Selecting materials for standard parts in the food and beverage industry: a buyers’ guide

Hygiene, anti-corrosion and quick delivery remain key factors in the selection of standard parts and machine accessories for the food and beverage sector. But, with material choices ranging from stainless steel varieties to plastics, how do you make the optimum choice for your application?

John Marshall, Technical Manager at WDS Components Parts Ltd., discusses the merits of the materials available for the food and beverage industry.

For food and beverage manufacture, storage or preparation, hygiene is imperative. Work areas must necessarily come into direct contact with bacteria: door handles are designed for physical contact, castors and wheels are susceptible to risk at floor-level and conveyor components are likely to make contact during packaging. As a result, the material composition of components used in the food and beverage industry must be resistant to bacteria as well as being easy to clean effectively.

Resistance to corrosion is also vital, especially where high acidity or salinity is commonplace. This is important to ensure long life of the component as well as maintaining its resistance to pitting and blemishes, making it more difficult to clean and degrading the level of hygiene. Anti-corrosion properties are also key for the cleaning process, where the rigorous application of water is combined with the use of cleaning fluids.

As a result of these demands, stainless steel is frequently the answer: it’s robust, resistant to corrosion and it looks attractive, being a clear marker of visible hygiene. It’s also highly suited to the rigours of a thorough washdown and the applied finish can also remove surface imperfections, such as microscopic blemishes, which could otherwise retain bacteria.

When to specify ‘Food Grade’ materials

The most common type of stainless steel is Type 304, with a higher level of carbon (between 04% and 0.10%) which means it can withstand temperatures up to around 870°C, easily exceeding the tolerance required for food production. Containing up to 10.5% nickel and up to 20% chromium, this makes Type 304 stainless steel widely resistant to corrosion and free from rust. It’s a more economical type of stainless steel, and while it can be used in direct contact with food substances, it’s preferable to use it for applications with less frequent contact to corrosive substances including saline and chloride. It’s frequently found in uses such as door handles, fittings and hinges, and is most suited to areas which require only a mild washdown.

Type 303 stainless steel is also used and its properties are very similar to Type 304. It has a marginally lower durability, however it has improved machinability, a benefit which comes into effect when very low tolerances are involved, such as machining a thread.

The premium level of durability and protection against corrosion is provided by Type 316 stainless steel, suited to uses which have direct contact to food and beverages, including machinery and bowls. Its quality earns it the name ‘food grade’ and it remains the first choice material for the food and beverage industry. Food and beverage OEMs, for example, specify its use throughout.

Adding molybdenum to the alloy makes it highly resistant to corrosion; especially to pitting. In addition to its anti-corrosion properties, Type 316 can also face the demands of an intensive and frequent washdown, vital to maintaining optimum hygiene. It is more expensive than Type 304, though the cost difference is no longer great – providing your chosen manufacturer has the capacity to procure adequate volume and pass on the cost saving to the end customer.

Specific uses of Type 316 include gas struts, frequently used on serving hatches of mobile kitchens, or for ventilation grills where a high level of hygiene is demanded. These applications can often be located outside, open to the elements, or in hostile environments such as a cooking area with the potential of splashes of hot oil or corrosive ingredients.

Other materials suitable for washdown environments

For peripheral, non-food contact items in a food and beverage environment, including some uses of handles, aluminium can also be used. Anodising gives some protection and is ideal if various colour finishes are required, however it can attract an oxide coating which can flake off over time.

Plastics are commonly used for castor wheels, where the softer structure reduces noise and increases grip. Phenolic plastic offers a hygiene level comparable to stainless steel and can be used in temperatures as low as -40°C up to 280°C, useful for example if moving foods from a freezer to an oven. Plastic can also be optionally used for base pads of stainless steel levelling feet, should there be a concern with floor damage using stainless steel directly. Anti-microbial additives can be added to polypropylene, which can be offered in a wide variety of colours.

Expert support for food & beverage manufacturers

When procuring standard parts, it’s important to ensure manufacturing quality and the standard the manufacturer should meet is BS EN ISO 9001:2015, which helps ensure quality management and demonstrates a robust planning and testing process.

WDS designs and manufactures in-house at its Leeds facility, with capabilities including CNC milling, turning, drilling, grinding and honing. Because of our relationship with food and beverage industry specifiers, we’ve been able to implement specific designs, for example a range of hinges with rounded rather than square edges, which decrease build-up of bacteria. Manufacturing quality for the food and beverage industry is also vital, for example we understand the need to ensure a precise finish to optimise resistance to corrosion which improves hygiene. This includes a rigorous test procedure which involves extensive machine operator training, with operators involved in initial testing before thorough batch control. Manufacturing repeat batches every four to six weeks, control data ensures repeatability, delivering consistently high quality each time.

While WDS has an extensive catalogue of over 20,000 parts, an experienced technical team is directly available via telephone to provide advice on material and component selection. The website also hosts 2D and 3D CAD drawings to assist with design integration.

Whatever standard part or machine accessory you need, fast availability is key. WDS has a stock holding which enables next day delivery in the UK across its range. 90% of items are despatched on the same day as order and delivery is worldwide. In addition to a growing customer base in North America, WDS supplies as far afield as the Pacific islands.