MechChem Africa July 2017

July 2017

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MechChem Africa

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Power transmission, bearings, bushes and seals

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n emphasis on the hygiene element

of thedesignof equipment canplay

an important role in controlling

the safety of manufactured food

products. However, applying this too broadly

without focusing specifically on the hygienic

design of the components part of the system

can potentially risk the spread of bacteria

trapped within bearings, says Davide Zanghi,

theperson responsible for thehygienicdesign

office at SKF.

Hygienic design considers specificallyhow

problems suchas corrosion, lubricant leakage,

cleaning and self-drying could adversely af-

fectfoodsafety–andappliesdesignprinciples

to solve the problem. In essence, it is a design

philosophy applied through dedicated and

specific rules. Just as ergonomic design pays

close attention to the physical needs of prod-

uct users, hygienic design has a laser focus

on preventing issues of food contamination.

In November 2016, Denmark ran its bien-

nialWorldCongress atwhichSKF–amember

of the European Hygienic Engineering &

Design Group (EHEDG) since 2006 – high-

lighted its long recordusing thesedesignprin-

ciples. In general, EHEDGguidelines consider

bearings an easy place to trap food particles

and water and therefore these are seen as

potential breeding grounds that will harbour

bacteria. The best advice is to keep bearings

well away from food product contact areas.

This is very much the case with recent

guidelines on hygienic design of belt con-

veyors for the food industry, where EHEDG

addresses two of themajor challenges in safe

food production: how to avoid contamina-

tion of food through inadequately designed

processing equipment and how to improve

food safety without raising operating costs

for cleaning and production hygiene. Even if

a great deal of attention is concentrated on

systems design, major components such as

belts, bearing and bearing units consistently

have a low profile within the overall hygienic

system design.

However, even if not in direct contact

with the food zone, bearings are often in the

proximity of food products and, with high-

pressure water or dry cleaning regimes, they

Bearings are easy places to trap food particles. SKF has considered this

for a long time in its design principles for bearings, especially so in the

case of the food safety product ranges. SKF has its own hygienic design

offices and has been a member of the European Hygienic Engineering &

Design Group since 2006.

Hygienic design of bearing is key to food safety.

SKF’s hygienic design office. Hygienic design considers specifically how problems such as corrosion,

lubricant leakage, cleaning and self-drying could adversely affect food safety – and applies design principles

to solve the problem.

Hygienic design of bearings

is key to food safety

pose the risk that bacteria – if present

– can become airborne and potentially

contaminate the food product.

In order to minimise the risk of

contamination, designing bearings

with hygienic design principles

in mind is a key consideration.

One of the most important

principles underpinninghygienic design is the

ability to clean effectively. For bearings and

bearing units, thismay be easy to understand

but it is often difficult to achieve in practice.

For a start, the products shouldbemade from

non-corrosive and non-porous materials,

such as stainless steel, or composites, and

with shapes that are cleanable and allow for

self-draining. Bearing units should have filled

bases, which removes cavities where germs

may fester.

In general, materials used such as elas-

tomers, composites and grease, should be

compliant with food safety directives and

regulations. In all instances, any potential for

grease leakage onto the food product during

operation should be avoided.

Ideally, bearingunits shouldhaveeffective

endcoversthatpreventprocesscontaminants

and cleaning fluids fromentering the bearing

units’ cavities and, at the same time, allow for

frequent visual inspection.

Other important aspects include:

• Avoiding metal-to-metal contacts in-

betweenunit components and in-between

units and attaching surfaces.

• Avoiding re-lubrication as much as

possible.

• Achieving a high service life despite

very demanding operating and cleaning

regimes.

Hygienic design applies to food production

andpackagingmachinery in their entirety. But

dealing specificallywithoneof themost prob-

lematiccomponents–bearings–canonlyhelp

to improve the overall risk strategy.