Fixed Piston Gravity Corer

The Calypso and Kullenberg corers are tools used for taking samples of sediment located on the sea floor.

They can retrieve large quantities of sediment without disrupting the historical record.

The piston corer comprises a weight of up to 10 tonnes fitted to an assembly of steel tubes which is tipped with a cutter bit to ensure penetration into the sediment.

The trigger mechanism comprises a lever from which hangs a counterweight. The cable between the lever and the counterweight is as long as the corer plus the desired length of the fall.

In order to collect the sediment, inside the tubes is a plastic liner of approximately 100 mm in diameter which contains a sliding piston of a similar diameter.

The piston’s starting position is just behind the cutter bit. A cable connects it to the lever. The piston cable runs up the inside of the tubes and exits at the top of the weight, where it forms a loop whose length is equal to the distance the corer drops. The piston cable may be given additional slack to compensate for the elastic quality of the cable connecting the trigger mechanism to the ship.

The piston helps the sediment enter the sleeve by creating a depression between the bottom of the piston and the sediment during penetration.

If the ship is unable to withdraw the corer, then the tube can be jettisoned using an acoustic release in order to recover the other parts of the corer. The acoustic release also serves as a beacon to mark the position of the corer on the sea floor.

The Cinema application is used to calculate the optimal configuration of the corer (drop height, weight, counterweight, length of piston cable, etc.).
It can also be used to generate kinematic curves from measurements taken during coring operations, to model coring operations, and to calculate the real position of sedimentary layers in the cores.

The Calypso corer can collect tubular samples of sediment of between 3 m and 70 m in length.

The Calypso is equipped with an acoustic release. The device serves to jettison the tube if it cannot be withdrawn from the sediment or if it is too damaged to be recovered safely by the crew. The acoustic release also serves as a beacon to mark the position of the corer on the sea floor.

General  architecture

The corer comprises the following parts:

1. Steel tube:

  • internal/external diameter: 5½ inches
  • thickness: 10.5 mm
  • PVC sleeve: 100 m internal diameter, 7 mm thick

Diameter of the core: 100 mm.

2. Weight 

3. Trigger 

 

This assembly is connected to the ship via the deep-water cable (textile or steel).

The Kullenberg corer is designed to collect tubular samples of sediment of between 1 m and 20 m.

The corer comprises a trigger, a weight, a steel tube lined with a PVC sleeve, and a piston. The piston does not suck up the sediment, instead it helps the sediment enter the sleeve by creating a slight depression between the bottom of the piston and sediment during penetration.

The corer is triggered at a height of several metres above the sea bottom using a lever-type trigger system.

The depth of the coring operation is limited by the working load limit of the side gantry used to deploy it in the water.

Kullenberg

General architecture

The corer comprises the following parts:

1. Steel tube (external diameter 114 mm, thickness 6 mm, 16 kg per metre of tube) containing PVC sleeve (internal diameter 90 mm, thickness 4 mm).

2. Weight 

3. Trigger lever

This assembly is connected to the ship using the deep-water cable (steel).

Know more