Porvair, filtration and environmental technology group, expects its first-half revenues to be at or ahead market forecasts thanks to a smooth progress in large projects.Despite further work in the pipeline, revenues from large projects will be lower when compared with the same period in 2014, as expected.The group has been investing in new plants in the UK and US, while its expansion in China continues "on schedule and to budget", Porvair said in a statement.The company said its net cash will be £7m higher than same time last year while order books for the second half are healthy.Shares were up 0.75% to 336.75p on Tuesday at 14:11.