Skuld P&I Club advises on Loss Prevention
Cement cargoes, which account for about 5% of the dry bulk trade, can prove to be extremely problematic when carried in conventional bulk carriers as opposed to specialized cement carriers. If not dealt with in an appropriate manner, cement carriage can result in cleaning expenses of over USD 100,000 and delay the vessel for a significant period of time.
Image Credit: Skuld P&I Club
BEFORE LOADING:
The main problems with cement cargo arise when holds are not initially dry, clean and watertight. The majority of claims arising from cement cargo are caused by the following factors:
- Solidification when wet
- Contamination by residues of previous cargoes
- Retention of heat when loaded warm
Packaging:
- Cement, if not carried in bulk, is usually shipped in 50 kg paper bags or one/two tonne polypropylene bags.
- These must be further packaged in water-proof material as absorption of moisture or carbon dioxide from the air can significantly deteriorate cement over time.
- The deterioration may not be visible but it significantly reduces its performance.
Solidification:
- It is crucial to ensure all holds and bilges are completely dry prior to loading.
- It is also of paramount importance that all valves in the drain and bilge systems are thoroughly checked and confirmed to be operational. Dysfunctional valves can allow water to seep into holds through the bilge line system causing the cement in the holds to solidify.
Contamination:
- Cargo holds must be clean and odour-free.
- It must be clarified in the charterparty what level of cleanliness is required on delivery and an independent surveyor can be employed to make sure the vessel is ready to load cement.
- Cargo residues such as sugar and fertilizers may result in the contamination of cement cargoes. Raw sugar reacts with cement and even small amounts seriously affect the setting and hardening performance of cement. As little as 0.001% of sugar, if mixed with cement, renders it worthless. Some cement companies do not allow cement to be carried on vessels which have carried previous sugar cargoes.
Temperature:
- It is important to check the temperature of cement before loading, as its temperature can be as high as 110C when leaving the production site. This should especially be considered when loading takes place alongside the factory and cargo is loaded as soon as it is passed through the kilns.
- Loading cement at high temperatures (over 100C), not only damages hold coatings, but also leads to the production of water vapour within the holds.
- Conducting pre-loading surveys to ensure all cargo is below 100C can prevent cargo and vessel damage
When incoming air has a lower temperature than the cargo in the holds, the surrounding air cools and produces vapour which condenses. This results in the solidification of cement in the cargo holds. The wet cement dries in the holds and hardens, leading to troublesome cleaning problems.
- Good ventilation can reduce the occurrence of this, but only when the weather is not extremely humid.
- The temperature can also be raised and the cargo damaged due to heat transfer from the Double Bottom Fuel Oil Tanks. High viscosity, low quality, heavy fuel oil is unpumpable at low temperatures and so heating of the oil becomes necessary. The number of tanks varies depending on the type of vessel, but generally these fuel tanks are located only underneath holds 5, 6 and 7. When the fuel is overheated, the heat is transferred to the plating above the tanks to the holds. The extent of damage varies with the moisture content of the cargo and the duration of the heating. A common cause of this problem is the lack of communication between the Engine and Deck Departments. The Engine Department often does not understand the nature of the cargo loaded on the vessel and thus do not consider the effect of overheating the fuel oil. Another common cause of overheating of fuel oil is the incorrect operation and poor maintenance of steam values, which if not completely closed result in a continuous flow of steam through the heating lines, leading to unnecessary prolonged heating.
Precautions:
- There exist special chemicals that may be applied to the cargo holds before loading that serve to protect the surface from the cargo and subsequent cleaning processes. However, these chemicals must be applied according to the manufacturer’s recommendations as they may prove to be difficult to remove and cause problems when the holds are repainted.
DURING LOADING:
- If it is warm and humid at the port of loading, hatch covers should be closed as soon as loading has been completed to retain dry air inside the holds.
- Hatch covers should also be kept closed during intervals in loading, especially if there is a possibility of rain.
Closed loading systems:
- Closed loading systems entail pumping cargo under high pressure into the holds through a loading chute, while the hold covers remain closed.
- When loading cement in this manner it could result in a large amount of cement dust sticking to the hatch cover undersides, hatch trackways, hatch coamings, drain holes and drain channels. Incorrect loading equipment could worsen the situation. If this cement dust is not cleaned, it would harden and result in the blockage of the drain holes and channels on coming into contact with rainwater or seawater during the vessel’s journey.
AFTER LOADING, BUT BEFORE DEPARTURE
- The main deck, hatch covers, hatch coamings, drain holes and draining channels should be swept and washed down before departure of the vessel.
- If not forbidden by the port due to anti-pollution regulations, these areas should be cleaned with compressed air.
- This prevents any loose cement in these areas from hardening if exposed to water.
Image Credit: Skuld P&I Club
DURING DISCHARGE
- Discharge should not be undertaken during periods of bad weather.
- Charterers may be asked for a LOI if they insist on discharge. This would usually serve to place all liability and damage risks on charterers.
- If charterers have CLH cover, that could be prejudiced by the terms of the LOI.
AFTER DISCHARGE
- After discharge, dry residue and pockets of cement remain loosely adhered to exposed surfaces in the hold, including bilge wells, cargo hold bulkheads, hatch cover undersides and hatch coamings.
- The cement dust in these areas should be cleaned using brooms, brushes and air guns with the help of Cherry Pickers. When all cement dust has been swept away, all areas should be washed with seawater using high pressure hoses (2,500 psi).
- If there is semi-hardened cement visible on the hold surfaces, a more aggressive approach should be employed from the start. Stiff bristle brushes and hand scrapers should be used to remove as much as the cement as possible. If hardened, pressure hoses will not successfully remove the cement and only worsen the situation. Water will aid in the hardening process of the cement, causing more damage and further delaying the cleaning process.
- If manually sweeping and scraping the surface does not remove the hardened cement, additional equipment such as very high pressure washers (20,000 psi) may have to be loaded on board. These are expensive, extremely heavy and cause delay.
- If the hard residues can still not be removed by high pressure water/air, it may become necessary to remove the hardened cement with acid cleaners or specialized machines. The acid may cause damage to the hold paint and thus must be diluted with freshwater. Check the hold paint manufacturer’s recommendation as to which acid cleaners they suggest be used. Acid cleaners must be used with great precaution as they can cause harm to the cleaning crew. Material Safety Data Sheets should always be consulted
Cement dust loosely adhered to exposed surfaces in the holds that must be swept away after discharge (Image Credit: Skuld P&I Club)
For more information visit Skuld P&I Club Cargo Section.
Source:Skuld P&I.