Steam trap and pump specialist Spirax-Sarco has enjoyed a strong first half with sales and margins both rising sharply."Since the AGM, trading conditions continue to be positive and sales for the first half-year were ahead 8% at constant currency, including a 2% contribution from acquisitions; also, the order book increased," the engineer said.Growth continues to be led by Watson-Marlow Pumps and in the steam business by the Americas and Asia Pacific. Currencies added 2% to sales in the first half-year. Margins have also improved from 15% in the first half of 2009 to above 19% for the first half of 2010.Operational gearing from the increase in sales, last year's cost reduction measures, small exchange gains and a favourable product mix have all contributed, the firm said.The one note of caution is on material costs, which were favourable this year so far but are rising and "We anticipate this impacting the second half of the year", Spirax said.