supply of roof turbine air ventilators of 21 inch neck size with 26 vanes , design, manufacturing, supply, fitment and commissioning of roof turbine air ventilators of 21 inch neck size with 26 vanes at diesel loco shed, new guwahati, complete in all respects, suitable for c ontinuous outdoor industrial operation, with all major components such as vanes, top cover, bottom ring an d housing made of stainless steel ss 410 (vane thickness minimum 0.40 mm, top cover and bottom ring th ckness minimum 0.50 mm), complete with double sealed, self-lubricating ball bearings of make fag/skf/n bc, stainless steel / corrosion-resistant fasteners, center shaft of stainless steel / high carbon steel with zin c plating (minimum 12 mm dia), and frp / polycarbonate / gi base plate of minimum 2 mm thickness, inclu ding cutting of roof sheet, proper fixing, sealing, alignment and commissioning, ensuring smooth, noise-fre e and vibration-free operation, continuous ventilation without electrical power, minimum air extraction capa city of 700 cfm, complete as per standard industrial practice and to the satisfaction of the consignee. [ wa rranty period: 30 months after the date of delivery ] ]