Top 4 Things to Know About Hygienic Pipe Fabrication

Next, we'll look at what materials sanitary pipeline systems are made from, as well as where and how they're constructed. Then, we'll discuss how sections of sanitary tubes are joined together, exploring the relative advantages and disadvantages of threaded, flanged (e.g., Tri-Clamp), and welded connection approaches.

Next, we provide an overview of the myriad of sanitary connector types used to join pipe sections together (elbows, tees, crosses, Y-bends, caps, and reducers). Finally, we'll end with a brief review of additional items to consider when designing and installing sanitary pipe systems, including pipe and tube support and insulation.

1. How Sanitary Pipe and Tube Systems Are Designed

Sanitary process tube networks are complex systems that are generally considered to include the complete interconnection of pipes and their components, including pipe connectors and other fittings and equipment such as pumps, heat exchangers, tanks, and valves.

Let's start with some definitions. While we'll use both the terms "sanitary pipe" and "sanitary tube" interchangeably in this article, the vast majority of the piping used in sanitary processing systems is sanitary tubing.

• Sanitary tubes have thinner walls than pipes, and are more suitable for achieving a cleanable, autogenous, single-pass TIG weld when sections of material are joined together.
• Sanitary tubes are also mechanically polished on their inside surfaces for more effective cleaning.

Improved cleanability is the primary reason why sanitary tubes are preferred over pipes in hygienic processing applications.

Properly engineering and installing a hygienic piping system helps a manufacturer produce high-quality, consistent products, while allowing for efficient and effective Clean-In-Place of their system.

~ Paul Marcink, Director - Installations Services, Central States Industrial

In developing these finished specifications for a sanitary process tubing system, process engineers create two engineering design documents, defined below:

1. Process Flow Diagram (PFD) - shows the relationship between the major pieces of equipment in the product flow system such as pumps, tanks, heat exchangers, etc., and the piping systems to and from the significant pieces of equipment.
2. Piping and Instrument Diagram (P&ID) - shows all major pieces of equipment and system components; tubing details (service, size, specs, rating, insulation, etc.); instrumentation details (all pressure, temperature, and flow instruments required, control and safety pressure valves, meters, etc.); and the actual pipe routing conditions (such as free flow, slope, the maximum length of pipe runs, etc.)

While both documents are critical to the sanitary pipe system design effort, the P&ID is the primary document utilized by process engineers for material procurement and determining pipe routing.

Process piping system design must also include a stress analysis to ensure that pipe and tube routes, nozzle loads, hangers, and supports are properly placed and selected. This analysis confirms the allowable pipe stress is not exceeded under different conditions, including operating loads, pressure testing, etc. This stress analysis is governed by the various international agencies that regulate the hygienic processing industries.

Industry-specific design requirements exist for process tubing systems in each of the different sanitary processing industries. Critical requirements for each of these industries are described below:

Due to the complexity in adequately designing and fabricating sanitary process pipe and tube networks, CSI offers complete design and engineering services that couple 3-D scanning capabilities with CAD data integration.

We’re here to help solve specific hygienic process issues, optimize existing processes, and develop new systems. CSI is also an expert in sanitary pipe welding, custom pipe and fabrication, and quality sanitary surface finishing. From mechanical fabrication, precision machining, sheet metal fab, electrical panel shop, automation and assembly services, we offer custom solutions, precision craftsmanship, and consistent manufacturing results.

2. What Materials Sanitary Pipe and Tube are Made From

Sanitary process piping used in the dairy, food & beverage processing, and biopharmaceutical manufacturing industries must be made from specific materials suitable for producing products under sanitary conditions. Pipes and tubes that carry product flows must be made from corrosion-resistant metal alloys such as stainless steel in compounds 304, 316, and 316L.

AL-6XN® and Hastelloy® C-22® are utilized in some product applications involving highly corrosive ingredients. Steel unable to withstand corrosive materials are not acceptable for product-carrying applications. However, fabricators may use these materials in pipes and tubes carrying utilities such as steam.

Process pipes and tubes used in sanitary processing systems are either fabricated in a pipe shop or in the final field location in which they’re to be installed.

While some piping spools can be pre-fabricated from isometric tubing drawings in a shop, most pipes and tubes for a custom process pipe system are fabricated in the field. To this end, various specialized tools are used in the final assembly of pipe networks at the installation site, including pipe jacks, pipe rollers, pipe cutting and bending equipment, tube facing machines, grinders, and welders (GTAW/TIG manual and automatic orbital).

In particular, using a GTAW/TIG welding process using proper gas purging protocols is a requirement for permanently welded sanitary processing systems. This process produces a consistent, cleanable, high-quality weld when performed by a skilled craftsman.

3. Methods of Joining Sanitary Pipes and Tubes

Regardless of the method used in joining together sections of sanitary pipes, there are some general requirements common to all:

• The pipe connections must be leak-proof. Leaks pose several problems. If process fluids leak out of a pipe joint, contaminates can get in. Additionally, leaking fluids can pose a safety hazard to plant personnel. Product loss from leaking connections is also an issue.
• Like the pipes themselves, connectors (also called ferrules) must be constructed from an approved material such as austenitic stainless steel or a noble alloy such as AL-6XN or Hastelloy.
• Sanitary connectors must have a smooth and polished surface on all surfaces exposed to the product. 32 is the minimally acceptable Roughness Average (or RA) that is allowable for a connector to be deemed sanitary. In certain applications — primarily in biopharmaceutical manufacturing — the surface exposed to the product is often electropolished.

There are several types of connection methods that are approved for use with pipes and tubes in the sanitary processing industries. Each is described in the paragraphs below.

4. Common Types of Connectors Used in Sanitary Pipe Systems

There are various standard types of connectors or fittings used in the sanitary processing industries to form pipe networks, joining together pipes and tubes using one of the methods described in the previous section. Each of these is described in the paragraphs below.

Additional Considerations

Two other items are essential to consider when talking about sanitary pipe and tube installations, namely, pipe supports and pipe insulation.

1. Pipe Supports

Sanitary pipe and tube networks must be supported in such a way so that:

• The combined weight of the pipes and the products they carry do not cause the line to sag.
• Allowing for movement of the pipe due to expansion and contraction.

Various hanger types are used in supporting pipe systems, including straps, clamps, and U-bolts.

2. Pipe Insulation

Many sanitary process pipe networks carry fluids that are hotter or colder than the surrounding environment and must be insulated. Materials suitable for insulating sanitary pipe or tube networks exhibit the following qualities:

• A high-insulation value
• Long life
• Vermin-proof
• Non-corrosive
• Ability to retain shape/insulating value when wet
• Easy to install
• Wash-down rated

Materials suitable for sanitary process tubing insulation include diatomaceous silica, asbestos, calcium silicate, cellular glass, magnesium carbonate, glass fiber, and certain plastic foams.

Contributing Author

Paul Marcink is the Director of Site Services for CSI’s Installation and Service teams. Paul received his M.S. degree in Project Management and B.S. degree in Drafting and Design Technology from Missouri State University in Springfield, Missouri, and brings over 24 years of experience in engineering, designing, fabricating, installing, and maintaining process piping and equipment in the food, beverage, dairy, pharmaceutical, and biotech markets. Paul focuses on leading a team of highly-skilled individuals with passion to help customers achieve their goals.