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Comparing Base, Mid, and High-level Sanitary Finishes [Infographic]

Categorizing levels of sanitary design is helpful to professionals new to compliance regulated industries requiring custom vessels because it bridges communications regarding standards and design requirements.

In hygienic applications, stainless equipment requires a sanitary finish which generally refers to a smooth, scratch-free, non-corrosive finish.  The fineness of the finish, which determines its performance, is measured in RA (roughness average). The infographic illustrates the RA of different types of mill, mechanical, and chemical finishes.  The smaller the RA reading in microinches (height in millionths of an inch), the smoother the finish. 

When collaborating to qualify a project, we define a Base Level Finish as a 2B/Mill, 304 or 316 stainless materials that is pickle passivated.  The welds are continuous and crack and crevice-free.  This type of finish is paired with a Base Level Sanitary Design and is cleaned manually. Apache’s standard portable vessel line are an example of the base sanitary design and finish level.

A Mid-Level Finish is also composed of 304 or 316 stainless material and involves a secondary process of mechanical polishing greater than 32RA, with final finishing to include pickle or nitric passivation. The welds are continuous, crack and crevice-free, and are also ground flush and polished smooth to a specific RA.  Sanitary fittings, mechanical polishing, additional passivation processes and a cleanable design with removable components are categorized as Mid-Level Sanitary Design features.

Providing the smoothest RA readings is an electropolished finish after a series of processes, including mechanical finishing to less than 32 RA, passivation, and nitric passivation, which are common for High-Level Finishes.  The base material is 304/316 stainless. The welds are continuous, crack and crevice-free, ground flush and polished smooth to a specific RA designation less than 32RA.  The sanitary fittings are also electropolished.  Vessels with this level of specifications are typically cleaned automatically.

The specifications, construction and finishing of a vessel is often driven by standards and compliance requirements. All three categories, qualify for ASME UM, ASME U, FDA, 3-A, CRN, PED, BPE.

There are other factors that fall in these base, mid and high-level sanitary design categories, including construction features, processing applications and time to delivery.  Download our e-book “Guide to Sanitary Design for Custom Vessels in Hygienic Industries".


Anatomy of a Sanitary Design Vessel

When evaluating a custom vessel manufacturing partner for a new project, consider the manufacturing capabilities and experience that support the vessel’s application and sanitary requirements.

All custom design stainless vessels for the food, life sciences, pharmaceutical and health industries require sanitary construction. It is the application and automation that drives the level of sanitary componentry.

In reviewing each new custom vessel project, Apache identifies the sanitary requirements to categorize the vessel into a base, mid- or high-level design.  Apache offers a standard line of vessels that qualify for various regulatory compliance agencies.  However, these designs are considered a base level sanitary design, especially because the cleaning of the equipment is manual.  Apache identifies a mid-level sanitary design vessel as having COP (Clean Out of Place) components.

In the video, a custom vessel is animated to walk through characteristics and examples in the highest and most automated level of sanitary design custom vessels.

High-Level Sanitary Design Characteristics Include:

  • CIP (Clean in Place) Process and Components
  • Continuous, crack and crevice-free welds, ground flush and polished smooth to specific RA (Roughness Average) <32 RA
  • 304 or 316 stainless material, mechanically finished to <32 RA
  • Electropolished and Nitric passivated finishing
  • Electropolished sanitary fittings, including:
    • Tri-clamp ferrules
    • Tube connections
    • NA Connects
    • Flush mount outlet valves
    • Sight glasses
    • Orbitally welded j-tubes
    • Dip-tubes
    • Polished internal coils
    • Samples Ports
    • Spray devices
    • Control panels
    • External thermal jacketing

Processes and application in high-level sanitary design vessels include heating and cooling vessels, mixing and processing tanks, WFI tanks, filtering and R & D lab equipment.

Certification requirements is an important part of the sanitary design criteria.  Sanitary design standards include:

3A – A regulation of the design for processing equipment in the food and drug industries. A 3A certificate is proof of FDA compliance.

ASME U and ASME UM -  A regulation of the design of boilers and pressure vessels, including traceability of materials, procedures, testing and documentation.

BPE – A standard within ASME that drives equipment design for the bio-processing, pharmaceutical and other hygienic required industries.

In qualifying design, safety, automation other application details, Apache will facilitate the required compliance for the vessel and provide well communicated delivery, cost and approvals required for a successful project.


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