Meeting digitisation challenges with innovative mandatory lift inspection tests

When first brought into use, lifts must meet the requirements for safety and conformity in their design, construction and installation, and thereafter lift owners are legally bound to ensure the safety of their lifts and all passengers along the operation life cycle.

Systems, including passenger lifts, construction lifts and transport platforms, must be inspected by an authorised inspection agency (AIA) before they are taken into operation, and thereafter inspected periodically. For example, in Germany, the scope, intervals and responsibilities of these mandatory inspections are defined in Annex 2 of the German Ordinance on Industrial Safety and Health (BetrSichV). Lift owners also have a responsibility under the law to keep up to date with any changes that might affect their lift equipment and all inspections must be documented, as specified in Section 17 of the BetrSichV.

Digitisation transforms risk

The dynamic progress of digitalisation is seeing safety-related digital control circuits increasingly replacing or augmenting more traditional mechanical safety devices. This results in a changed risk profile, which impacts equipment operation and inspection, and it requires expert guidance.

?The key characteristic of any equipment that is subject to mandatory inspection is its increased hazard potential. For example, lift systems involve risks such as uncontrolled movements of the lift car, and while the landing doors are open this has the potential to cause significant injury hazards. However, Unintended Car Movement Protection (UCMP) systems should prevent such incidents.

Previously, purely mechanical safety devices, such as classic safety gears, which are intrinsically self-triggering by virtue of their physical design, were relied upon. Today, new digital UCMP safety devices are being integrated into modern lift models. The software of the programmable logic controller (PLC) in these systems captures the lift car’s position, acceleration, velocity and many other parameters. The safety system monitors aspects such as the car’s position during travel and at the landing levels, immediately identifying any unintended movement. If a problem is identified, the PLC shuts off the frequency inverter output, triggers the brakes and ensures a minimum vertical distance of one metre between the sill or transom of the car doors and landing doors. This leaves enough room for passengers to escape shearing and crushing injuries when evacuating the lift.[1]

Increased complexity

Whereas previously the periodic safety inspection of mechanical safety devices required visual testing, followed by a traceable function and effectiveness test, UCMP systems involve a more complex approach and therefore require highly specialised support. It must be ensured that the entire safety chain functions properly to prevent hazards for lift to users or maintenances personnel. For example, various safety-related questions include: “Do the sensors function reliably and as specified? Is the parameterisation of the PLC software correct? Do the brakes work and are they effectively controlled by the PLC?” While digitisation reduces risk, it also adds complexity to mandatory inspections.

The software logic of the firmware behind the application software layer in most PLCs can be particularly difficult – or almost impossible – to examine and understand for lift technicians, safety engineers and third-party experts. In other words, it is impossible to identify at first glance whether a digital safety application is in place and operable, and whether it functions as intended when triggered.

Also, while UCMP electronic controls have various functions for fault diagnosis and self-diagnosis, most are limited to electrical systems and circuits. Continuous monitoring of mechanical components and reporting of diagnosis results, such as brake wear, to the PLC is a rarity. This frequently leaves a “blind spot” in safety assessment, where the status LED of the self-test function displays green, suggesting that everything is in perfect order, while at the same time the control fails to recognise that the brakes are worn. In this case, the safety function would fail in the event of an emergency.

Given these issues, additional new test concepts are required which address the changed hazard potential of equipment subject to mandatory inspection.

Inspection innovation

Traditional test approaches are no longer adequate for modern, digitally controlled and monitored installations. During an inspection, to assess the overall situation effectively, functional safety and cybersecurity knowledge is critical, as the test methods must be verified and aligned to every individual installation. To achieve this, experts require in-depth knowledge of the dependencies between all safety-relevant sub-systems, that are a result of factors such as connectivity. TüV SüD’s experts support managers and operators of lift equipment that is subject to mandatory monitoring, ensuring they apply the specific industrial safety rules correctly.

To identify, assess and reduce possible hazards, TüV SüD has developed its own in-house testing and inspection equipment and methods, for lifts and other installations that are subject to mandatory inspection. For example, TüV SüD ADIASYSTEM supports independent testing of lift traction and the effectiveness of safety gears. The system also facilitates the testing process by eliminating the tedious transport of weights into the elevators e.g. for traction testing.

In-depth inspection experience is of paramount importance, particularly for the final assessment before equipment is put into operation. The inspection must verify that all digital and mechanical components of safety equipment have been configured and parametrised for the specific equipment, and that they have been thoroughly tested and are safe for everyday use, in terms of industrial health and safety. Given this, a thorough analysis must be conducted of the entire installation, that is subject to mandatory inspection, and its safety devices. Inspectors will also be required to review the entire safety chain during periodic inspections, with all components tested, safety functions released, and measurements performed independently of self-diagnosis.

Lift safety compliance and mandatory inspection is a complex process and a highly specialised field, requiring expert advice. The safety of your lift passengers and the reputation of your business may depend upon it. For more information, visit our lifts and escalators website .

[1] Source: https://www.aufzuege.de/bestandsanlagen/nachruestungen-nach-gefaehrdungsbeurteilung/schutzeinrichtung-gegen-unkontrollierte-bewegung-des-fahrkorbes/