A lower command is not safety monitoring

Requesting a lower speed on an operator screen is a process command. An SLS function includes the specified safety monitoring to detect a limit violation and initiate its defined response. This distinction belongs within Machinery safety functions and performance level.

Different architectures obtain speed information in different ways. Not every system requires the same sensor. Check the solution accepted by the manufacturer and the safety performance achieved by the complete arrangement, rather than assuming that a particular component is always necessary.

Choose the limit from the hazard

The permissible speed depends on geometry, available clearance, accessible motion and the consequences of contact or trapping. Identical motor rotation can produce different linear speeds when a transmission or tool diameter changes.

There is no universal figure authorising access to every machine. Observation, adjustment and material removal involve different exposures. The assessment must justify which task is permitted and which additional safeguards remain necessary. A slowly moving mechanism can still exert dangerous force or trap a person against a fixed object.

The transition matters too

When SLS is requested, the machine may still be running above the supervised range. Define how it reaches that range and when the intended operation becomes permissible. A request signal alone does not demonstrate that the required condition has been reached.

If the limit is exceeded or essential information fails, the response must bring the application to its engineered state. Assess interactions with other functions, inertia and movement driven by external loads. These checks prevent a nominally correct speed function from being used in an unsuitable mechanical situation.

Integration and continued validity

SLS does not automatically replace Machine guards or Interlocking devices. It can be combined with other measures for authorised tasks, but that combination must be specified and validated. Slow motion is not a justification for bypassing a protective device.

Retain the basis for the limit, the approved configuration and the results of validation tests. Changes to a transmission, sensor or relevant parameter require a review before returning the machine to service. This preserves the relationship between the speed being monitored and the actual hazard faced by the person performing the task.