METHOD AND DEVICE FOR DECIDING FASTENING STATE OF PIPE COUPLING

PURPOSE:To reliably automatically decide propriety of the fastening state of a pipe coupling and to save a man power for a deciding work with high reliability by storing fastening torque and the number of turns during fastening of a pipe coupling and picking up a point, where the rate of change of fastening torque is reduced to a value lower than a given value, as a point of inflection. CONSTITUTION:A difference computing part 51 collectively reads memory data from a sampling memory part 50 and picks up a set of memory data to satisfy a condition having the number of turns where a difference with a number Nn of turns is lower than a given value alpha. The rate of change of fastening torque is computed to input a result to a reference value setting part 52 and a point of inflection picking-up part 53. The reference value setting part 52 determines a maximum value Xmax, then multiplies the maximum value by a given factor to set a reference value X, and inputs a result to the point of reflection picking-up part 53. The point of reflection picking-up part 53 compares difference data with the reference value X and picks up a difference value first decreased to a value lower than the reference valve X to input memory data as data, corresponding to a point A of reflection to a deciding part 54. The deciding part 54 decides the memory data, and decides the data as defective fastening when it is not within a proper range to feed the result to a display device 8.