AUTOMATIC PRE-PROCESSING DEVICE FOR MEASURING CONCENTRATION OF HYDROFLUORIC ACID, AND AUTOMATIC HYDROFLUORIC ACID SUPPLYING DEVICE

摘要

PROBLEM TO BE SOLVED: To stabilize the manufacture of cathode-ray tube, to lower the cost, and to secure the safety of a worker while automating the maintenance of the hydrofluoric acid washing liquid by providing a device for filtering the hydrofluoric acid used for a glass washing process with a filter before measuring the concentration thereof and for reversely washing the filter. SOLUTION: A function for measuring a time to be required for filtering and for generating an alarm in the case where the filtering time exceeds the predetermined time is desirably provided. Reverse washing of a filter is desirably performed by using gas. During the filtering with a first filter 120, a time to be required for filtering a constant quantity of the liquid to be measured is measured, and an inlet side cock 115 and a filter side cock 116 are switched so as to generate an alarm in the case where the measured time exceeds the filtering time and while so as to flow the liquid to be measured to the other filter 121. Filtering time is measured by measuring the liquid level rising time of a gas-liquid separator 117 with a liquid level sensor 118. The reverse washing is performed by passing the compressed air into the filter 120 (or 121) in a direction opposite to the filtering direction.