Sanitary Design Connections - Spring 2020

Sanitary Design Connections - Spring 2020

Contributed for 3-A Sanitary Standards, Inc. by Dennis Glick, U.S. Department of Agriculture, Agricultural Marketing Service

Mar 2020

Why be concerned with the nonproduct contact surfaces when the product does not touch them? This is something I have heard many times during my many years as a USDA Equipment Inspector. Although the criteria for the nonproduct contact areas are not as critical as a product contact area, these areas have the potential for being a source of contamination. The chances of cross contamination from these surfaces increases as there is a human interface between product and non-contact surfaces

First, we need to define what exactly a product contact surface is to better understand what constitutes a nonproduct contact surface. We observe the following definitions in the ANSI/3-A 00-01-2018, 3-A Sanitary Standard for General Requirements:

Product Contact Surfaces: All surfaces which are exposed to the product and from which splashed product, liquids, or soil may drain, drop, diffuse or be drawn into the product or onto surfaces that come into contact with product contact surfaces of packaging materials.

Nonproduct Contact Surfaces: All exposed surfaces from which splashed product, liquids, or other soil cannot drain, drop, diffuse or be drawn into or onto the product, product contact surfaces, open packages, or the product contact surfaces of package components.

The nonproduct surfaces of the equipment must be made of material that will remain corrosion resistant under the conditions of use. This means a surface treatment or material of construction may be corrosion resistant in a dry environment and not be acceptable where high levels of moisture are present. I have found that corrosion can occur between dissimilar metals. Stainless steel is corrosion resistant under most wet and dry conditions. However, when in contact with aluminum or other dissimilar metal, corrosion can take place at this juncture. This condition creates micro harborages that are difficult to clean and create an area for possible cross contamination. If these harborage points are left unchecked, this could ultimately lead to contamination of the product.

During a USDA Plant Inspection, inspectors are instructed to review not only the product contact areas of equipment, but also the nonproduct contact areas. The nonproduct contact surfaces are inspected for proper construction that will not promote unsanitary conditions. This includes poor welds, crevices, hidden areas or difficult to access portions of the equipment. Nonproduct contact areas must be smooth and cleanable. Many potential contamination problems can be avoided by simple routine cleaning these surfaces. In addition, priority must be given to the nonproduct areas that could be subjected to product residues. These areas must be free of all crevices and pockets that will allow accumulation of residues and liquids. A bolted connection here can be a concern as liquids and residues can be drawn into the crevice created and into the threads by capillary action. In some cases, these areas are difficult to access and because of this, they tend to be overlooked during routine cleaning. This can lead to the growth of bacteria, mold and other unwanted conditions. These conditions can also be avoided by identifying these problem areas and adding them as part of normal cleaning procedures.

Exposed threads in a nonproduct contact area that may be subjected to product residues need to be avoided. This may be accomplished by covering the threads with a cap nut or properly shielding the threaded areas from residues.

Electrical control boxes can be an area of concern for a few reasons. The continuous piano type hinges on the door of the control cabinet need to be avoided as these areas have crevices that cannot be cleaned. Another area of concern is the method of mounting the control box or cabinet. These control boxes should be placed on stand-offs to provide at least one inch clearance between the box and the mounting surface to allow inspection and proper cleaning of this area.

In conclusion, the design, maintenance, and cleaning of equipment nonproduct contact surfaces are all important parts of maintaining the integrity of your processing operations.

The ANSI/3-A 00-01-2018, 3-A Sanitary Standard for General Requirements is available for purchase from 3-A SSI, visit

Dennis Glick is Equipment Review Specialist for the U.S. Dept. of Agriculture/AMS. He has served 33 years with USDA, 24 as an equipment specialist. He is a member of the 3-A SSI Board of Directors, the 3-A Steering Committee and he serves as a Certified Conformance Evaluator.

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