The invention relates to a flow activated circulating valve. The effect is that a high molecular weight polyamide can be obtained in a shorter production time. The inlet and outlet housings are operatively coupled to the inlet and outlet ends of the pipe, respectively and defme an internal fluid flow path in fluid communication with the pipe. The methods and arrangements further involve providingobtaining an indication specifying whether the prediction, Cpred, corresponds to C, and when the prediction, Cpred, is indicated to correspond to C, the encoded block, Be, is decoded based on the prediction Cpred. The abnormality-processing object is provided with a program of object-oriented design to comprehensively determine an abnormality-detection result for a plurality of abnormality-detection targets, and to ultimately decide whether an abnormality-indicating lamp should be illuminated. When the welding is completed, the eyeglasses would quickly return to their sun tinted state allowing them to be used as a conventional pair of sunglasses.