The Czech gas companies that make up the RWE-CZ group (formerly JMP, SČP, SMP, STP, VČP, ZČP and Transgas) currently operate more than 34 500 km of steel gas mains. Of these, more than 15 200 km have cathodic protection, and the rest--more than 19 300 km--are protected only passively, by insulation.
Built into these gas mains are more than 1300 cathodic protection systems (SKAO, EPD, ESA) and more than 31 500 measuring outlets (PO, SO, KVO). The efficiency and quality of the anti-corrosion protection (ACP) for all this is the responsibility of some 70 fitters and 30 technicians, including ACP foremen. In total, there are approximately 100 ACP employees, 86 of whom are employed internally and around 14 work for external firms.
This means that each ACP fitter has to inspect and maintain almost 500 km of steel gas mains with around 20 cathodic protection systems and more than 450 measuring outlets. For technicians and foremen, the extent of gas mains and ACP in their care is more than double that figure. The inspections and maintenance during which the required measurements are taken are set at intervals ranging from twice a month (EPD) to once a year (measurement along the gas mains route at all measuring points).
In order to be able to determine the required scope of the measurement and the subsequent assessment of the efficiency and quality of ACP in the gas mains and ACP facilities at these times, with an ever-decreasing number of ACP workers, the gas companies making up RWE-CZ decided to introduce a unified SW + HW support system, which would build on the earlier GASACOR system used within the former companies comprising ČPP. The new SW + HW system was named GASACOR 2.
Reference SW + HW of the GASACOR 2 System
It is first necessary to mention that when giving the number of measuring sites, which moreover continually changes as the extent and layout of the gas mains change, it is not possible to make effective use of any kind of ACP SW + HW support system without it being linked to a GIS system.
In the individual gas companies that made up ČPP, the previous GASACOR system was linked to various autonomous GIS systems created by a variety of different designers. This change brought major problems when transferring data from the different GIS systems to the new unified system. These problems still exist, and it is therefore still not possible to compare data and assess measurements taken using the original GASACOR system with fresh data in the GASACOR 2 system. Moreover, the original GASACOR system was rashly discontinued at many workplaces. I therefore recommend that if future users are to link the GASACOR 2 system to any original ACP system SW, they should always archive the data from the original system well in advance so that this data can be compared in the new GASACOR 2 system SW.
It is also necessary to specify the resistance measurement possibilities available using the MEg 20 recorder. In terms of users, when designing the GASACOR 2 system, emphasis was placed primarily on the need for small, mobile HW that is highly resistant to wear and tear when used in various conditions in the terrain, particularly in regards to resistance to dust and water getting into the device. Another important factor was the long battery life of the device, especially when taking time measurements. These requirements cannot be reconciled with the need for a highly efficient (hard) source of direct-current and alternating voltage for the device, such as on instruments for measuring earth resistance.
For this reason, the MEg 20 cannot be used to measure the resistance of pipes – earth, insulation joints, and protectors. This equipment generally does not have a superimposed powerful alternating voltage, particularly from high-voltage and very-high-voltage distribution mains. Due to the fact that the power supply of the MEg 20 is much weaker, this interfering voltage cannot be adequately dampened to ensure the right level of accuracy when measuring resistance on this equipment. Resistance can therefore be measured using this instrument in a similar manner as with standard multimeters, where the power supply is the same strength.
Measurement Along the Route
Measurement along the route is currently only used in RWE DS – Jih (formerly JMP, a.s) and partially in DS – Sever 2 (formerly VČP, a.s.), where the data in the GIS is modified and adapted for import into the GASACOR 2 system. Other gas companies are working to specify and modify data so it can be imported into the GASACOR 2 system, and it is expected that the productive GASACOR 2 system will be in use from the beginning of 2009.
Time Measurement
This kind of measurement is primarily used:
a) when taking measurements along gas mains with cathodic protection in areas which are more or greatly affected by stray current, i.e. where corrosion surveys have shown an increased to very high density of current in an extraneous current filed in compliance with the requirements of ČSN EN 13509, TPG 920 22 and TPG 905 01;
b) when performing diagnostics on steel gas mains mostly on local networks (NTL and STL) in compliance with TPG 700 02 and TPG 905 01.
These measurements are generally not linked with the data specified in GIS (these are primarily measurements taken as part of diagnostics procedures as described in point b). The GASACOR 2 system can be fully used for this kind of measurements, and, for example, ACP fitters in RWE DS – Jih now have no other measuring equipment at their disposal.
Time measurement, performed as part of measurement along a route, will become topical when the revised version of ČSN EN 12954 comes into effect. This revised standard, as part of the EU, introduces the requirement to measure the potential of pipes – soil on gas mains with cathodic protection with no IR gradient (EIR free) at all measuring points. These measurements will always need to be taken as time measurements.
Polar Measurement
This kind of measurement is primarily used when performing a corrosion survey in compliance with ČSN 03 8375. The problems with the polar graph and assessment of the results of measurements taken using the GASACOR 2 software have now been resolved, and the system can be fully used for polar measurement.
