TY JOUR TI ENSURE SAFETY MEASURES DURING MAINTENANCE OF MAN-MADE OBJECTS KW technogenic objects KW repair works KW hull constructions KW protective means KW electric welding works JO Problems of risk management in the technosphere AU Troyanov, O.M. AU Reva, Y.V. AU Rybin, O.A. PY 2018 IS 2018 PB Saint-Petersburg University of State Fire Service of Emercom of Russia