Bevel-helical gearboxes B4 e No supplement th and th positionData position B4-DH-12-A

Flender/Flender Gear Units/Bevel-helical gearboxes B4

tuations. Someof the factors inuencing fumigation include temperature, relative humidity, grain types and their conditions (size, moisture content, impurities present), storage structure, and type of insect pests and their resistance status. Fumigants enter the insect mainly throughthe respiratory system and the poisoning of insects is inuenced by the rate of respiration.The rate of respiration of insects increases in response to the rise in temperature. Thus,fumigations are generally more effective at more than 2 , assuming other favorable conditions exist. At lower temperatures, sorption of the fumigant by the commodity isincreased; therefore, some allowance in dosage will be needed. For phosphine, fumigation at temperatures less than 1 is not recommended, as the fumigant is less effective at lower temperatures, and some additional requirement such as vaporizer is required duringthe application of methyl bromide. Fumigants are sorbed by grains during the exposureperiod. The rate of sorption depends on the characteristics of the fumigant and the grainand the prevailing temperature (. The fumigant may react with the grain constituents 2 Rajendran forming xed residues (irreversible sorption) or is desorbed on termination of the treatment (reversible sorption). Fine materials and other impurities impede gas distribution in bulkstorage and absorb the fumigant more than that by the grain itself, resulting in inadequategas concentration. Relative humidity is important in phosphine fumigation when the rateof decomposition of aluminium phosphide formulations to liberate phosphine gas is deter- mined by the humidity. To facilitate decomposition, minimum of 3% humidity is neces- sary, when aluminium phosphide preparations are used for grain fumigations. The typeof storage, particularly the standard of gas tightness of structure, matters in successfultreatments. In rigid structures such as silos and whole godowns, sealing should be doneperfectly to prevent the gas loss t