gas pipes 181 natural gas 43 pipelines 30 gasworks industry 25 house gas pipelines 22 material testing 22 corrosion of material 20 more ... material defects 14 oil pipes 12 technical standards 11 measurement 9 corrosion protection 9 repairs 9 wandering currents 8 natural gas energy sources 8 building equipments 8 cleaning 8 damage 7 power engineering 6 plumbing works 6 flow measurement 6 preservation of material 6 flowmeters 6 simulation and modelling 6 welding 6 supply 6 house connections 5 pressure 5 maintenance 5 safety 4 less ...