The invention is for a clamping device for retaining an explosion panel on the safety opening of holders in which there is a powder, gas or vapour, which explosion panel in the event of excess pressure, for example resulting from an explosion in the holder, is thrown open or blown away, so that the holder sustains little or no damage.

European patent application 88201561.3 of applicant des¬ cribes a clamping device of this sort in which use is made of a stiff explosion panel in stainless steel which is provided all around with a side with a clamping edge which is folded inwards, on which grip the free ends of several inclined clip strips which are directed towards said clamping strip and which are attached to a frame provided around the safety opening of the holder and thus press the explosion panel firmly to the frame.

When an explosion occurs in the holder, the explosion panel is raised by the generated pressure and the stiff clamping edge of the explosion panel bends the free ends of the clip strips upwards, causing the explosion panel to slide freely over the clip strips and be blown away from the safety opening.

A disadvantage of such an explosion panel with clamping edges is that the stainless steel from which the panel is made is an expensive material and that moreover the pro- duction of such a panel which must be pressed into a cer¬ tain form in order to give it adequate stiffness is ex¬ pensive. Another disadvantage is that dirt can easily

lodge between the clip strips and the clamping edge of the panel, so that it is more difficult for the clip strips to react and only when the pressure on the explo¬ sion panel is greater than intended. Another disadvantage is that when the opening pressure of the explosion panel is high, the inclined clip strips must hold the clamping edge of the panel firmly against the edge of the safety opening, so that for blowing away the panel, the addition¬ al friction which arises during the raising of the panel between the panel and the frame provided around the safety opening, must be overcome. The opening pressure required for this is consequently difficult to predict.

In order to remedy these disadvantages a clamping device has, pursuant to the chief characteristic of the invention, been realized which consists of several upright connecting blocks, for each connecting block a housing which fits over same for protecting the connecting block, in each housing two clamping edges which lie opposite one another, which clamping blocks and housings are mounted at a dist- ance from one another around the perimeter of the explo¬ sion panel and the frame, and in each housing at least two diverging clip strips one end of which is mounted on the connecting block while the other end presses on one of the clamping edges of the housing for connecting the housing with the connecting block or the explosion panel with the holder.

The use of two diverging clip strips means that the re¬ sultant of the two pressures acting obliquely on the clamping edges is vertical, so that the whole is in equi- librium and the explosion panel is blown away vertically, so that furthermore all friction between the explosion panel and the frame fastened around the safety opening is avoided. Another advantage is that each individual clamp¬ ing device is sheltered in a sealed housing, so that no

problems with the accumulation of dirt need be feared and that the replacement of the clamping means is easy to carry out. Another major advantage is that this clamping device permits the use of a common and inexpensive com- posite panel such as used in building structures and which are less subject to deformation than explosion panels in stainless steel. Moreover such panels have ex¬ tremely good thermal insulating characteristics and in many cases prevent the formation of condensation on the panel.

By way of example a more detailed description of a pre¬ ferred but in no way limited embodiment of the clamping device pursuant to the invention follows below. This des¬ cription refers to the attached drawings where : fig. 1 shows a front elevation of the clamping device and the explosion panel mounted on the holder; fig. 2 shows a plan view of the same; fig. 3 shows an enlarged longitudinal section through one of the elements of the clamping device along line III-III in fig. 2; fig. 4 shows the same longitudinal section as that in fig. 3 but where the explosion panel is released from the holder; fig. 5 shows a cross section of one element of the clamp- ing device along line V-V in fig. 3.

In these figures can be seen the holder 1 in which any sort of powder, gas or vapour is present and which is pro¬ vided with a safety opening 2 which must be closed. Around this opening a frame 3 is mounted on the holder in any way whatsoever. On this frame several upright connecting blocks 4 are mounted at a distance from one another by means of screws 5. Each connecting block 4 has a threaded opening 6 in which the height of a screw 7 can be set. This screw passes through an opening which is provided in

a bearing element 8 the cross section of which is an in¬ verted L and on which the head of screw 7, which serves to preset the tension, can exert pressure. One end of each of the two diverging straight clip strips 9 which lie in a plane which runs parallel to the longitudinal direction of frame 3 engages in this bearing element 8. The other end of each clip strip 9 engages in a clamping edge 10 provided on the lower edge of each end surface of a housing 11 the bottom surface of which is open and which fits over the connecting block 4 and closes against its base, so that the whole is adequately protected against deposits of dirt. Each housing 11 is attached by one side surface by means of screws 12 to the side of a stiff ex¬ plosion panel 13 which consists by preference of a compo- site panel such as used in building structures. Each housing 11 is provided with a cover 14 which enables the clip strips 9 to be easily installed in the housing and the screw 7 and the supporting element 8 to be adjusted in height so that preset tension of the clip strips 9 and consequently the clamping force between the housing 11 and the connecting block is adjustable. The pressure at which the explosion panel will be blown away is determined by the buckling strength of the clip strips and thus lar¬ gely depends on the material selected and the dimensions of the clip strips.

When an explosion occurs in the holder 1, the generated pressure exerts upward pressure on the explosion panel 13, which pressure is transferred by the housings 11 with clamping edges 10 to the clip strips 9. When the buckling strength of the clip strips 9 is exceeded, these strips buckle, so that the explosion panel 13 with the housings 11 slides vertically over the connecting blocks 4 and is blown away from the safety opening 2 of the holder 1. After a mild explosion the explosion panel is usually not damaged and it is sufficient to replace the clip

strips and/or the connecting blocks 4 and the housings 11 in order to return the clamping device to service.

It goes without saying that the form, the number and the dimensions of the components described above may differ and that some of these components might be replaced by others which are intended for the same purpose. Thus in¬ stead of straight clip strips use could be made of pre¬ formed single or multiple clip strips.