a confined volume of liquid to be measured.

This invention relates to a method of degasing a confined volume of liquid to be measured, during the transportation of the liquid from a liquid supply vessel to a liquid storage vessel, which comprises withdrawing the liquid from the liquid supply vessel and passing it to a gas separation vessel and, simultaneously, or non-simultaneously with the supply to the gas separation vessel, withdrawing the liquid from the gas separation vessel, and passing it by way of a volumeter to the liquid storage vessel, and in which at least the discharge of the liquid from the gas separation vessel by way of the volumeter to the liquid storage vessel is made dependent on the pressure in the gas separation vessel.

Such a method is described in Dutch patent application 76.07497. In the prior method, the liquid discharge from the gas separation vessel is mainly controlled by a super-atmospheric pressure that is maintained in the gas separation vessel.

It is an object of the present invention to provide an improved method which makes it possible to make more accurate measurements, which is of great importance, in particular when used in a milk collecting tanker, as the amount paid to the farmer is directly proportional to the metered amount of milk taken in.

The present invention is characterized in that the supply and discharge of the liquid to, and from, the gas separation vessel is made dependent on a subatmospheric pressure to be maintained in the gas separation vessel.

The method according to the invention makes it possible that in the separation vessel smaller air bubbles entrained in the liquid can also expand and escape, whereby the accuracy of the volumetric measurement is greatly promoted.

The invention also relates to an apparatus suitable for carrying out the method according to the invention, in which the gas separation vessel is provided with a liquid supply conduit to be connected to the liquid supply vessel, a liquid discharge conduit to be connected by way of the volumeter and then a first valve to the liquid storage vessel, and a gas discharge conduit comprising a second valve, and which comprises a bottom portion to be connected to the liquid discharge conduit, said bottom portion being of greatly reduced cross-sectional area relative to that of the top portion, to which the liquid supply conduit is connected, a level switch responsive to the liquid level in the bottom portion and affecting the position of the first and the second valve, and being connected with a first time switch, and a control means responsive to a higher liquid level present in the separation vessel, which apparatus is characterized in that said liquid discharge conduit comprises after the first valve a liquid pump means which is also capable of transporting gas to a sufficient extent, and the suction side of which pump is connected to the gas discharge conduit comprising the second valve, and the control means is a second level switch affecting the position of the first and the second valve either simultaneously or non-simultaneously, said level switch being connected with a second time switch.

A liquid pump means suitable for use in the apparatus according to the invention is for example, the Jabsco pump, marketed by ITT, which is provided with a liquid impeller made of rubber material.

In normal use, this is a self-priming pump to an elevation of approximately 5 metres, and even up to approximately 7 metres, if previously filled with the liquid to be pumped. Other liquid pumps, however, such as displacement pumps, which are capable of transporting gas, such as air, to a sufficient extent, are suitable for use in the arrangement of the apparatus according to the invention.

One embodiment of the invention will now be described with reference to the accompanying diagrammatic drawing.

The embodiment shown in the drawing is suitable for use with a milk collecting system in which, in accordance with a pre-determined schedule, a tanker collects milk produced on the farms, and often stored in cooled milk tanks, for transportation to dairy factories for further processing. The quantity by volume registered as the milk is being taken in by the tanker forms a basis for the price to be paid to the farmer. Accurate- measurement, therefore, is of prime importance.

Referring to the drawing, there is shown a gas separation vessel 1. Reference numeral 2 designates a milk supply conduit, through which milk is supplied to the gas separation vessel. Conduit 2 is to be connected in gas-tight fashion to the milk tank on the farm by means of a hose 3 in a manner not shown.

At the bottom, the gas separation vessel, which is strongly tapered downwards, is provided with a milk discharge conduit 4, which via throughflow quantity meter 5, valve 6, which for example may be an electrically operable value, and purnp 7 is connected to the milk storage vessel 8 present on the tanker.

Pump 7 is connected on the suction side thereof also via a gas discharge conduit (air discharge conduit) 12, equipped with a valve 11, also preferably electrically operable, to the top of gas separation vessel 1.

At different levels, namely in the narrow bottom portion and in the wider top portion of the gas separation vessel, there are provided two level switches 14 and 13, respectively, each connected to first and second time switches, respectively, not shown. Level switch 14 responds to level 17 of the milk in the gas separation vessel in the sense that always a minimum stock of milk, as represented approximately by milk level 17, is maintained.

Switch 13 reacts in an analogous manner to a maximum stock of milk to be maintained in gas separation vessel 1, approximately represented by milk level 16.

The operation of the embodiment of the apparatus according to the invention shown in the drawing can be described as follows.

After connection of hose 3 to the milk tank present on the farm, pump 7 is switched on. When pumping begins, gas separation vessel 2 contains the mini mum stock of milk to level 17, valve 6 being closed and valve 11 being opened. In this combination of positions of valves 6 and 11, pump 7 will withdraw air from the gas separation vessel 1 and generate a subatmospheric pressure therein. Through hose 3 and milk supply conduit 2, milk is supplied to the gas separation vessel. As the milk level 17 is increased, switch 14 will operate the first time switch, the function of which will be described later. The increasing milk level ultimately reaches level switch 13, by means of which valve 6 is opened and valve 11 is closed.Under the influence of the suction by pump 7, milk is now withdrawn from gas separation vessel 1, and, while the quantity by volume thereof is simultaneously measured in meter 5, pumped via a non-return valve 9 and a valve 10 into milk tank 8.

During the pumping away of milk from the gas separation vessel, the supply of milk to this vessel naturally continues. If, during this phase, owing to unforeseen contingencies, an extra quantity of air is supplied to the gas separation vessel along with the milk, the result will be that the maximum milk level is decreased, as a result of which level switch 13 is put into operation, and as a consequence of which valve 6 is closed and valve 11 is opened. The extra amount of air supplied is then withdrawn from the gas separation vessel by pump 7 and the milk level is increased again until level switch 13 opens and closes the two valves 6 and 11, respectively and the discharge of milk from the gas separation vessel is resumed.

When the tank on the farm has been emptied, a large amount of air will be abruptly supplied via hose 3 and conduit 2 to the gas separation vessel. As a consequence, the milk level in the gas separation vessel will decrease to a considerable extent, as a consequence of which, under the influence of level switch 13, valve 6 is closed and simultaneously valve 11 is opened, and the second time switch is put into operation. During this period, the remainder of milk present in the farm tank and hose 3 are supplied to the gas separation vessel. When the time set through the second time switch has lapsed, the time switch switches valve 6 back into its open position and valve 11 into its closed position, whereafter the milk present in the gas separation vessel is again withdrawn.When the milk has reached the mini mum level 17, level switch 14will close valve 6 and open valve 11, and this terminates the cycle.

Thefunction of the first time switch connected with level switch 14 is that, if after the pump has begun to draw milk from the farm tank the amount of milk supplied to the gas separation vessel is insuffi client to cause the milk level to rise to level switch 13, valve 16 will be opened and valve 11 will be closed after the time set by the first time switch has lapsed.

If, when a given volumeter 5 is used and the flow resistance is too high, and consequently the capacity of the installation insufficient, or, if for any other reason, it is desirable for the pump capacity with regard to the milk to be pumped from the gas separating vessel to be increased, this can be achieved by including in discharge conduit 4 a second pump, either upstream or downstream of pump 7, which is connected so that it is preferably put into operation if the milk level exceeds level 16.

The apparatus shown in the drawing comprising provisions through which the installation, in particular milk storage vessel 8, can be cleaned. Via a switch not shown, for this purpose the level switches 14 and 13 can be put out of operation and valves 6 and 11 can be opened and closed, respectively. Furthermore, valve 18 is opened and valve 10 is closed.

Hose 3 is connected to a supply vessel containing a cleaning fluid. Pump 7 is put into operation and will pump the cleansing fluid through hose 3, gas separation vessel 1, meterS, non-return valve 9, valve 18, conduit 19 and one or more spray bulbs 20 into milk tank 8, which together with all the piping is cleaned.

Naturally the embodiment of the apparatus described above and shown in the accompanying drawing can be modified without departing from the scope of the invention. Thus, for example, the electrically operated level switches, which may be float switches, and the air operated valves 11 and 6 can be replaced by analogously operating devices.

Claims

1. A method of degasing a confined volume of liquid to be measured, during the transportation of the liquid from a liquid supply vessel to a liquid storage vessel, which comprises withdrawing the liquid from the liquid supply vessel and passing it to a gas separation vessel and, simultaneously, or non-simultaneously with the supply to the gas separation vessel, withdrawing the liquid from the gas separation vessel, and passing it by way of a volumeter to the liquid storage vessel, and in which at least the discharge of the liquid from the gas separation vessel by way of the volumeter to the liquid storage vessel is made dependent on the pressure in the gas separation vessel, characterized in that the supply and discharge of the liquid to, and from, the gas separation vessel is made dependent on a subatmospheric pressure to be maintained in the gas separation vessel.

2. Apparatus suitable for carrying out the method according to claim 1, in which the gas separation vessel is provided with a liquid supply conduit to be connected to the liquid supply vessel, a liquid discharge conduit to be connected by way of the volumeter and then a first valve to the liquid storage vessel, and a gas discharge conduit comprising a second valve, and which gas separation vessel comprises a bottom portion to be connected to the liquid discharge conduit, said bottom portion being of greatly reduced cross-sectional area relative to that of the top portion, to which the liquid switch responsive to the liquid level in the bottom portion and affecting the position of the first and the second valve, and being connected with a first time switch, and a control means responsive to a higher liquid level present in the separation vessel, characterized in that said liquid discharge conduit comprises after the first valve a liquid pump means which is also capable of transporting gas to a sufficient extent, and the suction side of which pump is connected to the gas discharge conduit comprising the second valve, and the control means is a second level switch affecting the position of the first and the second valve either simultaneously or non-simultaneously, said level switch being connected with a second time switch.

3. Apparatus according to claim 2, wherein said liquid discharge conduit comprises a second pump upstream of said liquid pump means.

4. A method of degasing a confined volume of liquid to be measured, substantially as hereinbefore described with reference to the accompanying drawing.

5. Apparatus for degasing a confined volume of liquid to be measured, substantially as herein before described with reference to the accompanying drawing.