Engineering firm Weir Group said its guidance for the full year remains unchanged despite growing currency headwinds and mixed trading conditions in the second quarter.In a capital markets presentation to shareholders and analysts on Tuesday, the company is expected to confirm that overall trading in April and May was in line with expectations and consistent with its recent outlook.The Oil & Gas division, which accounted for 30% of group revenues last year, is said to have benefitted from improving trends in the pressure pumping market.However, the mining end markets - which form part of the Minerals division (40% of group revenues) - remain "challenging", affected by the ongoing platinum mine strikes in South Africa.There was no comment on the Power and Industrial divisions."Foreign currency headwinds have strengthened over the course of the first half of 2014, contributing to full-year reported revenue and profit being weighted more towards the second half," Weir said. "The group's full-year constant currency revenue and margin guidance remains unchanged."The company said in February that it expects to report "good" constant currency revenue and profit growth in 2014 with margins broadly flat on last year.BC