GB2147823A - Pressure vessel with cooling coil - Google Patents

Abstract

An autoclave 10 is provided with a cooling channel 12 attached directly to the inner surface of the autoclave container with inlet and outlet ducts 17, 18 passing through the wall of the container and connected with a refrigeration plant 22 located outside the container whereby refrigerated medium is circulated through the channel. The coding channel may be in the form of a coil, as shown or may be a jacket (26) (Figure 3, not shown). <IMAGE>

Description

SPECIFICATION Pressure vessel with cooling coil This invention relates to pressure vessels provided with cooling coils commonly known as autoclaves and used for example by hospitals, pathological laboratories, breweries and food production factories.

An autoclave of this kind is usually required to maintain an interior steam pressure of 30 square inches at a temperature of 1 21"C for 15 minutes or a higher pressure and temperature for a shorter time.

A common size is 18 inches internal diameter and 34 inches deep and such an autoclave in one test required 1 hour 12 minutes to cool down to 80"C which is necessary before it can be opened and replenished for treatment of further materials. This cooling down time greatly reduces the quantity of materials which can be treated per working day.

With a view to overcoming this problem we proposed to provide a water cooling coil fastened to the inner surface of the lid of the autoclave or around the outside of the autoclave and this was the subject of patent application 8019857 (published specification No. 2056311A). We experimented with this arrangement but found it to be unsatisfactory both as to engineering construction and as to reduction of cooling time. Consequently until now the idea of cooling such an autoclave was considered impractical and the project was abandoned and the patent application was allowed to lapse.

We have however achieved a remarkably successful result in a manner which is not difficult from an engineering point of view and although initially expensive, will rapidly pay for itself because of the increased number of times per day which it can be opened, replenished and closed.

According to the present invention we provide a cooling channel attached directly to the inner surface of the autoclave container with inlet and outlet ducts passing through the wall of the container and connected with a refrigeration plant located outside the container whereby refrigerated medium is circulated through the channel.

By means of this invention we found that with the aforesaid autoclave of 18 inches diameter and 34 inches depth at 30 square pressure at 121"C filled with items to be sterilized, a cooling period was achieved down to 80"C in 12 minutes (compared with 1 hour 12 minutes formerly required).

The cooling channel may be provided by a small bore pipe of one quarter two half inch exterior diameter e.g. three eighths inch and a length of 25 to 75 feet according to the size of autoclave and cooling time required.

The cooling channel may alternatively be provided by attaching a jacket to the inner surface of the autoclave container.

The invention will be further described by way of example with reference to the accompanying drawings wherein Figure 1 is a vertical section of a particularly effective autoclave made in accordance with the invention; Figure 2 is a cross-sectional view thereof; and Figure 3 is a part vertical sectional view showing a modified construction.

A vertical autoclave cylinder 10 has a conventional type lid 11 so that this does not have to carry pipes.

Within the cylinder close to the inner surface thereof is a cooling coil 12 of copper tubing located as a helix. In the drawing there are shown 8 helices but we may use about 6 to 16 according to requirements.

The cooling coil is located in the upper third of the height of the cylinder and it is fixed to the inner surface of the cylinder by three brckets 13 attached by screws 14 or by welding or brazing. The coil has an inlet pipe 17 and outlet pipe 18 which pass through the wall of the container through stuffing boxes 20,21. The coil may be touching the inner surface of the cylinder or may be spaced two or three tengths of an inch from it.

The inlet and outlet pipes are connected to a refrigerating plant 22 e.g. the type using CHCIF2/ C2CIF5 as refrigerant The plant includes a pump of suitable output to circulate the refrigerant through the cooling coil fast enough to achieve the required cooling rate and to keep the coil at below -4 C e.g.

about -10"C during cooling.

Suitable means (not shown) are provided on which the autoclave is mounted so as to stand vertically on the floor.

Figure 3 shows a modified construction in which in place of a coil of tubing a casing 26 is attached to the inner surface of the cylinder to form a channel for refrigerant between it and the inner surface of the cylinder.

The refrigeration unit will be specially designed according to the size of autoclave and rate of cooling required although it will be based on known refriger atordesign principles.

1. An autoclave having a cooling channel attached directly to the inner surface of the autoclave container with inlet and outlet ducts passing through the wall of the container and connected with a refrigeration plant located outside the container whereby refrigerated medium is circulated through the channel.

2. An autoclave as claimed in claim 1 wherein the cooling channel is formed by a pipe of one quarter to half inch diameter in the form of a helix.

3. An autoclave as claimed in claim 1 wherein the cooling channel is in the form of a jacket attached to the inner surface of the container.

4. An autoclave as claimed in claim 2 wherein the pipe has 6 to 16 turns of the helix, and is fixed to the container by brackets and is located in the upper third of the container.

5. An autoclave substantially as descirbed with reference to Figure 1 and 2 or 3 of the accompanying drawings.

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

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Pressure vessel with cooling coil This invention relates to pressure vessels provided with cooling coils commonly known as autoclaves and used for example by hospitals, pathological laboratories, breweries and food production factories. An autoclave of this kind is usually required to maintain an interior steam pressure of 30 square inches at a temperature of 1 21"C for 15 minutes or a higher pressure and temperature for a shorter time. A common size is 18 inches internal diameter and 34 inches deep and such an autoclave in one test required 1 hour 12 minutes to cool down to 80"C which is necessary before it can be opened and replenished for treatment of further materials. This cooling down time greatly reduces the quantity of materials which can be treated per working day. With a view to overcoming this problem we proposed to provide a water cooling coil fastened to the inner surface of the lid of the autoclave or around the outside of the autoclave and this was the subject of patent application 8019857 (published specification No. 2056311A). We experimented with this arrangement but found it to be unsatisfactory both as to engineering construction and as to reduction of cooling time. Consequently until now the idea of cooling such an autoclave was considered impractical and the project was abandoned and the patent application was allowed to lapse. We have however achieved a remarkably successful result in a manner which is not difficult from an engineering point of view and although initially expensive, will rapidly pay for itself because of the increased number of times per day which it can be opened, replenished and closed. According to the present invention we provide a cooling channel attached directly to the inner surface of the autoclave container with inlet and outlet ducts passing through the wall of the container and connected with a refrigeration plant located outside the container whereby refrigerated medium is circulated through the channel. By means of this invention we found that with the aforesaid autoclave of 18 inches diameter and 34 inches depth at 30 square pressure at 121"C filled with items to be sterilized, a cooling period was achieved down to 80"C in 12 minutes (compared with 1 hour 12 minutes formerly required). The cooling channel may be provided by a small bore pipe of one quarter two half inch exterior diameter e.g. three eighths inch and a length of 25 to 75 feet according to the size of autoclave and cooling time required. The cooling channel may alternatively be provided by attaching a jacket to the inner surface of the autoclave container. The invention will be further described by way of example with reference to the accompanying drawings wherein Figure 1 is a vertical section of a particularly effective autoclave made in accordance with the invention; Figure 2 is a cross-sectional view thereof; and Figure 3 is a part vertical sectional view showing a modified construction. A vertical autoclave cylinder 10 has a conventional type lid 11 so that this does not have to carry pipes. Within the cylinder close to the inner surface thereof is a cooling coil 12 of copper tubing located as a helix. In the drawing there are shown 8 helices but we may use about 6 to 16 according to requirements. The cooling coil is located in the upper third of the height of the cylinder and it is fixed to the inner surface of the cylinder by three brckets 13 attached by screws 14 or by welding or brazing. The coil has an inlet pipe 17 and outlet pipe 18 which pass through the wall of the container through stuffing boxes 20,21. The coil may be touching the inner surface of the cylinder or may be spaced two or three tengths of an inch from it. The inlet and outlet pipes are connected to a refrigerating plant 22 e.g. the type using CHCIF2/ C2CIF5 as refrigerant The plant includes a pump of suitable output to circulate the refrigerant through the cooling coil fast enough to achieve the required cooling rate and to keep the coil at below -4 C e.g. about -10"C during cooling. Suitable means (not shown) are provided on which the autoclave is mounted so as to stand vertically on the floor. Figure 3 shows a modified construction in which in place of a coil of tubing a casing 26 is attached to the inner surface of the cylinder to form a channel for refrigerant between it and the inner surface of the cylinder. The refrigeration unit will be specially designed according to the size of autoclave and rate of cooling required although it will be based on known refriger atordesign principles. CLAIMS

1. An autoclave having a cooling channel attached directly to the inner surface of the autoclave container with inlet and outlet ducts passing through the wall of the container and connected with a refrigeration plant located outside the container whereby refrigerated medium is circulated through the channel.

2. An autoclave as claimed in claim 1 wherein the cooling channel is formed by a pipe of one quarter to half inch diameter in the form of a helix.

3. An autoclave as claimed in claim 1 wherein the cooling channel is in the form of a jacket attached to the inner surface of the container.

4. An autoclave as claimed in claim 2 wherein the pipe has 6 to 16 turns of the helix, and is fixed to the container by brackets and is located in the upper third of the container.

5. An autoclave substantially as descirbed with reference to Figure 1 and 2 or 3 of the accompanying drawings.