One of the most frequent and serious problems valve face is gland leakage,results in wasted and increased plant downtime . Apart from the high cost of energy losses, Gland leakages can also cause serious environmental , ecological and health hazards to plant workers and personnel , Leakage of sensitive material can also constitude to a fire hazard , explosion, or damage to equipment by corrosive material . Air entering the pipeline could produce inflammable explosive or poisonous mixtures. Gland packed valves ofen demand continual maintenance in accessibility creating particular difficulties . The bellows complies to conditions at high temperatures and are capable of withstanding over 10,000 cycles without failure.