Choosing the right safety interlocks and guarding for a food production line means balancing two things that do not always sit comfortably together: keeping people safe around moving machinery, and keeping the equipment itself easy to clean to a high hygiene standard. Get the balance wrong and you either compromise safety or end up with switches and guards that trap residue and become a contamination risk in their own right. This guide sets out the main considerations, the relevant standards, and the questions worth asking before you specify or replace safety equipment on a line.
Why machine safety in food production is a specific discipline
Most industrial safety switches and interlocks were originally designed for general manufacturing, where the main concern is preventing access to moving parts. Food and drink production adds a second requirement on top of that: the equipment itself has to survive frequent washdown, resist corrosion from cleaning chemicals, and avoid any design feature that could harbour bacteria.
This is why hygienic design has become its own specialist category within machine safety, rather than something bolted onto a general purpose switch. A safety interlock with sharp edges, exposed screw heads or hard to reach crevices is a genuine food safety risk, not just an inconvenience, because those features create places for residue and bacteria to collect between cleaning cycles.
The standards worth knowing
A handful of standards come up repeatedly when specifying safety equipment for food manufacturing, and it is worth understanding what each one actually covers.
ISO 14119 sets out the principles for designing and selecting interlocking devices associated with machine guards. It defines coding levels for actuators, from low to high, which determine how difficult a switch is to defeat or bypass. For applications where tampering is a real risk, a higher coding level is the relevant specification to ask about.
EHEDG, the European Hygienic Engineering and Design Group, publishes guidelines specifically on hygienic design for food processing equipment, including guidance relevant to machine guarding. Equipment that carries EHEDG recognition has been assessed against criteria for cleanability and resistance to bacterial growth, which is a useful shorthand when comparing options.
IP ratings describe how well a switch resists dust and water ingress. For washdown environments, IP69K is the rating to look for, since it specifically covers resistance to high pressure, high temperature hose cleaning, which is standard practice in most food production environments.
EN ISO 13849 covers the safety related parts of control systems more broadly, including the performance level a safety function needs to achieve. This matters when an interlock is part of a wider safety circuit, since the switch itself is only as good as the system it is wired into.
The main types of safety interlock, and where each fits
Mechanical and tongue operated interlocks physically couple a guard door to the machine's power source. They are straightforward, well understood, and widely used, but moving parts and physical actuators can be harder to keep fully clean in a wet environment compared with non contact alternatives.
Non contact interlocks, often using RFID or magnetic coding, detect whether a guard is open or closed without any physical contact between the switch and the actuator. This avoids wear and reduces the build up of debris, which is one reason non contact designs have become common in food and drink applications specifically.
Power to lock and power to release mechanisms differ in what happens if power is lost. A power to lock switch releases the guard immediately if power is cut, which suits situations where a hazard can be made safe quickly once power is removed. A power to release switch keeps the guard locked until power is deliberately restored and a release signal given, which suits machinery with a run down time, such as mixers or equipment with significant inertia, where access needs to wait until the hazard has genuinely stopped.
Network enabled and Ethernet integrated switches are a newer addition, allowing safety devices to communicate status directly over the same industrial network used for control and monitoring. This can simplify wiring and give better visibility of switch status across a line, which is useful on larger or more complex production lines with many access points to monitor.
Questions worth asking before you specify or replace equipment
What hygiene rating does this switch carry, and is it suitable for the washdown regime actually used on this line, not just a generic food grade label.
What is the coding level under ISO 14119, and is it appropriate given how easy or difficult this guard would be to defeat.
Is this a power to lock or power to release design, and does that match how the machine actually behaves if power is lost, including any run down time.
Does the switch material and finish suit the specific cleaning chemicals and temperatures used on this line, rather than a generic stainless steel claim.
If this is replacing an existing switch, will the new device integrate with the existing safety circuit and performance level, or does the wider system need reviewing at the same time.
Getting the balance right
There is sometimes a temptation to treat machine safety as a box ticking exercise, buy a switch with the right certifications and move on. In practice, the right choice depends on the specific machine, the cleaning regime, and how the guard is actually used day to day on the line. A switch that is technically compliant but awkward to use correctly is more likely to be defeated or bypassed in practice, which defeats the purpose entirely.
Manufacturers reviewing their safety equipment, whether as part of a wider line upgrade or simply due for replacement, will find a number of specialist suppliers in our Machinery & Automation directory, covering hygienic interlocks, guarding systems and related safety components for food and drink production environments.
Frequently asked questions
What hygiene rating should a safety switch have for food production? For washdown environments, IP69K is the rating to look for, since it covers resistance to high pressure, high temperature hose cleaning, which is standard practice across most food and drink production sites.
What is the difference between power to lock and power to release interlocks? A power to lock switch releases the guard as soon as power is cut, suiting hazards that become safe quickly once power is removed. A power to release switch keeps the guard locked until a deliberate release signal is given, suiting machinery with a run down time, such as mixers, where access needs to wait until movement has genuinely stopped.
Why are non contact interlocks common in food manufacturing specifically? Non contact interlocks, typically using RFID or magnetic coding, avoid physical contact between the switch and actuator. This reduces wear and avoids the kind of crevices and moving parts that can trap residue, which makes them easier to keep clean in a washdown environment.
Does EHEDG certification replace the need for ISO 14119 compliance? No. They cover different things. ISO 14119 addresses the design and selection of interlocking devices for safe machine guarding. EHEDG guidelines address hygienic design and cleanability. Equipment used in food production typically needs to satisfy both, since safety and hygiene are separate requirements that both have to be met.
REFERENCES
International Organisation for Standardisation, ISO 14119, Safety of machinery, interlocking devices associated with guards, principles for design and selection.
European Hygienic Engineering and Design Group, hygienic design guidelines and certification documentation.
International Organisation for Standardisation, ISO 13849 1, safety of machinery, safety related parts of control systems.
GlobalSpec, mechanical safety interlock switches selection guide, types, features, applications.
Food Safety Magazine, hygienic design of equipment in food processing.
Disclaimer: This article is for general information only and does not constitute engineering, safety or regulatory advice. Food and Drink Network UK is not a safety consultant. Specific machine safety requirements vary by application and should be assessed by a qualified safety engineer in line with current standards and your own risk assessment before any equipment is specified or installed.
