SU725006A1 - Method of testing insulation coating of underground structure - Google Patents

Description

The invention relates to the field of protection of underground metal structures from corrosion - and can be used to determine the state of the insulation coating of various underground metal structures, to determine the effectiveness of cathodic protection and the timing of the re-insulation of underground metal structures.

Known methods for determining the electrode potentials of 10 underground metal structures under conditions of cathodic corrosion protection. In these methods, cathodic protection is carried out by applying voltage to the underground structure to maintain the protective potential on it.

However, this method does not allow one to judge the decrease in the zone of protective potential due to aging of the insulating coating and, therefore, does not make it possible to control the effectiveness of cathodic protection and determine the reinsulation time of underground metal coopy ^j .

The technical solution closest to the invention is a method for determining the quality of the insulation coating on the finished sections of the main pipelines, which consists in connecting a current source to 30 ² .... ....

insulated underground metal structure and anode grounding. In this case, the state of the insulation coating is evaluated by the offset of the potential difference "pipe - ground" at the end of the section, called polarization. In this case, the insulation coating is considered satisfactory if the bias of the potential difference. at the end of the section is not less than 0.4 V in absolute value, and the current strength has a certain value indicated in the nomogram. However, this method can give a very rough assessment of the condition of the insulation coating for the following reasons: leakage current density and the “pipe-ground” potential depend on the resistivity of the soil in which the pipeline is located; The potential of an underground structure depends on the transition resistance of the pipe - ground.

These factors introduce large errors in measurements. In addition, the method does not allow to assess the quality of the insulation coating during the operation of the underground metal structure.

The purpose of the invention is to improve the accuracy of monitoring the status of an underground structure.

This goal is achieved by the fact that they pass an alternating current of high frequency in the circuit underground metal soor / l ·.

ι zhepie - · anode grounding, then the period ^^ dag ^ set ~ 'B''· the period' of exploitation is measured ~~ ^; loss tangent (tan δ), Insulation coating aging coefficient is calculated as the ratio of the loss tangent (tan δ) during operation (/> 0) to the loss tangent (tg bo) during the initial operation (/ -0), determined by COEFFICIENCY OF THE “AGING” OF THE INSULATING COAT The effectiveness of the cathodic protection and “'ус Т ус ус й сроки’ are the deadlines for re-insulating the underground metal structure. During the * * operation of the underground 'metallic with' ^^ fujeyyi ', an' insulating 'coating ages, which is proportional to the loss tangent (tanδ), therefore, the loss tangent grows, so the value increases insulating fenny 'Pbkry

------- _{kazyva (} (. _t how many times worsened from .............. lational 'coverage by the equilibrium with its state in the initial ffCpTid® ~ ^ kCffkyaTation. Based on these data determine the effectiveness of cathodic protection 'and' terms ^: ..... reinsulation; underground metal structures.

An example of the method: to measure the gas pipeline in the initial period of operation at t - 0, the loss tangent tg6o = 0.05, during / operation, for one year t - 0.2, the loss tangent tan δ = 0.07 , t = 0.4, the loss tangent δ = 0.08, t = 0.6, the loss tangent tg 6 = 0.09, / = 0.8, the loss tangent tg 6 = 0.1. Thus, the change in the loss tangent over time is expressed by the function - · ---------------------------- tg6 = tgδο + 0.05 \, t = 1, ι2 ... n (years). , - - This expression makes it possible to predict the state of the insulation coating,

that is, after 5 years, the loss tangent and, accordingly, the aging coefficient. insulation (en-coatings K - β ' ^:: ' -θ · This indicates ⁵ em that the state of the insulation coating ......, on the gas pipeline after 5 years worsen in;

time. Moreover, in order to provide cathodic protection for a given section of the gas pipeline, it will be necessary to proportionally increase the protective current увеличитьθ by almost 6 times. This leads to a significant increase in operating costs for electricity, reconstruction of anode grounding, and the construction of additional cathodic protection devices. Therefore, the costs for a certain period of operation for the re-insulation of the underground metal structure will be lower than for the reconstruction of the cathodic protection. This point in time t is the most ²⁰ more favorable for the re-isolation of an underground metal structure, i.e.

^: repair time ._______, Thus, the loss tangent tan δ ²⁵ practically determines the effectiveness of cathodic protection AND / the term of re-insulation of an underground metal structure.

Claims (1)

The claims of The method of monitoring the state of isolation. ground cover of the underground structure, consisting in the fact that they connect an istpcp of current to the underground structure and 35 anode grounding, characterized in that, in order to increase the control efficiency, they pass high-frequency alternating current into the underground structure of the circuit. - anode grounding, measure the tan ⁴⁰ gene of the angle of loss ·, the aging coefficient of the insulating coating, [the value of which determines the state of the insulating coating ......