Profile: Controlled Flame Boilers Ltd. offers horizontal range of boilers. Series 4VT is a tubeless design boiler which ensures efficiency with silent operation. The combustion gases pass generated heat over the water heating surfaces four times, which helps the boiler reach full pressure in around fifteen minutes. Our boiler utilizes natural gas, propane, or can be oil fired. Flame boilers range of compact electric boilers are capable of producing 9 to 77 kg/hr of steam at an operating pressure of 7 to 8 bars.