WO2002016045A1

WO2002016045A1 - Fluid distribution system

Info

Publication number: WO2002016045A1
Application number: PCT/GB2001/003621
Authority: WO
Inventors: Anthony Martin
Original assignee: Bioquell Uk Limited
Priority date: 2000-08-22
Filing date: 2001-08-10
Publication date: 2002-02-28
Also published as: GB0020736D0; AU2001276566A1; GB2368303A

Abstract

The disclosure relates to a fluid distribution system for delivering a fluid to a confined space comprising a nozzle (4) for connection to a fluid supply and having a discharge axis (A-A) in which a fluid from the supply can be delivered. The nozzle is mounted (3) for rotation about a first axis (B-B) extending transversely of the nozzle axis and for rotation about a second axis (C-C) extending transversely to the first axis and spaced from the nozzle axis. A motor rotates the nozzle through a drive mechanism about both the first and second axes with a predetermined drive ratio between said rotations to discharge fluid throughout said confined space.

Description

FLUID DISTRIBUTION SYSTEM

The invention relates to a fluid distribution system for delivering a fluid to a confined space.

The invention is particularly although not exclusively applicable to a gas distribution system for delivering a sealed chamber to ensure even distribution and achieve faster sterilisation. Most of the gaseous surface sterilisation techniques are more effective in the presence of water, and it has been shown by Watling et al, (The Implications of the Physical Properties of Mixtures of Hydrogen Peroxide and Water on the Sterilisation Process, ISPE Conference Zurich, September 1998), that condensation of the gas is an important factor in achieving rapid sterilisation.

The normal technique used to obtain a homogenous mixture of the sterilising gas inside the. sealed chamber is to place a fan or other stirring device inside the chamber to generate turbulent flow. Whilst this may well give good mixing of the gas it will not necessary give an even amount of condensation on all surfaces. Gas is normally introduced into the chamber at an elevated temperature, and it is the reduction in the gas temperature inside the chamber that causes the condensation. If this reduction of temperature occurs before the hot gas enters the mixing system then preferential condensation will occur in that area in which the gas cools. A further problem with a fixed fan stirring system is that the gas is always directed around the chamber in the same pattern. Within this pattern will be a fixed temperature gradient again giving preferential condensation in some areas of the sealed chamber.

To overcome this difficultly it is necessary to distribute the hot gas around the sealed chamber before it has cooled, and in this way reduce the problem of preferential condensation in some areas of the chamber.

This invention provides fluid distribution system for delivering a fluid to a confined space comprising a nozzle for connection to a fluid supply and having a discharge axis in which a fluid from the supply can be delivered, means to mount the nozzle for rotation about a first axis extending transversely of the nozzle axis and for rotation about a second axis extending transversely to the first axis and spaced from the nozzle axis, and drive means for rotating the nozzle about the first and second axes with a predetermined drive ratio between said rotations to discharge fluid^' throughout said confined space.

The device of the present invention overcomes the problems referred to above by directing the hot gas in a moving pattern towards all of the surfaces in a regular pattern. This moving pattern is achieved by a gas nozzle on a mechanism that rotates about both a vertical and horizontal axis. The speed of rotation about these axes is fixed, and the gas velocity leaving the nozzle is controlled by the nozzle diameter and the available gas pressure. The area covered by the nozzle will depend, on the gas velocity and mass flow. If the velocity is maintained constant then as the mass flow is increased then the gas will reach a greater distance.

There are two significant disadvantages to preferential condensation, as created by the conventional fixed fan. Firstly, if some surfaces have more condensation than others, then it takes a longer time and a greater mass of sterilant to achieve the required mass on those areas where condensation is less. Secondly it increases the time to aerate the chamber because surfaces will have been exposed for a greater length of time. Preferably nozzle mounting means include conduit means for supporting the nozzle for rotation about said first and second axis and for delivering fluid from a supply to the nozzle.

More specifically the conduit means may comprise a first conduit closed at one end and having said nozzle mounted at the other end for rotation about an axis extending lengthwise through the conduit and a second conduit to one end of which the first conduit is mounted and the other end of which is supported in a mounting for rotation about an axis extending lengthwise through the second conduit to provide said second axis of rotation of the nozzle, and means being provided for connecting said other end of the second conduit to a fluid supply.

By way of example said mounting may include a drive motor driveably connected to the second conduit for rotating the conduit about said second axis and means for generating rotation of the nozzle about the first conduit in response to rotation of the second conduit with respect to the mounting.

In the latter arrangement the means for generating rotation of the nozzle with respect to the first conduit in response to rotation of the second conduit comprise a drive shaft mounted for rotation in the first conduit and coupled to the nozzle to rotate the nozzle with respect to the first conduit, a mechanism connected to the draft shaft having an input coupled to the mounting for the second conduit, the mechanism converting rotation of the second conduits with respect to the mounting in to rotation of the drive shaft in the first conduit to rotate the nozzle with respect to the first conduit as the second conduit rotates with respect to the mounting. The mechanism for converting rotation of the second conduit into rotation of the drive shaft in the first conduit may comprise a gear box having an output driveably connected to the shaft and an input to which a further fixed shaft extending through the second conduit is connected, the fixed shaft being anchored to the mounting for the second conduit thereby rotation of the second shaft around the fixed drive shaft causes the shaft in the first conduit to rotate in the conduit to rotate the nozzle.

In any of the above arrangements the means to rotate the second conduit may comprise a drive motor located within the housing and having a direct drive connection to the second shaft. The direct drive connection between the motor and second shaft may comprises a gear wheel encircling and attached to the second shaft with which a pinion on the drive motor engages.

It has been found by experiment that an exit velocity from the nozzle of between 25 to 30 m/sec gives a satisfactory distribution of gas. At this velocity, depending on the mass flow, the gas will be projected with sufficient velocity to be effective a distance of about 6 metres. The hot gas leaving the nozzle at high velocity is projected onto the cold surface of the chamber, and the temperature differential between the gas and the surfaces causes the gas to become saturated and deposit a film of condensation. For this process to be effective the plume of hot gas must be directed towards each part of the surface for a sufficient length of time for the condensation to form and become stable, but as the gas must be projected to all parts of the room it is also essential that it moves at such a speed as to achieve coverage in a reasonable period of time. Some compromises will be required because of room geometry and size, and it has been found that with a gas velocity from the nozzle of about 25/30 m/sec that a rotational speed about the vertical axis of 3 r.p.m, and a gearing ratio of 20:1 between the vertical and horizontal axis giving a rotation about the horizontal axis of 0.15 r.p.m, good coverage of surfaces is achieved with fast and reproducible surface decontamination.

In small chambers up to about 10m³ the gas concentration may quickly be raised to saturated vapour pressure causing rapid condensation. In much larger volumes such as Clean Rooms it will take longer to raise the concentration to the saturated vapour pressure. In these large rooms the hot gas will still cause local condensation before the saturated vapour pressure has been reached but it is likely that this condensation will evaporate, thus causing the surface to be wetted and then dry until saturated vapour pressure has been reached. This wetting and drying has the advantage of ensuring that the final layer of condensation is at the correct concentration of active ingredient instead of being diluted with any moisture that might have been present at the start of the gassing process.

The same wetting and drying will not occur in small chambers and it is therefore necessary to ensure that the surfaces are dry before the gas is introduced. It has been found by experiment that in small chambers an initial R.H of 40% is sufficient for this purpose.

The following is a description of a specific embodiment of the invention, reference being made to the accompanying drawings, in which:

Figure 1 is the general arrangement of the apparatus; and

Figure 2 is a section showing the mechanical details. The apparatus would normally be fixed to the ceiling of a "Clean Room" or "Sealed Chamber"^'. It is also possible to mount the apparatus the other way up and support it from a movable tripod, or even horizontally through a wall. The apparatus is connected to a gas supply pipe 6 and an electrical power source (not shown), to drive the motor.

The mounting/drive unit 1 support the nozzle which has a discharge axis indicated at A-A. The nozzle is rotated at the end of horizontal gas tube 3 about an axis B-B extending orthogonally to the discharge axis. The gas tube 3 is, in turn, rotated about an axis C-C through the vertical gas tube 2.

The electric motor and drive gear are placed in the mounting and drive unit 1 and this is so arranged as to rotate the vertical gas tube 2 at 3 r.p.m. A fixed drive shaft is placed in the centre of this vertical tube 2 and connects with a gearbox in the horizontal gas tube 3. As the vertical gas tube 2 rotates this drives the 20:1 gear box which is connected to the horizontal gas tube 3 causing the nozzle 4 to rotate.

Reference is now made to Figure 2 which shows how the system works. Details of rotational and thrust bearings have been omitted for clarity. The mounting and drive unit 1 is fixed in space and houses this motor 8 and the vertical drive shaft 11, which is unable to rotate relative to the mounting and drive unit 1. An inner vertical bearing tube 12 is fitted inside the housing, which may rotate about a vertical axis but is restrained from moving vertically. Attached to the inner vertical bearing tube is a gear wheel 10, which is driven by the pinion 9, mounted on the motor. The motor 8 pinion 9 and gear wheel 10 are selected to give the inner vertical bearing tube 12 and the vertical gas tube 2 a rotational speed of 3 r.p.m. The inner vertical bearing tube 12 and the vertical gas tube 2 are fixed together so that these two items rotate together at the same speed.

The lower end of the vertical gas tube 3 which also rotates .about the vertical axis at the same speed as the inner vertical bearing tube 12 and the vertical gas tube 2. Fixed inside the horizontal gas tube is a gearbox 13, which is supported on the horizontal drive shaft 14. One end of the horizontal drive shaft is supported in a bearing 18 and the other end is attached to the nozzle by a fixing 16.

The vertical drive shaft 11 is also attached to the gear box 18 and because the vertical drive shaft, while the horizontal gas tube 3 and gear box 13 rotate the horizontal drive shaft 14 is also caused to rotate. The rotation of the horizontal drive shaft 14 is transmitted to the nozzle 4 through the horizontal drive shaft fixing 16. The nozzle 4 is supported by the inner horizontal bearing tube 17.

The sterilizing gas thus passes down through the vertical gas tube 2, and then the horizontal gas tube 3 before leaving the system at high velocity through the nozzle 4.

The rotational energy imparted by the motor 8 to the vertical gas tube 2 is also transmitted to the nozzle. This combination of vertical and horizontal rotation causes the nozzle to point in all directions in a fixed pattern.

Claims

CLAIMS :

1. A fluid distribution system for delivering a fluid to a confined space comprising a nozzle for connection to a fluid supply and having a discharge axis in which a fluid from the supply can be delivered, means to mount the nozzle for rotation about a first axis extending transversely of the nozzle axis and for rotation about a second axis extending transversely to the first axis and spaced from the nozzle axis, and drive means for rotating the nozzle about the first and second axes with a predetermined drive ratio between said rotations to discharge fluid throughout said confined space.

2. A fluid distribution system as claimed in claim 1, wherein the nozzle mounting means include conduit means for supporting the nozzle for rotation about said first and second axis and for delivering fluid from a supply to the nozzle.

3. A fluid distribution system as claimed in claim 1 or claim 2, wherein the conduit means comprise a first conduit closed at one end and having said nozzle mounted at the other end for rotation about an axis extending lengthwise through the conduit and a second conduit to one end of which the first conduit is mounted and the other end of which is supported in a mounting for rotation about an axis extending lengthwise through the second conduit to provide said second axis of rotation of the nozzle, and means being provided for connecting said other end of the second conduit to a fluid supply.

4. A fluid distribution system as claimed in claim 3, wherein said mounting includes a drive motor driveably connected to the second conduit for rotating the conduit about said second axis and means being provided for generating rotation of the nozzle about the first conduit in response to rotation of the second conduit with respect to the mounting.

5. A fluid distribution system as claimed in claim 4, wherein the means for generating rotation of the nozzle with respect to the first conduit in response to rotation of the second conduit comprise a drive shaft mounted for rotation in the first conduit and coupled to the nozzle to rotate the nozzle with respect to the first conduit, a mechanism connected to the draft shaft having an input coupled to the mounting for the second conduit, the mechanism converting rotation of the second conduits with respect to the mounting in to rotation of the drive shaft in the first conduit to rotate the nozzle with respect to the first conduit as the second conduit rotates with respect to the mounting.

6. A distribution system as claimed in claim 5, wherein the mechanism for converting rotation of the second conduit into rotation of the drive shaft in the first conduit comprises a gear box having an output driveably connected to the shaft and an input to which a further fixed shaft extending through the second conduit is connected, the fixed shaft being anchored to the mounting for the second conduit thereby rotation of the second shaft around the fixed drive shaft causes the shaft in the first conduit to rotate in the conduit to rotate the nozzle.

7. A fluid distribution system as claimed in any of the claims 3 to 6, wherein the means to rotate the second conduit comprise a drive motor located within the housing and having a direct drive connection to the second shaft.

8. A fluid distribution system as claimed in claim 8, wherein the direct drive connection between the motor and second shaft comprises a gear wheel encircling and attached to the second shaft with which a pinion on the drive motor engages.