Вестник МГТУ. 2018, №4.

Власов А. Б. Метод определения качества герметика кабельных гермовводов... УДК 621.3.048:621.315.61 A. B. Vlasov Method for determining the quality of cable inlets sealant using infrared thermography The results of applying the quality control method to cable inlets sealant (hermetic lead, sealed lead-in, cable boxes) have been considered. Cable inlets are designed to prevent the spread of fire in adjacent areas through cable sealing boxes, e. g. on sea vessels. The known methods for determining the quality of cable inlets sealant are laborious and in some cases even impossible to implement when used on sea vessels. This applies to cases when the room through which the cables pass is being poured with water and some pressure stipulated by the ship specifications is being created there, or when the air pressure increases in such rooms. The novelty of the present method lies in the fact that it is based on the principles of pulsed thermal non-destructive testing of a material. The FLUKE thermovision camera Ti400 has been used as a technical means recording the temperature field of the sealant surface after exposure to a thermal pulse. The method approbation has indicated that thermal non­ destructive testing can be used to detect relatively small penetration defects in the sealant volume. Key words: sealant quality control method, cable inlets, defect, thermal pulse method, infrared thermography. Results The sealant quality is characterized by the absence of cracks and violations in its volume. The presence of cracks in the sealant leads to the possible water and air permeability, which is unacceptable due to fire safety. The method under development [1] enables a quick assessment of the sealing box quality (sealed lead- in) designed to protect against the penetration of fire, water, and gases through impermeable bulkheads. There are several ways known to determine the quality of cable inlets sealant 1 [2; 3]. For example, the cable room is filled with water which creates the pressure indicated in the technical characteristics of the vessel. The pressure is maintained within the time set by the test programme. Water leaks through the pressure seal construction are controlled visually on the other side of the bulkheads. However, this method can only be used in special-purpose premises, which can be flooded with water during normal operation of the vessel. In order to check the sealing devices located on the upper decks of the ships, another method is used, according to which the sealing structures for cable passage are watered under the pressure of 2 kg/cm 2 from 5 m distance and from any direction during 5 min time. The quality of cable passage points sealing is considered to be satisfactory if no water is detected from the opposite side of the bulkhead. The disadvantage of this method is the complexity of its use in internal premises with electrical equipment. Finally, to check the sealing devices located in the vessel service premises and domestic compartments, pressure cable boxes are blown with compressed air from a hose with a diameter of at least 1/2 inches from a 100 mm distance. Air leaks (defects) through the sealant structures are controlled by lubricating their other side with soap solution. The sealing quality of cable passage points is considered to be satisfactory if no air leaks are detected on the opposite side of the bulkhead or deck, or inside the room or electrical box. The methods described above are characterized by significant complexity and in some cases cannot be implemented, e. g. during the vessel operation or its repair. The method under development [1] determines thermophysical properties of materials and structures by measuring their surface temperature with a thermovision camera [4-6]. It is known as the "flash method" [4] - stimulating the test object with a thermal pulse from heat radiation sources (IR lamps, incandescent lamps). During the testing process, analysis of the conditions for the passage of a heat wave in the volume of the material under study has been carried out. In contrast to the methods described in [4; 5], the proposed method [1] uses thermal activation by a stream of warm air, which produces abnormal local heating on the surface opposite to the heated surface while penetrating through sealant defects (openings, cavities, pores). Application features of the heat pulses method are presented in the literature [6-11]. The present invention results [1] in improving the accuracy of the sealant continuity quality control, as well as in the localization of the air leakage point in the construction that should be water- and airtight. The method implementation scheme is presented in Fig. 1. The method is implemented as follows. The front surface (Fig. 1) of the cable inlet is blown with heated air from a blow dryer. A pyrometer can be used to record the temperature of the sealant front surface. A penetration defect has been created in the volume of the epoxy compound with the help of a metal string or a flat tie during the sealant polymerization (Fig. 2). Emissivity value of the epoxy compound like most polymeric materials is handled as s = 0.92-0.95 [12]. The front surface of the sealant is blown with a blow drier 1 OST 5R.1180-93. Industry-specific standard. Vessels. Test methods and standards for permeability and tightness. Central Research Institute "Lot", 1993 ; GOST 3285-77. Metal ship hulls. Test methods for impermeability and tightness. M., 1978. 632