Thermoelectric mat of soil heating for technological connection
The article deals with the growing number of requests for technological connection and the period of its implementation limited by legislative instruments. Special difficulties and a big waste of time occur in the winter because of digging trenches in the frozen ground for laying the cable lines of technological connections. The basic designs of thermoelectric mats, which were used for soil heating during winter operation, have been considered. One of the first thermoelectric mats developed in our country was heated by nichrome wire. Its main drawback was the low mechanical tensile strength of this wire when heated. A wide application of thermoelectric mats TM-800 using infrared films (made in South Korea) for heating the soil has recently been found. The high cost of these mats limits their use. Under these circumstances a thermoelectric mat based on a domestic film-type electric heater was developed at South Ural State Agrarian University. It is characterized by a relatively low cost and high operational capacity. Particular importance in the choice of thermoelectric mat type for soil heating is paid to the indicators of its reliability. In this regard, the experimental evaluation of the operability indicators of manufactured thermoelectric mats is one of the steps in deciding whether it is expedient or not to use it in specific operating conditions. Tests for reliability can be determinative and control. Determinative tests for the reliability of the object are conducted to assess the actual values of performance indicators. Based on the results of these tests, the parameters of failures distribution laws are determined; and thus the correspondence degree of performance indicators to specific operating conditions is assessed. Control tests for reliability indicate the correspondence degree of performance indicators to the requirements of technical specifications or government standards. Control tests are carried out systematically after a certain period according to the normative and technical requirements. According to expert estimates, it has been revealed that the resource of domestic thermoelectric mats is equal to at least 80 % of the resource of foreign analogs. Based on the analysis of the methods involving the heating of frozen ground, it is recommended to use thermoelectric mats on the basis of film electric heaters with a resistive element made of high-resistance wire