Porvair, the filtration and technology specialist, said market demand was 'encouraging' as profits climbed 10pc.

The King's Lynn-based firm saw pre-tax profits reach £4.2m compared to £3.8m last year despite an expected drop in revenues.

The EDP Top100 company said the 9pc revenue fall to £46.3m was sparked by a strong period in 2014 when it secured a number of new contracts. It includes $5.5m worth of deals for spare orders in America, India and South Korea, which the company expects to deliver stronger revenue growth later this year. Revenues excluding the contracts expanded 8pc in its half year results to May 31 2015.

It comes as it continued its acquisition trail by snapping-up steel foundry business Fiber Ceramics to add new products and boost capacity in its metals filtration arm.

Elsewhere, its microfiltration division saw 44pc revenue growth in its American business, with underlying revenues up 9pc.

Ben Stocks, chief executive, said: 'Overall market demand is encouraging and order books continue to be healthy. We are winning market share with new products, notably in metals filtration and Seal Analytical [a laboratory products manufacturer]. The group has a strong balance sheet, a promising project pipeline and has made a good start to 2015.'

The company, which has its headquarters on the North Lynn Industrial Estate and employs about 350 people in the UK, said its interim dividend had increased 8pc to 1.3 pence.

Chris Tyler, finance director, said Porvair was constantly looking out for acquisitions that 'fitted tightly' with its current business model.