GB2283065A

GB2283065A - Fluidic pumping system

Info

Publication number: GB2283065A
Application number: GB9418574A
Authority: GB
Inventors: Peter David Wilson
Original assignee: British Nuclear Fuels PLC
Current assignee: Sellafield Ltd
Priority date: 1993-10-13
Filing date: 1994-09-15
Publication date: 1995-04-26
Also published as: JPH07158600A; KR950011843A; GB9418574D0; GB9321074D0; FR2711191A1

Abstract

A fluidic pumping system comprises two charge vessels (1, 2) which communicate with a liquid inlet (5) and a liquid outlet (6) through a fluidic bridge rectifier (4). A pressurising and depressurising arrangement (3) for alternately pressurising and depressurising the charge vessels (1, 2) comprises a chamber (7) containing a piston (8) and being in communication with the charge vessels. Drive means (9, 10) not mechanically connected to the piston are provided for causing reciprocatory movement of the piston. Movement of the piston in one direction causes pressurisation of one charge vessel to discharge a liquid therefrom through the liquid outlet. Simultaneously, the other charge vessel is depressurised to draw liquid from the liquid inlet into the depressurised charge vessel. Preferably, the drive means for the piston comprises an external solenoid winding (9, 10) at each end of a horizontally arranged chamber. Alternatively, the chamber may be vertically disposed with an external solenoid winding at the upper end of the chamber to effect upward movement of the piston, the piston then falling under gravity upon de-energisation of the winding. <IMAGE>

Description

Fluidic Pumping Svstems This invention relates to fluidic pumping systems.

Fluidic pumping systems have been found to be suitable for moving radioactive or hazardous liquids because they do not contain moving parts which could require maintenance with consequent risk to maintenance personnel.

A typical known fluidic pumping system includes a charge vessel containing the liquid to be pumped and connected to feed and discharge pipes through fluidic devices, such as vortex diodes. The charge vessel is alternately pressurised with a driving gas and then vented so that when pressurised the charge vessel expels liquid through the discharge pipe and when vented draws liquid from the feed pipe.

A disadvantage with this known system is that the driving gas comes into direct contact with the liquid being pumped. This results in possible contamination of the driving gas which, when vented, must be treated to removed contaminants before discharge to the atmosphere.

Since flows of driving gas can constitute major inputs to the gas treatment system, the treatment system is required to be substantially larger and more expensive than would otherwise be necessary.

One method of overcoming this problem is to provide a barrier liquid between the driving gas and the radioactive liquid being pumped. An example of this method is disclosed in GB Patent No 2220709B in which a secondary gas is trapped between the barrier liquid and the radioactive liquid. When a pressurised driving gas is applied to the barrier liquid, the trapped secondary gas is pressurised to drive the radioactive liquid from a displacement vessel and then through a fluidic rectifying device to a discharge pipe. Thus, the driving gas does not come into contact with the radioactive liquid.

However, the barrier liquid itself could become contaminated through diffusion or over-driving, and so may not provide sufficient protection against indirect contamination to allow the vented gas to be discharged to the atmosphere without being subjected at least to a precautionary treatment. A further disadvantage of this pumping system is the need for a rather complicated priming procedure.

It is an object of this invention to provide a fluidic pumping system having an improved arrangement for pressurising and depressurising the charge vessel in which the aforementioned disadvantages are overcome.

According to the invention there is provided a fluidic pumping system comprising at least one charge vessel containing a liquid to be pumped and being in communication with a liquid outlet and a liquid inlet, a first fluidic device located between the liquid outlet and the charge vessel, a second fluidic device located between the liquid inlet and the charge vessel, said first and second fluidic devices presenting a low resistance to liquid flow in one direction and a high resistance to liquid flow in the opposite direction, and a pressurising and depressurising arrangement for alternately pressurising and depressurising the charge vessel such that on pressurising the charge vessel the liquid is discharged through the first fluidic device and the liquid outlet, and on depressurising the charge vessel the liquid is drawn through the liquid inlet and the second fluidic device, wherein the pressurising and depressurising arrangement comprises a chamber in communication with the charge vessel, a piston arranged within the chamber, and drive means operative to cause reciprocatory movement of the piston without mechanical connection therewith, whereby movement of the piston in one direction causes pressurisation of the charge vessel and movement of the piston in the other direction causes depressurisation of the charge vessel.

The drive means for the piston preferably comprises a solenoid winding and an electrical source for energising the solenoid winding, whereby upon energisation of the solenoid winding the piston is caused to move by magnetic attraction.

Preferably, the drive means includes control means which may comprise at least one detector for sensing the presence of the piston and adapted for initiating electrical energisation of the solenoid winding upon sensing the presence of the piston.

In a preferred embodiment of the invention the drive means comprises a first solenoid winding arranged externally of the chamber adjacent one end thereof, and a second solenoid winding arranged externally of the chamber adjacent the other end thereof, the control means being adapted to alternately energise each solenoid winding in turn so as to cause reciprocatory movement of the piston.

The control means may comprise at least two detectors for sensing the presence of the piston, one of the detectors being arranged towards one end of the chamber and the other detector being arranged towards the other end of the chamber, the arrangement being such that the detectors, upon sensing the presence of the piston, initiate energisation of the solenoid winding at an end opposite from that at which the piston is sensed.

In a preferred embodiment of the invention the first and second fluidic devices each comprises a vortex diode.

Desirably, the fluidic pumping system comprises two charge vessels, one of which communicates with one end of the chamber and the other of which communicates with the other end of the chamber, whereby reciprocatory movement of the piston causes alternate pressurising and depressurising of each of the charge vessels in antiphase.

Preferably, each of the charge vessels communicates with the liquid outlet through a first vortex diode and communicates with the liquid inlet through a second vortex diode, the vortex diodes associated with one of the charge vessels and the vortex diodes associated with the other change vessel forming a fluidic bridge rectifier.

The chamber may be disposed vertically and provided with a solenoid winding arranged externally of the chamber towards an upper end thereof, whereby the piston is raised upon energisation of the solenoid winding and falls under gravity towards the lower end of the chamber upon de-energisation of the solenoid winding.

The liquid to be pumped may contain radioactive substances.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic representation of a fluidic pumping system in accordance with a preferred embodiment of the invention, and Figure 2 is a diagrammatic representation of a fluidic pumping system in accordance with a further aspect of the invention.

Referring to Figure 1, a fluidic pumping system includes two charge vessels 1, 2, an alternating pressurising and depressurising arrangement 3 and a vortex diode bridge rectifier 4. Liquid to be pumped enters the system through a feed inlet pipe 5 and is discharged through an outlet pipe 6.

The pressurising and depressurising arrangement 3 comprises a horizontally arranged cylindrical chamber 7 housing a piston 8 which incorporates a magnetic material and is an easy sliding fit within the housing. At each end of the chamber 7 is an external solenoid winding 9, 10. One end of each of the windings 9, 10 is connected to a first terminal of an electrical power source 11, which may be a battery as shown. Other sources of electrical power for providing an AC or DC supply could be used if desired. The other end of each of the solenoid windings 9, 10 is connected to the contacts of a switch 12 which, in turn, is connected to a second terminal of the electrical power source 11. A series of detectors 13, 13a, only two of which are shown, is provided adjacent the external surface of the chamber 7 for sensing the position of the piston 8.Various types of detector may be used, examples of which are those operating on acoustic, magnetic or capacitative principles. One possible type of detector could operate by measuring the influence of the piston 8 on the reactance of the solenoid windings 9, 10.

The detectors 13, 13a are connected to a controller 14 which controls the operation of the switch 12 in such a way that the solenoid windings 9, 10 are alternately energised, thereby causing reciprocation of the piston 8, as will be described later.

The interior of the chamber 7 communicates with the interior of the charge vessel 1 by means of a pipe 15 leading from the chamber at an end adjacent the solenoid winding 9. The chamber 7 also communicates with the interior of the charge vessel 2 by a pipe 16 leading from the other end of the chamber. Contained in each of the charge vessels 1, 2 is a liquid L, for example a radioactive or other type of hazardous liquid, forming part of the liquid to be discharged through the outlet pipe 6. A driving gas or coupling fluid F is provided in the chamber 7 on each side of the piston 8, the coupling fluid also filling the pipes 15, 16 and the charge vessels 1, 2 above the level of the liquid L.

Suitably, the coupling fluid may comprise kerosene if the liquid to be pumped is aqueous or, in certain cases, it may comprise the feed liquid itself. In circumstances allowing compression losses to be tolerated, the coupling fluid may be air or an inert gas. Where the coupling fluid is a liquid it may be introduced into the pipes 15, 16 through branch connections, not shown, which are then closed and take no further part in the operation of the pump.

At the end remote from the pipe 15, the charge vessel 1 communicates with the vortex diode bridge rectifier 4 by means of a pipe 17. Similarly, at the end remote from the pipe 16 the charge vessel 2 communicates with the bridge rectifier 4 by means of a pipe 18. The pipe 17 leading from the charge vessel 1 branches into a pipe 19 which interconnects two fluidic devices 20, 21. Similarly, the pipe 18 leading from the charge vessel 2 branches into a pipe 22 which interconnects two further fluidic devices 23, 24. The fluidic devices 20, 21, 23, 24 comprise vortex diodes which allow easy flow of liquid in one direction, but present high resistance to flow in the other direction. Thus, the vortex diodes function in a manner similar to non-return valves, but differ in that they do not contain any moving parts and so do not require any maintenance.This is particularly advantageous when the liquid L to be moved is radioactive and exposure to maintenance personnel is to be avoided.

The inlet pipe 5 for the feed liquid branches into a pipe 25 which forms a link between the two vortex diodes 20, 23. A pipe 26, from which the outlet pipe 6 branches, forms a link between the two vortex diodes 21, 24.

The pumping system operates as follows. The system is primed so that the liquid L to be pumped partially fills each of the charge vessels 1, 2. The coupling fluid F fills the remaining volume of the charge vessels 1, 2, the pipes 15, 16 and the interior of the chamber 7 on either side of the piston 7. One of the solenoid windings, say winding 9, is energised by means of an electrical supply derived from the electrical power source 11 and supplied through the switch 12. The magnetic material in the piston 8 is attracted by the magnetic field set up by the energised solenoid winding 9 so that the piston moves to the left hand end of the chamber 7, as viewed in Figure 1.

Through the medium of the coupling liquid F the charge vessel 1 is pressurised so that the liquid L is expelled.

The expelled liquid is mostly discharged through the outlet pipe 6 via the pipe 17, vortex diode 21 and pipe 26. The vortex diode 21 allows liquid to pass through to the outlet pipe 6, but vortex diode 20 resists the passage of liquid flowing in a direction towards the inlet pipe 5.

Simultaneously, the charge vessel 2 is depressurised when the piston 8 moves towards the solenoid winding 9 so that the coupling fluid F flows through the pipe 16 into the chamber 7. This causes feed liquid to be drawn through the inlet pipe 5 into the charge vessel 2 via the pipe 25, vortex diode 23 and pipe 18. The vortex diode 23 allows liquid to pass through to the charge vessel 2, but vortex diode 24 resists the passage of liquid flowing in a direction from the outlet pipe 6.

As the piston 8 approaches the solenoid winding 9, its position is sensed by the detector 13 which emits a signal to the controller 14. As a result, the controller 14 initiates actuation of the switch 12 so that an electrical supply from the electrical power source 11 energises the solenoid winding 10 while solenoid winding 9 is deenergised. This causes a reversal of the movement of piston 8 so that it now moves under the influence of the energised winding 10 to the right hand end of the chamber 7, as viewed in Figure 1. Thus, through the medium of the coupling fluid F, the charge vessel 2 now becomes pressurised. Some of the liquid L is expelled from the vessel 2 and discharged through the outlet pipe 6 via pipe 18, vortex diode 24 and pipe 26. The vortex diode 24 allows the liquid to flow in this direction, but vortex diode 23 resists a flow of liquid towards the inlet pipe 5.

At the same time the charge vessel 1 is depressurised, so allowing feed liquid to be drawn through the inlet pipe 5 into the vessel 1 through the pipe 25, vortex diode 20 and pipes 19 and 17. ln this case, the vortex diode 20 allows liquid to pass through to the charge vessel 1, but vortex diode 21 resists the passage of liquid flowing in a direction from the outlet pipe 6. The presence of the piston 8 in the vicinity of the solenoid winding 10 is sensed by the detector 13a which initiates energisation of the other winding 9 so that the pumping cycle is repeated.

The number, location and output connections to the controller 14 of the series of detectors 13, 13a are arranged so as to maintain a reciprocatory motion of the piston 8. Thus, the two charge vessels 1, 2 are alternately pressurised and depressurised. By operating in antiphase, the two charge vessels, in conjunction with the vortex diode bridge rectifier 4, maintain a substantially continuous flow of liquid through the outlet pipe 6.

Figure 2 shows a further embodiment of the invention in which numerals corresponding to those in Figure 1 indicate similar parts. In this further embodiment, the chamber 7 for the pressurising and depressurising arrangement is disposed vertically and has a single solenoid winding 10 arranged externally of the chamber towards an upper end thereof. In operation, the solenoid winding 10 is energised by means of an electrical supply derived from the electrical power source 11 and supplied through the switch 12. The piston 8 is thus raised towards the upper end of the chamber 7 by the magnetic attraction set up by the energised solenoid winding 10.

This causes pressurisation of the charge vessel 2 and simultaneous depressurisation of the charge vessel 1.

As the piston 8 approaches the solenoid winding 10 its presence is sensed by the detector 13a which emits a signal to the controller 14. The controller 14 initiates actuation of the switch 12 so that the solenoid winding is de-energised. This allows the piston 8 to fall under gravity to the lower end of the chamber 7, so causing pressurisation of the charge vessel 1 and simultaneous depressurisation of the charge vessel 2. On reaching the lower end of the chamber 7 the piston is sensed by the detector 13 and the pumping cycle described above is repeated. Thus, as in the embodiment described with reference to Figure 1, an alternating liquid pressure is applied to the vortex diode bridge rectifier 4 so as to produce a continuous flow of liquid through the outlet pipe 6.

If desired, the pressurising and depressurising arrangement 3 can be adapted to operate a simpler pumping system providing an intermittent discharge of liquid, subject during the non-delivering phase of each cycle to a limited reverse flow of a magnitude depending on the operating characteristics of the vortex diodes. In this system, only one charge vessel and a co-operating pair of vortex diodes are required. For example, the charge vessel 1 would have an associated pair of vortex diodes 20, 21, but the charge vessel 2 and its associated vortex diodes 23, 24 would be omitted. A vessel connected to the pipe 16 is provided for receiving the coupling fluid F expelled by the piston 8 during the depressurising stroke and to replenish the fluid due to the inevitable leakage through the annular gap between the piston 8 and the inner surface of the chamber 7.

The coupling fluid F used for pressurising and depressurising the charge vessels is totally enclosed.

Therefore, there is no requirement to treat the fluid routinely in an active treatment system, unlike certain prior art arrangements where it is necessary to subject a regular discharge of driving air to such treatment.

Claims

1. A fluidic pumping system comprising at least one charge vessel containing a liquid to be pumped and being in communication with a liquid outlet and a liquid inlet, a first fluidic device located between the liquid outlet and the charge vessel, a second fluidic device located between the liquid inlet and the charge vessel, said first and second fluidic devices presenting a low resistance to liquid flow in one direction and a high resistance to liquid flow in the opposite direction, and a pressurising and depressurising arrangement for alternately pressurising and depressurising the charge vessel such that on pressurising the charge vessel the liquid is discharged through the first fluidic device and the liquid outlet, and on depressurising the charge vessel the liquid is drawn through the liquid inlet and the second fluidic device, wherein the pressurising and depressurising arrangement comprises a chamber in communication with the charge vessel, a piston arranged within the chamber, and drive means operative to cause reciprocatory movement of the piston without mechanical connection therewith, whereby movement of the piston in one direction causes pressurisation of the charge vessel and movement of the piston in the other direction causes depressurisation of the charge vessel.

2. A fluidic pumping system according to Claim 1, wherein the drive means for the piston comprises a solenoid winding and an electrical source for energising the solenoid winding, whereby upon energisation of the solenoid winding the piston is caused to move by magnetic attraction.

3. A fluidic pumping system according to Claim 1 or Claim 2, wherein the drive means includes control means comprising at least one detector for sensing the presence of the piston and adapted for initiating electrical energisation of the solenoid winding upon sensing the presence of the piston.

4. A fluidic pumping system according to Claim 3, wherein the chamber is substantially horizontally disposed and the drive means comprises a first solenoid winding arranged externally of the chamber adjacent one end thereof, and a second solenoid winding arranged externally of the chamber at the other end thereof, the control means being adapted to alternately energise each solenoid winding in turn so as to cause reciprocatory movement of the piston.

5. A fluidic pumping system according to Claim 4, wherein the control means comprises at least two detectors for sensing the presence of the piston, one of the detectors being arranged towards one end of the chamber and the other detector being arranged towards the other end of the chamber, the arrangement being such that the detectors, upon sensing the presence of the piston, initiate energisation of the solenoid winding at an end of the chamber opposite from that at which the piston is sensed.

6. A fluidic pumping system according to any one of the preceding Claims, wherein the first and second fluidic devices each comprises a vortex diode.

7. A fluidic pumping system according to any one of the preceding Claims, wherein the system comprises two charge vessels, one of which communicates with one end of the chamber and the other of which communicates with the other end of the chamber, whereby reciprocatory movement of the piston causes alternate pressurising and depressurising of each of the charge vessels in antiphase.

8. A fluidic pumping system according to Claim 7, wherein each of the charge vessels communicates with the liquid outlet through a first vortex diode and communicates with the liquid inlet through a second vortex diode, the vortex diodes associated with one of the charge vessels and the vortex diodes associated with the other charge vessel forming a fluidic bridge rectifier.

9. A fluidic pumping system according to Claim 2, wherein the chamber is disposed vertically and is provided with a solenoid winding arranged externally of the chamber towards an upper end thereof, whereby the piston is raised towards the upper end of the chamber upon energisation of the solenoid winding and falls under gravity towards the lower end of the chamber upon de-energisation of the solenoid winding.

10. A fluidic pumping system according to any one of the preceding Claims, wherein the liquid to be pumped contains radioactive substances.

11. A fluidic pumping system substantially as hereinbefore described and as illustrated in the accompanying drawings.