ASME BPE Surface Finish Designations: Ensuring Purity and Smooth Surfaces in High Purity Piping and Fittings

ASME BPE Surface Finish Designations: Ensuring Purity and Smooth Surfaces in High Purity Piping and Fittings

The increase in high purity manufacturing has led to a surge in demand in requests for ASME BPE surface finishing for piping and tubing. This is due to the simple fact that product is only as pure as the materials that go into it which are in turn only as pure as the systems they flow through.

ASME BPE Standards for Fluid Processing Equipment

In general, ASME BPE standards cover specifications for the design and construction of fluid processing equipment that require a defined level of control for purity and bioburden. These standards apply to the materials used, the design and construction methods, as well as the inspections, testing and certification of the finished system. Surfaces which are in contact with the product or raw materials during the manufacturing and storage are the primary subjects, but any other system involved in the process, such as filtration, clean steam, water for injection (WFI) and sanitization also fall under these guidelines.

While the finished product may wind up in a tank or other vessel, approximately 90% of the time fluid products and ingredients are in contact with a surface, it takes place within the piping and fittings. Therefore, it is necessary to ensure that the interior surfaces of those components do not contribute to any contamination of the fluids.

ASME Surface Finish Designations: From SF0 to SF6

To this end, ASME has designated seven levels of surface finish, with each having specific requirements regarding how the surface is prepared and its smoothness. These surface finishes are designated SF0 through SF6. Briefly, surface smoothness is defined by its roughness average or Ra value.

The chart below shows a comparison of the different SF designations, how they are achieved and the required smoothness:

Source: Rodger Industries Inc

Surface Finish Designation Requirements

As can be seen in the chart, the order of increasing smoothness does not directly correspond to the numerical designation. SF0 is basic piping and is typically used for non-product contact fluids such as compressed air, chilled water, and steam. By contrast, SF4 is the smoothest surface designation and is therefore the most used in pharmaceutical applications. It is achieved through a combination of mechanical polishing using power equipment and electrochemical process to remove the peaks from any rough surfaces left behind by the mechanical polishing process. One of the key measurements is Max Ra. This measurement ensures that any outlier measurements, such as the tallest ridge on the surface, is brought down to meet specifications.

Importance of Smooth Surfaces in Piping and Fittings

The goal of electropolishing is to achieve a surface which is so smooth, that fluids or solids cannot accumulate. A build-up of debris – even of a purified product – can serve as the starting point for contamination or corrosion. And, as it is happening within the system itself, it may not be caught by filtration mechanisms and go unnoticed until a product fails.

Further, a smooth surface aids cleaning of the system by allowing any remaining ingredients to be flushed reducing the need for cleaning agents that may not be compatible with the manufacturing process.

Processing and Installation of High Purity Piping

It’s also important to remember that this is neither a “plug and play” nor a “set it and forget it” process. To ensure that the piping is going to meet the needs of a high purity manufacturing process, care must be taken before, during and after construction.  In some cases, the tubing can be processed off-site by the manufacturer, transported in sealed packaging, and safely installed on-site without compromising the internal purity of the pipe. But in many cases, the construction or assembly environment will contaminate the tubing interior the moment it leaves the packaging. To meet the necessary standards, it’s common practice to electropolish the piping before installation, followed by cleaning and passivation after installation. This involves removing any debris that may have entered during the assembly process and purging any atmospheric pollutants. The electropolishing process before installation ensures compliance with industry standards, and the subsequent cleaning and passivation after installation further ensure the tubing meets the high purity standards required for manufacturing processes.

Benefits of Proper Maintenance Reduced Downtime & Product Quality

Of course, a properly designed system will have internal filters and a regular schedule for checking and changing them during its operational lifetime. Beyond that, there should also be a science-based schedule for regular maintenance activities such as inspections, cleaning, derouging, and repassivation. In this manner, the integrity, longevity, and reliability of the system can be maintained. This leads to monetary and operational advantages in terms of greater service life, reduced unplanned downtime and fewer – if any – batches of ruined product.

Why Adhere to ASME BPE Standards?

In conclusion, adhering to ASME BPE standards for surface finishing of piping and tubing is crucial for high purity manufacturing processes. The surface finish designations ensure that the interior surfaces of components do not contribute to contamination of fluids, and the electropolishing process before installation guarantees compliance with industry standards. Proper maintenance activities such as inspections, cleaning, derouging, and repassivation can maintain the integrity, longevity, and reliability of the system, resulting in reduced unplanned downtime and improved product quality. Designing to the current ASME BPE standards for high purity can also give companies a competitive edge.

By collaborating with experts in the field like Astro Pak, companies can ensure their systems meet operational goals and take advantage of decades of real-world, practical experience and best practices.

About the

David Taylor

David Taylor

As Astro Pak's Technical Sales Manager for the Gulf Coast Region, David Taylor brings over 10 years of engineering experience with a Bachelor's degree in Chemical Engineering from Missouri University of Science and Technology. David has worked in several industries including cosmetics, food and beverage, chemical, consumer goods, and nutritional supplements. Additionally, his expertise in process and system design, commissioning, validation, maintenance, and project management allows him to guide customers in crafting chemical cleaning and metal finishing solutions to address their unique challenges.

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