by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Spring-Energized Seals for the Food and Dairy Industries

The food and dairy industries are tough on seals, whether its extreme pressures and temperatures or the limitations posed by using only FDA-approved materials. Spring-energized seals, however, can prove an excellent solution for the challenges posed by these industries. In this week’s blog post, we will discuss spring energized seals in the food and dairy industries. 

Issues for Seals in the Food and Dairy Industries

There are several key issues involving seals for the food and dairy industries. The most obvious is FDA approval, but these seals are also exposed to both extreme temperatures and high pressures. Sanitation procedures are extremely harsh, often involving steam, hot water, and aggressive chemicals to achieve hygienic conditions. In addition, the seals will often be exposed to water for extended periods of time, which could be absorbed by the seal material and result in compromising dimensional changes. Lubrication can also be an issue, which means seals may have to be self-lubricating. Finally, the seals must be reliable, able to perform in less than ideal circumstances.

Spring-Energized Seals

Unlike traditional seals, spring-energized seals include an energized seal provides permanent resilience to the seal jacket. The energizer compensates for hardware misalignment, jacket eccentricity, and wear. These seals are typically made of strong, corrosion-resistant stainless steel with a polymer jacket.

FDA Approved Materials

FDA CFR 177, contained in Title 21 of the Code of Federal Regulations, deals with indirect food additives (i.e., substances that inadvertently make their way into food) in the form of polymers. In addition to FDA regulations, there are other standards in place that apply, including (EU) 1935/2004, NSF/ANSI standard 61 for drinking water systems, and 3A Dairy sanitary standards 18-03 and 20-27.

Spring-energized seals are available in materials that are FDA approved. These materials include UHMW PE (Ultra High Molecular Weight Polyethylene) and PTFE (both virgin and certain grades of mineral-filled) and are both known for low friction, chemical inertness, and the ability to handle rugged sterilization and cleaning procedures that can involve steam, hot water, and aggressive chemicals. Other polymers that might be considered  dependent on the application are certain grades of PEEK and Acetal. In addition, UHMW PE, PTFE, and Acetal are also 3A-Dairy and USDA compliant.

Extreme Temperatures and Extreme Pressures

Food and dairy seals must provide reliable performance in extreme pressures and temperatures. Spring-energized seals are able to maintain a tight seal in temperatures and pressures that would cause more traditional seals to fail. This is primarily due to the spring-energizer that keeps the seal lip intact regardless of dimensional changes due to temperature variation as well as pressure fluctuations. Spring-energized seals are well known for their sealing ability at extreme pressures, including vacuum pressures. In addition, they work extremely well in cryogenic temperatures.

Sanitation Procedures for the Food and Dairy Industries

Food and dairy applications almost invariably involve harsh sanitation procedures that can compromise the performance of typical seals. For example, steam and hot water can cause a significant temperature difference, but the spring-energizer is able to maintain a positive seal even if the seal lip changes dimensions. The right choice of an FDA-approved material can ensure that the seal jacket will remain undamaged in the presence of any aggressive chemicals used. 

Hygroscopic Effects

When seals are exposed to moisture, water, or humidity for extended times, the seal jacket material may absorb that moisture. This can lead to dimensional changes that compromise the performance of the seal. However, with a spring-energized seal, the energizer allows the seal to maintain contact regardless of those dimensional changes. And with a material such as PTFE or UHMW PE for the seal jacket, the possibility of moisture absorption and associated hygroscopic effects is further reduced.

Lubrication

In food and dairy applications, it may not be possible to lubricate seals because of the possibility of contamination. Choosing the right FDA-approved material for a spring-energized seal can eliminate the need for a lubricant because both UHMW-PE and PTFE are dry running, self-lubricating materials.

Reliable Performance

Seals are critical in food and dairy processing: a failed seal can contaminate goods and, if undetected, can put consumers in danger. Spring-energized seals are extremely reliable, both for the reasons already discussed as well as their ability to compensate for issues such as wear, out-of-roundness, eccentricity, and issues with the surface of the shaft. These seals can perform where traditional seals would fail, again thanks to the spring-energizer that keeps the lip of the seal in contact with the shaft. 

Additional Benefits of Spring-Energized Seals

Spring-energized seals can also be used as direct replacements for traditional seals that have failed, even for failures. Because of their durability and resistance to corrosion and contamination, spring-energized seals last longer which in turn leads to reduced downtime and repair costs.

Conclusion

Spring-energized seals are needed in various applications related to the food and dairy 

Industry, including blenders, homogenizers, mixers, process vessels, and hygienic piping systems. For reliable, durable, high performing seals for the food and dairy industries, consider the use of spring-energized seals.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Why PTFE Rotary Shaft Seals Are a Great Choice for Food Processing Applications

While there are several options when it comes to approved polymeric or elastomeric seals for food processing applications, PTFE is one of the more popular choices–and that includes rotary shaft seals, as well.

Why are PTFE rotary shaft seals good for food processing applications? Rotary shaft seals for food processing equipment have to do more than an ordinary seal:  they also need to withstand aggressive cleaning and sanitation regimens that may involve corrosive chemicals, be approved for contact with food, and offer effective, reliable performance. 

How PTFE Rotary Shaft Seals are Used in Food Processing Applications

Food processing machines that make use of shaft seals include mixers, food portioning equipment, dry product filling systems, ice cream dispensers, milk dispensers, high-pressure homogenizers, water purification equipment, and distilled water pumps. They may be used with adhesives, flavorings, water, powders, preservatives, sauces, condiments, steam, and various fluids.

Operating Conditions

Rotary shaft seals for use in the food processing industry must be able to handle the standard operating conditions involved such as speed, temperature, and pressure. However, their operating environment can involve more than that: consideration has to be given to the type of media they will be exposed to (e.g., powders, extremely viscous fluids). 

PTFE is one of the polymers that have a proven track record with rotary shaft seals that have to function over a wide range of temperatures, pressures, and speeds, with various grades available that can offer more customized performance.

CIP/SIP

Rotary shaft seals must withstand the sterilization or cleaning procedures involved. CIP (Clean in Place), SIP (Sterilize in Place), and COP (Clean Out of Place) methods often require aggressive cleaning agents and/or superheated steam, powerful disinfectants, and potentially corrosive acids. 

PTFE is highly resistant to a wide range of aggressive chemicals, can handle repeated exposure to hot water and superheated steam, and will not react chemically to the powerful disinfectants and sanitizers that food processing equipment is exposed to.

Safe for Contact with Food

Any part of a rotary shaft seal that comes into contact with food must conform to the appropriate regulations, such as  FDA 21 CFR 177.1680, (EC) No. 1935/2004, and/or USP Class VI. Such approval is not easy to achieve: it takes into account whether the material releases any chemicals, tends to absorb moisture, goes through physical changes when exposed to high temperatures, reacts chemically to ingredients that are acidic, exhibits off-gassing, and more. 

PTFE comes in grades that are fully compliant with regulations regarding contact with food and FDA approved, making it a safe choice for rotary shaft seals for food processing equipment. In addition, it is the most chemically unreactive polymer on the market today.

Conclusion

Finally, PTFE rotary shaft seals have proven themselves to be highly reliable, which is why you will see them used in dangerous, mission-critical applications where safety and ruggedness are vital, such as those found in the oil and gas or aerospace industries. If you are looking for an FDA-approved rotary shaft seal for use in food processing applications, PTFE seals should be at the top of your list.