A device for simultaneous determination of the impact resistance and hardness of insulating coatings of pipelines
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A DEVICE FOR SIMULTANEOUS DETERMINATION OF THE IMPACT RESISTANCE AND HARDNESS OF INSULATING COATINGS OF PIPELINES I. P. Gnyp, M. V. Marukha, B. Ya. Heneha, and V. A. Chervatyuk
UDC 669.14: 620.178
We propose a hand-operated device for simultaneous determination of the impact resistance and hardness of anticorrosive insulating coatings, which completely models the work of a U-1 standard vertical impact testing machine. The proposed device is a prototype of the Poldi impact hardness gauge, however, unlike the latter, our device is used with a hammer of mass 1 kg, which equates it to the U-1 impact testing machine and enables one to determine simultaneously the hardness and impact resistance of protective coatings. When the hammer strikes, the indenter contacts simultaneously with the coating and indicator metal (a square bar), which has been calibrated on the U-1 impact testing machine and a stationary hardness gauge. This calibration results in a relation between the diameter of indentation and the energy of impact with a one-kilogram weight. Striking upon our device with a one-kilogram weight, measuring the diameter of indentation on the bar, and using the relation mentioned above, we can find the impact resistance, and the ratio between the diameters of indentations on the bar and coating enables us to determine its hardness according to GOST 18661-73.
Unlike the U-1 impact testing machine, the proposed device makes it possible to find the impact resistance of coatings on different surfaces (vertical, ceiling, or inclined to the horizon at arbitrary angles) and at the sites of geometrical stress concentrators: welded collectors, stop valve, pipeline branchings, etc. The characteristics of the impact resistance of coatings are important for gas and oil main pipelines and enter into GOST [1], DSTU [2], normative documents of the oil and gas complex of Ukraine [3], and foreign procedures [4]. This is due to the necessity to preserve coatings on pipes undamaged in the course of their laying into trenches, covering with ground, and operation of pipelines. According to GOST [1] and DSTU [2], to determine the impact resistance of protective coatings of a pipeline under field conditions, one installs on the latter a U-1 device, setting its directing pipe vertically, and makes a series of strikes with a weight of mass 1 kg with a hemispherical steel mouthpiece–indenter 8 mm in diameter, which is thrown down from different heights. With the help of an electric spark flaw detector, one measures the impact energy leading to the disturbance of dielectric entirety of the coating. However, this method is inconvenient and does not enable one to measure the impact resistance of coatings on vertical and ceiling surfaces near notches, e.g., on collectors, gate valves, and branchings of oil and gas pipelines. Design of the Device for Simultaneous Determination of the Impact Resistance and Hardness of Coatings We developed a hand-operated impact hardness gauge RUT-1 (we call it “device” in what follows), which completely models the
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