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Method of clearing bulk cargo hang-ups - Self-unloaders procedure - The Cardox System

Dealing with Cargo Hang-Ups Methods:
  1. Hammering on hopper sides.
  2. Using vibrators.
  3. Using fresh water hose from the gate-side or hold side, this being subject to written permission being obtained from the consignee, and informing the relevant Management Office and Owners accordingly.
  4. Air-lances, using compressed air from gate-side or hold-side.
  5. Complete the checklist for man-entry and carry out the man-entry procedure.
  6. The cardox system. NB Use of Cardox System is prohibited without prior approval from the management office.


Note the following for CSL / Marbulk vessels:

If hang-ups are encountered during discharge and vibrators and hammering have no effect, then the CSL office contingency team must be contacted in order to obtain further expert advice with respect to procedures and to liase with the customers at the discharge port.

For vessels calling at Point Tupper it should be noted that the following preventative measures are to be adopted in order to avoid hang-ups of gypsum during the winter season:

The Cardox System:

The Cardox system is a potentially lethal method of clearing hang-ups and is only to be used with office approval and after a full risk assessment has been made. The cardox system was developed in the United Kingdom during the 1920’s for use in coal mines where there was a high methane content in the coal. It uses the rapid expansion of carbon dioxide gas as an explosive force to break up large masses of material. The system consists of steel “shells” which are rechargeable. The shell consists of three sections:
  1. Activating head.
  2. Main CO2 Chamber.
  3. Discharge Cap.

The main CO2 chamber has a heater or detonator fitted at the upper end which has to be replaced after an explosion. The heater is connected electrically via the activating head. It is very important that the electrical connection of the heater is checked for continuity before the shell is charged, as the shell will not explode if the circuit is incomplete.



Between the lower end of the main chamber and the discharge, a bursting disc cap is fitted, which has to be replaced after each explosion. The shell has to be fully assembled, weighed and the weight recorded and then placed into the charging stand where it is connected to a charging pump. The charging pump is in turn connected to a CO2 bottle. The charging pump has a pumping ratio of 60 to 1, (which means that very high pressures are involved inside the Cardox shell). The charging valves can then be opened and charging can commence. Charging is complete when the charging pump stalls (usually after 2 to 5 minutes). If the charging pump does not stall the CO2 bottle is becoming depleted and should be changed for a fresh bottle.

The charging valves are closed and the shell weighed again. The weight of the shell should have increased by 1.25 KG (full charge) although 1.10 KG is acceptable. Any less than this will result in a failed charge. The shell is then ready for use.

When using the cardox system it will be necessary for all “cargo hold man entry” precautions to be carried out. The cardox shell is most effective when a hole is drilled into the base of the hang-up. The hole must be deep enough so that the charge is buried with only the activating head visible. A length of heaving line is to be tied to the eye bolt in the activating head as the Cardox shell drives itself forward into the pile when it explodes. The heaving line will make retrieval of the shell much easier after the explosion. The two electrical conductor wires are then connected to the length of blasting wire and the man entry team retreats to a safe distance.

The team must either leave the cargo hold together or take cover in an empty door away from the hang-up. The electrical detonator is then, and only then, connected to the open end of the blasting wire. When it has been ascertained that everyone is aware that the Cardox is set to explode, and has taken cover, the detonate button may be pressed.

The Cardox shell will emit a powerful explosive force, which is capable of shifting up to two tonnes of material. Several Cardox shells can be connected together in parallel, and detonated simultaneously to create a larger effect on the hang-up. All spent Cardox shells must be retrieved from the hold so that they cannot pass though the gate onto the belt system.


Precautions Against Hang-Ups:




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  23. Directing gate operation, gate problems & crew duties

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  25. Procedure for transporting coal on self- unloading bulk carriers


Our detail pages illustrated many safety aspects of Bulk carrier

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