SISTEMA DE LIMPIEZA DE FILTRO PARA UN MONITOR DE OPACIDAD

摘要

A filter cleaning system for an opacity monitor which has a light source and a light sensor on opposite sides of a first optical path through a gas whose opacity is to be measured, comprises a mechanism for calibrating the opacity monitor during a calibration period and a purging air arrangement for supplying purging air to pipes in the first optical path to keep the interior of the pipes clean. A primary filter is connected to the blower for filtering the purging air. Three-way valves are connected to the input and the output of the blower so that a secondary filter can be utilized to supply clean air in a reverse flow through the primary filter to clean the primary filter. The primary filter is cleaned during this blow-down period at the same time that calibration is taking place for the opacity monitor. In this way, no measuring time is wasted and still the life of the primary filter is extended.