gas pipes 172 natural gas 43 pipelines 30 gasworks industry 26 house gas pipelines 25 material testing 22 corrosion of material 20 more ... material defects 14 technical standards 11 measurement 9 corrosion protection 9 repairs 9 oil pipes 9 wandering currents 8 natural gas energy sources 8 building equipments 8 cleaning 8 damage 7 power engineering 6 flow measurement 6 preservation of material 6 flowmeters 6 simulation and modelling 6 welding 6 supply 6 house connections 5 plumbing works 5 gas heating 5 pressure 5 maintenance 5 less ...