Samples of rock, nodules or cobbles from the seabed can provide geologists with valuable insights into the underlying strata and its properties. To obtain these samples efficiently and safely, KUMO developed the Chain Bag Dredge.

Attached to a vessel, the dredge is simply dragged across the desired seabed location, collecting large rock samples while allowing for unconsolidated sediment to wash out. The dredge is available in two sizes and can be optionally equipped with four sediment tubes mounted to the corners of the dredge mouth.

Based on customer information about the load strength of their vessel’s wire rope, KUMO will provide dredge and safety wire ropes with appropriate load strength. Dredge wire rope should have the lowest load strength, while safety wire rope should have a lower load strength than the vessel’s wire rope.

The vessel wire rope is attached directly to both the short dredge wire and the safety wire, forming a dual-wire setup with the dredge wire acting on the front of the dredge and dragging it along the seabed. The safety wire is attached to the back of the dredge for use during the recovery process if required.

The dredge comes equipped with a chain bag to collect the rocks in which cell dimensions can be customised to consolidate a sample size in line with customer requirements.

If the dredge bag gets stuck, the dredge wire can be broken by applying a force in excess of its breaking load. Once the dredge wire rope is broken, the vessel’s wire rope is only attached to the rear of the dredge via the safety wire rope and pulls the dredge away from the rock, rather than towards it. In this way, although the samples may be lost, the dredge itself can be recovered safely. In the rare case that the rescue procedure fails, the safety wire rope can be broken as well. Although the dredge itself will be lost, the vessel’s wire rope is freed and can be recovered safely.