Over temperature / pressure safety device and method for diesel particulate filters

Abstract

A safety device for an exhaust gas aftertreatment system provides an alternative exhaust route in case of high temperatures or pressures within the regenerating particulate filter of the exhaust gas aftertreatment system that may cause damage to the particulate filter. The safety device comprises a valve that redirects the flow of exhaust gas from the regenerating particulate filter when specified temperature or pressure thresholds are met or exceeded.

What is claimed is: 
     
         1 . A method for controlling an exhaust gas aftertreatment system comprising:
 determining whether a maximum safe level of particulate loading on a particulate filter of the exhaust gas aftertreatment system has been reached;   determining whether a pre-set time limit has been reached;   activating a safety device configured to redirect a flow exhaust gas from the particulate filter of the exhaust gas aftertreatment system if the maximum safe level of particulate loading has been reached; and   activating the safety device configured to redirect the flow of exhaust gas from the particulate filter of the exhaust gas aftertreatment system if the pre-set time limit has been reached.   
     
     
         2 . The method of  claim 1 , wherein activating the safety device further comprises the steps of sending a signal from a controller to close a valve and block the flow of exhaust gas from entering the particulate filter. 
     
     
         3 . The method of  claim 1 , wherein determining a maximum safe level of particulate loading on a particulate filter further comprises the steps of measuring a temperature at an inlet of the particulate filter and comparing the temperature at the inlet to a predetermined limit. 
     
     
         4 . The method of  claim 3 , wherein the predetermined limit is 750 degrees C. 
     
     
         5 . The method of  claim 1 , wherein determining a maximum safe level of particulate loading on a particulate filter further comprises the steps of measuring a temperature at an inlet of the particulate filter and measuring a temperature at an outlet of the particulate filter and comparing the temperature differential between the inlet and the outlet of the particulate filter to a predetermined limit. 
     
     
         6 . The method of  claim 5 , wherein determining a maximum safe level of particulate loading on a particulate filter further comprises the step of comparing the temperature at the inlet to an inlet temperature predetermined limit. 
     
     
         7 . The method of  claim 1 , wherein determining a maximum safe level of particulate loading on a particulate filter further comprises the steps of measuring a temperature at an outlet of the particulate filter and comparing the temperature at the outlet to a predetermined limit. 
     
     
         8 . The method of  claim 1 , wherein determining a maximum safe level of particulate loading on a particulate filter further comprises the steps of calculating an upstream pressure of the particulate filter and comparing the upstream pressure value to a predetermined limit. 
     
     
         9 . The method of  claim 8 , wherein calculating an upstream pressure of the particulate filter further comprises calculating a time-weighted average of a plurality of instantaneous upstream pressure measurements of the particulate filter and calculating an overall time-weighted average peak pressure measurement using the time-weight average of the plurality of pressure measurements and coefficients determined by a particulate loading of the particulate filter. 
     
     
         10 . A method for controlling an exhaust gas aftertreatment system comprising:
 Performing a diagnostic evaluation of a safety device of the exhaust gas aftertreatment system;   determining whether a maximum safe level of particulate loading on a particulate filter of the exhaust gas aftertreatment system has been reached;   determining whether a pre-set time limit has been reached;   activating the safety device configured to redirect a flow exhaust gas from the particulate filter of the exhaust gas aftertreatment system if the maximum safe level of particulate loading has been reached; and   activating the safety device configured to redirect the flow of exhaust gas from the particulate filter of the exhaust gas aftertreatment system if the pre-set time limit has been reached.