Development of high speed slurry flow finishing of the inner wall of stainless steel capillary: Polishing and gas flow characteristics of various size of capillaries

A new finishing method for inner wall of capillaries has been developed, in which the polishing is performed by letting the slurry flow through the capillary at high speed. With the increasing number of slurry passes, the surface roughness of as-received capillaries decreases rapidly in the early stage of the low number of slurry passes, and then tends to saturate to a certain level depending on the diameter of the capillaries. It is also found that the decreasing surface roughness of the inner wall results in the increasing conductance of gas flow through the capillary. Accounting for the effect of the capillary diameter D on the differential pressure which is measured in nitrogen gas flow through the capillary at a constant flow rate, an empirical equation is found between the differential pressure P and the surface roughness Ra, logP · D4 = 0.362 + logRa1/6.