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Reusable fittings: a cost-effective solution

1st April 2013


Any opportunity to extend the service life of equipment and save on cost and replacement, while maintaining or even improving sanitary levels, can be a game-changer for the industry. Jeff Nielson and Robert Safren report.

Fluid transfer can be a demanding and costly element of food and beverage processing. In addition to the need for adherence to the highest standards of sanitation in every step of the process, the equipment is put under considerable stress in these aggressive and active applications from everyday wear and tear.

An important technology component used in food and beverage processing is the hose assembly. It serves as a good example of the kinds of pressures and demands placed on industry equipment. Initially an expensive part of the process, the hose assembly has undergone significant redesign and improvement in recent years and has, subsequently, become a much more cost-effective solution for processing companies.

A lot of effort is made - both by equipment manufacturers and food and beverage processors themselves - to ensure that all elements of these assemblies are sanitary. Whatever the media, hoses are required to impart no taste or flavour to their contents, even after withstanding frequent cleaning - under pressure, at high temperatures - and often with aggressive cleaners.

Hose assemblies must be able to withstand prolonged rough use, especially in high traffic areas like receiving bays, where they are dragged about, constantly mishandled, and are sometimes even run over by heavy equipment like trucks. These are aggressive, active applications. As a result, hoses need to be replaced frequently.

Hoses used in these applications have traditionally had crimped fittings attached - a tight seal has been ensured by compressing the fittings at extremely high pressure. The problem with this practice is that when the used hose is inevitably discarded - because of wear and tear - the fitting also needs to be thrown away, because it cannot be removed and then reused.

Food and beverage processing requires high performance component assemblies in every stage of the process. For hoses, this often means ones that are specially designed for higher temperatures and demanding chemical applications. These hoses must be able to withstand frequent cleaning and sterilization without imparting taste or odour.

In other areas, crush-resistant high pressure hoses must guarantee a secure and flexible connection between system components and piping. These are used for loading and unloading raw products in high-traffic areas.

The same requirements are made for fittings, which are usually made of stainless steel because of the need to stand up to the same rigorous conditions. Fittings that do include plastic components must also meet the same standards as the hoses, in terms of durability and sanitation.

Crimping is a good choice for enclosed, minimal contact applications, where the hose and fitting are left alone. In an enclosed space a well-treated hose can last several years. However, for applications where hoses need to be replaced frequently, this is not a cost effective choice - new hoses cost a fraction of the price of new fittings, yet both have to be replaced on each occasion.

Reusable fittings that could be removed and attached to new hoses would be a better choice for aggressive applications.

The problem that has always come up, however, is how to make a fitting that is practical to reuse. Crimping is not an option because it permanently distorts the metal.

Most designers have considered variations of a two-piece fitting. A stem goes inside the hose, while a sleeve, goes on the outside and screws onto a protruding section of the stem. In this manner, a sleeve can be unscrewed when the hose needs replacing and both parts are recoverable for future use. However, this raises the question of how to deal with galling - the metal to metal displacement that occurs when a stainless steel stem (which is required for sanitary reasons) is threaded into a steel sleeve that goes around the outside.

The fittings have traditionally been made of stainless steel in order to remain sanitary. However, if these components begin to gall during assembly, they can lock in place. This would require them to be physically cut off the hose. Lubricants can be applied to the threads to prevent galling, but these quickly wash away during regular cleaning and do not solve the problem.

As a result, reusable fittings did not seem to be a viable solution.

The advent of new technology, however, opened up a whole new range of reusable fittings for the food and beverage industry.

The problem of galling was solved through an ingenious approach. Reusable fittings were developed with a threaded insert of sterile thermoplastic fixed inside the stainless steel sleeve.

When the separate stainless steel stem was then inserted inside the hose, it would screw into the insert, rather than the sleeve itself. In this way the metal didn't rub against metal, and so galling no longer occurred.

To ensure sanitation levels are met, an O-ring is used to protect the point where the stem and sleeve join; ensuring that when the assembly is washed down, nothing gets into either the hose or the fitting itself. Consequently, reusable fittings can be classified as completely sanitary and the connections can attain 3-A Sanitary Standard approval in the highest regard. The result is fittings that last longer and are completely reusable - able to be removed and reattached multiple times. The sleeve and stem can both be removed and reattached to replacement hoses without the additional cost of purchasing new fittings, which in turn offers considerable savings on standard replacement costs.

Reusable fittings make perfect sense for those aggressive and active applications that proved so costly to crimped fittings. Because the fitting's functionality is not damaged by abuse - only the hoses are - this approach enables processors to replace the low-cost hoses whenever necessary while keeping the same, higher-value fitting. In effect, they can "kill the hose and save the fitting."

In order to meet the varying requirements of the industry, polymeric lines of reusable fittings have now been introduced, as well as metal ones. While the stem remains stainless steel - which is all that the media will come into contact with - the sleeve can be composed of a range of plastics that suit the application needs. The plastic sleeves do not last as long as their metal counterparts, but the result is still a completely sanitary fitting that can be reused several times, saves end-users time and money, without adding any complications.

Ultimately, food and beverage processing companies expect these fittings and hoses to work right from the start - in effect they want to be able to install the products and then forget them. That is what resealing technology now offers - a headache-free experience.

Reliable products and new ways to innovate and improve their practices are key to food and beverage processing companies. That is why it is so important to work with a knowledgeable partner - more than the products themselves, it is experience that is valuable. Saint-Gobain Performance Plastics, has been selling reusable fittings under the ReSeal brand for more than 10 years. In practice, this means ensuring that you partner with an innovative company - one that has deep materials science knowledge and can customise solutions per your requirements, to identify issues and propose effective solutions.

Jeff Nielson is Project Engineer and Robert Safren is Engineering Manager, Saint-Gobain Performance Plastics, Bridgewater, New Jersey, USA. www.process.saint-gobain.eu





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