During industrial safety audits, the question often arises:

Why exactly every five years?

Many people believe that this is required by a specific standard. The reality is more complex than that. The frequency of measurement is actually determined by a combination of legislation, standards, and the operating environment.

To understand the logic behind this, it is worth taking a closer look at:

• what the law says,
• what the standards say,
• and how this relates to measuring the aftermath.

Legal basis: maintaining safe technical condition

In Hungary, the obligation to inspect non-hazardous work equipment is determined by several pieces of legislation. Decree 10/2016. (IV. 5.) NGM stipulates that work equipment must be inspected before being put into service and then undergo periodic inspections at regular intervals during operation.

The frequency of inspections is determined by the operator, taking into account:

• operating conditions
• the rules on occupational safety
• the manufacturer’s documentation

However, it is important to note that the review period cannot exceed five years. This means that if neither legislation nor standards require more frequent inspections, the five-year period is the upper limit.

In the case of dangerous work equipment

Act XCIII of 1993 on occupational safety further reinforces this requirement.

The Act stipulates that hazardous technologies and work equipment must undergo periodic safety inspections to ensure that they remain in a safe technical condition.

The implementing regulation of the Occupational Safety Act (Decree 5/1993 MüM) is more specific:

unless other legislation, standards, or operating instructions prescribe a shorter interval, inspections must be carried out at least every five years.

This rule has become a general reference point in industrial practice.

The role of standards

Machine safety standards primarily define design principles and rarely specify specific inspection intervals. Widely used standards such as EN ISO 13855, which deals with the determination of safety distances, or EN ISO 13849-1/-2, which regulates the design of safety controls, focus primarily on the design and engineering approach.

However, there are also standards that refer to inspections required during operation. EN IEC 62046:2018, for example, deals with the use of non-contact protective devices and recommends a maximum inspection frequency of twelve months. At the same time, the standard also contains an important provision: if local legislation prescribes a different inspection frequency, the provisions of the legislation shall prevail.

In Hungary, this means in practice that the five-year cycle specified in the legislation is often used as the default reference value, especially if there are no stricter regulations for the specific equipment.

Where does stop time measurement come into the picture?

Stop time measurement is related to checking the response time of safety systems.

This is particularly important, for example:

• light curtains
• laser scanners
• other non-contact protective devices

The total reaction time of the system also determines the required safety distance.

If, during use:

• wear
• mechanical change
• system modification

…affects reaction time, it can also alter the safety distance.

Therefore, periodic checking of the reaction time, i.e., measuring the lag time, can be an important part of safety reviews. The purpose of the measurement is to verify that the system is still operating according to the design parameters and that the safety distance is still adequate.

It is important to note that the response time of protective devices does not change over time if their settings remain unchanged. Changes and worn-out components of the system pose the real risk.

Why exactly five years?

In industrial practice, therefore, the five-year measurement cycle does not originate from a single standard. Rather, it is the result of a system in which legislation defines the framework for periodic reviews and standards provide the technical logic for the operation of safety systems.

The five-year interval can thus be interpreted as an upper limit set by legislation. If the operating conditions of the equipment, the manufacturer’s specifications, or standards justify a shorter inspection cycle, then that is what should be applied.

Practice is always risk-based

Ultimately, the frequency of safety system inspections is always determined by the risk associated with the application in question. On an intensively used production line, where drives and actuators are subject to continuous stress, regular inspections may be justified even on a six-monthly basis. In other cases, a five-year interval may be sufficient to verify safe operation.

The bottom line is the same in all cases: the functioning of safety functions must be verified throughout their entire service life. Backtracking measurement is one tool in this inspection process that helps ensure that the system’s response time and safety distance continue to meet safety requirements.