WO1994000378A1

WO1994000378A1 - Safety system and safety cabinet

Info

Publication number: WO1994000378A1
Application number: PCT/SE1993/000349
Authority: WO
Inventors: Lennart Olausson
Original assignee: Lennart Olausson
Priority date: 1992-06-30
Filing date: 1993-04-23
Publication date: 1994-01-06
Also published as: SE9202006L; SE9202006D0; NO945087D0; AU4362793A; NO945087L

Abstract

A safety system for the deposition and feeding of liquid chemicals, is characterized in that the chemicals are deposited in at least one container in a safety cabinet (23, 23a), that there is at least one dosage feeding pump (4, 4a) in the safety cabinet and at least one suction conduit (3, 3a) through which said chemicals can be conveyed up from the said at least one container for said dosage feeding, that a surrounding embankment (29, 29a) is provided in the bottom portion of the safety cabinet, said embankment consisting of a material which is resistant to the chemicals contained in the container or containers in the safety cabinet and which embankment can accommodate the content of container or containers placed in the cabinet, that one or more first sensors (21, 21a) sensitive to liquid are provided inside the embankment, and that the safety system includes a control unit (12, 12x) in connection with said sensor or sensors provided to stop the dosage feeding pump if liquid would contact the said first sensor or sensors.

Description

SAFETY SYSTEM AND SAFETY CABINET

TECHNICAL FIELD The invention concerns a safety system relating to the deposition and feeding of liquid chemicals. In the concept "chemicals" shall also be included the case when "the chemicals" consist of one chemical only, although in the normal case at least a solvent or carrier is present besides an active chemical agent. The invention also relates to a safety cabinet which may be an integrated part of the safety system, but which also can find use in other applications than in the safety system.

PRIOR ART AND BACKGROUND OF THE INVENTION Liquid chemicals which are a danger to the environment often are kept in cans and similar containers in public baths, hospitals, laboratories, factories, etc. The chemicals can be corrosive and/or release dangerous gases and often they are intended to be fed to another liquid, e.g. water or to process chemicals, wherein the composition of the water and/or the production procedure may be the determining factor for when and how much that shall be supplied.

According to existing regulations, containers, which contain dangerous liquids of the said kind, shall be deposited in spaces with surrounding embankments of a chemically resistant material. Moreover the embankments shall be able to house a volume corresponding to the volume of the container or the containers. The containers for such chemcials often are made of glass-reinforced plastics, e.g. polyester plastics, and the embankments can be made of concrete, which satisfies the demands as far as chemical resistance and tightness are concerned. If several different chemicals are used on one working place, each embankment must not accomodate more than one type of dangerous chemical agent or compound.

Such repositories therefore according to prior art are comparatively expensive and also the cost for ventilation adds to the costs of construction. The provision of such embankments in older buildings or in buildings, where such measurements have not been considered when the building originally was planned, will often be extremely expensive.

For example, a certain concentration of sodium hypochlorite has to be maintained in the_.swimming pool in public baths. The content of sodium hypochlorite of the swimming pool therefore is measured regularly or continuously, and when the concentration falls below a predetermined value, a certain amount of sodium hypochlorite is supplied. Such supply or feeding of a chemical agent or compound can be made completely manual, which can be satisfactory if the quantities which shall be supplied are moderate and if the intervals between the feeding occasions are long. The manual handling, however, is troublesome and time consuming.

If the feeding intervals are short and if the feeding quantities are considerable, the manual handling will be expensive, since in this case one or more persons have to devote a major part of the working time to feeding chemicals to the water. In many cases the chemical feeding also has to be performed also during the night or other inconvenient working hours, which makes the manual handling still more difficult and expensive.

In view of the above, experiments have been made for automatizing the feeding of chemicals. Thus, in connection to a container with for example sodium hypochlorite a pump has been provided, which via a conduit pumps the dangerous liquid to a nozzle at the chemical feed place. The pump can be controlled by a sensor, which registers the concentration, e.g. in a swimming pool. The pump is started when the concentration falls below a predetermined concentration level and is stopped when a predetermined higher level has been achieved. Such devices can be combined with one or more transmitters and with more or less complicated regulation and control equipment for maintaining desired concentration levels.

ihese devices, however, has the drawback that they, if for example there is a failure in the conduit between the pump and the swimming pool, will continue to pump out dangerous liquid, which will not reach the swimming pool, where one or more sensors will continue to transmit signals to the pump to supply still more dangerous liquid.

When the chemicals, which are dangerous for people and/or for the environment, are used in an automatically controlled pump system of this type, the connection between the pump and the chemical feeding nozzle is a particular risk factor because a failure in the connection conduit may cause that a considerable amount of the dangerous liquid will be spread out in spaces where people can be seriously injured or in spaces which are difficult to decontaminate.

Further, in existing facilities, deposition spaces for dangerous chemicals with the said embankments often are not situated in direct connection to the place of dosage, which means that the conduit between the container surrounded by the embankment and the place of dosage, i.e. the place where the chemicals are fed in, can be comparatively long and therefore is a particular risk factor.

DISCLOSURE OF THE INVENTION

It is an object of the invention to provide an improved system for the deposition and supply of dangerous chemicals. According to one aspect, the invention concerns an improved system for feeding dangerous chemicals, wherein, by means of the system, the drawbacks connected with devices according to prior art can be eliminated. According to another aspect, the invention concerns a safety cabinet made of a material resistant to chemicals for the deposition of liquid chemicals in at least one container placed in the cabinet.

The safety system according to the invention is characterized in that the chemicals are deposited in at least one container in a safety cabinet, that there is at least one feeding pump in the safety cabinet and at least one suction conduit, through which said chemicals can be conveyed up from the said at least one container for said feeding, that a surrounding embankment is provided in the bottom portion of the safety cabinet, said embankment consisting of a material which is resistant to the chemicals contained in the container or containers in the safety cabinet and which embankment can accomodate the content of the container or containers placed in the cabinet, that one or more first sensors sensitive to liquid are provided inside the surrounding embankment, and that the safety system includes a control unit in connection with said sensor or sensors provided to stop the feeding pump, if liquid will contact said first sensor or sensors.

The cabinet is equipped with a ventilation device provided to secure that an underpressure is maintained in the cabinet and at least one air inlet opening in the bottom portion of the cabinet but at a level above the embankment.

A first embodiment of the safety system more particularly is characterized in that said at least one conduit comprises a suction conduit between the container and the dosage feeding pump and a dosage conduit which extends from the dosage feeding pump to a dosage point and is provided with a protective casing surrounding the dosage feeding conduit, the space between the dosage feeding conduit and the protective casing being a volume which is tightly closed with the exception of an opening which is located in said safety cabinet. The safety cabinet according to this embodiment may be equipped with a hose or pipe conduit provided to lead away any liquid, which possibly may appear at said opening, to the region surrounded by the embankment in the bottom portion of the cabinet. In the space between the dosage feeding conduit and the protective casing there can further be provided one or more second sensors, which are sensitive to liquid, preferably close to one or both ends of the cases, wherein also these second sensors are connected to said control unit in order to stop the dosage feeding pump, if liquid would contact said second sensors.

A second embodiment of the safety system is characterized in that a dosage receiving conduit extends through the safety cabinet, that a liquid, to which said chemicals shall be supplied, is provided to be conveyed through said dosage receiving conduit, which extends through the cabinet, and that the dosage feeding conduit does not extend outside of the safety cabinet but entirely inside the cabinet between the dosage feeding pump and the dosage point, which is located in the region of that portion of the dosage receiving conduit which extends through the safety cabinet. This embodiment should be regarded as an improvement over the first mentioned embodiment therein that no conduits containing tie dangerous chemical or chemicals in concentrated form are laid outside the safety cabinet but only in the cabinet. The embodiment also offers other advantages, which can be achieved particularly if the dosage receiving conduit is a by-pass conduit (in parallel with) of a main conduit for the liquid to which said chemical or chemicals shall be supplied, wherein means are provided for the feeding of a predetermined, adjustable flow of the liquid from the main conduit through the by-pass conduit in which the chemicals are supplied to the liquid and further into the main conduit again and finally to a final recipient body of liquid, wherein the chemicals successively are mixed into and diluted in the liquid. Herein it is possible essentially to eliminate any more prc' unced oscillations of the concentration of the chemicals in the liquid of the final recipient body. Suitably, in this embodiment of the safety system, a flow meter is provided in the by-pass conduit and is connected to said control unit to emit a signal to stop the dosage feeding pump or pumps if the flow in the by-pass conduit would fall below a predetermined value.

If a plurality of different chemicals shall be supplied to the liquid, which chemicals must not be mixed with each other when they are concentrated, the chemicals are deposited in separate safety cabinets which can be coupled in series such that said by-pass conduit extends in series through the safety cabinets arranged in series, wherein the chemicals successively are supplied to said by-pass conduit inside each safety cabinet. In this case it is sufficient to provide just one flow meter in the by-pass conduit, which flow meter can emit a signal to the control unit to stop all the dosage pumps in the safety cabinets connected to each other in series.

The basic principles of the safety cabinet which can be an integrated part in the safety system, but which also can be used in other applications, have been described in the foregoing. It is thus a characteristic feature that the bottom and lower parts of the safety cabinets have a surrounding embankment which can accomodate the content of the container or containers placed in the cabinet. At least this embankment is made of a material which is resistant to the chemical or chemicals which are contained in the container or containers in the cabinet, but most advantageously the entire cabinet is made of such a chemical resistant material. The embankment can be a separate unit in the cabinet or be an integrated part of the bottom portion of the cabinet but is most advantageously defined by the bottom portion of the cabinet, which for this purpose suitably has the shape of a trough or tub having preferably a rectangular horizontal section and straight walls. In order that the space surrounded by the embankment shall be able to accomodate the entire volume of the container or containers in the safety cabinet, it should have a comparatively large bottom area in order that the height need not be inconveniently large. On the other hand, it is not necessary that the top portion of the safety cabinet has a correspondingly large horizontal section. To the contrary, it is an advantage from a ventilation point of view if the top portion has a comparatively small horizontal section. Therefore, it is recommended that the front of the safety cabinet is inclined inwards-upwards, while the rear and side walls can be vertical and be extensions of the corresponding rear and side walls of the trough; the embankment. If the inclined front moreover is provided with one or more doors, the handling of the containers, due to the said geometrical design of the safety cabinet, is facilitated, when the containers shall be placed in the cabinet or be moved in it.

The doors can be made of the same material as the other parts of the safety cabinet, but it is also possible to make them of a transparent plastic material in order to facilitate the control of the interior of the cabinet. It is also conceivable to make the doors of stainless or acid resistant steel, aluminium or other metals, which besides resistance to chemicals also have a good mechanical strength, which is important if the safety cabinet contains containers containing chemicals which have to be protected against unauthorized access. It is also possible to make the whole safety cabinet of stainless or acid resistant steel, aluminium or other metals having good resistance to chemicals. Normally, however, the main parts of the safety cabinet are made of glass-reinforced plastics. In order to promote a practical and low cost production the cabinet suitably consists of a number of sections, each one of which is made in one piece, and which generally are united to each other through flange joints. A first one of these sections is the trough shaped bottom portion which defines or includes the surrounding embankment, which also is made in one piece in order to prevent any risk for leakage. Further, the end sections are made of separate pieces. Between the end portions there is at least one intermediate section, which in its turn can consist of two or more parts, which together form the main part of the rear wall of the cabinet, the top portion and the front above the opening in the front which is covered by said door or doors. The different sections of glass-reinforced plastics, suitably polyester plastics, are united to each other through gluing in tight, glued and riveted flange joints.

Further advantages, aspects and characteristic features of the invention will be apparent from the appending claims and from the following description of preferred embodiments.

BRIEF DESCRIPTION OF DRAWINGS

In the following description of preferred embodiments, reference will be made to the appending drawings, in which

Fig. 1 schematically illustrates a first embodiment of the safety system according to the invention;

Fig. 2 is a perspective, schematical view of the safety cabinet, a section of which is shown in Fig. 1,. and which can be included as part of the safety system according to the invention but which also can find use in other applications for the deposition of dangerous chemicals;

Fig. 3 is a section through a joint of a coaxial protective casing surrounding a dosage feeding conduit; Fig. 4 shows the provision of the protective casing in connection to a nozzle adjacent to a dosage feeding point;

Fig. 5 is a flow chart illustrating a second embodiment of the safety system according to the invention;

Fig. 6 is a perspective view of a safety cabinet, which is an improvement from a manufacturing point of view of the cabinet shown in Figs. 1 and 2 and which is equipped to be used in the safety system according to Fig. 5; and

Fig. 7 shows the safety cabinet according to Fig. 6 in a perspective view as viewed obliquely from rear.

DESCRIPTION OF PREFERRED EMBODIMENTS

In Fig. 1 a container made for example of glass-reinforced polyester plastics, intended to contain a dangerous chemical agent or compound, is designated 2. The container 2 is placed in a safety cabinet 23. The material of the cabinet, which for example can consist of glass- reinforced polyester plastics, is resistant to the dangerous chemical agent or composition contained in container 2. The bottom of the cabinet and the lower part of the walls moreover are designed to define a surrounding embankment 29 which can accomodate the content of the container 2, if the container would leak or overturn. The surrounding embankment 29, according to the embodiment, is defined by the bottom portion of the cabinet and is limited by the two side walls 2δ, the rear wall 27 and the comparatively low front wall 26. The height of the embankment 29 corresponds to the height of the front wall 26.

Inside the safety cabinet 23, on one_, of its walls, there is mounted a dosage feeding pump 4, which can suck up chemicals from the container 2 through a suction conduit 3. The pump 4 is by means of a dosage feeding conduit 5 connected to a dispensing nozzle 6 at a dispensing or dosage point for dispensing or supplying said chemical to a recipient body generally designated 1. The dosage feeding conduit 5 is surrounded by a casing 9, which, at the passage through the roof 24 of safety cabinet 23, is provided with a screw fitting 9c, which is tightly connected to a casing portion 9a, which in its turn is connected to a T-pipe 9b, the latter one being connected with a pipe conduit or hose 11a and a casing portion 9d. The casing 9 and the screw fitting 9c, the T-pipe 9b and the casing portions 9a and 9d define a space 9', which surrounds the dosage feeing conduit 5 and is tight relative to the dosage conduit and to the surrounding with the exception of an opening 13 to conduit 11a.

Fig. 2 shows a perspective view of the safety cabinet 23, which is provided with doors 30 above the embankment 29. The doors 30 make it possible to place the container 2 in the safety cabinet 23 and also to take it out of the cabinet easily. The safety cabinet 23 also is equipped with a control unit 12a and with a ventilation device 31, which ensures that an underpressure is maintained in the cabinet, and with a conduit 32 for leading away the ventilation air.

It is also conceivable to provide a plurality of containers 2 in the safety cabinet 23 and to provide each such container with a dosage feeding pump 4. If each such container contains the same type of chemical, an embankment 29 common to all the containers can be used, but if the containers contain different chemicals, the bottom portion of the safety cabinet must be separated into a plurality of embankments, each one surrounding one each of such containers. In Fig. 2 there is schematically shown that a plurality of dosage feeding conduits 5 with casings 9 thus can be used in connection with one cabinet. It shall, however, be noted that also a plurality of separate safety cabinets can be provided in a safety system in order to keep the chemicals completely apart, wherein each type of chemical has its separate cabinet and hence also its separate surrounding embankment.

The dosage feeding conduit 5 according to this embodiment may have a considerable length, i.e. be about 20-30 long, which means that it for practical reasons can be difficult to make the casing as one single piece. Fig. 3 shows a joint member 40, which can be used for joining portions 9e and 9f of the casing 9, which in this case may consist of hose sections 9e, 9f made of a chemically resistant plastic material. The joint member 40 is a standardized part of a chemically resistant plastic material and will not be described more in detail.

Fig. 4 shows more in detail how the casing 9 can be connected to the dosage supply nozzle 6. In the embodiment shown in Fig. 4 the terminating section 9h of the casing 9, which section 9h lies close to the dosage supply nozzle 6, is designed as a transparent piece of a hose, which by means of hose clamps 41a, 41b is secured to a fitting member 42 and to the nozzle 6, respectively. By the provision of a transparent hose portion defining the terminating part 9h of the casing 9 in connection to the dosage supply nozzle 6, also a visual control is made possible for checking that there is no leakage from the dosage feeding conduit 5 adjacent to the dosage supply nozzle 6.

Contact electrodes 7 are placed in the space 9' close to the pump 4. These electrodes have the function of being sensors and register if liquid is present in space 9' between the dosage feeding conduit 5 and casing 9 adjacent to the dosage feeding pump 4. The electrodes 7 are connected with the control device 12 through conduits 14, so that the control device 12 will stop the dosage feeding pump (the pump motor 4') if liquid would collect in the region of the electrodes 7.

Electrodes 8 also are provided close to the dosage supply nozzle 6, said electrodes having the same function as electrodes 7. These electrodes 8 are connected with the control device 12 through conduits 15, said control device being provided to stop the dosage feeding pump 4 (the pump motor 4') if liquid would collect in space 9' between casing 9 and dosage feeding conduit 5 near the dosage supply nozzle 6.

In the equipment according to Figs. 1-4 the safety system operates in the following way. If a break or leakage would occur in the dosage feeding pump 4 and the dosage supply nozzle 6, i.e. on the pressure side of the dosage "feeding pump 4, the dangerous liquid would leak or spurt out into the space 9' between the dosage feeding conduit 5 and the casing 9. Since this space 9' between casing 9 and conduit 5 is tight with the exception of the opening 13, the liquid will collect either near the pump 4 or near the dosage supply nozzle 6. In the first case, the liquid will be detected by the sensors 7, which will stop the dosage feeding pump 4 (the pump motor 4¹). If, on the other hand, a leakage would occur nearer the dosage supply nozzle 6, the liquid will first be detected by the electrodes 8 between the dosage feeding conduit 5 and the casing 9 near the dosage supply nozzle 6 and also in this case the pump 4 will be stopped via the control unit 12. If, however, liquid would leak out into the space 9' without being detected by any of the elctrodes 7, 8, and if the space 9* successively would be filled with liquid, the liquid will be drained away to the region surrounded by the embankment 9 in the bottom portion of the safety cabinet 23 through the drainage conduit 11a, and in the bottom portion sensors 21 will react to close the pump motor 4' of the dosage feeding pump 4 via the control unit 12. The same thing will occur if liquid would leak out directly to the region surrounded by the embankment 29 from container 2.

Fig. 5 is a flow chart illustrating a safety system for the deposition and supply (dosage) of chemicals, more particularly of hydrochloric acid and sodium hypochlorite to a recipient body of water 1 in a swimming pool 41. Clean water is supplied through a main conduit 40 to the body of water 1 in the swimming pool 41 from one or more pressurized sand filters generally designated F. A return conduit is designated 42 and a main pump is designated 43. The main pump 43 drives the water at a constant flow through the main conduit 40. A by-pass flow of water is led through a by-pass conduit 44. This by-pass flow, which may correspond to about 10 % of the total flow through the main conduit 40, can be controlled by means of a constriction valve 45 in that part 46 of the main conduit 40 which is in parallel with the by-pass conduit 44. From the by-pass conduit 44 a negligible flow is led away through a conduit 47 to a metering unit E, in which the content of hydrochloric acid and sodium hypochlorite in the water is analyzed. From the metering unit E this negligible flow is further conveyed through a conduit 48 to the return conduit 42. The rest is conveyed through two safety cabinets 23a and 23b connected in series. In the system there is also included a control valve 49 and a number of closure valves 50, 51, 52, 53 and two manometers EM, PM. In the by-pass conduit 44 a flow meter 55 is arranged before the first safety cabinet 23a.

A section 44 of the by-pass conduit 44 extends through the safety cabinet 23a, and a section 44b of the by-pass duct 44 extends through the safety cabinet 23b. The two sections 44a and 44b are connected to each other by a connection piece 44' between the two safety cabinets 23a and 23b.

In the lower part of the safety cabinet 23a there is an embankment 29a surrounding the container 2a (which for example may contain sodium hypochlorite). The cabinet also contains a dosage feeding pump 4a together with its motor (integrated in the unit 4a), a suction conduit 3a from the container 2a to the pump 4a, and a dosage feeding conduit 5a from pump 4a to a dosage supply point 6a on the conduit section 44a in the safety cabinet 23a.

The foregoing description of the safety cabinet 23a also applies to the safety cabinet 23b, which is equipped in identically the same way, corresponding details being given the same reference numerals with the addition b.

Usually, however, the container 2b in the second safety cabinet contains another chemical than the container 2a in the first cabinet, for example concentrated hydrochloric acid.

The two safety cabinets 23a and 23b have a control unit 12x in common which controls the two pumps 4a and 4b such that the pumps will feed the intended amount of chemicals from the two containers 2a and 2b in response to measuring data received from the metering unit E. If the flow in the conduit 44 would fall below a certain critical value, the flow meter 55 will emit a signal to the control unit 12x, so that the power supply to the motors of the pumps 4a and 4b will be stopped. This makes it impossible that any liquid having a dangerously high concentration of the chemicals in question can leave the safety cabinets 23a and 23b via the by-pass conduit 44. Further, in the region of the embankment 29a there is a number of sensors 21a provided to emit a signal to the control unit 12x in case liquid would be detected inside the embankment 29a, for example because of leakage from the container 2a, from the suction conduit 3a, the dosage supply conduit 5a, the pump 4a, the dosage supply point 6a, or from the conduit section 44a, i.e. from any of those units which convey or which contain the chemical in question in the safety cabinet 23a, the control unit 12x being responsible for stopping the pump 4a.

The safety cabinet 23a also has a number of air inlet openings 20a at a level above the embankment 29a, and at the top there is a suction fan 31a with a duct for leading away the sucked out air from the premises.

It should be noted that the safety system described with reference to Fig. 5 has the great advantage that chemicals at a high concentration will never leave the safety cabinets 23a and 23b, ^respectively, since the very dosage supply will be performed inside the cabinets, in the present case to a by-pass conduit 44 of a main conduit 40 conveying the liquid to be treated to a final recipient body 1. The system at the same time has the advantage that the supply chemicals are supplied successively and are diluted in the receiving liquid; first in the by-pass conduit 44 when they are dispensed in the dispensing or dosage supply points 6a and 6b in the safety cabinets 23a and 23b, respectively, thereafter in the main conduit 40 and finally in the main recipient 1.

Figs. 6 and 7 show more in detail how a safety cabinet 23a is designed according to a preferred embodiment. The general construction of the cabinet 23a corresponds to that of the cabinet 23, which has been described in the foregoing with reference to Figs. 1 and 2. The difference in the first place lies in the arrangement of conduits in the cabinet and in the construction principles which are based on the use of a number of premanufactured units or sections which are united to each other. The bottom portion of the cabinet 23a is designed as a trough or a tub made in one piece of glass-reinforced polyester plastics. This trough or tub according to the embodiment has an essentially flat bottom and straight vertical walls, which form the embankment 29a. In the trough/embankment 29a two containers 2a and 2a' are placed, the latter one 2a' being a spare can to be used when the first container/can 2a has been emptied. The embankment/tub 29a has a sufficient volume to accomodate the content of the two cans 2a, 2a¹.

The cabinet 23a further consists of two end sections 28a' and 28a' ' and two identical intermediate sections 60a, which in their turn each consists of a top portion 24a and a rear portion 27a. The top portion 24a extends downwards a piece on the front side as well as on the rear side. The main part of the front is used for an opening 61a, which can be closed by means of two doors 30a made of a transparent polycarbonate plastics. The embankment, the walls and the roof of the cabinet can be made e.g. of an ABS-plastic based material with an acryl plastic coating but they can also be made of a stainless or an acid resistant steel, aluminium, etc, if the cabinet shall be more burgler-safe. It should also be noted that the whole of the cabinet 23a can be made e.g. of a stainless or an acid resistant steel, aluminium or other metals which are resistant to those chemicals which are kept in the containers in the cabinet. According to the disclosed embodiment, however, the cabinet completely consists of glass- reinforced polyester plastics with the exception of the doors 30a, which consist of a transparent material. The doors 30a are fastened on the end sections 28a', 28a' ' by means of hinges, while the other parts of the cabinet are secured to each other by means of flange joints, the flanges being directed outwards and facing each other, being glued and riveted. A flange joint of this type between the two roof portions 24a has been designated 62a. A bar 63a extends between the united roof portions 24a and the bottom trough/embankment 29a.

The section 44a of the by-pass conduit 44 of the main conduit 40 shown in Fig. 5 extends through the safety cabinet 23a. At the exterior of one end section 28a', on the inlet side of the by-pass conduit, there is a flow meter 55, which is in common for the two cabinets 23a and 23b, Fig. 5. The flow meter 55 is of a type which allows visual reading and which also is provided with a sensor 55' placed on the end section 28a', and which will emit a signal to the control unit 12x, if the flow would fall below a certain predetermined value. More particularly, the flow meter 55 is of a type which contains a floating body in a graduated conical passage of transparent material. The floating body may consist of a magnetic material, which can be detected by sensor 55' .

The sensors 21a, which are placed at different points close to the bottom of the embankment 29a, are only indicated schematically.

On top of the cabinet 23a there is a fan 31a and a conduit for sucking out air from the premises in which the cabinet 23a is placed. Between the doors 30a of the cabinet and the embankment/bottom trough 29a there is a gap 20a, which functions as an air entrance opening.

In Fig. 6 there is also shown how the suction conduit 3a extends up from the container 2a to the pump 4a and further by a dosage feeding conduit 5a to the dosage supply point 6a on the conduit section 44a, which extends through the cabinet 23a.

The invention is not restricted to the disclosed embodiments, and modifications are conceivable within the frame of the invention. The safety cabinet thus need not necessarily have the geometrical design which has been described in the foregoing. Among conceivable modifications can be mentioned that the walls of the embankment not necessarily need to be defined by the outer walls of the bottom portion. Instead a surrounding embankment can be provided inside the outer walls of the bottom portion, so that there is formed a circumferential trench between the embankment and the outer walls of the bottom portion. It is also possible per se to combine the different embodiments described in the foregoing with each other.

Claims

1. Safety system for the deposition and feeding of liquid chemicals, c h a r a c t e r i z e d in that the chemicals are deposited in at least one container in a safety cabinet (23, 23a), that there is at least one dosage feeding pump (4, 4a) in the safety cabinet and at least one suction conduit (3, 3a) through which said chemicals can be conveyed up from the said at least one container for said dosage feeding, that a surrounding embankment (29, 29a) is provided in the bottom portion of the safety cabinet, said embankment consisting of a material which is resistant to the chemicals contained in the container or containers in the safety cabinet and which embankment can accomodate the content of container or containers placed in the cabinet, that one or more first sensors (21, 21a) sensitive to liquid are provided inside the surrounding embankment, and that the safety system includes a control unit (12, 12x) in connection with said sensor or sensors provided to stop the dosage feeding pump if liquid would contact the said first sensor or sensors.

2. Safety system according to claim 1, c h a r a c t e r i z e d in that the safety cabinet is equipped with a ventilation device (31,

31a) provided to secure that an underpressure is maintained in the cabinet, and at least one air inlet opening (20, 20a) in the bottom portion of the cabinet but at a level above the embankment.

3. Safety system accdording to claim 1 or 2, c h a r a c t e r i z e d in that said at least one conduit comprises a suction conduit (3) between the container and the dosage feeding pump (4) and a dosage feeding conduit (5) which extends from the dosage feeding pump to a dosage point (6) and is provided with a protective casing (9) surrounding the dosage feeding conduit, the space (9') between the dosage feeding conduit (5) and the protective casing (9) being a volume which is tightly closed with the exception of an opening (13) which is located in said safety cabinet.

4. Safety system according to claim 3, c h a r a c t e r i z e d in that the safety cabinet (23) is equipped with a hose or pipe conduit (11a) provided to lead away any liquid, which possibly may appear at said opening (13), to the region surrounded by the embankment (29) in the bottom portion of the cabinet.

5. Safety system according to any of claims 1-4, c h a r a c t e r i z e d in that one or more sensors (7, 8) sensitive to liquid are provided in the space (9') between the dosage feeding conduit and the surrounding protective casing (9'), preferably on one or both ends of the casing, which second sensors are connected to said control unit in order to stop the dosage feeding pump (4) if liquid would contact said second sensors.

6. Safety system according to claim 1 or 2, c h a r a c t e r i z e d in that a dosage receiving conduit (44a) extends through the safety cabinet (23a), that a liquid to which the said chemicals shall be supplied is provided to be conveyed through said dosage receiving conduit (44a) which extends through the cabinet, and that the dosage feeding conduit (5a) does not extend outside of the safety cabinet but entirely inside the cabinet between the dosage feeding pump (4a) and the dosage supply point (6a), which is located in the safety cabinet.

7. Safety system according to claim 6, c h a r a c t e r i z e d in that the dosage receiving conduit is a by-pass conduit (44) of a main conduit (40) for that liquid to which said chemicals shall be supplied, wherein means are provided for leading a predetermined, adjustable flow of the liquid from the main conduit through the by-pass conduit in which the chemicals are supplied to the liquid and further into the main conduit again and eventually to a final recipient body (1) of liquid, wherein the chemicals successively are mixed into and diluted in the liquid.

8. Safety system according to claim 7, c h a r a c t e r i z e d in that a flow meter (55) is provided in the by-pass conduit (44) and is connected to said control unit (12x) to emit a signal to stop the dosage feeding pump (4a) or pumps (4a, 4b) if the flow in the by-pass conduit would fall below a predetermined value.

9. Safety cabinet for the deposition of liquid chemicals contained in at least one container placed in the cabinet, c h a r a c t e r i z e d in that a surrounding embankment (29) is provided in the bottom portion of the cabinet, said embankment consisting of a material which is resistant to the content of the container or containers placed in the cabinet and that one or more sensors (21, 21a) sensitive to liquid are provided inside the surrounding embankment.

10. Safety cabinet according to claim 9, c h a r a c t e r i z e d in that the cabinet is equipped with a ventilation device (31, 31a) provided to secure that an underpressure is maintained in the cabinet and at least one air inlet opening (20, 20a) in the bottom portion of the cabinet but at a level above the embankment.

11. Safety cabinet according to claim 9 or 10, c h a r a c t e r i z e d in that the bottom portion of the cabinet has a larger extension in the horizontal direction than the top portion of the cabinet.

12. Safety cabinet according to claim 11, c h a r a c t e r i z e d in that the bottom portion of the cabinet has the shape of a trough which is rectangular in horizontal section and has straight walls, said trough defining said embankment (29a), that the side walls and the rear wall of the cabinet above the embankment are vertical, stright extensions of the side walls and of the rear wall of the trough, while the front of the cabinet is inclined inwards, and that at least one opening (61a) is provided in the inclined front, which opening can be closed and opened by at least one door (30, 30a).

13. Safety cabinet according to any of claims 9-12, c h a r a c t e r i z e d therein that in the cabinet there is at least one dosage feeding pump (4, 4a) with a suction conduit (3, 3a) by means of which chemicals can be sucked up from said at least one container in the cabinet.

14. Safety cabinet according to any of claims 9-13, c h a r a c t e r i z e d in that the cabinet is equipped with a control unit (12) connected to the sensor or sensors (21, 21a) inside the embankment and provided to stop the pump (4, 4a) if liquid would contact the sensor or sensors.

15. Safety cabinet according to any of claims 9-14, c h a r a c t e r i z e d in that a through conduit (44a) extends through the cabinet (23a) at a level above the embankment, and that the dosage feeding conduit (5a) terminates in said through conduit for the supply of said chemicals from said container.

16. Safety cabinet according to any of claims 9-15, c h a r a c t e r i z e d in that it mainly consists of a number of sections, each one of which is made in one piece and which generally are united to each other through flange joints (62a), said sections being said trough shaped bottom portion (29a), two end sections (28a¹, 28a'¹), and at least one intermediate section (60a) defining the main part of the rear wall of the cabinet, the top portion of the cabinet and the front above said opening of the cabinet.

17. Safety cabinet according to claim 16, c h a r a c t e r i z e d in that it has two or more equal intermediate sections arranged side by side between the end sections, which intermediate sections in their turn may consist of a top portion and a rear portion.