GEODETIC WORKS FOR SLOVAK GAS INDUSTRY
Jan HARDOS, Slovakia
Key words: surveying the lines and objects of
transition system, setting-out and surveying the pipeline defects,
measurement of displacement and settlement, mapping of local
distribution networks.
Abstract
The Slovak Gas Industry (further SGI) is a natural state monopoly
enterprise in the field of gas industry in Slovakia. It deals with
purchase, transit, distribution and sale of natural gas. It buys the
natural gas from Russia and assures its transit across the Slovak
territory to Czech Republic, Austria, Croatia, Slovenia, Italy,
Germany and France. The SGI is the second biggest gas transporter in
the world. The length of transit pipeline system is 2,260 km in 4 - 5
lines (pipelines with diameter of 900 - 1400 mm). The distribution
long-distance pipelines measure approximately 5,880 km and the local
distribution network is about19,660 km long. Together with the transit
system it represents about 27,800 km gas pipelines installed on the
Slovak territory.
Surveying the lines of transition gas pipeline system started in
70-ties of the past century. The pipelines were surveyed partially in
an open trench, but regarding the conditions of construction site
(fast burring of pipeline in the trench) they were in most cases
surveyed only after pipeline burial, i.e. the pipeline axis was found
by electromagnetic locators followed with measurement at each about
100 m in the straight line or more frequently in the curves. The
surface equipment of gas pipeline (orientation poles, connecting
objects and outputs of cathodic protection) and other underground
equipment related to the pipeline (anode victims, connecting cables,
long-distance telemetric metallic cables, crossing foreign engineering
networks seen in the trench etc.) was measured additionally. The
results of surveying were plotted in analogue manner to the state maps
in 1 : 5,000 scale, containing also the lists of co-ordinates of the
surveyed points. Approximately since 1990, the digital mapping and
processing is employed.
Geodetic works at the anticorrosion inspection of pipelines by use
of the so-called intelligent pig consist of setting-out of pipeline
defects and surveying the defects and welds after reparation. The main
problem is that the accuracy of distance measured by the pig for long
distances is much lower that the possibilities of geodetic methods.
The transit gas pipeline system represents a certain potential risk
for its surrounding owing to very high gas pressures and therefore
some of its elements must be subjected to a regular safety monitoring.
This, besides the other aspects, involves a special geodetic
measurement of spatial stability of some technological equipment
situated on the surface. A significant static damage of the equipment
may result in the breakdown with catastrophic consequences on
ecological safety of the surroundings and may also cause considerable
losses due to interruption of gas transfer. Such equipment is for
example the air passages of large-diameter pipelines over the
waterways and compressor stations.
Measurement of displacement on the passages over the waterways and
measurement of settlement of technological equipment on the compressor
stations.
Majority of geodetic works is being performed for the local
distribution networks in the villages and town, i.e. from the
regulation stations of natural gas on the village borders thorough the
main distribution systems in the village up to the individual
connections to the houses (users) terminated with the main house
closing valves. The local networks are mostly surveyed during the
construction of new networks, but also the existing old networks,
which were not mapped digitally in the past are added gradually. In
the recent years also topology of measured elements (line, point,
area) has been maintained with their links, to facilitate the loading
of measured data into an object-oriented GIS.
These works done for the SGI have brought about a considerable
merit, owing to a rapid technological modernisation and development of
the Slovak geodetic companies, which are today employing the most
advanced measuring, computing and image processing technology,
starting with the total stations and GPS to AutoCad 2000, MicroStation
under the Windows NT, Geomedia etc.
CONTACT
Dipl.Ing. Jan Hardos
SIGEO s.r.o.
Racianska 71
832 59 Bratislava
SLOVAKIA
Tel & fax + 421 7 4445 8342
Email: sigeo@netax.sk
23 March 2001
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