Patent Number: 048658030
Section: description

DESCRIPTION OF A PREFERRED EMBODIMENT As shown in FIG. 1 a plurality of modular conduit units 1 are screwed to one another so as to be sealed by gaskets 2 disposed at their interfaces. The conduit units as such are shown in FIG. 2. Together they form discharge conduit structure 10 providing a discharge path from the interior of a reactor safety containment to the atmosphere, generally by way of an exhaust stack associated with the reactor plant. At their sides the modular conduit units have side openings 3 and 4 bounded by flanges 5 and 6. The bottoms 7 of the modular conduit units 1 are preferably recessed so that they are somewhat lower than the lower edge of the side openings 3 and 4 as shown in FIG. 1 so as to retain therein any condensate. The flanges 5 and 6 consist of angle iron frames which are welded to the units 1. All the units 1 are supported on a support frame 8. The conduit units have attached thereto filter stages 12 each including a prefilter 9 and a main filter 11 both consisting of stainless steel fiber packs as filter elements. The filters 9 and 11 as shown in FIG. 3 are stainless steel fiber mats whose fibers may have a diameter down to 2 .mu.m. The filter stages 12 of the conduit structure 10 shown in FIG. 1 are arranged in a particular manner. The filter stages 12 are formed by identical frame members 13 and 14 which are mounted together by bolts 15 and 16 in a manner such that they are sealed with respect to one another. The frame members 13 and 14 consist of hollow sheet metal casings which have flanges 17, 18 and 19, 20 welded to the opposite ends thereof. The frame member 13 is bolted with its flange 17 to the flange 6 or, on the opposite side of the unit 1, flange 5 (see FIG. 2), with the gasket 21 sealingly disposed therebetween. Further bolting connections of the filter stages 12 are made in the same manner. A U-shaped member 22 is welded with its back side 23 to the flat face at the inner end of flange 18 such that the legs 24 of the U-shaped member project from the flange face. The edges 25 and 26 of the filter packs 9 and 11 are disposed between the projecting legs 24 of the U-shaped member 22 and the flange 19 of the adjacent frame member 14 so that, upon tightening of the bolts 16, the edges 25, 26 of the filters are firmly clamped therebetween thereby forming circumferential concentric seals 27 and 28 providing for a double seal structure. In the process the circumferential edges 25 and 26 of the filters are compressed to a fraction of their original thickness. The flanges 19 of the frame members 14 have perforated retaining plates 29 welded thereto at their inner edges so that the filters 9 and 11 may be flatly supported thereby at their flat downstream sides 30. Additional perforated plates 31 are inserted into the interior of the frame members 13 which engage the filters 9 and 11 at their curved upstream side 32. The curved upstream side 32 is further provided with a stainless steel cloth 33 which follows the curved filter surface and engages and retains the filter fibers so as to prevent fraying of the filter packs. The stainless steel cloth 33 is clamped between the flanges 18 and 19 together with the filter edges 25 and 26. The space remaining between the flanges around the filter edges 25 and 26 in the area of the bolts 16 is filled with a heat resistant sealing material which is cast into that space. The normal flow direction is given by arrow 35, that is, the discharge air is supplied to the filter stages from the curved side 32 of the filters as shown in FIG. 3, but the filter stages may also be arranged in the manner opposite to that shown in FIG. 3. The conduit unit together with the filter elements on their sides are disposed in a discharge collection chamber which is in communication with an exhaust stack so that the discharge air, after passage through the filter elements, is collected for discharge through the exhaust stack. REFERENCE NUMERALS 1: Modular conduit unit 2: Gaskets 3, 4: Side openings 5, 6: Flanges 7: Recessed bottom 8: Support frame 9: Prefilter 10: Discharge conduit structure 11: Main filter 12: Filter stages 13, 14: Frame members 15, 16: Bolts 17, 18: Flanges 19, 20: Flanges 21: Gasket 22: U-shaped member 23: Back side 24: Legs 25, 26: Edges 27, 28: Seals 29: Perforated retaining plate 30: Flat downstream side 31: Perforated plate 32: Curved filter side 33: Stainless steel cloth 34: Sealing material 35: Flow direction arrow.