ISG indirect steam generator

The ISG indirect steam generator draws its heat not from a burner but from a hot fluid: thermal oil, steam, hot water, waste oil or another hot process medium. A flanged U-tube bundle transfers this heat to the water in a closed pressure vessel, producing saturated or superheated steam. It delivers up to 30 000 kg/h of steam (up to about 21 000 kW) at up to 60 bar. Because the thermal oil on the primary side can be heated up to 350 °C, the unit can supply saturated steam at up to 60 bar and can also produce hot water or high-temperature air.

With no burner, flue, fuel supply or fuel storage required, it saves cost and space; no ventilation is needed, and it is smaller and lighter than a conventional boiler. Heat passes directly into the water in the steam space, and according to TSB the steam reaches 99.95 % purity across the operating range. With a pressure difference of two bar, economical hygienic steam can be generated from a plant's own steam. An optional all-stainless build allows clean steam production, and hygienic versions are made of AISI 304L/316L, AISI 316Ti or duplex stainless steel.

Design and manufacture follow EN 13445, PED 2014/68/EU and ASME VIII Div. 1; the generator falls outside the scope of TRD, EN 12952 and EN 12953. It is the right choice where enough primary energy is available, burner exhaust cannot be discharged, open flame is not allowed or the fuel supply is limited. Typical uses are hygienic steam in hospitals, SIP, CIP and sterilisation in pharmaceutical production, cooking and pasteurisation in food and beverage, refineries and petrochemicals, building materials, textiles, and packaging and paper.