Crane load testing with the Water Bags method – how does it work?
An onboard crane operates under significant loads whenever it lifts cargo, which is why its lifting capacity must be verified under controlled conditions. This is the purpose of load testing, which ETMAL, a Gdynia-based company, carries out under a PRS certificate of recognition using water weights. The shipowner benefits from the experience of a team that prepares the test, monitors its course and documents the results required to confirm the equipment’s operational condition. The Water Bags method makes it possible to test a crane without transporting heavy weights onto the vessel, while ETMAL performs load tests of up to 500 tonnes.
What are Water Bags and when are they an alternative to solid weights?
Water Bags are flexible containers filled with water which, when suspended from a crane hook, create a test load. Instead of dozens of tonnes of steel or concrete weights being brought on board, folded bags are transported to the vessel and filled with water on site. This solution is mobile, easy to transport and allows the test load to be adjusted to the specific requirements of the test. As a result, the service can be performed directly at a quay, in a port or at a shipyard, without the need to organise complex logistics.
How does the test proceed step by step?
The scope of work depends on the type of crane and the requirements of the classification society, but the general procedure is similar. First, the documentation and technical condition of the equipment are verified, followed by the determination of test parameters, including the required load and operating radius. The water bags are then positioned, attached to the hook and filled with a controlled amount of water. The crane lifts the load and performs the planned movements while the service team monitors the structure, drive systems and brakes. Once the test is complete, the load is lowered, the water is discharged and the results are recorded in a test report. The exact procedure and test parameters are determined individually for each vessel.
When are load tests carried out?
The schedule depends on the requirements of the classification society and the equipment manufacturer. For equipment subject to PRS supervision, a detailed inspection is carried out at least once every 12 months, while testing of lifting appliances installed on a vessel is required at least once every five years. A test may also be required after a major repair or modification, for example following the replacement of structural components or parts of the hydraulic system. The exact schedule should always be confirmed against the vessel’s classification documentation.
Test documentation and results
Following the test, a report is prepared describing the conditions, the load applied and the assessment of the crane’s performance, in accordance with classification requirements. ETMAL documents every stage of the work in service reports supported by photographs. A positive test result, together with the relevant documentation, forms part of the process of confirming the crane’s ability to continue operating in accordance with the requirements of the relevant supervisory authority. If any irregularities are identified, the report provides the shipowner with a clear starting point for carrying out the necessary repairs.
Is your crane inspection or load test approaching? Contact the ETMAL team and schedule the test in advance so that your crane is ready to work when it is needed most.
