A complete range of PPS valves for handling liquid foodstuffs, and more besides.
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Over time, growing concerns over the the release of toxic substances into foodstuffs and drinking water have resulted in a series of restrictions relating to the nature of many materials used in the food and beverage industry.
These materials include brass, which, in 2012, attracted the attention of surveillance bodies due to the presence of lead in some of its standard formulations. Indeed, in order limit tool wear in milling and turning operations, the copper and zinc alloy (OT58 or CW614n) traditionally used in hot press moulding and in the subsequent metal cutting process contains lead in a proportion of around 3%. OT58 is, in fact, traditionally used in the production of valves, taps, fittings and other accessories used in contact with drinking water and various liquid foodstuffs.
The main problem, especially during the initial phase of use of brass products, is the gradual leaching of this heavy metal into water, due to the continuous washing action. This phenomenon, which can cause lead contamination in quantities well above the limits recommended by the WHO, has been studied by several international institutes and become the focus of explicit restrictions (see, for example, OEHHA's Proposition 65 List).
The simplest alternative to OT58 is to choose alloys with a very low or no lead content, precisely in order to avoid any modification of the sensory characteristics of the water and, above all, any health risks. Brass alloys with a low lead content are thus becoming the new materials of choice for applications in the plumbing, heating and sanitary sector, for which OT58 would previously have been chosen.
The time has indeed come to explore some innovative solutions.
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The need to prevent the release of lead and nickel in food applications is pushing many traditional users of OT58 to consider alternative materials for the manufacture of their components and accessories.
One such user, which figures among those more than willing to explore new solutions, is the Italian company ODE (www.ode.it). Headquartered in Colico (Lecco), ODE operates in the design and manufacture of solenoid valves, coils and fluid power systems used, in particular, in the field of automatic vending machines and in office coffee service machines (OCS).
Founded in the 1960s and traditionally prone to the use of brass, ODE recognises the transition to new materials as more than just a technical and engineering challenge. Above all, it sees it as a cultural and practical leap forward in a niche sector in which reliability and reputation carry great weight, given the direct relationship with clients and their very high expectations in terms of quality and technical service.
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The typical project specifications for valves are indeed very strict and rule out the possibility of any exception.
Firstly, the continuous contact with drinking water and other liquid foodstuffs. The material must be compatible with this use and certified by an accredited international body. It cannot therefore release any substance that poses a threat to human health or may otherwise alter the sensory characteristics and nature of the beverage.
The second important specification concerns the temperature of the fluids in the inner chambers of the valves. A vending machines normally handles water at 95°C when preparing hot drinks. At this temperature, the robustness and integrity of the valve body must be guaranteed. Even any liquid leakage from seals or load losses due to local deformations must be absolutely prevented and avoided.
From a mechanical point of view, the pressure exerted on liquids generates considerable stress. Although the infusion process is normally carried out at 16 bars, ODE checks the performance of its devices at pressures higher than 80 bars. The stress is applied statically and pulsating for an extended period of time, simulating the actual operating conditions of the solenoid valves.
As an element belonging to an electromechanical device, if necessary the valve body must be flame proof and carry the UL self-extinguishing certificate.
Finally, life expectancy and the frequency of maintenance operations are fundamental factors, and in both cases should be comparable to those of traditional brass elements, or even better.
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Faced with such a complex combination of technical requirements and the risk scenario inherent to all breakthroughs, ODE's design staff opted for a a 40% glassfibre-reinforced PPS-based compound, i.e. LARTON G/40 by LATI.
The decision to adopt PPS for the innovative generation of valves made of engineering polymer was taken in agreement with LATI’s technicians following a careful analysis of possible alternatives, all discarded for one reason or another: PP and POM for their thermal limits, PA for its hygroscopicity, polyester for hydrolysis problems, PPA for dimensional issues, PEEK for budget constraints.
The final choice is supported by the countless successful applications of PPS-based compounds in the most diverse sectors and under extreme operating conditions.
The most interesting feature of PPS is certainly its considerable resistance to high temperatures, surpassed only by PEEK and very few other high-performance polymers which are however significantly more expensive and complex to process.
The particular chemical-physical nature and structure of PPS macromolecules make this polymer particularly suitable for the injection moulding of very complex thin-wall geometries. Differential shrinkage is minimal, thus ensuring a dimensional accuracy that is often precluded to other thermoplastic resins.
Extremely resistant to aggressive organic and inorganic chemicals, even at high temperature, PPS is also anhygroscopic and therefore its main properties do not deteriorate as a result of prolonged exposure to water or steam.
Thanks to its inherent flame resistance, PPS does not require self-extinguishing additives that could affect not only its mechanical properties but above all its suitability for contact with drinking water.
LARTON G/40 is a compound capable of good structural performance for extreme metal replacement applications thanks to 40% short and thin glassfibre content, a combination that optimizes the reinforcement/matrix interface ensuring the full exploitation of the reinforcement system. The elastic module of LARTON G/40 exceeds 17 GPa with stress at break close to 200 MPa. These values are far superior to those of basic polymers and more than satisfactory when combined with properly designed geometries.
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The first feasibility checks have been carried out by ODE in collaboration with LATI, with FEM analyses aiming to assess the state of stress on the material of the individual valve body during the application of the test pressure at room temperature. The 80 bars of pressure, distributed on the internal surfaces of the two-way and three-way modules, result in local peaks of Von Mises stress below the safety limit (95 MPa) thanks to the application of an aggregate safety factor of 1.8. The resulting deformations were analysed carefully, with the aim of avoiding leaks through the seals. The calculations indicate that deformation under load is limited to a few hundredths of a millimeter.
As a practice, the first prototypes have been subjected to laboratory tests – also including 900 consecutive hours of operation – which are essential for developing the geometry of the valve body, the mould and the production process. As soon as the tests are successfully completed, the mould production process receives the green light.
First on the market, ODE offers its family of PPS valves made in Italy that will quickly allow the company to become the market leader in its sector.
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A few years have now gone by since ODE’s first new product (21JP and 31JP) came out, and the company’s range for the food grade solenoid valve market now contains dozens of different solutions in PPS, PSU, POM and other engineering polymers.
Whether it is used for standard valve bodies, or for NSF-51 certified parts used for example in freestanding automatic drink vending machines or for OCS machines, reinforced PPS, thanks to its peculiar characteristics, can cope with hot food water at 95°C.
The tests on polymers have then highlighted a number of additional strengths. Firstly, a lower tendency to form limescale sediments compared to traditional elements, to the benefit of the reliability and service life of the equipment on the market. PPS valve bodies also allow a considerable reduction in weight compared to metal since the density of LARTON G/40 is 1.67 g/cm3 compared to brass , for example, which is 8.73 g/ cm3. It also ensures a reduction in heat and energy consumption thanks to the thermal conductivity of the polymer which is inferior to that of brass.
All these aspects have also contributed to successfully establishing ODE valves in the hotellerie, restaurant and catering sector (HoReCa) where beverages must be delivered impeccably in line with top quality standards, controlling the flowrate, pressure and temperature of hot water.
Modern ODE PPS valves can also handle other fluids smoothly, such as steam at 140 °C, inert gas, compressed air and liquid foodstuffs. ODE's engineeering polymer systems are therefore used successfully in sectors other than vending machines, including pneumatic systems, industrial automation, medical and sterilization applications.
The growing prominence of solenoid valves made of engineering polymers in the food & beverage sector is strengthened, in particular, by their compliance with the various food industry certifications in force at international level.
All this adds up to a resounding success story for Italian manufacturing — an adventure strongly supported and guided by the synergy of leading companies in their respective sectors.
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