Questions & answers
Safety
Testing the pipeline: what makes pipelines the safest method of transporting natural gas?
Are gas pipelines safe?
WINGAS GmbH & Co. KG, as the OPAL contractor, has already installed more than 2,000 kilometers of pipeline in Germany. The OPAL will also be built in accordance with Germany’s high safety standards. The construction work will be monitored by the TÜV, Germany’s Technical Inspection Agency - and on more than one occasion.
The pipes used for the OPAL are made of high-quality steel welded together. Each welding seam is checked and x-rayed. The pipeline is also subjected to a pressure test before coming on stream. During this so-called stress test, pressure is exerted on the pipeline right up to the material’s yield point. This test places considerably more pressure on the pipeline than during standard operations.
Once in operation the gas pipeline is also checked at regular intervals. A fiber-optic cable is installed beside the pipe so that the flow can be observed round the clock by means of telemonitoring. In addition, operating staff drive along and fly over the route.
The law requires operators of high pressure gas pipelines to carry out continuous servicing and maintenance and to have a constant stand-by service (GW 1200) to guarantee that the pipeline is operating safely and to ensure a rapid response in the case of faults. All this makes pipelines the safest method of transport for natural gas.
Before coming on stream a natural gas pipeline is subjected to numerous tests. What are these tests?
• Welding seams check: The pipes are welded together into one continuous pipeline by specially trained and certified welders. Each welding seam is subjected to a test which is then appraised and approved by the TÜV, Germany’s Technical Inspection Agency, or by certified experts. The result of the test is documented (DVGW work sheet GW 350 together with DIN EN 12732).
• Test methods: These include the radiographic test (a source of radiation such as x-ray tubes or isotope radiators is beamed onto the welding seams), the ultrasound test (ultra sound waves are projected onto the welding seams) and the pressure test. Once the construction phase has been completed the entire pipeline is subjected to a special pressure test using water. During this so-called stress test, pressure is exerted on the pipeline right up to the material’s yield point. This test places considerably more pressure on the pipeline than during standard operations.
Once in operation the gas pipeline is also checked at regular intervals. These inspections (route inspections) are carried out by walking, driving along or flying over the route and paying attention to all the construction activities and any other incidents along the pipeline route. Any irregularities are reported to the operator responsible straight away.
The law requires operators of high pressure gas pipelines to carry out continuous servicing and maintenance and to have a constant stand-by service (GW 1200) to guarantee that the pipeline is operating safely and to ensure a rapid response in the case of faults. All this makes pipelines the safest method of transport for gas.
In what circumstances can natural gas explode?
Natural gas is a highly flammable, colorless and odorless gas with an ignition temperature of about 600°C. It is lighter than air and does not therefore collect in recesses in the ground, hollows, dips, cellars and shafts. There is only the danger of explosion when mixed with air in certain quantities.
Is natural gas poisonous?
Natural gas is an important raw material for the petrochemical industry as well as a fuel gas for generating energy and for heating purposes. Natural gas is a non-poisonous gas which consists mostly of methane. It has no effect on human organisms or the environment. Natural gas is not irritant, sensitizing or carcinogenic.
Natural gas pipelines are installed at least one meter underground? Is that deep enough?
The covering of one meter is enough. Normal soil cultivation goes about 40 cm deep. If a farmer wants to dig deeper, for example in order to install drainages, then he checks back with the building contractor as stipulated in the right of way agreements made. This prevents any damage occurring to the pipes.
The pipes are stored in storage yards in the open air long before they are lowered into the earth. Doesn’t that lead to rusting?
The pipes have an epoxy resin coating on the inside and a polyethylene coating on the outside. There is only a small area on the welding seam which could corrode. However, once the welding seam has been finished, this area is cleaned and also sealed with a moisture-proof synthetic coating. Corrosion is not possible inside the pipe because the gas that flows through the pipeline is dry, in other words, it does not contain any moisture, which would be necessary for the corrosion process.
In addition to the pipeline, which is completely encapsulated in a synthetic coating, electric protective devices are installed on the steel to prevent electro-chemical corrosion processes taking place. A small electrical voltage in the millivolts (mV) range neutralizes any potential electro-chemical corrosion process.
How is the building site made safe while the pipeline is being laid?
Pipeline building sites have signs indicating that construction work is taking place, similar to street or motorway building sites. It is not possible to completely fence in the building site because of the vastness of the project. Individual areas that are particularly dangerous are, however, protected with fences.
There is much talk of the need to keep pipelines together. Doesn’t this mean there is a greater danger of damaging other pipelines when building a new pipeline?
There is always a safety distance between different pipelines on one pipeline track. Construction works in these areas are always strictly monitored by the authorities.
