DE112010005206T5 - Method for producing an insulated exhaust device - Google Patents

Abstract

There is provided a method of manufacturing an exhaust aftertreatment or acoustic device (18) having a maximum operating temperature Tmax. The method comprises the steps of providing a blanket (28) of silica fiber insulation material having a weight percent SiO 2 greater than 65%; Heating the blanket (28) so that all of the silica fiber insulating material is heated to a temperature T greater than Tmax; and inserting the blanket (28) into the device (18) after the heating step.

Description

CROSS REFERENCE TO SIMILAR APPLICATIONS

Not applicable.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

MICROFICHE / COPYRIGHT REFERENCE

Not applicable.

FIELD OF THE INVENTION

This invention relates to exhaust aftertreatment and / or acoustics systems and the devices used therein which use insulating blankets or fiber mats.

STATE OF THE ART

Heat-insulating fiber mats and blankets are used in exhaust systems to provide thermal insulation to the system's acoustic and aftertreatment devices to control heat transfer to and from the devices. It is known to bring such heat insulating blankets between adjacent wall surfaces of such a device, wherein the material of the heat insulating blanket is compressed to provide a desired installed density for the material so as to help the heat insulating blanket in its mounting position by frictional forces between the blanket Ceiling and the adjacent wall surfaces to hold. Cost is usually an important issue in any commercial system, and a cost efficient thermal insulation blanket material is made from silica fiber insulation material that has a weight percent SiO ₂ of greater than 65%. Unfortunately, when such a material was used in an exhaust aftertreatment device, the material failed after a period of time because the thermal insulation blanket was unable to maintain adequate frictional engagement with the adjacent side walls to prevent destructive movement of the insulation blanket in the component.

BRIEF SUMMARY OF THE INVENTION

According to a feature of the invention, there is provided a method of manufacturing an exhaust aftertreatment or acoustic device having a maximum operating temperature Tmax. The method comprises the steps of: providing a blanket of silica fiber insulation material having a weight percent SiO ₂ greater than 65%; Heating the blanket so that all of the silica fiber insulating material is heated to a temperature T greater than Tmax; and installing the blanket in the device after the heating step.

As a feature, T is at least 1.05 × Tmax.

In one feature, the installation step includes inserting the blanket so that the blanket is compressed between two adjacent faces of the device to achieve an average built-in density of 0.18 grams / cubic centimeter to 0.30 grams / cubic centimeter of the insulation material in the blanket.

In one feature, the blanket is in an uncompressed state during the heating step.

As one feature, during the heating step, the blanket is heated in a rolled condition, the blanket being formed into a roll having a central axis. In another feature, the blanket is rotated about the central axis during the heating step.

According to one feature, the blanket is flat during the heating step.

In one feature, Tmax is in the range of 300 ° C to 1100 ° C.

As one feature, the installation step includes inserting the blanket so that the blanket encloses a core of the device through which the exhaust gas flows.

In one feature, the silica fiber insulating material has a weight percentage of SiO ₂ of more than 95%.

According to a feature of the invention, there is provided a method of manufacturing an exhaust aftertreatment or acoustic device having a maximum operating temperature Tmax. The method comprises the steps of: providing a blanket of silica fiber insulation material having a weight percent SiO ₂ greater than 65%; Heating the blanket so that all of the silica fiber insulating material is heated to a temperature T greater than Tmax; and inserting the blanket into the device after the heating step so that the blanket encloses a core of the device through which the exhaust flows, and the blanket is pressed between two adjacent faces of the device to an average built-in density of 0.18 grams / cubic centimeter up to 0.30 grams / Cubic centimeter of insulation material in the ceiling.

Other objects, features and advantages of the invention will be apparent from a review of the entire specification including the appended claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

1 is a schematic representation of an exhaust system which employs the invention;

2 is a sectional view of an exhaust system component, the invention of 1 in use, with a view from line 2-2 in 1 ;

3 Fig. 12 is a schematic side elevational view of a heat treatment process used in the invention;

4 Fig. 12 is a schematic perspective view illustration of an alternative heat treatment process used in the invention; and

5 Figure 11 is a plan view of another schematic showing another alternative embodiment of a heat treatment process used in the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An exhaust system 10 is in 1 shown in the form of a diesel exhaust aftertreatment system for treating the exhaust gas 12 from a diesel combustion process 14 serves, such as from a diesel engine 16 , The exhaust 12 typically contains oxides of nitrogen (NO _x ), such as nitrogen oxide (NO) and nitrogen dioxide (NO ₂ ) among others, particulate matter PM, hydrocarbons, carbon monoxide (CO) and other combustion by-products. The system 10 includes one or more exhaust acoustic and / or aftertreatment devices or components 18 , wherein each device has a corresponding operating temperature Tmax, which during operation of system 10 can be achieved. Examples of such devices 18 include catalytic converters, diesel oxidation catalysts, diesel particulate filters, gas particulate filters, NO _x storage catalytic converters, selective catalytic reduction monoliths, burners, manifolds, interconnecting pipes, mufflers, resonators, exhaust pipes, exhaust control system housings, isolation rings, insulated tips, insulated end caps, insulated inlet pipes and insulated exhaust pipes, all with random ones Cross-sectional geometry, many of which are known. As those skilled in the art will recognize, some of the foregoing devices are 18 purely metallic components with a central core 19 through which the exhaust gas 12 streams, and other devices 18 can a core 19 in the form of a ceramic monolithic structure and / or a metallic fabric structure through which the exhaust gas 12 flows. These devices 18 They are commonly used in motor vehicles (diesel or gasoline), construction equipment, locomotive applications (diesel or petrol), marine engine applications (diesel or gasoline), small internal combustion engines (diesel or gasoline) and stationary power generation (diesel or gasoline).

2 shows an example of such a device 18 for use in system 10 in the form of a catalytic unit 20 that have a catalytic core 22 , a mounting mat 24 , a cylindrical inner housing or box 26 and the thermal insulation blanket or fiber mat 28 and a cylindrical outer casing or sheath 30 Has. The core 22 is usually a ceramic substrate 32 which has a monolithic structure with a catalyst coated thereon, and usually has an oval or circular cross-section. The mounting mat 24 is sandwiched between the core 22 and the can 26 as an aid in protecting the core 22 against shock and vibration forces coming from the can 26 to the core 22 can be transmitted. Normally, the mounting mat 24 made of a heat-resistant and shock-absorbing material, such as a mat of glass fibers or mineral wool, and is compressed between the can and the carrier to produce a desired holding force.

The heat insulation blanket 28 consists of a silica fiber insulation material having a weight percent SiO ₂ greater than 65% and in preferred embodiments more than 95% and in the best embodiments more than 98%. Such a material is known and commercially available, a suitable example of BGF Industries, Inc. is supplied under the trade name SilcoSoft ^®, and a further suitable example of Asglawo techno GmbH fiber is supplied under the trade name Asglasil ^®. Such material is usually supplied in rolls, with the individual blankets 28 to the appropriate length and width for the appropriate device 18 punched after the material has been removed from the roll. The ceiling 28 is preferably sandwiched or compressed in the annular gap 34 between the outer surface 36 the can 26 and the inner surface 38 of the housing 30 to an average build density of 0.18 grams / cubic centimeter to 0.30 grams / cubic centimeter of the silica fiber insulation blanket material 28 to reach. This ensures a sufficient friction connection between the ceiling 28 and the surfaces 36 and 38 to keep the blanket in its desired location. It can be seen that the ceiling 28 between other adjacent surfaces of a device, including, for example, a pair of planar adjacent surfaces, a pair of non-planar adjacent surfaces, a pair of conical adjacent surfaces, or any other pair of adjacent surfaces used in acoustic or post-treatment devices Exhaust systems are found, though the ceiling 28 in a compressed state in the annular gap 34 between the cylindrical box 26 and the housing 30 will be shown.

According to the invention, the blanket 28 heat treated before the ceiling 28 into the device 18 is used to achieve a calcination of the silica fiber insulation material. In this regard, the ceiling is 28 so that heats all the silica fiber insulation material in the ceiling 28 to a temperature T greater than the maximum operating temperature Tmax of the device 18 is brought. This heat treatment improves the resistance and erosion resistance of the silica fiber insulating material and also eliminates the potential for a "heat cure failure mode" that can result when the silica fiber material is in place in the device 18 during operation of the system 10 would be calcined. This heat treatment preferably takes place with the ceiling 28 in an uncompressed or free state, with no compressive forces acting on the silica fiber insulation material of the blanket 28 be applied. The temperature T preferably has a certain safety margin above the maximum operating temperature Tmax of the device 18 , where the preferred safety margin is 1.05 x Tmax.

As in 3 It is also preferable that the heat treatment be performed using an industrial furnace 40 takes place, wherein the silica fiber heat insulating material from a supply roll 42 of the material unwound and just through the oven 40 on a conveyor belt 43 is sent, leaving the ceiling 28 during the heat treatment is even to different heating of the material of the ceiling 28 and variations in the thickness of the material in the ceiling 28 to reduce or prevent. After the heat treatment, the individual ceilings can 28 be punched to the desired length and width before moving in device 18 to be built in. As an alternative, the entire delivery roll 42 of the silica fiber thermal insulation material, with or without rotation of the roll 42 around its central axis 44 in a stove 46 heat treated, as in 4 shown. In this regard, it is believed that turning the roll 42 around its axis 44 serves to prevent a different warming in the role. Again, the individual ceilings 28 to the desired length and width after the heat treatment and before installation in the device 18 be punched. As a further alternative, the silica fiber insulation material may be stamped prior to the heat treatment, with the blanket 28 slightly oversized in length and width to account for shrinkage during heat treatment. The die-cut ceilings 28 can then in an oven 40 or 46 heat treated while lying flat on a flat surface, such as in 5 shown.

It has been found that by the heat treatment of the silica fiber thermal insulation material to the temperature T greater than Tmax before the ceiling 28 into a device 18 is used, the heat-treated ceiling 28 into a device 18 can be used, leaving the ceiling 28 between two adjacent faces of the device 18 is compressed and by suitable frictional contact with the surfaces during the desired service life of the device 18 can be fixed because the silica fiber insulation material of the ceiling 28 maintains its elasticity and not by the maximum operating temperature Tmax of the device 18 "Heat-set" is.

It will be appreciated that despite the description herein in connection with a diesel combustion process in the form of a diesel engine 16 the invention can be applied to devices used in exhaust systems for other types of combustion processes, including other types of internal combustion engines, including, for example, internal combustion engines using gasoline or other alternative fuels.

Claims (19)

A method of manufacturing an exhaust aftertreatment or acoustic device having a maximum operating temperature Tmax, the method comprising the steps of: providing a blanket of silica fiber insulation material having a weight percent SiO ₂ greater than 65%; Heating the blanket so that all of the silica fiber insulating material is heated to a temperature T greater than Tmax; and installation of the blanket in the device after the heating step. The method of claim 1, wherein T is at least 1.05 x Tmax. The method of claim 1, wherein the installing step comprises inserting the blanket so that the blanket between two adjacent faces of the device is compressed about one average mounting density from 0.18 grams / cubic centimeter to 0.30 grams / cubic centimeter of the insulation material in the ceiling. The method of claim 1, wherein the blanket is in an uncompressed state during the heating step. The method of claim 1, wherein the blanket is heated during the heating step in a rolled condition, the blanket being formed into a roll having a central axis. The method of claim 5, wherein the blanket is rotated about the central axis during the heating step. The method of claim 1, wherein the blanket is flat during the heating step. The method of claim 1, wherein Tmax is in the range of 300 ° C to 1100 ° C. The method of claim 1, wherein the installing step comprises inserting the blanket so that the blanket encloses a core of the device through which the exhaust gas flows. The method of claim 1, wherein the silica fiber insulating material has a weight percentage of SiO ₂ of more than 95%. A method of manufacturing an exhaust aftertreatment or acoustic device having a maximum operating temperature Tmax, the method comprising the steps of: providing a blanket of silica fiber insulation material having a weight percent SiO ₂ greater than 65%; Heating the blanket so that all of the silica fiber insulating material is heated to a temperature T greater than Tmax; and inserting the blanket into the device after the heating step so that the blanket encloses a core of the device through which the exhaust flows and the blanket is pressed between two adjacent faces of the device to an average built-in density of 0.18 grams / cubic centimeter to reach 0.30 grams / cubic centimeter of the insulation material in the ceiling. The method of claim 11, wherein T is at least 1.05 x Tmax. The method of claim 11, wherein the blanket is in an uncompressed state during the heating step. The method of claim 11, wherein the blanket is heated in a rolled condition during the heating step, the blanket being formed into a roll having a central axis. The method of claim 14, wherein the blanket is rotated about the central axis during the heating step. The method of claim 11, wherein the blanket is flat during the heating step. The method of claim 11, wherein Tmax is in the range of 300 ° C to 1100 ° C. The method of claim 11, wherein the silica fiber insulating material has a weight percentage of SiO ₂ of more than 95%. The method of claim 11, wherein the two adjacent surfaces are cylindrical surfaces.

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