Three levels of control coexist on a tower crane: the crane operator's checks (daily, weekly, fortnightly and monthly), the maintenance company's inspections (every four months) and the inspections by the inspection body (commissioning and every two years).
Daily checks at the start of the shift (annex IV, point 5.1.1)
- Visual check: state of the support base, of the end-of-travel stops and ramps (if it travels), of the plumb, that there is no loss of base ballast or overhead counterweight, the power supply cable, the earth cable and the earth connections of rails, structure and board.
- Operate: disconnect weathervane mode, the start switch, the emergency stop button, the no-load controls of each mechanism and the brakes.
- Check the limiters with the calibrated loads (the values from module 4).
- Deficiencies are noted in the daily check report only on the day they appear, so that the person in charge of the site informs the maintenance company; if there is no note, the crane is taken to be in order.
The crane operator's periodic checks (annex IV, point 5.2)
| Frequency | What is checked |
|---|---|
| Weekly | Track levelling, stops and limit switches; earthing, supply and residual current device; hoisting and trolley limit switches; moment, maximum load and high speed limiters |
| Fortnightly | Brakes; base ballast and counterweights; oil level of the gearboxes; ropes, pulleys and hook; retightening of structure bolts |
| Monthly | Slewing ring |
NTP 701 adds that the crane operator checks daily the steel ropes, the lifting accessories and the safety latch of the hook, and that the residual current device (minimum sensitivity 300 mA) is tested at least once a month. All the check reports are included in the instruction manual while the crane is on site.
Inspections by the maintenance company (article 8)
- Installed cranes and their accessories are inspected periodically at least every four months.
- The user must have a maintenance contract with an authorised maintenance company while the crane is installed.
- A crane that has been out of service for more than three months is inspected before being put back into service.
Inspections by the inspection body (articles 5.5 and 11)
In addition to the two commissioning inspections (before and after erection), a crane kept at the same location for a long time undergoes an extraordinary inspection every two years from commissioning, carried out by an authorised inspection body and without needing to dismantle it.
Essential modifications (article 12)
Changing the reach, the erection height, the load chart, the composition of the mast, jib or counter-jib, the ropes (type or diameter), the ballast and counterweight masses, the speeds or the safety elements is an essential modification: it requires the installation and commissioning documentation, and no modification not foreseen by the manufacturer is allowed.
Source: Real Decreto 836/2003, ITC MIE-AEM-2 del Reglamento de aparatos de elevación y manutención, grúas torre (tower cranes, consolidated text, in Spanish), articles 8, 11 and 12 and annex IV, points 5.1.1 and 5.2 · INSST, NTP 701: Grúas torre. Recomendaciones de seguridad en su manipulación (tower cranes: safety recommendations for their handling, 2005, in Spanish), crane operator's checks