Porvair has started 2014 strongly and expects half-year profit to be well ahead of last year, the filtration group said in a trading statement.Porvair, which serves the aviation, energy and industrial process, environmental laboratory and molten metal markets, said it expects to report revenues around 33% ahead of the first six months of 2013, of which a quarter was due to specific, previously identified large contracts.It expects underlying revenues to be 8% ahead and 11% up at constant currencies. "Order books for the second half are healthy," it added.Porvair reports interim results for the six months to May 31st on Monday June 23rd.Its shares were up 7.11% to 324p at 08:12 on Tuesday.PW