PROCESS FOR LEAK DETECTION IN CATALYST PRODUCTION

Abstract

The present invention is directed to a process, which can be used in the production of exhaust catalysts. In particular, the present process describes way of testing the leak-tightness of the coating equipment before a new coating campaign begins or during a running campaign.

Claims

1. Process for leak detection in a device (122) used for the production of automotive exhaust catalysts, the device (122) comprising a coating chamber (127) in which at least two sensors (123, 126) for measuring the height of the washcoat are positioned at different levels within the coating chamber (127) and being connected to a controlling unit (125), comprising the steps of: a) introducing washcoat (113) into the coating chamber (127) up to a fixed level (130) between the lower (126) and the upper sensor (123); b) waiting at least 5 s; and c) analyzing whether the controlling unit (125) signals that the washcoat level (130) continues to increase and touches the upper sensor (123) or signals if the contact to lower sensor (126) is lost.

2. Process according to claim 1, characterized in that, the time for waiting is more than 5 s but below 30 s.

3. Process according to claim 1, characterized in that, a conductivity sensor is used.

4. Process according to claim 1, characterized in that, the at least two sensors (123) and (126) are positioned at a level distance of 20-1 mm within the coating chamber (127).

5. Process according to claim 1, characterized in that, this process is performed before starting a new campaign for zone coating monoliths.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 (example of prior art for coating a carrier): [0034] 100 actuator [0035] 101 piston [0036] 102 cylinder [0037] 103 liquid [0038] 104 connection [0039] 110 channels—in the substrate 121 [0040] 111 displacement body [0041] 112 tank [0042] 113 coating medium [0043] 114 line section [0044] 115 multiway valve [0045] 116 line section [0046] 117 filling flow direction [0047] 118 return flow direction to remove coating medium 113 [0048] 119 discharge pump [0049] 120 connecting line leading to the reservoir for the coating medium [0050] 121 substrate [0051] 122 coating device [0052] 123 upper sensor for detecting the level 130 [0053] 125 control unit [0054] 130 first washcoat level—of 113 in the coating device 122 [0055] 132 second washcoat level—of 113 in the substrate 121

[0056] FIG. 2 (example of prior art for coating a carrier): [0057] 200 actuator [0058] 201 piston [0059] 202 cylinder [0060] 203 liquid [0061] 204 connection [0062] 210 channels—in the substrate 221 [0063] 211 displacement body [0064] 212 tank [0065] 213 coating medium [0066] 214 line section [0067] 215 multiway valve [0068] 216 line section [0069] 217 filling direction [0070] 218 extraction flow direction of 213 [0071] 219 discharge and extraction pump [0072] 220 connecting line leading to the reservoir for excess coating medium 213 [0073] 221 substrate [0074] 222 coating device [0075] 223 upper sensor for detecting the level 230 [0076] 225 control unit [0077] 230 first washcoat level—of 213 in the coating device 222 [0078] 232 second washcoat level—of 213 in the substrate 221

[0079] FIG. 3: [0080] 300 substrate [0081] 301 end face [0082] 302 circumferential surface [0083] 303 first partial length zone [0084] 304 spacing—between the two partial lengths 303 and 305 [0085] 305 second partial length zone [0086] 310 channels—in the substrate 300 [0087] 330 first coating—in the channels 310 [0088] 340 second coating—in the channels 310 [0089] L total length of the substrate 300

[0090] FIG. 4 (partial picture taken from FIG. 1 showing upper and lower sensor arrangement for detecting leaks according to the invention):

[0091] Numerals like FIG. 1 [0092] 126 lower sensor [0093] 127 coating chamber

[0094] FIG. 5: [0095] 427 coating chamber [0096] 440 flap

DETAILED DESCRIPTION OF THE DRAWINGS

[0097] FIG. 1 shows an arrangement according to DE102010007499 for coating channels (110) in a substrate (121), which has a piston (101), actuated by an actuator (100), in a cylinder (102), which is filled with liquid (103) and, through a connection (104) of the cylinder (102) to the displacement body (111), allows the actuation of the displacement body (111) in the tank (112), which is filled with liquid coating medium (113) and has two line sections (114, 116) with an interposed multiway valve (115) between the tank (112) and the coating device (122), wherein the coating device (122) is provided with the substrate (121) and with sensors (123) for determining the first level (130). Additional sensors (124) are used to monitor the displacement volume of the coating medium (113) and the state of the displacement body (111) in the tank (112).

[0098] The values determined by the sensors (123, 124) are transmitted to a control unit (125) which, for its part, controls the actuator (100) and hence the piston (101).

[0099] On the one hand, the multiway valve (115) switches the filling of the coating device (122) with coating medium (113) up to the first level (130) in the filling flow direction (117) and, on the other hand, after the second level (132) in the substrate (121) is reached, switches, in the return flow direction (118), the connection to the discharge pump (119) and to the connecting line (120) leading to a storage tank for excess coating medium (113) and for holding it ready for further use.

[0100] All the control commands required for this purpose are preferably likewise output by the central control unit (125).

[0101] FIG. 2 shows an arrangement according to DE102010007499 for coating channels (210) in a substrate (221), which has a piston (201), actuated by an actuator (200), in a cylinder (202), which is filled with liquid (203) and, through a connection (204) of the cylinder (202), communicates with the tank (212), in which the displacement body (211) is situated, which contains liquid coating medium (213) and is connected via two line sections (214, 216) with an interposed multiway valve (215) to the coating device (222), which is provided with a substrate (221) and sensors (223) for determining the first level (230) of coating medium (213).

[0102] By means of the additional sensors (224) on the tank (212), the displacement volume of coating medium and the state of the displacement body (211) in the tank (212) are monitored. The values determined by the sensors (223, 224) are transmitted to a control unit (225) which, for its part, controls the actuator (200) and hence the piston (201).

[0103] On the one hand, the multiway valve (215) switches the filling of the coating device (222) with coating medium (213) up to the first level (230) in the filling flow direction (217) and, on the other hand, after the second level (232) in the substrate (221) is reached, switches, in the return flow direction (218), the connection to the discharge pump (219) and to the connecting line (220) leading to a storage tank for excess coating medium (213) and for holding it ready for further use. All the control commands required for this purpose are preferably likewise output by the central control unit (225).

[0104] FIGS. 3A and 3B show in perspective a substrate (300), which has a section broken away in three planes in the central part thereof to make it possible to see into the coating structure according to the invention.

[0105] The substrate (300), which is coated in two partial length zones (303, 305), has two end faces (301), a circumferential surface (302) and a length (L) and is traversed by a multiplicity of channels (310) between the two end faces (301).

[0106] A first coating (330) is applied to a first partial length zone (303) in the channels (310), while a further partial length zone (305) is provided with a second coating (340).

[0107] Between the two partial length zones (303) and (305) or between the two coatings (330) and (340) there is a coating-free zone (304), as FIG. 3B, in particular, shows on an enlarged scale.

[0108] FIG. 4 shows an exemplary arrangement of the invention for coating channels (110) in a substrate (121). The liquid coating medium (113) is filled through line sections (116) into the coating apparatus (122), wherein the coating apparatus (122) is provided with the substrate (121) and with sensors (123, 126) for determining the first level (130) and its accuracy. The values determined by the sensors (via 123 and 126) are transmitted to a control unit (125) which, for its part, controls at least the further pumping or suction of the coating slurry based on the above-mentioned analysis. After being submitted into the coating chamber (127) the washcoat surface (130) lies between both sensors (123, 126). It is monitored whether this surface (130) migrates with time upwards or downwards as described above. The time needed to receive a signal from either sensor (126) or sensor (123) can relate to the magnitude of leakage present.

[0109] FIG. 5 shows a further arrangement to which the present invention can be applied advantageously. Displayed is a cross-section of a coating chamber (427) which comprises a different filling and emptying mechanism than presented in FIGS. 1 and 2, respectively. Here the filling of the coating chamber is done by lines approaching the chamber (427) at its side (not shown). Discharging the washcoat out of the chamber (427) is done through the flap (440) which disconnects the discharging line (not shown) to a sub-pressure tank (not shown).

[0110] Hence, with this invention in an initial trial before starting a new coating campaign or even during a running campaign an easy check can be made with regard to leak-tightness of the coating equipment used. This invention achieves a preferable coating result in a very easy but nonetheless surprisingly effective manner. In that at least two sensors are located in the coating chamber in an intelligent way it is possible not only to measure the level of the coating slurry directly in the coating chamber before coating begins to a more precise extent but one may, on the other hand, also determine whether a leak exists which would lead to false zone coated parts. The present invention greatly helps to avoid this and thus serves to have less coated monoliths falling out of specification. Hence, this invention allows to improve the economy of a process for coating exhaust catalysts. This was not made obvious from the prior art teaching at the date of this invention.