Most machines that need safety work do not need replacing. An obsolete relay, a defeated guard, a new access point or an added robot cell changes one part of the safety architecture — and the engineering task is to establish precisely which parts must change and which can justifiably remain.
A retrofit is rarely a general upgrade. It is normally one specific event that makes the existing safety architecture inadequate or unmaintainable.
A device is no longer available and no verified equivalent has been identified.
A guard switch or protective device cannot be replaced like for like.
Machine layout changes leave operators too far from a stop command.
A new door, hatch or maintenance access is added to an existing enclosure.
Manual intervention increases and fixed guarding is no longer workable.
Setup work requires monitored movement rather than a full power-off.
A gravity-loaded axis must be held safely, not merely stopped.
A cell is re-laid out, extended, or a robot is added to an existing line.
The order matters. Documenting the machine and defining the safety functions before selecting products is what prevents an expensive part-by-part replacement.
Record the existing safety devices, circuits, part numbers, stopping elements and how the machine actually behaves today.
State each required function, its operating modes, its response and the risk reduction it must achieve.
Establish which existing devices, wiring and stopping elements are technically justified to retain.
Separate genuine obsolescence and inadequacy from equipment that is simply old but still suitable.
Choose the evaluation route, the protective devices and the output arrangement as one architecture rather than device by device.
Prove each function in every operating mode, and record the evidence, versions and configuration for the machine file.
A retrofit usually touches two or three of these. They are listed in the order the architecture is normally rebuilt: evaluation first, then detection, then motion and access.
Replacing an obsolete relay, or consolidating several hardwired functions into a maintainable device.
PNOZsigma · myPNOZ · PNOZ X · PNOZcompact · PNOZ s30Adding a guard, upgrading a defeated switch, or introducing locking where run-down demands it.
PSENcode · PSENslock 2 · PSENmlock · PSENhinge · PSENmgate · PITgateboxReplacing fixed guarding with detection where manual intervention has become part of the cycle.
PSENopt II · PSENopt · PSENscan · PSENradarMoving from an expanding set of wired relays to a configurable controller with diagnostics.
PNOZmulti 2 · PSS 4000 · distributed safe I/OAdding monitored standstill or reduced speed so setup work no longer requires a full power-off.
PNOZ s30 · PNOZmulti 2 motion · PMCprotego · safe brake controlRestricting who may operate or enter the machine, and controlling which operating mode is available.
PITreader · PITgatebox · PITmode · PITestopUse the right-hand column when preparing the enquiry. Providing that information is what allows a route to be confirmed rather than guessed.
| Existing requirement | Typical problem | Safety architecture route | Products to review | Information required |
|---|---|---|---|---|
| Single obsolete safety relay | One defined safety function, device no longer available | Safety-relay modernisation | PNOZ X, PNOZsigma, PNOZcompact | Old part number, circuit diagram, the safety function it performs |
| Several relays across one machine | Wiring has grown unmaintainable; no diagnostics | Consolidation into configurable control | myPNOZ, PNOZmulti 2 | Full function list, safe I/O counts, operating modes |
| Guard switch repeatedly defeated | Operators bypass the guard to save time | Coded sensing, and review of why it is bypassed | PSENcode, PSENmlock, PITgatebox | Why access is needed mid-cycle, and how often |
| Guard opens before movement stops | Hazardous run-down after the stop command | Guard locking, or standstill monitoring | PSENmlock, PNOZ s30 | Measured run-down time, load and inertia |
| New manual intervention point | Fixed guarding blocks a needed operation | Electro-sensitive protective equipment | PSENopt II, PSENscan | Opening geometry, stopping time, approach direction |
| Setup done with guards defeated | Adjustment requires movement to be observed | Monitored safe speed with enabling | PNOZ s30, PNOZmulti 2 motion | Drive and feedback details, required safe speed |
| Untrained staff operating the machine | Shared keys; no record of who did what | Identification and access management | PITreader, PITmode | Roles, permissions and the operating modes in use |
| Robot cell extended or re-laid out | Existing protection no longer covers the reach | Area protection with controller evaluation | PSENscan, PNOZmulti 2 | Cell layout, robot reach envelope, access points |
Retrofits rarely stay within one product area. These are the combinations that occur most often in practice.
Format changeover and threading need movement while an operator is close to the machine, so guarding and monitored motion are retrofitted together.
A changed reach envelope or a new access route leaves the original guarding incomplete, and area protection replaces or supplements the fence.
Spindles and flywheels coast well past the stop command, so guard release is moved from a timer to monitored standstill.
Manual loading at each stroke requires detection at the opening rather than a gate, together with a dependable stop and reset arrangement.
Lines extended in stages accumulate relays and pull-wires until the stop zones become unclear, and consolidation into one controller restores clarity.
Frequent intervention by mixed teams leads to shared keys and defeated guards, which access management and mode control address directly.
A retrofit cannot be priced from a photograph of a panel. These items let the existing architecture be understood and a route confirmed rather than assumed.