GB1575522A

GB1575522A - Sterilising apparatus

Info

Publication number: GB1575522A
Application number: GB3766976A
Authority: GB
Original assignee: Chas F Thackray Ltd
Current assignee: SSL CC Services Ltd
Priority date: 1977-09-08
Filing date: 1977-09-08
Publication date: 1980-09-24

Description

(54) STERILISING APPARATUS (71) We, CHAS. F. TIIACKRAY LIMITED, of P.O. Box 171, Park Street, Leeds, LS1 1 RQ, West Yorkshire, a British Company, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to sterilising apparatus which includes a chamber known as an autoclave that can be filled with steam under pressure and into which articles etc., can be placed so that they may be sterilised.

The autoclave initially contains air and in known autoclaves this air is displaced through a thermostatic trap by the steam which is being admitted to the autoclave. Thus the autoclave is eventually filled enturely with steam at a particular pressure and temperature and the contents of the autoclave are allowed to reach the temperature of the steam so that they may be sterilised. The contents of the autoclave are then allowed to cool down; for instance, this may be achieved by spraying cold water over the contents of the autoclave.

Where the autoclave is being used to sterilise fluids in rigid containers, the use of conventional autoclaves can result in air leaking through an imperfect seal of a container and so contaminating the fluid within the container.

For instance, in a typical conventional autoclave, steam is admitted to the autoclave at a pressure of, say, 10 or 15 Ibs. p.s.i. and air is gravity displaced by means of a thermostatic trap which is located in the draining system of the autoclave. The steam heats the container and the fluids contained therein up to the sterilising temperature. This temperature within the autoclave is maintained for a predetermined time, following which cooling water is sprayed over the containers until they are at a suitable handling temperature.

In a typical case of the use of a conventional autoclave to sterilise fluids in rigid containers, a temperature of 121" C was attained in the fluid within the containers by means of steam at a temperature of 121" C and a pressure of 15 Ibs.

p.s.i. However the pressure within the containers was 35-36 Ibs. p.s.i. due to the expansion of air or other gases within the containers.

Accordingly there is a pressure difference of 20-21 Ibs. p.s.i. between the inside and outside of the containers. Unless the containers are provided with perfect seals, air will leak out of the containers. Accordingly upon cooling a partial vacuum may be created within the containers which can result in material which is not sterile being drawn into the containers and so contaminating the contents of the containers.

A problem can also arise in the case where a conventional autoclave is being used to sterilise fluids in non-rigid containers. In this case the containers are normally completely filled with fluid and so the pressure difference during the sterilising stage is relatively small. However when cooling water is sprayed into the autoclave the steam contained therein is quickly condensed causing a sudden drop in chamber pressure. However, the pressure in the containers will remain relatively high and accordingly, the containers may rapidly expand and burst. The conventional way of overcoming this difficulty is to inject air under pressure into the autoclave during the cooling stage in order to maintain approximately the same pressure both inside and outside the containers.How ever, this air must be sterilised before being passed into the autoclave or it must at least be passed through very fine and sophisticated filters. In either case the use of additional expensive equipment is involved.

According to the present invention there is provided sterilising apparatus comprising an autoclave, means for introducing steam into the autoclave, means for removing condensed steam from the autoclave, means for re-introducing said condensed steam to the autoclave so that said condensed steam is mixed with uncondensed steam, in the autoclave, the arrangement being such that, during operation of the apparatus, a major proportion of the gas in the autoclave before steam is introduced is maintained in the autoclave during said operation of the apparatus. Preferably, the whole of the gas in the autoclave before steam is introduced is retained in the autoclave during operation of the apparatus.

Accordingly in apparatus according to the present invention air within the autoclave is not gravity displaced during the introduction of the steam but remains within the autoclave.

Where the autoclave is being used to sterilise fluids in rigid containers, then the pressure both inside and the outside the containers remains the same at all stages during the sterilisation process. For instance, for a sterilising temperature of fluid within the containers of 121 0C, steam may be introduced until the pressure both inside and outside the containers rises to 35-36 Ibs. p.s.i. During cooling the pressure difference remains close to zero and accordingly there is no danger of leakage of air through an imperfect seal during the sterilisng stage and resultant ingress of a contaminating substance during cooling.

In a case where apparatus in accordance with the present invention is being used to sterilise fluid in non-rigid containers, there is no sudden drop in pressure outside the container since when cooling water is sprayed into the autoclave, the steam condenses but the pressure of the expanded air in the autoclave balances the pressure within the containers. Since the air within the autoclave has of course been steril wised dung the sterilising stage, air pressure ballasting is achieved without any additional equipment being necessary.

The present invention also provides a method for 5 sterilising an article placing the article in an autoclave, introducing steam into the autoclave, removing condensed steam from the autoclave, and re-introducing said condensed steam to the autoclave so that said condensed steam is mixed with uncondensed steam in the autoclave, a major proportion of the gas in the autoclave before steam is introduced being maintained in the autoclave during operation thereof.

An embodiment of the present invention will now be described, by way of example only, and with reference to the accompanying drawing which is a diagram showing an autoclave and associated fluid pipe-work and equipment.

Referring to the drawing, sterilising appar- atus in accordance with the present invention includes a chamber 1 having a double-skinned cavity wall 3 and a door 5 which may be a steam sealed by means of steam applied to a recess 7 behind door seal 13. Within the auto clave are provided racks for accommodating containers such as 15. The interior of the auto clave is also provided with a system ofjets 17 for spraying cooling water over the containers 15 within the autoclave.

At the floor of the autoclave there is pro vided an outlet 19 for condensed steam, as well as a drain 21. Chamber wall 23 of the autoclave is provided with an inlet 25 for admitting steam to the autoclave. Other features of the sterilising apparatus shown in the drawing will become clear in the following description of the operation of the apparatus.

The autoclave 1 is loaded with containers 1 5 which contain fluid which is to be sterilised.

The door 5 is then closed and valve 27 is opened. This allows steam from a steam supply source (not shown) to pass to recess 7 behind door seal 13 so that the door is sealed. Steam pressure continues to build up in the door seal recess 7 and its associated pipe-work until it reaches a pressure sufficient to open a pressure operated servo valve 29. Valve 31 has been opened at the same time as the opening of valve 27; accordingly steam now passes into the autoclave 1 via reducing valve 33 and servo valve 29.

Since the autoclave and the articles located therein are initially cold, steam entering the autoclave initially condenses. The condensate collects in the bottom of the autoclave, passing out thorough outlet 19 and filling a heat exchanger unit 35 and its associated pipe-work.

At the same time as the opening of valves 27 and 31, a recirculating pump 37 is started.

Accordingly condensate which has passed out of the autoclave and through lieat exchange unit 35 is pumped by pump 37 through water filter 39 via non-return valve 41 and into the jet arrangement 1 7 within the autoclave via inlet 43.The pressure in this pipe-work may be monitored by means of pressure gauge 45.

Thus, the condensate is sprayed back into the autoclave through the jet arrangement 17 where it is re-sterilised by means of the steam within the autoclave.

The chamber drain outlet 21 includes a pipe 47 running to drain and also includes a float trap 49 with a pipe running from float trap 49 to an inlet 51 in the upper wall of the chamber 1. Thus when the steam is admitted to the chamber 1 the air contained within the chamber 1 when the door is closed is substantially maintained within the chamber 1 and is not gravity displaced through a thermostatic trap as in the case of a conventional autoclave. The steam condensate being forced through the jet arrangement 17 creates a sufficient turbulence within the autoclave to ensure a complete mixing of the air and steam and thus an even temperature throughout the autoclave and the articles contained therein.

When the autoclave has been held at the required temperature for the appropriate length of time, valve 31 is closed and a valve 53 is opened. This allows cold water from a supply (not shown) to the heat exchanger 35 which cools the steam condensate passing through the heat exchanger 35. Accordingly the articles within the autoclave are now cooled.

Furthermore the cooling water itself, having passed through the heat exchange unit then passes to the cavity 55 between the walls of the autoclave and helps to cool the autoclave even more quickly. In fact, the water initially passing to the jacket is warm due to its passage througll the heat exchanger and this has the advantage that the walls of the jacket are not subjected to the stresses of too sudden a drop in temperature. Cooling water passes from the jacket to drain via tundish 56.

Should there be any escape of air from the autoclave during any previous stage of the operation thereof, air will be drawn in via a bacterial filter 52 and one way valve 54, so that there can be no danger of a partial vacuum.

in the autoclave leading to the explosion of bottles.

When the temperature within the autoclave has been reduced sufficiently (say, to about 80"C), motorised valve 57 in the drain line is opened and pump 37 then pumps the condensate to drain. Thus, in the next operation of the apparatus entirely fresh condensate is used.

When the apparatus has been emptied of condensate, pump 37 stops and valves 27 and 53 are closed, the closing of valve 27 causing servo valve 29 to close. Valves 61 and 63 are now opened. The opening of valve 63 puts a supply of water to an ejector unit 65 so that a vacuum caused therein exhausts the recess behind the door seal and causes the seal to be withdrawn back into the recess, so freeing the door and allowing it to be opened. When the door has been opened valve 63 is closed.

Valve 67 is an isolating valve provided for maintenance purposes. Thus, to test whether jets 17 are blocked, valve 67 is opened and water is supplied directly to the jets.

It should be appreciated that, in the above described embodiment, the spraying of the condensed steam back into the autoclave acts to cause turbulence within the autoclave and hence mix the air uniformly with the steam.

Without such mixing pockets or layers of air would be present in the autoclave, and within these pockets or layers the sterilisation might be ineffective.

WHAT WE CLAIM IS: 1. Sterilising apparatus comprising an autoclave, means for introducing steam into the autoclave, means for removing condensed steam from the autoclave, means for re-intro ducing said condensed steam to the autoclave so that said condensed stream is mixed with uncondensed steam in the autoclave, the arrangement being such that during operation of the apparatus a major proportion of the gas in the autoclave before steam is introduced is maintained in the autoclave during said oper ation of the apparatus.

2. Sterilising apparatus according to claim 1 wherein the whole of the gas in the autoclave before steam is introduced is retained in the autoclave during operation of the apparatus.

3. Sterilising apparatus according to claim I or claim 2 wherein the autoclave is provided with a drain outlet, the drain outlet including a float trap, there being a pipe extending from the float trap to the autoclave to return to the autoclave any gas which is displaced from the autoclave during operation of the apparatus.

4. Sterilising apparatus according to any of the preceding claims wherein means are pro vided for spraying water into the autoclave.

5. Sterilising apparatus according to any of the preceding claims wherein the autoclave includes a door having a seal, there being lo cated behind the seal a recess to which steam under pressure may be applied to urge the seal into contact with the door.

6. Sterilising apparatus substantially as here in described with reference to the accompany ing drawing.

7. A method for sterilising an article com prising placing the article in an autoclave, intro ducing steam into the autoclave, removing con densed steam from the autoclave, and re-intro ducing said condensed steam to the autoclave so that said condensed steam is mixed with uncondensed steam in the autoclave, a major proportion of the gas in the autoclave before steam is introduced being maintained in the autoclave during operation thereof.

8. A method for sterilising an article sub stantially as herein described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

53 is opened. This allows cold water from a supply (not shown) to the heat exchanger 35 which cools the steam condensate passing through the heat exchanger 35. Accordingly the articles within the autoclave are now cooled.

Furthermore the cooling water itself, having passed through the heat exchange unit then passes to the cavity 55 between the walls of the autoclave and helps to cool the autoclave even more quickly. In fact, the water initially passing to the jacket is warm due to its passage througll the heat exchanger and this has the advantage that the walls of the jacket are not subjected to the stresses of too sudden a drop in temperature. Cooling water passes from the jacket to drain via tundish 56.

Should there be any escape of air from the autoclave during any previous stage of the operation thereof, air will be drawn in via a bacterial filter 52 and one way valve 54, so that there can be no danger of a partial vacuum.

in the autoclave leading to the explosion of bottles.

When the temperature within the autoclave has been reduced sufficiently (say, to about 80"C), motorised valve 57 in the drain line is opened and pump 37 then pumps the condensate to drain. Thus, in the next operation of the apparatus entirely fresh condensate is used.

When the apparatus has been emptied of condensate, pump 37 stops and valves 27 and 53 are closed, the closing of valve 27 causing servo valve 29 to close. Valves 61 and 63 are now opened. The opening of valve 63 puts a supply of water to an ejector unit 65 so that a vacuum caused therein exhausts the recess behind the door seal and causes the seal to be withdrawn back into the recess, so freeing the door and allowing it to be opened. When the door has been opened valve 63 is closed.

Valve 67 is an isolating valve provided for maintenance purposes. Thus, to test whether jets 17 are blocked, valve 67 is opened and water is supplied directly to the jets.

It should be appreciated that, in the above described embodiment, the spraying of the condensed steam back into the autoclave acts to cause turbulence within the autoclave and hence mix the air uniformly with the steam.

Without such mixing pockets or layers of air would be present in the autoclave, and within these pockets or layers the sterilisation might be ineffective.

WHAT WE CLAIM IS: 1. Sterilising apparatus comprising an autoclave, means for introducing steam into the autoclave, means for removing condensed steam from the autoclave, means for re-intro ducing said condensed steam to the autoclave so that said condensed stream is mixed with uncondensed steam in the autoclave, the arrangement being such that during operation of the apparatus a major proportion of the gas in the autoclave before steam is introduced is maintained in the autoclave during said oper ation of the apparatus.
2. Sterilising apparatus according to claim 1 wherein the whole of the gas in the autoclave before steam is introduced is retained in the autoclave during operation of the apparatus.
3. Sterilising apparatus according to claim I or claim 2 wherein the autoclave is provided with a drain outlet, the drain outlet including a float trap, there being a pipe extending from the float trap to the autoclave to return to the autoclave any gas which is displaced from the autoclave during operation of the apparatus.
4. Sterilising apparatus according to any of the preceding claims wherein means are pro vided for spraying water into the autoclave.
5. Sterilising apparatus according to any of the preceding claims wherein the autoclave includes a door having a seal, there being lo cated behind the seal a recess to which steam under pressure may be applied to urge the seal into contact with the door.
6. Sterilising apparatus substantially as here in described with reference to the accompany ing drawing.
7. A method for sterilising an article com prising placing the article in an autoclave, intro ducing steam into the autoclave, removing con densed steam from the autoclave, and re-intro ducing said condensed steam to the autoclave so that said condensed steam is mixed with uncondensed steam in the autoclave, a major proportion of the gas in the autoclave before steam is introduced being maintained in the autoclave during operation thereof.
8. A method for sterilising an article sub stantially as herein described with reference to the accompanying drawing.