Biomass water tube boilers for steam generation in two designs: a rectangular box type suitable for any solid fuel, and a Yarrow type suitable for biomass and wood. Every boiler is tested at 600psi on a hydraulic testing machine and has a working pressure of 160psi. It is insulated with cera wool on all sides, and a water feed pump is included. Accessories are a water level gauge set, pressure gauge, safety valve, 20ft chimney (1 set), interconnecting pipe lines, valves and pipe fittings. The unit has a black casing with a sloped top and bolted panels, a front door opening onto a grate, a water level gauge glass and a red-handled ball valve near the base. Box type (heating surface sq. ft. / steam Kg/hour / approx. weight Kg / W x D x H inches): 400/1000/2800/80" x 80" x 90"; 500/1250/3000/85" x 80" x 90"; 800/2000/4200/100" x 80" x 90"; 1000/2500/4800/120" x 80" x 90"; 1200/3000/5500/140" x 80" x 90"; 1600/4000/7500/200" x 80" x 90"; 2000/5000/9000/5mt x 2mt x 2.5mt Yarrow type (same columns): 58/120/200/42" x 35" x 39"; 100/200/600/58" x 44" x 55"; 150/300/1120/82" x 43" x 62"; 200/400/1200/92" x 51" x 71"; 265/500/1430/90" x 64" x 75"; 330/650/2025/92" x 92" x 78"