Sassenheim-based UCM-Holland, Used Cranes and Materials, hired us to solve a leak in the boom of a Grove TMS 540 mobile crane in Sfax (Tunisia). The seal kit was delivered by them and the crane was repaired with own equipment on the rental company’s premises. The cause appeared to be two seals at the bottom of the upper cylinder, which meant that the entire mast had to be disassembled. After the cylinder repair, the boom was mounted and adjusted again, so that the crane worked again without leakage. We also re-calibrated he load moment limiter.