At one of our pharmaceutical plants,an old powder weight-feeder system appears to be failing: the weights are correct most of the time but our rejects have increased significantly in the past few weeks.Some managers see this as a justification to get rid of the system,which doesn't integrate with our new distributed control system,and install one that does.However,I'm opposed to ditching what has been a very reliable system.This setup consists of a bin,a cyclone on a three-point scale,and a vacuum system.The powder is pelletized into pills in the next step.I've carefully compiled a list of changes made in the area recently.The ones that stand out in my mind are: 1)a larger blower was installed to meet additional air filtration requirements;2)the seals were replaced on the bin rotary valve;3)some timers were adjusted in the controls to compensate for the dust accumulation in the bin,to lengthen the time between filter changeout;4)a tank dike next to the cyclone was dismantled-doing this required jack hammers and removal of old pipe and conduit;and 5)some terminals were re-arranged in an intrinsically safe barrier box also used by the feeder system.
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