Views:4 Author:Site Editor Publish Time: 2018-03-13 Origin:mantis
It is essential that planned preventive maintenance is carried out at intervals which ensure that worn and damaged components are replaced before the tower crane becomes unsafe, breaks down or fails. Breakdown will cause downtime and a consequent loss of production for the user, whilst a component failure may well result in a partial or total collapse of the crane with potentially fatal consequences for persons in the vicinity of the crane.
Pre-delivery Maintenance and Inspection
Before a tower crane is delivered to site, prior to each erection or alteration, it is essential that it is inspected thoroughly to identify any worn or faulty components and that these are replaced. The results of the inspection should be recorded. This record may be required by the competent person carrying out thorough examination of the crane.
It is considerably easier and less costly to replace components and carry out lubrication and adjustments in a depot, than when the crane has been erected on site. Work on an erected tower crane always involves work at height and presents difficulty in handling heavy components.
Pre-delivery maintenance provides a good opportunity for the completion of supplementary tests before the crane is erected. It is also strongly recommended that the tower crane’s drive and control systems should be powered up and checked for correct functioning during pre-delivery maintenance.
The direct transfer of cranes between sites should be approached with extreme caution as it often leads to both delays in erection and time lost through the correction of faults. Best practice guidance is for direct transfers not to be undertaken and for cranes to be taken back to a depot for full pre-delivery maintenance before the next erection takes place.
Following delivery of the crane components to site the erection supervisor should verify that the pre-delivery inspection was completed at the depot prior to despatch and that the items have not been damaged in transit. He should also verify that the correct components have been delivered in accordance with the build sheet and the manufacturer’s manual.
In-service Maintenance Interval
Once a tower crane has been erected on site it should be maintained at regular intervals to avoid breakdown, failure or collapse. The frequency at which maintenance is carried out should be based on the recommendations contained in the manufacture’s manual for the crane. This should however generally be taken as the maximum interval as various factors, including the following may require the maintenance interval to be reduced:
Usage – Double shifting, frequent lifting at or near the Rated Capacity, long hoist ropes and excessive slewing may accelerate wear of all components;
Environment – Corrosive environments such as marine or industrial sites may accelerate corrosion of structural components, fasteners and wire ropes;
Feedback – Feedback from maintenance records and Thorough Examination reports may indicate accelerated rates of wear and deterioration.
Once established the current maintenance interval should be recorded in the machine history file. Any variation from the manufacture’s recommended intervals must be recorded and justified each time a change is made.
Alteration or Dismantle Pre-Inspection
Before an erected tower crane is altered or dismantled it should be inspected to ensure that there are no defects which could affect the safety of the alteration or dismantling operation. Any defects found during such an inspection should be recorded for inclusion in the machine history file. The details of these defects, together with any corrective actions must be presented to the competent person at the time of the next thorough examination.
Second-hand Tower Cranes
When purchasing second-hand tower cranes their condition should be thoroughly assessed as nothing can be taken for granted. Where possible this assessment should include a review of maintenance records and previous reports of thorough examination.
Once the crane’s condition has been fully assessed any necessary repairs can be carried out and an appropriate in-service maintenance interval established