The American Society of Mechanical Engineers (ASME) is releasing its 2022 update of Biopharmaceutical Equipment (BPE) standards. The ASME BPE standards clarify that a passivation treatment is not the same as pre-operational flushing of a new system. This addresses a misconception among many operators that a pre-commissioning passivation treatment of a system’s product-contact surfaces is sufficient to remove construction debris. 

The problem largely arose due to a lack of communication. Operators can have the mechanical contractor, a passivation contractor such as Astro Pak, or their own in-house team perform the flushing operation as part of the necessary steps taken to put a new system into operation. However, the problem comes when the passivation provider assumes that flushing has been done while the operator assumes that the passivation treatment will flush the system.   

Flow Velocity and Turbulence Are Key

Most BPE systems are not installed in a cleanroom environment. Welding end facings, grinding dust and debris are just some examples of construction debris that can be left behind. Mechanical polishing of a vessel’s surface creates potential contaminants as well. 

While the passivation treatment involves moving chemistry through the tanks and tubing of a system, it is not required to do so at a velocity that will remove a large portion of debris. This is because the goals of the two procedures are completely different. Proper flushing requires a fluid to pass through the system with enough turbulence to physically move any solids out. On the other hand, passivation aims to make the stainless steel chemically inert. To achieve this, the citric acid solution is circulated at a standard flow rate of 2 feet per second or less at a set temperature with enough contact time to passivate the metal.  And instead of acidic chemicals, flushing uses deionized or reverse osmosis filtered water to avoid erosion, corrosion and the effect of chlorine, found in most potable water systems, upon stainless steel’s surface. 

Ideally, a system should be engineered for pre-operational flushing from the beginning. 

But even when that is the case, the system should be flushed in sections. Careful engineering studies are performed when planning the flushing. The ideal flow rate to remove debris is based on flow calculations. The flow rate to achieve that turbulence depends on the pipe size as well as the length of the run. The type of system is also a consideration. The needs of the system that will handle liquids or gasses differs from those designed to handle lubricants or hydraulic oils. Instead of the 2 feet per second flow velocity for citric acid passivation, flow velocities for proper flushing will need to be between 5 and 25 feet per second depending on the type of system. Frequently, multiple sections of a system can be flushed simultaneously, with flushing continuing through each pipe section until no more debris appears in the filters. 

Passivation contractors do not typically include flushing in the scope of work when submitting a bid to perform a cleaning and passivation service. As a result, if a contractor arrives at the job site only to find out that flushing has not happened, there can be a delay to bring the additional equipment – such as a bigger pump – onsite. 

The New 2022 Changes

The new standards for flushing of construction debris, referred to as SD-2, are evolutionary rather than revolutionary and some of the more important points can be summarized by the following: 

• Fabricators should ensure material traceability is maintained. 
• Sections should be pre-cleaned and capped for shipment to avoid contamination en route and during storage. 
• Cleaned for Oxygen Service systems require extra attention regarding their field storage, assembly and welding. 
• Flushing should be done post-installation using deionized water for liquid-service systems to remove debris prior to injection of chemicals. Those for gaseous services should be thoroughly blown through with clean air. 
• Flushing with an alkaline cleaning solution is discouraged and flushing with acidic solutions is to be avoided due to erosion and corrosion of narrow pathways. 
• Soft parts such as gaskets for valves and other components should be changed out after flushing and passivation activities. 
• The flushing procedure and conditions to confirm success should be laid out for each system. 

Astro Pak’s Role

Astro Pak has a long history of supporting ASME’s mission and that includes the involvement of three current and former employees in its standards committees. Jordan Schaecher, a regional sales manager is part of the BPE surface finishing subcommittee along with the recently-retired Patrick Banes who is the Chair of Surface Finish. Based on field experience, the committee suggested that the flushing standards be made clearer. The subcommittee approved this concept, creating a task group to study the problem with Mr. Schaecher in the lead. 

One incident that helped lead to the suggestion came about when an Astro Pak client discovered metal shavings in diaphragm valve elastomers that were part of a system that had been operating for a year. This was discovered during normally scheduled maintenance. After investigating the situation, it was revealed that while the customer had had the system passivated and the elastomers had been replaced immediately afterwards, the system had not been flushed. This allowed construction and fabrication debris to stay inside the system. The system was flushed and re-passivated before being returned to service. 

What This Means

If these changes are approved, there will be better communication and understanding about what a pre-operational flushing is, the steps needed to ensure it is successful and its importance as part of pre-operational readiness and commissioning procedures that includes flushing, cleaning and passivation. Astro Pak personnel have already been working to educate their clients on the importance of flushing as well as confirming that flushing has indeed been performed on new systems. Making these standards industry-wide benefits both the clients as well as the providers – the very thing ASME is intended to do.