Deconstructing Part SF (aka Surface Finish) of the ASME:BPE-2016
Editor’s Note: Diamond Brite Metals preeminence as the country’s expert on architectural and commercial metals polishing is not limited to the mechanical and artistic processes involved in polishing. End-users and Original Equipment Manufacturers (“OEM(s)”) across all industries rely on Diamond Brite Metals to provide substantive knowledge about design, surface finish, and installation to ensure that project specifications are met. Routinely, this includes guidance through the multitude of codes promulgated by standards organizations. In this article, we will distill Part of SF of ASME BPE-2016.
The American Society of Mechanical Engineers’ (ASME) Bioprocessing Equipment Standard (BPE Standard) covers the design and construction or manufacturing of equipment used in biopharmaceuticals. This includes bioprocessing and pharmaceutical end-uses. The standard’s purpose is to establish accepted criteria in the design and manufacturing processes to promote sanitary, hygienic, and safety requirements in these heavily regulated industries. Part SF, known colloquially as the Surface Finish part, governs the standards for surface finishes in metallic and polymeric materials.
Subsection 2.4, titled Surface Condition, mandates that all contact surfaces or those surfaces that come into direct contact with biopharmaceutical elements must be finished through mechanical polishing, cold working, machining, passivation, or electropolishing. Although this list is exhaustive, mechanical polishing is the preferred finishing method due to the ability to ensure surface quality and integrity.
Following the mechanical polishing of contact surfaces, the surface must be examined by either visual examination or through a surface roughness measurement device (i.e. a profilometer) pursuant to subsection 2.3. Only a profilometer will provide an unimpeachable measurement and certification as to surface finish roughness and quality. While a profilometer will measure the number of grit lines in the material in its calculation of surface roughness, a visual examination is necessary to adhere to Part SF’s metallic contact surface finish requirements. Taken together, the visual examination and the measurement by a profilometer after mechanical polishing ensure acceptable surface conditions and surface roughness.
Part SF does allow for some surface imperfections due to the fact that pipe, tube, plate, extrusions are formed through an industrial process. However, Part SF imposes acceptable limits on these imperfections so that they do not jeopardize the contact surface. Some of the accepted imperfections in the material after mechanical polishing are: pits (if diameter <0.020 in), finishing marks (if RA is met), welds (if flush with the base of metal), and scratches (if < respective lengths for tubing, fittings, and other vessels). Dents, nicks, surface cracks, and residuals are unacceptable. These criteria and their barometers ensure that bacteria or agents involved in the biopharmaceutical process does not coagulate in surface imperfections.
The contact surface must be polished to acceptable surface roughness parameters. Part SF defines standards SF0 to SF6 with corresponding RA finishes:
The corresponding RA readings are max values meaning all profilometer readings of the contact surface cannot exceed these values. The profilometer readings must be taken across the lay of the contact surface. Mechanical polishing provides the most exact way to achieve RA readings on contact surfaces.
Diamond Brite Metals routinely polishes material for pharmaceutical and bioprocessing end-uses in accordance with the BPE standard. Our Quality Management Systems ensure that all BPE criteria are met during these projects. Our intimate knowledge of the BPE standard allows us to help guide customer and OEMs in the processing of material subject to the BPE.
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