Ключевые слова: beijing, black, blue, closeup, color image, connection, contact, control, distributor, duct, electric, electrical, electricity, electronic, energy, engineering, factory, fitting, fluid, harmony, heavy, horizontal, hydraulic, industrial, industry, machine, machinery, mechanical, metal, no people, oil, part, pin, piping, power, pressure, process, protection, pump, relay, repair, service, shiny, steel, supply, switch, system, technology, tube,