On any Macawber dense-phase pneumatic conveying system, the quality of the convey air and control air are quoted separately. Why is it important that these specifications are observed on site?
a). The International standard for control air for pneumatic devices is-40 degrees, Pressure Dew Point.
b). This standard may also be applied to conveying air e.g. for most powders, food products, hygroscopic materials, etc. Other materials such as wet coal, silica sand, for instance, would not require dry air. The specification of the conveying air is determined by Application Engineering and/or the customer and is dependent upon the material to be conveyed and the prevailing site climate conditions.
c). The control air supply is always required to be dry to the international standard.
d). If the air supplies are not separated then when the system is in a conveying cycle, the control air pressure can be reduced to an extent that the control functions of the system are affected and a subsequent upset operating condition would occur.
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