GB2037180A - Gas bubbler for atmospheric sampling - Google Patents

Abstract

A non-spill gas bubbler designed to be carried or worn for monitoring of toxic components in the atmosphere has a hollow body member 2 which forms at its lower end a bubbling chamber for containing a liquid 5 for adsorbing a gas component for later analysis. The gas outlet pipe 10 and suitably also the gas inlet pipe 6 are surrounded by secondary chambers 1, 8, respectively, designed to catch liquid upon inversion of the bubbler. Suitably the main inlet pipe 6 is coaxial with the outlet pipe 10 and terminates above the intended level of liquid in the bubbling chamber, and the secondary chamber 8 surrounding the inlet extends as a transfer pipe 11 of reduced diameter to below the liquid surface. Deflectors may be spaced from the ends of the inlet and/or outlet pipes to prevent entry of liquid during inversion, e.g. secondary chamber 8 may be shaped to form a deflector 9 protecting the outlet pipe 10. <IMAGE>

Description

SPECIFICATION Gas bubbler for atmospheric sampling The present invention relates to gas bubblers for atmospheric sampling.

It is a feature of industrial life (both traditional and modern) that many workers may be exposed to toxic gases and vapours during the course of their employment. In many industrial countries, legislation has been enacted to deal with the occupational exposure of workers to chemicals, and strictly limits the amount oftoxic gas or vapourto which said workers can normally be exposed. These laws have forced all employers to become more conscious of, for example, the work conditions experienced by their employees, and in particular, employers now have to keep the levels of toxic gases and vapours found the in atmosphere of the factory and its surrounds within the set limits.

This means that quick and easy methods of evaluating the level of a given toxic material in the atmosphere are now required. Apparatus designed forthis purpose includes devices, that when exposed to a given atmosphere automatically register (by means of colour change, electrical current or other means) the percentage of toxic material in said atmosphere at a given time, and other devices that retain the toxic material found in a known volume of atmosphere and then allow later measurement of the volume of toxic material collected, indicating the time weighted average concentration. In the latter devices a favoured method of gas collection comprises drawing the atmosphere, by suction, through an adsorbing liquid that will dissolve all, or a known percentage, of the toxic gaseous material present.

When in use, said devices, known as gas bubblers, are normally either carried or worn by individual workers and since they are charged with a liquid it is likely that the contents will spill out if the carrier or wearer moves in a jerky manner or moves the bubbler away from its normal vertical position. Therefore there is a need for a gas bubbler designed to retain its liquid contents, whatever the motion or orientation of the carrier or wearer. Accordingly, the present invention provides a gas bubbler that not only provides a reliable means of evaluating occupational exposure to a toxic gas or vapour but also retains its liquid contents regardless of the position of the carrier or wearer.

According to the present invention there is provided a gas bubbler which comprises a hollow body memberforming at its lower end a bubbling chamber for containing an adsorbing liquid, gas inlet and outlet pipes and secondary chambers surrounding said inlet and outlet pipes to catch and retain any adsorbing liquid displaced by inversion of the device.

The main inlet pipe preferably terminates above the intended level of liquid in the bubbling chamber the secondary chamber surrounding the inlet extending as a transfer pipe, preferably of reduced diameter to a point below the surface of the liquid.

Preferably deflectors are placed across, but spaced from the ends of the inlet and/or outlet pipes to prevent direct entry of liquid into the pipes during inversion. In an especially convenient embodiment the inlet pipe is situated within the outlet pipe and extends further into the body member, the secondary chamber surrounding the inlet pipe itself being shaped such that its maximum width exceeds that of the entrance to the outlet pipe. In this way the said secondary chamber itself forms a deflector protecting the outlet pipe.

The transfer pipe terminates below the intended liquid level as a simple straight or bell-ended pipe, or as a bubbling head incorporating one or more apertures. In general gas pressure and/or the geometry of the bubbling head will limit the volume of liquid able to enterthetransfer pipe on inversion and hence the secondary chamber surrounding the inlet pipe may be of relatively small dimensions and may in some cases be omitted altogether.

The secondary chamber surrounding the outlet must be of sufficient volume from the entrance of the outlet upwards, to retain all of the liquid contained in the bubbling chamber. As it generally serves no shielding purpose its shape is immaterial, however straight, arcuate or bi-cuspidal side walls have been used. In addition to these secondary chambers further means designed to retain the liquid within the bubbler may also form part of the bubbler. For example, further chambers may be provided to trap any liquid which splashes into the inlet and outlet pipes in spite of the secondary chambers. In operation, the atmosphere to be tested may be drawn into the bubbler by any suitable conventional means, such as a battery operated vacuum pump attached to the outlet. This draws gas through the inlet and into the liquid. Undissolved gas is then drawn out of the outlet and into the pump.The rate of flow of gas through the bubbler would vary with analytical requirements, pump capacity, viscosity of the sampling liquid etc. but would be generally about 1 litre/minute.

Although the liquid used in the bubbler will not spill out at very high tilt-angles, gas may not be drawn through the liquid with the bubbler in this position. As a timing device is normally incorporated in the pump the indicated sampling period may be an overestimate unless a means, preferably a tiltswitch, is fitted to switch the pump off or on appropriately and automatically when the bubbler passes through the horizontal plane, for example when the wearer bends down and then returns to an upright position. The required modification can be introduced simply and at little cost by fitment of a mer cu ry tilt-switch. This may be either fitted, taking care to orientate it correctly, inside the pump or may be incorporated in the "shorted" electrical plug which is fitted to some pumps.

On drawing the sample atmosphere into the liquid the efficiency of solubilisation of the toxic gas or vapour in the adsorbing liquid can be increased by equipping the bubbling chamber with inwardly extending spines that break up the flow of gas bub bles through the liquid, thereby decreasing the sur face area of each bubble and thus increasing the degree of solution of the gas or vapour in the liquid.

Alternatively, the bubbling chamber may contain an inert packing material such as glass beads.

The gas bubbler of this invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 shows an all-glass model of the gas bub bler which is intended for use with liquids or gases that may attack or react with plastics materials and Figure 2 shows and all-plastics model of the gas bubbler which would be selected especially in view of its high impact resistance.

Figure 1 shows an all-glass model of the gas bubbler which comprises a hollow body member 1 made up of a lower 2 and upper section 3 which are joined by a ground glass joint 4. The simple removal of the lower section 2 from the upper section 3 facilitates the addition and removal of liquid to and from the bubbling chamber 5 forming part of the lower section. The main inlet pipe 6, which terminates above the level of the adsorbing liquid 7 in the bubbling chamber 5, is surrounded buy a secondary chamber 8. Said secondary chamber 8 comprises a section with arc-shaped walls 9, which deflect liquid away from the entrance to the outlet pipe 10 surrounding the inlet pipe 6 and a straight transfer pipe 11,which extends below the level of the liquid 7 in the bubbling chamber 5 and has a bell-shaped end 12.The outlet pipe 10 is also surrounded by a secondary chamber 13 formed by the bi-cuspidal walls 14 of the upper body section 3, said chamber 13 being of sufficient volume from the entrance to the outlet pipe 10 upwards, to retain all of the adsorbing liquid 7. The outlet pipe 10 communicates with a further chamber 15 surrounding the inlet pipe 6 and designed to retain any liquid inadvertently entering the outlet pipe 10. One wall 16 of this further chamber 15 is formed into an elongated side arm 17 which comprises anotherfurtherchamber 18 surrounding a further pipe 19. This pipe 19 may be open to the ambient or, in use, attached to a pump (not shown). When in use the surrounding atmosphere is drawn, by suction, along the inlet pipe 6 through the secondary chamber 8 and into the adsorbing liquid 7 in the bubbling chamber 5.The efficiency of solubilisation of the gas or vapour in the liquid 7 is increased by breaking up the gas bubbles by means of spines 20 which extend inwardly from the walls of the bubbling chamber 5. The all glass bubbler is afforded additional protection against breakage by a container 21 and slotted cap 22 which surround the hollow body member 1 and are held togther by a threaded ring 23. The container 21 and slotted cap 22 may be manufactured from, for example, plastics materials or treated cardboard. The container 21 is provided with apertures 24 through which can be passed a cord to facilitate the attachment of the bub blerto the wearer.

Figure 2 shows an all-plastics model of the gas bubbler. In a preferred embodiment the all-plastics bubbler is manufactured from polypropylene. The essential features of the all-plastics gas bubbler are very similar to those of the all-glass gas bubbler shown in Figure 1. The body section 31 is moulded in one piece with a separate threaded cap 33. The main inlet pipe 36, which terminates above the level of the adsorbing liquid 37 in the bubbling chamber 35, is surrounded by a secondary chamber 38. Said secondary chamber comprises a section with trapezoid-shaped walls 39 and a straight transfer pipe which has a bell-shaped end 42.The outlet pipe 40 surrounds the inlet pipe 36 and is in turn sur rounded by a secondary chamber 43 formed by the straight upper walls 44 of the body section 31 said chamber 43 being of sufficient volume from the entrance to the outlet pipe 40 upwards to retain all of the adsorbing liquid 37. The inlet pipe 36 is further surrounded by a further chamber 45 within the cap 33. Into one wall 46 of this further chamber 45 is set an elongated side arm 47 extending within the further chamber and outside the device and, which may be open to the ambient or, in use, attached to a pump (not shown).

Gas is passed, by suction, into the liquid 37 in the bubbling chamber 35 and the gas bubbles are broken up by spines 50 which extend inwardly from the walls of the bubbling chamber 35. Removal of the cap 33 from the unitary hollow body member 31 facilitates the addition and removal of liquid to and from the bubbling chamber 35. Rings 53 and 54 are attached to the outside of the hollow body member 31 and/or the cap 33. Cord may be passed through these rings 53 and 54 to facilitate the attachment of the bubbler to the wearer.

Claims (17)

1. A gas bubbler comprises a hollow body member forming at its lower end a bubbling chamber for containing an absorbing liquid, gas inlet and outlet pipes and secondary chambers surrounding said inlet and outlet pipes to catch and retain any absorbing liquid displaced by inversion of the device.

2. A gas bubbler according to Claim 1 wherein one or more deflectors are placed across but spaced from the end of the inlet pipe.

3. A gas bubbler according to Claim 1 or Claim 2 wherein one or more deflectors are placed across but spaced from the end of the outlet pipe.

4. A gas bubbler according to any preceding Claim wherein the secondary chamber surrounding the inlet pipe forms a deflector protecting the outlet pipe.

5. A gas bubbler according to any preceding Claim wherein the inlet pipe is situated within the outlet pipe.

6. A gas bubbler according to Claim 5 wherein the secondary chamber surrounding the inlet pipe has a maximum width that exceeds the width of the entrance to the outlet pipe and the inlet pipe extends further into the body member than the outlet pipe.

7. A gas bubbler according to any preceding Claim wherein the inlet pipe terminates above the level of the liquid in the bubbling chamber and the secondary chamber surrounding the inlet pipe extends as a transfer pipe to a point below the surface of the liquid in the bubbling chamber.

8. A gas bubbler according to Claim 7 wherein the transfer pipe terminates as a bell-ended pipe.

9. A gas bubbler according to Claim 7 wherein the transfer pipe terminates as a bubbling head incorporating one or more apertures.

10. A gas bubbler according to any preceding Claim wherein the secondary chamber surrounding the outlet pipe is of sufficient volume from the entrance of the outlet pipe upwards, to retain all of the liquid to be contained in the bubbling chamber.

11. A gas bubbler according to any preceding Claim wherein further chambers are provided to trap liquid which splashes into one or other of the inlet and outlet pipes.

12. A gas bubbler according to any preceding Claim wherein the bubbling chamber is provided with inwardly extending spines.

13. A gas bubbler according to any one of Claims 1 to 11 wherein the bubbling chamber contains inert packing material.

14. A gas bubbler according to Claim 13 wherein the inert packing material is glass beads.

15. A gas bubbler substantially as hereinbefore described, with particular reference to the Figures.

16. A method of evaluating the level of a gaseous material in an atmosphere comprises drawing, for a known period, the atmosphere, by suction, through a known volume of an absorbing liquid that will dissolve all, or a known percentage, of said gaseous material and that is contained within a gas bubbler according to Claim 1, removing said liquid from said bubbler and measuring, by any suitable means, the concentration of gaseous material absorbed in said liquid and thereby the time weighted average concentratino of gaseous material in said atmosphere.

17. A method of evaluating the level of gaseous material in an atmosphere substantially as hereinbefore described.