Professional Crane Audits: best to renovate old cranes

April 18, 2013 9:24 am

Professional Crane Audits: best to renovate old cranes
Professional Crane Audits (PCA) solution from Demag helps improve the safety, reliability, performance, or ergonomics of 5 to 7-year-old cranes. Bill Shukla writes the importance of PCA and how it works.
Bill Shukla,Business Head -RefurbishmentTerex Material HandlingDemag Cranes and Components (I)
Frequently maintenance planners are faced with the dilemma; whether to recommend replacement of a current equipment, e.g. EOT cranes or to continue using the same with certain modifications, upgrades or repairs, which is what we term as refurbishment.
Only a study of key problem areas will lead one toward the right answer. A decision can also be made if one is aware of the primary objective or a motive for the change or related to safety (current crane is not safe), reliability (crane is unreliable and erratic in performance) or performance (more maintenance required, frequent failures, and higher power consumption).To support the universe of maintenance managers and to provide production heads a decision support mechanism, Demag introduces professional crane audits (PCA) under which provide:• Physical inspections based on objective measurements• Non destructive testing of welds and other critical components• Cycle time study and customer interviews• Thermography and oil sampling• Safe working period (SWP) analysis• Pictorial reports with time-based recommendations based on IS/ISO standards
At the heart of the PCA is the safe working period (SWP) analysis. Based on use, the auditors determine the actual number of cycles the crane structure has been subjected to at the respective load spectrum. The actual number of running hours for hoisting machinery, cross travel machinery and long travel machinery are other parameters that are recorded or calculated.This is then compared with original design class of the crane and estimated crane use as shared by the user over a defined time span in the future.
If the combined utilisation does not exceed the design life, there is a clear case for  refurbishment. This exercise is based on ISO-12482-1, Cranes – Condition Monitoring which defines the various safety factors.
It should be recognised that the different parts of the crane reach their  design limits at different phases, depending on the nature of use and configuration of the crane. These differences are considered in PCA.If it is observed that the use has exceeded design life then a general overhaul (GO) is suggested for all machinery items. After completion of GO the machinery is deemed to have fresh life of 10 years subject to use as per design class.
If crane structures have  exceeded design life, there is likely to be a fatigue in the steel structure and loss of elasticity. If it is a business decision to continue to use the crane, special care has to be taken along with frequent inspections to ensure crane is operating safely for a limited period. In certain cases, the crane capacity or operating class may be derated.
In most cases, it has been observed that crane structure can sustain a few more years of use based on original design, past utilisation, environment and operating conditions. Hence, refurbishment can be carried out in those areas as required by the user.
Where the original design class of the crane is unknown, detailed structural analysis is carried out  along with girder dimensions to determine the class as per current standards. This exercise is difficult and time consuming but is worthwhile for large capacity cranes.
In summary, the PCA service from Demag is for those users who have 5 to 7-year-old cranes and are looking to improve the safety, reliability, performance, or ergonomics of the cranes. A team of professional auditors, studies the cranes and delivers a complete technical evaluation. The final report is one that provides a techno commercial evaluation of all options and is a decision support tool for plant, production and maintenance managers. The PCA audit team at Demag has completed more than 50 audits successfully at various sites.