September 21 (SeeNews) - Bulgarian machine engineering company Hydraulic Elements and Systems (HES) [BUL:HES] said on Tuesday that its sales revenue rose by 34.2% year-on-year in the first eight months of 2021, to 44.5 million levs ($26.7 million/22.7 million euro), after recording sales of 5.9 million levs in August.