GB2333958A

GB2333958A - A method of operating an autoclave.

Info

Publication number: GB2333958A
Application number: GB9802757A
Authority: GB
Inventors: Terry Ashenden
Original assignee: PRIOR CLAVE Ltd
Current assignee: PRIOR CLAVE Ltd
Priority date: 1998-02-09
Filing date: 1998-02-09
Publication date: 1999-08-11
Also published as: GB9802757D0

Abstract

A method of operating an autoclave (2), which method comprises reducing chamber pressure in the autoclave (2) by exhausting steam from the autoclave (2) to atmosphere, and then reducing the pressure to below atmospheric pressure, the reduction of the chamber pressure in the autoclave (2) being over a time period when a load (8) in the autoclave (2) is cooling to a temperature at which opening of the autoclave (2) is permitted, the reduction of the chamber pressure in the autoclave (2) being solely for promoting evaporation of water from the load (8) and thereby causing the load (8) to cool more rapidly than it would have done without the reduction of the chamber pressure in the autoclave, and the load (8) being an organic waste product load (8), an instrument load (8), or a laboratory glassware/plasticsware load (8).

Description

A METHOD OF OPERATING AN AUTOCLAVE This invention relates to a method of operating an autoclave.

Autoclaves are well known and they are commonly used for sterilising purposes. More specifically, the autoclaves are essentially vessels which are able to be pressurised with steam and which are controlled by appropriate control systems. The generated steam is utilised to sterilise a load in the autoclave. The load may be contaminated disposable laboratory equipment, used culture plates, Petri dishes, fluid samples and the like (known as discard load), an instrument load, or a laboratory glassware/plasticsware load. The sterilising of the load renders the load free of undesirable microbiological matter such for example as bacteria, viruses and other micro-organisms. Sterilised loads such for example as instruments and laboratory glassware/plasticsware can then safely be reused.

Sterilised loads such for example as disposable laboratory equipment can safely be disposed.

The killing of the microbiological matter is effected by the latent heat of steam. Thus autoclaves are traditionally operated by introducing a load to be sterilised into the autoclave, removing air from the autoclave, and then introducing steam to the autoclave. When the steam has attained a predetermined temperature, the load is subjected to the steam for a predetermined period of time which is sufficient to sterilise the load. The period of time during which the load is subjected to the steam for being sterilised is known as the sterilising process time. At the end of the sterilising process time, it is necessary for the load to cool down sufficiently before the autoclave can be opened and the load removed. In the United Kingdom, the opening of the autoclave is controlled by British Standard No. 2646, Part I, 1993. This British Standard specifies that it is not permitted to open the autoclave door until the load in the autoclave had cooled to 800C.

The cooling of the autoclave load to the temperature at which the opening of the autoclave is permitted takes an appreciable amount of time and, depending upon the load may take several hours.

Autoclaves are however expensive pieces of equipment and it is not always convenient for an autoclave to be lying idle whilst going through its cooling cycle.

It is an aim of the present invention to reduce the above mentioned problem by speeding up the cooling cycle and thereby enabling the autoclave to be ready for another use faster than it would otherwise have been.

Accordingly, in one non-limiting embodiment of the present invention there is provided a method of operating an autoclave, which method comprises reducing chamber pressure in the autoclave by exhausting steam from the autoclave to atmosphere, and then reducing the pressure to below atmospheric pressure, the reduction of the chamber pressure in the autoclave being over a time period when a load in the autoclave is cooling to a temperature at which opening of the autoclave is permitted, the reduction of the chamber pressure in the autoclave being solely for promoting evaporation of water from the load and thereby causing the load to cool more rapidly than it would have done without the reduction of the chamber pressure in the autoclave, and the load being a discard load, an instrument load, or a laboratory glassware/plasticsware load.

Depending upon the type of load in the autoclave, cooling cycle times can be reduced by up to one or two hours as compared with the cooling time that would otherwise have been taken by the same load if the chamber pressure had not been reduced in the autoclave as required by the method of the present invention.

With porous loads such for example as hospital sheets, it is already known to reduce chamber pressure in the autoclave after the sterilising process time.

This is effected by operating a vacuum pump in the autoclave to reduce the chamber pressure. The purpose of operating the vacuum pump to reduce the chamber pressure is solely to dry the porous load. There is no realisation that the reduction of cooling times of discard loads, instrument loads, and laboratory glassware/plasticsware loads can be achieved by reducing the chamber pressure in the autoclave.

There is also no general realisation that the reduction of the chamber pressure should be over the time period when the load in the autoclave is cooling to a temperature at which the opening of the autoclave is permitted.

With dense loads such as organic waste product loads, there is no air circulation in the dense loads.

Thus if the autoclave chamber is cooled, then the dense load will still not itself cool because there is insufficient air circulation throughout the autoclave chamber. The dense load just remains in the autoclave chamber as a hot load which takes a long time to cool down to the temperature at which opening of the autoclave is permitted. The introduction of fans, which is also a known idea, is difficult and costly, for example due to the need for a pressure seal where a fan shaft enters the autoclave chamber.

It will be appreciated from the above mentioned known efforts to cool loads, that the problem of speeding up cooling of loads has been recognised but, in spite of the recognition of the problem, no solution has hitherto been found with certain types of loads. Thus the method of the present invention overcomes a long established existing problem. It does so in a cost-effective manner since the reduction in the chamber pressure at the required time can relatively easily be effected simply by appropriately operating the controls of the autoclave. A substantial advantage results in that the autoclave is available for re-use much faster than it would otherwise have been.

The method of the present invention is preferably one in which the time period stops when the load is at 800C.

The method of the invention may be one in which the time period starts at sometime after the end of the sterilising process time. Thus, for example, the time period may start directly after the end of the sterilising process time. Alternatively, the time period may start at some predetermined time after the end of the sterilising process time. Preferably, the time period will start when the load is at 950C.

The method of the present invention may be one in which the reduction of the chamber pressure in the autoclave is achieved in a single step.

Alternatively, the reduction of the chamber pressure in the autoclave may be achieved in two or more separate steps.

The reduction of the chamber pressure in the autoclave is preferably effected using at least one vacuum pump, and at least one valve of the autoclave.

The vacuum pump and the valve will normally already be in the autoclave for other purposes and so it is merely necessary to utilise the control system of the autoclave such that the vacuum pump and the valve can be operated over the desired time period. In some cases, the autoclave may be provided with more than one vacuum pump, and in this case, all the available vacuum pumps can be utilised if desired. An ejector or other means may be used instead of a vacuum pump if desired.

The present invention also provides an autoclave when constructed to operate according to the method of the invention.

An embodiment of the invention will now be described solely by way of example and with reference to the accompanying drawing which shows schematically the operation of an autoclave.

Referring to the drawing, there is shown an autoclave 2 having a body 4, a door 6, and a chamber 7. The chamber 2 contains a load 8. The load 8 is shown as laboratory waste products 10 which are commonly with fluids. The laboratory waste products 10 are in a bag 12.

The autoclave 2 has a vacuum pump 14 which is able to exhaust steam 16 in the autoclave 2 to atmosphere as shown. The vacuum pump 4 is connected to a control valve 18.

In accordance with the method of the present invention, the chamber pressure in the autoclave 2 is reduced by exhausting the steam 16 to atmosphere. The reduction of the chamber pressure is over a time period when the load 8 in the autoclave 2 is cooling to a temperature at which opening of the autoclave 2 is permitted, that is 800C. The reduction of the chamber pressure in the autoclave 2 is solely for promoting evaporation of water from the load 8 and thereby causing the load 8 to cool more rapidly than it would have done without the reduction of the chamber pressure in the autoclave 2. The time period starts at the end of the sterilising process time, this being when the load is typically at 9 5 OC . The reduction in the chamber pressure in the autoclave 2 is effected with a single deep vacuum pull of the vacuum pump 14.

It is to be appreciated that the embodiment of the invention described above with reference to the accompanying drawing has been given by way of example only and that modifications may be effected. Thus, for example, the time period can start at any suitable and appropriate time after the end of the sterilising process time. The vacuum pump 14 can be operated to give two or more vacuum pulls to achieve the required vacuum instead of just one deep vacuum pull. The autoclave 2 can be any suitable and appropriate size, shape and construction so that, for example, the body 4 may be rectangular or circular. The pressure door 6 of the autoclave 2 can be of any suitable shape and it can be in any suitable position on the body 4.

Claims

CLAIMS 1. A method of operating an autoclave, which method comprises reducing chamber pressure in the autoclave by exhausting steam from the autoclave to atmosphere, and then reducing the pressure to below atmospheric pressure, the reduction of the chamber pressure in the autoclave being over a time period when a load in the autoclave is cooling to a temperature at which opening of the autoclave is permitted, the reduction of the chamber pressure in the autoclave being solely for promoting evaporation of water from the load and thereby causing the load to cool more rapidly than it would have done without the reduction of the chamber pressure in the autoclave, and the load being a discard load, an instrument load, or a laboratory glassware/plasticsware load.
2. A method according to claim 1 in which the time period stops when the load is at 800C.
3. A method according to claim 1 or claim 2 in which the time period starts at some time after the end of the sterilising process time.
4. A method according to claim 3 in which the time period starts directly after the end of the sterilising process time.
5. A method according to claim 3 or claim 4 in which the time period starts when the load is at 950C.
6. A method according to any one of the proceeding claims in which the reduction of the chamber pressure in the autoclave is achieved in a single step.
7. A method according to any one of claims 1 - 5 in which the reduction of the chamber pressure in the autoclave is achieved in two or more separate steps.
8. A method according to any one of the preceding claims in which the reduction of the chamber pressure is effected using at least one vacuum pump and at least one valve of the autoclave.
9. A method of operating an autoclave, substantially as herein described with reference to the accompanying drawings.
10. An autoclave when constructed to operate according to the method claimed in any one of the preceding claims.
11. An autoclave according to claim 10 and substantially as herein described with reference to the accompanying drawings.