WO2010089608A1

WO2010089608A1 - Lining system for vaporizers

Info

Publication number: WO2010089608A1
Application number: PCT/GB2010/050188
Authority: WO
Inventors: Bruce Philip Green
Original assignee: Tristel Plc
Priority date: 2009-02-06
Filing date: 2010-02-05
Publication date: 2010-08-12
Also published as: GB0901996D0

Abstract

A lining system for lining a chamber (10) of a formalin vaporizer (1), wherein the lining system comprises a receptacle(40) made from a perfluorinated polymer material and having an inlet (46) for adding fluids to the receptacle and at least one outlet (48) for the release of vapour from the receptacle.The invention extends to a vaporizer (1) having an evaporation chamber (10) lined with the receptacle (40), a method of using the vaporizer (1) and a kit (50) for converting a formalin vaporizer for use with sterilants that corrode stainless steel, aluminium or other corrodible materials.

Description

LINING SYSTEM FOR VAPORIZERS

BACKGROUND

a. Field of the Invention

This invention relates to the field of vaporizers for use in sterilizing biological, chemical and medical equipment, and in particular to formalin vaporizers for sterilizing safety cabinets and the like.

b. Related Art

The traditional method of sterilizing biological safety cabinets or fume hoods is to use a formalin vaporizer. Formalin is an aqueous solution of formaldehyde and is commonly used as a disinfectant as it kills most bacteria. In the disinfecting process, formalin is heated in a chamber of the vaporizer to produce a vapour which is then released into the safety cabinet or area to be disinfected.

However, formalin and formaldehyde are highly toxic and, therefore, the cabinet or area being disinfected must be well sealed from the surroundings during this process. In many cases, after a suitable length of time, a second solution, often ammonium bicarbonate, is released as a vapour, either from a second chamber of the vaporizer or from another apparatus, to neutralise the formaldehyde vapours.

Time is therefore required after sterilization to neutralise the formaldehyde vapours and remove them before it is safe to enter the area.

It would be preferable to use a different and less toxic sterilant, to replace formalin; for example chlorine dioxide, peracetic acid, hydrogen peroxide or chlorine. A particularly preferred sterilant is chlorine dioxide which is a broad-spectrum biocide and is relatively safe. However, the vaporizing chambers of formalin vaporizers are typically made from a material such as stainless steel or aluminium which would be corroded by chlorine dioxide or other oxidising agents. Therefore, in order to use chlorine dioxide, or another oxidising agent as a sterilant, different equipment without corrodible chambers would be required, which would be expensive.

SUMMARY OF THE INVENTION

Aspects of the invention are specified in the independent claims. Preferred features are specified in the dependent claims.

By providing a liner of a perfluohnated polymer material for a formalin vaporizer, the vaporizer may be modified to use more aggressive sterilants than formalin, notably chlorine dioxide, without substantially reducing the operating life of the vaporizing chamber. The invention enables existing vaporizers with corrodible boiling chambers to be simply converted for use with a wide range of sterilizing fluids. The term 'perfluorinated' is used herein to refer to a polymer material in which substantially all hydrogen atoms have been replaced by fluorine atoms, for example PTFE.

Suitable liners may be sold as add-ons for use with existing vaporizers, either individually or in packs. In a preferred embodiment, PTFE liners are included in a kit with a stehlant or one or more reagents for making a stehlant composition.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a prior art formalin vaporizer;

Figure 2 is a plan view from the end of the formalin vaporizer of Figure 1 ;

Figure 3 is a cross-sectional view along the line A-A of Figure 2;

Figure 4 is a cross-sectional view of the formalin vaporizer as shown in Figure 3, with a lining in accordance with an embodiment of the invention inserted in a chamber of the vaporizer;

Figure 5 shows a cross-sectional view of a chamber of the formalin vaporizer of Figure 3, with a lining including a receptacle, a washer and a pipe in accordance with a preferred embodiment of the invention;

Figure 6 shows a kit in accordance with an embodiment of the invention including two receptacles and reagents for forming a stehlant; and

Figure 7 is a perspective view of a lining system in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

Figure 1 shows a typical formalin vaporizer 1 used to decontaminate and disinfect biological safety cabinets. The vaporizer 1 comprises a body having a base 2, a top 4, and four sides 6. In the top 4 of the vaporizer 1 there is an opening 8.

Within the vaporizer 1 there is a vaporization or boiling chamber 10, in this example the chamber 10 is of a generally cylindrical shape, as shown in Figure 3. The chamber 10 in this example is bounded by a circular base 12 and cylindrical wall 14, the base and wall having both internal 16 and external 18 surfaces. Generally, at least the internal surfaces 16 of the chamber wall 14 and base 12 are made of stainless steel. The dimensions of the chamber 10 are substantially smaller than the dimensions of the body of the vaporizer 1 so that there is a space 20 between the external surfaces 18 of the chamber 10 and the body of the vaporizer 1 , for housing the electronics and heating element (not shown).

The wall 14 of the chamber 10 is connected to the top 4 of the vaporizer 1 proximate a top edge of the chamber wall 14, so that an upper section 22 of the chamber wall 14 protrudes from the top 4 of the vaporizer 1 through the opening 8.

The upper section 22 of the chamber wall 14 is shaped such that there is a tight fit between the chamber walls 14 and the opening 8 in the top 4 of the vaporizer 1. A retaining ring 24 surrounding the upper section 22 of the chamber wall 14 is used to secure the chamber 10 within the vaporizer 1 so that it is substantially suspended from the top 4 of the vaporizer 1.

A lid 26 is provided that fits over the upper section 22 of the chamber wall 14 and seals the top of the chamber 10. The lid 26 may be screwed on to the upper section 22 of the chamber wall 14, may be a push-fit lid or may be secured to the top of the chamber wall 14 by any other suitable means so as to seal the top of the chamber 10.

An aperture 28 is present in the wall 14 of the chamber 10 near the top of the wall 14 but below the top 4 of the vaporizer 1 . The aperture 28 is aligned with a similarly sized aperture 30 in a wall 6b of the vaporizer 1. An open ended tube 32 extends through both apertures 28, 30 so that a first inner end 33 of the tube 32 is flush with the internal surface 16 of the chamber wall 14 and the other outer end

35 of the tube 32 projects out from the wall 6b of the vaporizer 1. The tube 32 may be integrally formed with the wall 14 of the chamber 10.

On the outside face of the wall 6a of the vaporizer 1 is a switch 34 for switching on and off a heating element (not shown) inside the vaporizer 1 , used to heat the contents of the chamber 10.

When used to vaporize formalin, the sterilant is poured into the chamber 10 through the opening 8 at the top 4 of the vaporizer 1. The lid 26 is placed over the chamber 10 and the heater is switched on. The stainless steel walls 14 of the chamber 10 conduct the heat from the heater to the interior of the chamber 10 and heat the formalin to form a vapour. This vapour leaves the chamber 10 through the tube 32 and is released into the surrounding area.

We have found that a lining of a perfluohnated polymer material is uniquely suited to adapt the vaporizer 1 for use with more aggressive stehlants such as chlorine dioxide that would corrode the stainless steel, while providing effective conduction of the heat through the chamber walls. Additionally, the perfluohnated material is able to withstand the high temperatures required to vaporize the chosen sterilant. Suitable materials include poly(tetrafluoroethylene) (PTFE), fluorinated ethylene- propylene (FEP), and perfluoroalkoxy (PFA) polymer materials. It is particularly preferred that the material is PTFE, and the invention will for convenience be described with reference to a PTFE liner or receptacle. However it will be understood that the invention is not limited to this embodiment.

Figure 4 shows a vaporizer 1 which is similar to the vaporizer of Figures 1 -3, but includes a receptacle 40 for lining the chamber 10 according to one embodiment of the invention. The receptacle 40 is made from PTFE and, in this embodiment, has a base 42 and walls 44. The thickness of the PTFE is preferably such that both the base 42 and walls 44 of the receptacle 40 are flexible. This has the advantage that the receptacle is able to conform to the shape of the internal surfaces 16 of the chamber 10.

Suitable PTFE film material for making the receptacle 40 is available from DeWAL Industries, Inc; for example D/W-200 Skived Modified PTFE made from virgin resin, and conforming to ASTM-D3308, Type II, Grade I physical requirements. The receptacle should be made from a thin material, one which allows flexibility and at least partial conformation to the internal shape of the vaporizer chamber. The PTFE material may have a thickness in the range about 10 μm to about 500 μm. A preferred range is about 100 μm to about 300 μm, notably about 250 μm . Other preferred ranges are about 20-200 μm, preferably about 50- 150 μm. The thinner the material the better the heat transfer between the base 12 and wall 14 of the chamber 10 and the contents of the receptacle 40, so that the efficiency of the vaporizer 1 is not compromised. Suitable materials will be readily sourced by one skilled in the art once the invention is understood. In the present example, a PTFE material of thickness 0.005" (127 μm) was used.

The present invention provides a uniform protective barrier for the vaporizer chamber. Alternatives such as spray-coating the vaporizer chamber with a PTFE material suffer the drawback that uniform coverage is difficult to achieve, particularly for an end user. An area not adequately covered by the spray will be prone to corrosion. The invention provides an easy way for end users to modify vaporizers with stainless steel vaporization chambers for use with alternative sterilizing materials than formalin. Such vaporizers have been in use for many years, and the invention will extend their useful life by providing protection for the stainless steel of the vaporizer chamber, and by permitting the undesirable use of formalin to be phased out without requiring replacement equipment.

In a preferred embodiment and as shown in Figure 5, the walls 44 of the receptacle 40 extend fully the height of the wall 14 of the chamber 10, but do not extend beyond the upper section 22 of the chamber wall 14 so that the lid 26 may be used to seal the chamber 10. The receptacle 40 has an opening 46 at the top. Preferably, the diameter of the opening 46 is as large as possible to allow liquids to be added easily to the chamber 10, through the opening 46.

A second aperture 48 is provided in the wall 44 of the receptacle 40. This aperture 48 is aligned with the first inner end 33 of the tube 32 and the diameter of the aperture 48 is similar to the inner diameter of the tube 32. Preferably a cylindrical lip projects from the edge of the aperture. The lip may be in the form of a spout 50 comprising a short length of flexible tube. When the receptacle is placed in a chamber 10 of a vaporizer 1 , the projecting spout 50 is designed to be pushed into the inner end 33 of the tube 32. In this way, the spout 50 forms a PTFE lining in a first inner section of the tube and additionally helps to direct any vapours that pass through the aperture 48 from the chamber 10 to flow along the bore of the tube 32.

To line the remaining length of the bore of the tube 32 extending from the vaporizer 1 , in a preferred embodiment of the invention, there is provided a separate cylinder or pipe 52 made of PTFE. This PTFE pipe 52 is similar to a drinking straw and the thickness of the PTFE is such that the pipe 52 is sufficiently rigid that it can be pushed into the bore of the tube 32 from the outer end 35. The pipe is inserted until one end of the pipe 52 abuts the end of the spout 50 to create a continuous PTFE lining in the tube 32. Preferably, a short length of the pipe 52 extends from the end 35 of the tube 32 so that the pipe 52 can be removed easily when sterilization is complete. Alternatively, the pipe 52 may be cut to length if, for example, the pipe 52 is to remain in the vaporizer 1.

To form a complete lining in the chamber 10, a disc of PTFE may be provided to fit under the lid 26 of the vaporizer. With the lid 26 in place, the top edge of the PTFE receptacle would be in touching contact with the disc forming a complete PTFE lining. Alternatively, a PTFE washer 54 may be used to form a seal between the lid 26 and the top of the chamber 10 that would not be corroded by the stehlant vapours.

In a preferred embodiment the PTFE receptacle 40 has a circular base and cylindrical walls so that it fits within a cylindrical chamber 10 of a vaporizer 1. The flexibility of the PTFE means that the receptacle 40 could still be stored flat when not in use by forming a fold in the base of the receptacle 40.

Alternatively, the receptacle 40 may be constructed so that it does not have a base, but instead the lower edges of the walls of the receptacle are joined directly to each other. The advantages of this embodiment are that the receptacle 40 is more easily manufactured and, as this pouch-like receptacle is preferably made from flexible PTFE material, it would still substantially conform to the shape of the chamber 10 when it was filled with liquid during use. Although in this embodiment the inlet and outlet of the receptacle 40 are formed by two separate apertures, the design of the formalin vaporizer may be such that the inlet and outlet may be formed by a single aperture in the receptacle.

In a preferred embodiment the receptacle 40 is a flexible bag which may be inserted into an existing vaporizer chamber 10. The receptacle 40 may be sold and distributed as part of a kit 56, as shown in figure 6, including one or more receptacles 40. The kit 56 may contain a complete lining system, including PTFE receptacles 40, PTFE washers 54 or discs and PTFE lining pipes 52, as well as a suitable stehlant, or reagents for forming a sterilant 58.

So that the receptacles 40 may be used in a number of different types of vaporizer 1 , the receptacles 40 are preferably in the form of a bag made from thin PTFE sheet that is easily cut with scissors or other blade. This has the additional advantage that the bags may then be cut to the desired height to fit different vaporizer chambers 10.

A further embodiment is shown in Figure 7. Here the spout 50 is dimensioned to project through the entire length of the outlet tube 32 of the vaporizer 10, thereby improving protection of the inner surfaces of the tube 32 from aggressive sterilant vapours. The receptacle 40 is desirably as thin as practical for heat transfer and conformity, for example about 100-300 μm. Because heat transfer is not important in the spout 50, the spout may be formed either from the same gauge of perfluorinated polymer material or may be formed of a thicker material to aid rigidity and facilitate insertion into the tube 32.

Claims

1. A lining system for lining a vaporization chamber of a formalin vaporizer, wherein the lining system includes a receptacle made from a perfluohnated polymer material and the receptacle comprises an inlet for adding fluids to the receptacle and at least one outlet for the release of vapour from the receptacle.

2. A lining system as claimed in claim 1 , wherein the inlet and the outlet of the receptacle are a provided by a single aperture.

3. A lining system as claimed in claim 1 , wherein the outlet of the receptacle is a hole in a side of the receptacle.

4. A lining system as claimed in claim 1 , wherein the outlet of the receptacle comprises a spout extending from the side of the receptacle.

5. A lining system as claimed in any of claims 1 to 4, wherein the receptacle is a tube and wherein one end of the tube is sealed to form a base of the receptacle and the other end of the tube is open, forming the inlet for adding fluids to the receptacle.

6. A lining system as claimed in any preceding claim, wherein the lining system additionally comprises a pipe of a perfluohnated polymer material for lining an outlet of a formalin vaporizer.

7. A lining system as claimed in any preceding claim, wherein the vaporization chamber includes a lid, and wherein the lining system additionally comprises a washer of a perfluohnated polymer material for forming a seal between said lid and the vaporization chamber.

8. A lining system according to any preceding claim, wherein the perfluohnated polymer material is poly(tetrafluoroethylene) (PTFE).

9. A lining system according to any preceding claim, wherein the perfluohnated polymer material has a thickness in the range 10-500 μm, preferably 100-300 μm, particularly preferably about 250 μm

10. A formalin vaporizer comprising at least one vaporization chamber for vaporizing a stehlant, wherein said at least one chamber is lined with a lining system as claimed in any one of claims 1 -5.

11. A vaporizer as claimed in claim 10, further comprising a tube forming an outlet of the chamber, and wherein the tube is lined with a pipe of a perfluorinated polymer material.

12. A method for using a formalin vaporizer having a vaporization chamber to vaporize a stehlant that corrodes the material of the chamber, the method comprising the steps of: inserting a lining system as claimed in any of claims 1 to 5 into the evaporation chamber; adding said stehlant to the receptacle; heating the stehlant in the receptacle using said vaporizer so that a sterilizing vapour is formed; and releasing the sterilizing vapour from the receptacle through the outlet.

13. A method as claimed in claim 12 wherein the method includes the step of pushing a pipe as claimed in claim 6 into the tube forming the outlet of the vaporization chamber so as to form a lining in the tube.

14. A method as claimed in claim 12 or claim 13 wherein the vaporizer includes a lid for the vaporization chamber, and the method comprises the additional step of placing a washer of a perfluorinated polymer material between said lid and the chamber so as to form a seal.

15. A method as claimed in any of claims 12 to 14, wherein the sterilant is one of chlorine, chlorine dioxide, hydrogen peroxide or peracetic acid.

16. A kit for converting a formalin vaporizer for use with stehlants that corrode stainless steel, wherein the kit comprises: at least one lining system as claimed in any of claims 1 to 9 ; and - at least one stehlant or reagents for forming a stehlant.

17. A kit as claimed in claim 16, wherein the stehlant is one of chlorine, chlorine dioxide, hydrogen peroxide or peracetic acid.