Fiber Glass Greenhouses: single span greenhouse. Use 48mm diameter pipe, very strong structure, can withstand the sand storm. Fiber Glass Greenhouses: single span greenhouse.I-FrameworkThe arches are made from 48 mm diameter galvanized steel pipes.Arches are linked together with longitudinal galvanized pipes of 32 mm diameter.The front frame of the greenhouse is made from (32 x 32) mm cross- ...