Water Bag Load Testing Services

The empty water bags are attached to the lifting point, and water is pumped in gradually, raising the load in controlled increments rather than dropping the full test weight in one hit. The load is monitored throughout using calibrated load cells or flow meters, then held for a specified duration to confirm the stability and integrity of the appliance under full test load.

Once the hold is complete and the readings taken, the water is drained, and the bags come away light and easy to handle. The gradual build is the safety advantage over solid weights because, if anything begins to move, deflect, or misbehave, the loading stops immediately, with only part of the test load applied.

A water bag test examines the whole load path, not just the hook. It proves the structural integrity of the lifting points, the mechanical performance of the crane, davit, winch or hoist under load, and the behaviour of brakes and clutches when they are asked to hold and control a genuine test load. Wire ropes, sheaves, and hooks are monitored under stress, and the foundations and mounting points indicate whether they carry the reaction as intended by the design.

For beams and platforms, deflection and stability are measured against the figures the design allows. The result is a complete picture of how the appliance behaves at test load, recorded against calibrated readings, which is exactly the evidence a surveyor, insurer or LOLER thorough examination needs behind it.

Davit testing is where water bags earn their reputation. A davit or lifeboat launching system must be proven under load, but craning solid test weights aboard a vessel is slow, expensive and often simply impossible. Water bags travel empty, rig quickly, and draw their load from the sea or a dockside supply, which makes them the standard method for davits, rescue boat systems and lifeboat launching gear.

We test davit and lifeboat systems on vessels, in shipyards and dry docks, and on offshore platforms, holding the proof load for the required duration and certifying the result. Where the same vessel needs its wider lifting appliances examined, the work runs alongside our Marine LOLER 2006 inspections, so one visit covers the fleet’s obligations.

The method suits any environment where solid weights are impractical or unsafe to bring in. Marine cranes and davits are the classic case, along with offshore platforms, shipyards and dry docks, but the same advantages apply ashore to overhead cranes and hoists in industrial settings, construction lifting beams and gantries, and even theatre rigging and stage lifting systems, where the load must be applied gently above an auditorium floor.

However, there are practical limits worth knowing about. Water bag testing needs a water source and pumping equipment on site, it does not suit environments where water discharge is restricted, and the rigging and load monitoring call for trained personnel.

We assess all of that when we scope the job, and where water bags are not the right tool, our proof load testing service covers calibrated weights and hydraulic methods instead.