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.
EHEDG, the European Hygienic Engineering and Design Group, publishes guidelines specifically on hygienic design for food processing equipment, including guidance relevant to machine guarding.
IP ratings describe how well a switch resists dust and water ingress. For washdown environments, IP69K is the rating to look for, since it covers resistance to high pressure, high temperature hose cleaning.
EN ISO 13849 covers the safety related parts of control systems more broadly, including the performance level a safety function needs to achieve.
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 and well understood, but moving parts can be harder to keep fully clean in a wet environment.
Non contact interlocks, often using RFID or magnetic coding, detect whether a guard is open or closed without physical contact, reducing wear and debris build up.
Power to lock and power to release mechanisms differ in what happens if power is lost, suiting different machine behaviours and run down times.
Network enabled and Ethernet integrated switches allow safety devices to communicate status directly over the same industrial network used for control and monitoring.
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. What coding level under ISO 14119 is 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 the machine’s behaviour. Does the switch material and finish suit the specific cleaning chemicals and temperatures used. If replacing an existing switch, will it integrate with the existing safety circuit and performance level.
Getting the balance right
The right choice depends on the specific machine, the cleaning regime, and how the guard is actually used day to day. A switch that is technically compliant but awkward to use correctly is more likely to be defeated or bypassed in practice.
Manufacturers reviewing their safety equipment will find a number of specialist suppliers in our Machinery & Automation directory.
Frequently asked questions
What hygiene rating should a safety switch have for food production? For washdown environments, IP69K is the rating to look for.
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. A power to release switch keeps the guard locked until a deliberate release signal is given.
Why are non contact interlocks common in food manufacturing specifically? They avoid physical contact between switch and actuator, reducing wear and the kind of crevices that trap residue.
Does EHEDG certification replace the need for ISO 14119 compliance? No. ISO 14119 addresses safe machine guarding design. EHEDG addresses hygienic design and cleanability. Both typically need to be satisfied.
Disclaimer: This article is for general information only and does not constitute engineering, safety or regulatory advice. Specific machine safety requirements vary by application and should be assessed by a qualified safety engineer.
