Sanitary Fittings and Tubing for Food Processors

Introduction

Sanitary tubing and fitting types (referred to collectively as “piping”) and the standards that regulate their use have evolved over the years by trial and improvement. Consequently, a great variety of sanitary piping and standards are in use today. This fact sheet briefly explains the most common sanitary piping and standards and how they are applied. A section with sources of sanitary piping materials is also included.

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Materials

Stainless steel is the most common material used in sanitary piping. This metal has the advantage of cost, corrosion resistance and durability, relative to other materials. Table 1 shows some of the grades of stainless steel and their description. In general, the higher the grade, the better the corrosion resistance. Price increases with grade.

Table 1. Selected grades of stainless steel with brief descriptions.

Surface finish

Description of surface finish of stainless steel components is often confusing, since different reference scales are commonly used, depending upon industry and custom. Two of the most important scales used to measure surface roughness are: Ra and grit. Ra is the “roughness average” specified in the ANSI/ASME standard B46.1 -. The Ra value relates to an arithmetic average of the surface roughness as measured by the stylus motion of an instrument. For comparative purposes, an Ra of 4 corresponds to a “mirror” finish. In the dairy and food industry, surface finishes have traditionally been measured by grit. Grit is the number of abrasive grains per given area. The higher the grit number, the smoother the finish (similar to traditional sand-paper). Table 2 gives a guide for comparison of Ra and grit finish measurements. Comparison of grit to Ra finish is not exact and requires consideration of variable elements such as polishing equipment, materials and technique.

Table 2. Guide to comparison of grit finish and Ra (micro-inch) measurements.

Electro-polishing is a finishing technique that results in a smooth surface due to a chemical-electrical treatment that is most often applied after mechanical polishing steps. Electro-polished piping usually carries the initials “EP” and has a superior, mirror-like finish.

Product piping is polished on the inside, as a minimum, since the product-contact surface should be smooth to prevent attachment of soils and microorganisms. Polished finishes on the outside of piping are normally specified for appearance or to facilitate cleaning. Piping surfaces that are covered with insulation are often specified as unpolished. Industrial grade (mill finish) piping is frequently used for potable water, cleaning solutions or other applications where soil residues and microbial levels are low. Table 3 describes industry standard finish numbers commonly used for food and dairy tubing.

Table 3. Finish number and description for sanitary tubing.

Sanitary Tubing 

Fortunately, the wide acceptance of seamless stainless steel tubing and standardization within the metals fabrication industry has simplified tube selection. Outside diameter and gage is used to specify sanitary tubing. Sixteen-gage tubing is used for the vast majority of applications, except those with large-diameter and/or higher product pressures. Specifications for sanitary tubing are shown in table 4. Tubing is manufactured according to ASTM A270 “Specification for Seamless and Welded Austenitic Steel Sanitary Tubing.”

Table 4. Specifications of sanitary tubing.

Sanitary Pipeline Fittings are manufactured by a long list of companies utilizing a number of joint styles and sealing techniques including (in no particular order): Tri-Clamp or “clamp,” Butt-weld, Bevel Seat, DC, H-Line, HDI-Line, John Perry, S-Line, and I-line. Fitting types have been developed specifically for certain industries, manufacturers and user groups. Adaptors to connect different types of fittings are sometimes available, as well as adaptors to connect fittings to non-sanitary piping such as flanges, pipe thread, pipe OD (compression fitting) and other items. The system designer must select carefully, especially when mating new piping to existing piping and equipment.

In Oklahoma, clamp (figure 1) and bevel seat (figure 2) fittings are the most common for systems that require frequent disassembly. Butt-weld fittings (figure 3) are used for permanent piping systems. Hygienic design and sanitation standards for sanitary fittings and pipeline have been developed by and are available from the 3-A Sanitary Standards Institute (McLean, Va.). Fittings that have been manufactured according to the 3-A specifications and standards bear the 3-A symbol and are accepted nationwide by health inspectors. Sanitary fittings conform to an identification system based on numbers, with examples given in table 5.

Figure 1a. Disassembled clamp fitting, clamp and gasket

Figure 1b. Disassembled clamps

Figure 2. Bevel seat fittings

Figure 3. Butt-weld fittings

Table 5. Selected identification numbers of sanitary fittings.

Food-Grade Gasket Materials

As specified by the 3-A standards, food-grade rubber and plastic material can be used for gaskets in sanitary joints. Table 6 lists selected 3-A approved commercial gasket materials and their working temperature range.

Table 6. Selected list of approved gasket materials and their operating temperature range.

Pipeline Installation

Extreme care and planning must be considered before installation of sanitary pipelines. Professional help should be employed when possible. Installed cost of stainless piping can run from $30 to more than $300 per foot, depending upon many factors. Orbital welding techniques are used to join pipe fittings to tubes or equipment as necessary. Inert gas is employed to prevent weld contamination. Subsequent polishing steps may be necessary, depending upon welding methods selected. Pipeline installation mistakes and rework are costly. Some installation tips follow:

• Begin your project with a drawing (three-dimensional if possible) and include clearance areas for operations, cleaning and maintenance activities.
• Design to minimize piping, valves, joints and fittings.
• Slope lines to facilitate self-draining.
• Support piping at ample locations, considering thermal expansion and dynamic product loads.
• Potable water lines connected directly to sanitary tubing are a violation of plumbing code; lines must be isolated with a physical “air gap.”
• Use check valves and vacuum breakers in steam lines connected to sanitary tubing or cook vessels to prevent product “suck-back.”
• Eliminate dead legs that contain stagnant product in process lines.
• Use flexible connections (hose) at pumps, tanks and other devices that may be moved or frequently disconnected.
• Install quick-release fittings to facilitate cleaning and inspection.
• Insulate only when necessary to prevent operator injury or to protect product.
• Costs of installed piping systems can be dramatically reduced by prefabrication at an outside shop. Use of clamp fittings will facilitate shipping and eliminate or reduce the number of costly on-site welds needed. Warning–precise dimensions and specifications are required!

Summary

Sanitary piping systems are an important part of many food processing operations. When designed, fabricated and installed correctly, they require minimal attention and help to maintain product quality and integrity. Awareness of the great variety of fittings, materials, type and sizes of components available will help during the selection and installation of any sanitary piping system.

Select Sources of Sanitary Tubing and Fittings

National distributors/manufacturers

Alfa Laval

104th Street

Pleasant  Prairie, WI

800-558-

www.alfalaval.us 

Robert-James Sales, Inc.

PO Box

Walden Ave.

Buffalo, NY

800-666-

www.rjsales.com 

Top Line Process Equipment

P.O. Box 264

Bradford, PA

800-458-

www.toplineonline.com 

Waukesha Cherry-Burrell

611 Sugar Creek Road

Delavan, WI 

800-252-

www.gowcb.com 

SwageLock

Tulsa Valve & Fitting Co.

West Detroit

Broken Arrow, OK

918-258-

www.swagelok.com

Local food equipment supplier:

Crouch Supply Company, Inc.

413 Northwest 5th Street

Oklahoma City, OK

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405-235-

Local and mail-order dairy equipment suppliers

Double H Dairy Supply

Pryor, OK

918-825-

Farm Supply Inc.

Chickasha, OK

405-224-

Parts Dept

45 Lynwood Drive

Trumbull  CT 

800-245-

www.partsdeptonline.com 

Meltec Dairy Supplies

Country Farm Drive

Naperville, IL

877-973-

www.meltec.net 

References

3-A Sanitary Standards, Inc., Dolly Madison Boulevard, Suite 210, McLean, VA, -. website: www.3-a.org. 

ASTM (American Society for Testing and Materials), 100 Barr Harbor Drive, West Conshohocken, PA -. website: www.astm.org.

Tim Bowser
FAPC Food Process Engineer

Food processors the world over are facing stricter and stricter restrictions in the form of international regulations and compliance. This is a fact that contributes to the betterment of a healthy globe, but it also comes with a tight learning curve for processors.

You see, as technology evolves and more and more facilities are making use of autonomous components for faster production times, these new pieces of equipment must be tested and confirmed as being ‘food-grade’ first, and only contain materials and finishes that have been deemed safe for use in the food industry (such as food grade stainless steel).

This means that materials, such as food-grade stainless steel, will also be put to the test during audit-time –and if they don’t fit the bill to the letter, it could mean very bad news for the producer. 

So, if you work in food production or are part of a team that designs equipment for the industry, it’s high time that you educate yourself on the potential compliance headaches that can come with surface materials.

Today, we’re going to delve deep into food-grade stainless steel and the form that it must exist in when used in processing facilities.

Why Stainless Steel is The Best Choice for Processors

When it comes to equipment surfaces used in food processing, it’s safe to say that stainless steel is the gold standard for a multitude of reasons. For one, it comes in a wide variety of finishes that serve as strong, versatile options for the most cutting-edge food processing equipment used in today’s facilities.

Here are some more reasons why food grade stainless steel is so often used by food processors:

• Its impermeable surface prevents contamination
• It’s available in a wide range of versatile finishes
• Its smooth surface is designed with easy cleaning in mind
• In its highest quality form, it does not nick, dent, or break easily
• Food grade stainless steel isn’t susceptible to acid erosion that is sometimes created by certain foods
• Its surface provides chemical and bacteriological neutrality
• It’s made to blend easily with other finishes
• It’s made to handle frequent washings with noxious detergents
• Its finish is fire-resistant
• It acts as a neutral surface for food products, which means it doesn’t pick up or transfer any food smells
• When maintained sufficiently, it doesn’t fall victim to corrosion or aging
• It has stain and transfer-resistant properties

Of course, food grade stainless steel won’t be found in each and every component of a food facility, but it does represent most standard finishes. Here are some of its most common applications via Alliant Metals:

• Evaporator tubes
• Flour silos
• Syrup tanks
• Beer kegs
• Ice cream molds
• Conveyor systems
• Double wall food transport container
• Tanks holding dairy
• Food mixers
• Peeling machines
• Food pulverizers
• Confectionary equipment
• Industrial ovens

In addition to the stainless steel used for food-contact surfaces and other materials, food processing equipment is also equipped with equipment nameplates, which convey essential information such as the product name, health and safety warnings, and important equipment data.

Stainless steel equipment nameplates are the preferred choice in the food processing industry, thanks to stainless steel’s antibacterial properties, excellent resistance to dents, scratches, and stains, and superior performance in highly caustic or acidic environments.

Depending on the specifications of the facility and product, stainless steel finishes can also be used for a myriad of other tools and equipment. As you can see by the above applications, its versatile, ultra-smooth surface is appropriate for all kinds of materials and temperatures, whether the food is hot or cold, or in liquid or solid forms.

What Makes a Stainless Steel Food-Grade?

Because there are roughly 150 grades of stainless steel on the market today, it can be very easy to make the mistake of selecting a finish that doesn’t meet all FDA requirements. Having said that, many of the finishes may look similar, but in reality, they are very different when it comes to what they can handle on a day-to-day basis.

Generally speaking, food grade stainless steel boasts surfaces that are much less permeable – and much smoother – than the others. For example, these special forms of stainless steel must be able to withstand acids, alkalis, and chlorides, such as salt, which is frequently introduced to a steel’s surface during processing.

If the stainless steel doesn’t have this property, then these caustic materials could contribute to premature corrosion – and, once corrosion starts to form, the unit must be taken out of circulation immediately because of its uneven surface.

For industrial food applications, where this damaging corrosion is more prevalent, producers may make the choice to put the stainless steel through an electropolishing treatment. This one-time treatment enhances the acid-resistance properties, which could, ultimately, prevent corrosion that might lead to contamination.

Food Grade Stainless Steel Properties to Look for

Now that you know what types of stainless steel finishes make for food-safe and/or food-grade applications, let’s take a look at the properties that every producer needs to be aware of before introducing a component into its facility: 

• It is comprised of the right amount of chromium: In order to be considered stainless, the steel must have a chromium content of at least 11-percent. This factor is the one that makes it resistant to rust and corrosion. Looking at it in scientific terms, it is the chromium that gives the outer-layer of steel its ability to be oxygen-bound; this forms a passivation layer that makes it difficult for rust to form.
• It has a high resistance to heat: As mentioned, one of the reasons why stainless steel is so fitting for a variety of different food processing applications is the fact that it is highly resistant to heat. As a matter of fact, its finish also contains fireproof properties. If its nickel and chromium content (we’ll get more into this later) aren’t at the right levels, then the stainless steel might not be able to withstand the heat needed for industrial food applications.
• It can tolerate moisture and certain chemicals: Virtually all kinds of stainless steels are made to tolerate high levels of moisture and the application of certain chemicals, so it’s no surprise that the food-grade ones can handle these challenges with no fear of pitting, cracking, or corrosion.

The Best Food-Grade Stainless Steels for the Processing Industry

As stated above, there are roughly 150 different types of stainless steels available for use today, but there are only a few that are sturdy enough to be considered “food-grade.”

Though there are certain exceptions to the rule, almost all of the food grade stainless steel is manufactured from 300 and 400-series steel. Here’s why these series are the most suitable for food production applications:

• 300-series: This series is fabricated with both chromium and nickel, with about 18% and 8% by mass, respectively. With this specific formulation, the steel’s finish is non-magnetic.
• 400-series: This series contains mostly chromium paired with a small number of other assortments of other elements. Because of its special composition, the finish will always attract a magnet.

Note: The latter descriptions of both the 300- and 400-series stainless steels are important to pay attention to, as not every stainless steel component should have magnetic–or non-magnetic– properties in its application. If you have plans of purchasing a piece of stainless steel equipment, first ensure that its magnetic properties will fit well and/or not disrupt surrounding equipment or components.

Let’s take an even closer look at the options that are available for processors within the 300 and 400 stainless steel series:

• 304: This is the most commonly-used food-grade stainless steel option on the market today. It is most often used to process dairy, beer, and miscellaneous sanitation practices within a facility.
• 316: Yet another popular food grade stainless steel. It’s a variety that is used more often in commercial food production as it has better corrosion resistance than 304. This is because it contains more of the element nickel than its counterpart.
• 430: This form of food grade stainless steel contains less nickel than those seen in the 300-series, which means it’s more susceptible to corrosion in harsh environments than those that are part of the 400-series. Generally speaking, 430 must be dried soon after it encounters moisture in order to prevent rusting.

Another thing to note is that it’s common to see another set of numbers beside the grade, for instance, “18/8”; this is meant to stand for the stainless steel’s chromium and nickel contents.

If you are looking for a super-sturdy commercial food grade stainless steel, then the higher these numbers, the better. As you know, nickel prevents rusting, but it is not always included in high levels as only certain amounts of it can be consumed per day safely, especially if the person who is consuming the food has an allergy to the element.

These levels are yet another aspect to consider when selecting the stainless steel that will most safely integrate into your food production facility.

What the Food Processing Industry Needs to Know About Stainless Steel

Once the appropriate food grade stainless steel is selected, it’s time that you take pains to gain a working knowledge of your facility’s food-grade surfaces, whatever form they may be in.

Cleaning Your Food-Grade Stainless Steel Parts

From the moment your facility integrates its new stainless steel components, it’s key that you establish a clear, concise cleaning and maintenance plan. Of course, if you are working in commercial food production, then you will already be cleaning the stainless steel regularly in order to adhere to regulations, but the routine cleansing should not stop there. 

Depending on the variety of food-grade stainless steel selected and the food that is encountering the finish, you will choose from this list of appropriate cleaning methods:

• Steam cleaning with water only
• Mechanical scrubbing with customized machine
• Detergents and/or scouring powders
• Alkaline solutions for rust-prone finishes
• Organic solvents
• Nitric acid

Before forming your cleaning plan, be sure that you get advice from your vendor on what works best on your finish – and also be sure that you double-check regulations in order to see what cleaning agents can be used in your processing facility.

Safeguard Your Food-Grade Stainless Steel Against Corrosion

If you have taken the care to select a stainless steel that can withstand the environment of your production line, then you shouldn’t have to fear corrosion too much. But, if you don’t maintain its finish, then you could end up causing some degradation yourself.

One of the most common mistakes that those who are new to working with food-grade stainless steel make is that they clean its finish with a plain steel brush. Although you might use this on similar metal surfaces at home, it should never be used on stainless steel, especially chromium-rich food-grade stainless steel, as the coarseness of the bristles can easily break up the bonding oxide layer. This can lead to cracks, crevices, and rust that can give you compliance issues in the future.

In addition to caring for your stainless steel components, make sure that you follow any and all advice given to you by your vendor. And, because stainless steel, even the food-grade variety, can have pits and corrosion that may not be noticeable with the naked eye, it’s important that you use all of the necessary detection devices in order to ensure that your facility is in line with all binding laws and regulations.

Final Thoughts

Stainless steel is an essential material in the food processing industry due to its exceptional durability, corrosion resistance, and ease of cleaning, all of which contribute to maintaining food safety standards. Different grades, such as 304 and 316 stainless steel, offer varying levels of resistance to harsh environments and chemicals, making them suitable for different applications.

Proper selection, maintenance, and cleaning of stainless steel equipment ensure longevity and compliance with industry regulations. Investing in high-quality food-grade stainless steel ultimately enhances operational efficiency and safeguards consumer health.

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