Safety relays, interlock switches and guard locking switches are the hardware behind a machine's safety functions: the e-stop that drops power, the gate that has to be closed before the cell can run, the door that stays locked until a hazardous motion has stopped. Safety devices are also the parts a plant cannot improvise around, because an unguarded machine does not go back into production. MT.parts keeps 120+ safety devices in stock from the leading industrial brands, including models that are discontinued or no longer sold by the manufacturer.
Where these devices are used
- Robot cells and fenced work areas, with interlock switches on every access gate and guard locking on the ones that open into a hazard.
- Presses, stamping and forming machines, where e-stop and two-hand control circuits are monitored by safety relays.
- Packaging machines and palletizers, with long e-stop chains running across several stations.
- CNC machine tools, where movable guards must be closed and, on some machines, locked while the spindle turns.
- Conveyors and AGV lines, using pull-cord and e-stop devices along the run.
- Food and beverage plants, where washdown guarding favors non-contact switches and metal housings over mechanical actuators.
How to choose a replacement safety device
Safety hardware is not a generic swap, since the device defines how the circuit behaves. Check these before ordering:
- Part number first. The exact code on the device label is the safest match. Search it in our catalog.
- Function monitored, since a relay built for e-stop and gate monitoring is not the same as one for two-hand control, safety mats, light curtain inputs or standstill and speed monitoring.
- Output circuits, the number of normally open safety contacts, the auxiliary normally closed contacts, and whether the outputs are relay contacts or solid-state OSSD outputs, plus the switching capacity they have to handle.
- Input wiring and reset behavior, single channel versus dual channel, with or without cross-fault detection, and manual monitored reset versus automatic reset. Getting this wrong changes the behavior of the whole circuit.
- Supply and coil voltage, typically 24 V DC, 24 V AC, 120 V AC or 230 V AC, matched to what the existing panel provides.
- For interlock and guard locking switches, the actuation principle (magnetic, RFID coded or tongue actuator), the guard locking principle (power to lock versus power to release), holding force, housing material such as metal or plastic, IP rating, and whether the actuator is included or ordered separately.
Safety category, performance level (PL) under ISO 13849-1 and SIL under IEC 62061 are properties of a complete safety function as designed, wired and validated on the machine, not of a component bought on its own. Replacing like for like keeps the validated function as it was assessed. If you substitute a different model, the machine's risk assessment and the verification of the affected safety function have to be reviewed by whoever is responsible for the machine.
If you are unsure which code replaces yours, send us the label data and our team identifies the correct unit.
New, refurbished and obsolete safety devices
We supply three conditions, and the condition is always stated on the product page. New units are factory-sealed. Refurbished units are inspected, repaired where needed and functionally tested before shipping. Obsolete and hard-to-find safety relays and switches are models the manufacturer has discontinued, which is often the only way to restore an existing safety circuit exactly as it was designed and validated, instead of redesigning it. Every device we ship carries a 12-month warranty.
Safety brands and series we stock
- Allen-Bradley: GSR SI and GSR DI safety relays, safety monitoring relays, non-contact interlock switches (magnetic), guard locking switches (metal and RFID), Compact 5000 I/O (5069) safety digital input and output modules (8 points), ControlLogix 1756 digital input (16 points) and digital output (8 points) modules, EtherNet/IP network interfaces
- Omron: safety monitoring relays, non-contact interlock switches and guard locking switches
- Siemens: safety monitoring relays and interlock switches
- ABB: Jokab safety components, including safety relays and interlock switches
- Schneider Electric: safety monitoring relays and interlock switches
Frequently asked questions
What is the difference between a safety relay and a standard I/O module?
A standard I/O module reads and drives ordinary process signals, with no built-in fault detection on the signal path. A safety relay, or a safety-rated I/O module, is built for the safety function: redundant internal channels, cross-fault and short-circuit detection on the wiring, and a defined behavior on fault, which is to go to the safe state. A standard module cannot take the place of a safety device in a safety circuit.
Can I replace a discontinued safety relay with a newer model?
Sometimes, but the newer relay may have different terminals, a different number of output circuits or a different reset behavior, so the circuit has to be rewired and the affected safety function verified again. Replacing with the same discontinued part number restores the circuit as it was designed and validated. We stock obsolete safety relays and switches for exactly that reason.
Do refurbished safety devices come with a warranty?
Yes. New, refurbished and obsolete devices all ship with a 12-month warranty.
How fast can I get a quote?
We reply to quote requests within 24 hours, including part identification when you only have the device label data.
Do you ship internationally?
Yes. We ship worldwide, including to plants outside the United States.
Can't find your part number?
If the safety relay or switch you need is not listed, we source it. Send us the manufacturer, part number and quantity, and our team locates the unit, including discontinued models. Request a quote.
