This process uses torch similar to Bunsen burner and operates on the Bunsen Burner principle. The air is drawn into the torch as required and mixed with fuel flame. The gas is then ejected and ignited, producing an air-fuel flame. The common fuels used in the air-fuel welding are acetylene, natural gas, propane and butane. This type of welding has limited use since the temperature is lower than that attained by other gas processes. The air-fuel welding processes are used successfully in lead welding and many low-melting-temperature metals and alloys such as in brazing and soldering processes.
Electrical Comparators are used as a means of detecting and amplifying small movements of a work contacting elements. An electrical comparator consists essentially of a pick-up head or transducer for converting a displacement into a corresponding change in current and a meter or recorder connected in the circuit to indicate the electrical change, calibrated to show in terms of displacement. Generally, an amplifier is needed to provide the requisite sensitivity and to match the characteristics of different parts of the circuit. Electrical comparators can be classified according to the electrical principle used in the pick-up head. Most of the comparators use either a differential transformer, an inductance bridge, a strain gauge or a capacitor as a means of detecting movement of the gauging element. There are different types of electrical comparators. One kind called an electrolimit gauge is used to check or measure the outside diameter of a roll. The object to be checked is place
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