Bituminous Insulations Durability of Underground Metallic Pipelines I Field investigations

Abstract

The corrosion state of an underground metallic pipeline of �161 mm and 565 m length was assessed by specific electrical and electrochemical measurements. The investigated pipe, buried in 1997, was protected against corrosion by successive layers of bituminous material with a total thickness of 1 to 1.2 mm. The pipeline crosses three electrified railway lines (50 Hz - 28 kV), and then its route is approximately parallel to these lines; thus, the induced AC voltages between line and ground were calculated obtaining values between 4.05 and 7.1 Vrms, in good agreement with the values measured in the accessible points. The measurements regarding the insulation capacity against corrosion of the bituminous insulation, performed at one month and after 19 years of burial, showed an increase of the average cathode current density needed for obtaining the protection potential in the range �1.00 � �1.28 VCu/CuSO4 of approx. three times (from 6.65 up to 19.96 mA/m2), in good agreement with the evolution of the insulation resistance measured between the steel pipe (having a contact area with the ground of 270.5 m2) and a ground socket of 4 W, which decreased from 995 to 315 kW. Following the analysis and processing of the field collected data, it is considered that, by implementing a cheap cathodic protection system (without cathodic current power supply), based on the rectification of the AC induced voltage, the safe operation period of the investigated pipeline may be extended by at least 50 years.

Ageing of Some Lacquers Due to Microbiological Stress

“…), which has the consequence of increasing the share of harmonic signals generated in electrical networks [46][47][48][49]. In these conditions, both electrical stresses that affect insulation systems (especially the polymer ones) and electromagnetic pollution level of the environment increase -with all the consequences on the natural bioelectrochemical processes in the biosphere [36,50] and on the durability of materials in the built systems [7,39,[51][52][53][54][55][56][57][58].…”

Studies on the Behavior Some Paints in Electro-insulating Fluid Based on Vegetable Esters

“…As a result of these processes, in extreme situations occurs explosions and incineration of electro-insulating fluid equipment [37][38][39] with serious consequences for the population [40,41] by the pollution of the environment [42,43] (soil, surface waters, groundwater, the air with gaseous harmful emissions, particulate matter and smoke etc.) and EE supply disruptions (consumers remain unpowered until remediation) as well as urban utilities subterranean distribution networks (underground power cables, PVC pipes, PE and corrosion protection of steel pipes are degraded [44][45][46][47][48][49][50].…”

Electromagnetic Pollution of the Environment and its Effects on the Materials from the Built up Media

“…Analyzing the depiction from figure 1 it is noted that the I VD component decrease may be achieved by increasing the insulation level between the railroad and soil as well as between the perturbed metallic structure and soil (electroinsulating layers applied on the pipes [19][20][21]). Figure 1 and figure 2 show that in practice the ELF extremely low frequency (power frequency and harmonics) AC stray currents which disturbs the metallic structures operating in electro-conductive environments of II order (soil and / or reinforced concrete) come primarily from tree phase power system by both induction and voltage drop (due to imbalances between phases and / or major consumers specifics such as electrified railroads).…”