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Quotes - Engineering - SalesU-Tube Heat Exchangers For
Surface Finish, Polish and Passivation
U-Tube Duty
Ra is the arithmetic average deviation of the surface profile, measured in microinches. Lower is smoother. On sanitary work, 32 Ra on product contact and 40 Ra on exterior surfaces are the numbers most specifications settle on.
Mechanical polishing. Progressive abrasive work to a target roughness. It is economical and effective, and it can smear metal over small defects and occasionally embed abrasive particles.
Passivation. A chemical treatment removing free iron and encouraging the chromium oxide layer to reform. It is a distinct step from polishing, and it is required after fabrication regardless of how the surface was finished.
Request a QuoteSurface Finish, Polish and Passivation Applications
Below 32 Ra, Consistency Beats the Number
Cleanability improves as roughness falls, and the returns diminish. Below about 32 Ra the practical benefit comes more from uniformity and freedom from defects than from a lower average.
A surface at 20 Ra with a scratch, a fold or a patch of heat tint is worse in service than a consistent 32 Ra surface with none of those. Specify what will be verified and verify it.
Selection Data We Need
Flow rate and identity of both fluids, inlet and required outlet temperatures, operating and design pressures, allowable pressure drop on each side, and any code, alloy or hygienic requirement. Fouling history, turndown range and cleaning method matter as much as the design point.
