Maintaining compliance with crane safety standards

The BS 7121 - Code of practice for safe use, inspection, maintenance and thorough examination of cranes has a special status in standards as it is classed as ‘Quasi-legal’ because it gives practical guidance and advice on how to comply with the UK law and is referenced in the LOLER ACOP. So, by following the standard, you will be doing enough to comply with those aspects of UK law covered by the code.

Alternative methods to those set out in the code can be used to comply with the law. However, if you are prosecuted for a breach of health and safety law and it is proved that you did not follow the relevant provisions of the code, you will need to show that you have complied with the law in some other way or a court will find you culpable.

The code of practice for safe use of cranes was first introduced in 1989. In 1991 the inspection, maintenance and thorough examination side of the standards were introduced and form Part 2 of the Series. These parts have been modified over the years, and the most recent versions include many key changes that will apply to common crane types.

The biggest revisions are to the Inspection, Maintenance and Thorough Examination series. Previously Part 2 of the BS7121 series covered inspection and thorough examination and was applicable to all types of crane, however its requirements were heavily biased towards Mobile and Tower Cranes, which caused confusion with other crane types. So the standard was split into parts with specific sections for each crane type and a general section covering all crane types.

A new section is dedicated to maintenance requirements, which did not previously exist. There is now detailed guidance on attributes, skills, training, assessment or competence and CPD (Continuing Professional Development) of those carrying out pre-checks, interim inspections, maintenance and thorough examination. Defined scopes of thorough examination have been introduced and testing requirements have been modernised, while maintaining the requirements for in-service legacy cranes.

Maintenance

BS7121 covers three types of maintenance management. The first is condition monitoring-based planned maintenance. This is a predictive approach because it estimates the remaining life of a crane based on the classification compared with the actual utilisation. This is known as the Design Working Period (DWP) of a crane. Next is planned preventative maintenance. This is a comparative method as maintenance follows a number of cycles or a specific date based on similar historical or experience. Third is breakdown maintenance, which adopts a reactive method: basically fix the crane when it breaks down.

These approaches are not recommended for all crane types and best practice for maintenance is described in the specific crane sections. Condition monitoring is fundamental throughout and is now expected for most crane types. Maintenance record keeping and best practice support for machine history files is included, which is vital for understanding the history of a crane.

There are now sections discussing the attributes of personnel carrying out pre-use checks, in-service inspections, maintenance and thorough examination, of the people – ie, they need to be comfortable working at height, have adequate eyesight, etc. Competence is also mentioned, ie: are they fully conversant with the crane, procedure for working at height, etc? There is guidance on competency assessment and training, necessary training plans and the training records required. What should be done for CPD is also included.

Defined scopes have to be drawn up in advance of an examination. They must be specific for each crane type, however generic scopes are allowed for certain crane types. They must reflect the service history and future use. So basically, before an examination there should be a predefined list of everything to be examined on the specific crane type – and the standard provides example for each crane type.

Supplementary testing

A big change is that periodic overload testing is no longer recommended for cranes. The reason being is that it can overstress the crane and shorten its life. Also, some manufacturers do not recommend overload tests, except following exceptional circumstances or installations – ie, following major modification or repair or to check the integrity of new installation.

Repeated overloads can cause deterioration over time. Most structural failures are the result of fatigue cracking. Defects such as fatigue cracking can be made worse by overload testing but it doesn’t necessarily demonstrate that this defect is present. If it did, then the equipment would fail and that could be expensive and probably dangerous, so there is no defined structural or mechanical benefit – this comes from lots of safety authorities around the world. Finally, some insurance policies won’t cover a crane that has been overloaded in any circumstance, even as a routine test.

The biggest problem with supplementary testing came in the form of BS7121-2-7 for Bridge and Gantry Cranes conflicting with the European CEN standard EN15011. The CEN standard now has the Limit State Design Principle (LSDP) as opposed to the Maximum Stress Principle (MSP) for the design of cranes previously used in the UK. The difference is that the MSP gave a big margin in terms of safety of the structures. This simplified approach to designing cranes worked and led to more robust, long lasting cranes. The testing was proportional to the design criteria; when designing to the MSP, the deflection limit would be 1/750th of the span. With the new LSDP criteria, however, the deflection limit becomes a variable so LSDP cranes designed for low duty, for example, can deflect quite considerably. This causes concern due to the fact that very low duty cranes can bend considerably, acting like a spring, thus making it difficult for an operator to manipulate a load that is bouncing around. A situation might also arise where a crane can bounce off its track. We’ve yet to see this, but the concerns require looking at improvements to EN15011.

On the other side of the coin, a very heavy-duty crane deflects very little. Therefore in the EN15011 standard, the crane manufacturer now has to specify the deflection limit. In the BS7121 series, the person doing the examination after installation must obtain that information from the manufacturer and then test the crane. If the deflection is within 10 per cent of that specified deflection limit then it will have passed. If not, it warrants further examination and inspection to establish the issues.

The BS7121 series has a new philosophy for testing cranes. Traditionally in the UK there would be a static test and a dynamic test. For the latter, the crane is taken through all of its motions at a speed allowed by the control system. Changes to the standard come with the static test, which previously would take the load through a complete cycle to test every tooth and chain of the gear. On the Continent of Europe, the dynamic test is applied and when everything settles down, an additional, static test load is applied, which means that no dynamics are in the crane mechanism. Applying the static load test with motion was not really a problem on old cranes as they were robust enough to take it. But with new LSDP cranes with very low duties, there is a risk of the static load test damaging the crane and causing failure, so it cannot be taken through a motion. This is a considerable safety issue and the reason for changing the UK’s testing philosophy for these cranes.

These are all significant recent changes to the BS7121 series of standards for the safe use of cranes. LEEA will be producing guidance and educating our members on all of the differences as well as updating our training courses in accordance. If you wish to ensure your compliance, I would highly recommend investing the time to study them. In the meantime, LEEA will continue to broadcast the excellence in service, training, maintenance, design, systems, and products provided by LEEA members and ensure that it is delivered to end users and legislative bodies.