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Bulk cement - Preparations, loading, carrying & handling precautions

In the most general sense of the word, cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum, cimentum, cäment and cement.



Cement used in construction is characterized as hydraulic or non-hydraulic. Hydraulic cements (e.g., Portland cement) harden because of hydration chemical reactions that occur independently of the mixture's water content; they can harden even underwater or when constantly exposed to wet weather. The chemical reaction that results when the anhydrous cement powder is mixed with water produces hydrates that are not water-soluble. Non-hydraulic cements (e.g., lime and gypsum plaster) must be kept dry in order to retain their strength.

Concrete should not be confused with cement because the term cement refers to the material used to bind the aggregate materials of concrete. Concrete is a combination of a cement and aggregate.

Bulk cement in good condition

Fig :Bulk cement in good condition prior loading

Cement is a finely ground powder which becomes almost fluid in nature when aerated or significantly disturbed, thereby creating a very minimal angle of repose. After loading is completed, de-aeration occurs almost immediately and the product settles into a stable mass. Cement dust can be a major concern during loading and discharge if vessel is not specially designed as a cement carrier or shore equipment is not fitted with special dust control.

Hazard :It may sift when aerated. This cargo is non-combustible or has a low fire risk.
Stowage & segregation : No special requirement.
Hold cleanliness : Clean and dry as relevant to the hazards of the cargo .
Ventilation : Shall not be ventilate during voyage.

wet cement

Fig :Wet cement must be segregated prior loading




Loading

The ship shall be kept upright during loading of this cargo. This cargo shall be so trimmed to the boundaries of the cargo space that the angle of the surface of the cargo with horizontal plane does not exceed 25 deg. Both the specific gravity and the flow characteristics of this cargo are dependent on the volume of air in the cargo. The volume of air in this cargo may be up to 12 %.

This cargo show fluid state prior to settlement. The ship carrying this cargo shall not depart until the cargo settled. After the settlement, shifting of the cargo is not liable to occur unless the angle of the surface with the horizontal plane excesses 30 deg. This cargo shall be kept as dry as practicable. This cargo shall not be handled during precipitation. During handling of this cargo, all non working hatches of the cargo spaces into which the cargo is loaded or to be loaded shall be closed

Temperature

It is important to check the temperature of cement before loading, as its temperature can be as high as 110°C 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 100°C), 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 100°C 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.

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.
Loading cement using a closed loading system
Fig: Loading cement using a closed loading system


Precautions

Appropriate precautions shall be taken to protect machinery and accommodation spaces from the dust of the cargo. Bilge wells of the cargo spaces shall be protected from ingress of the cargo.

Person who may be exposed the dust of the cargo shall wear protective clothing, goggles or other equivalent dust eye protection and dust filter masks, as necessary. Bilge wells shall be clean, dry and covered as appropriate, to prevent ingress of the cargo.

The loading process into holds results in the creation of large amounts of cement dust settling on all exposed areas. All areas must be swept and/ or washed down after the completion of loading to prevent loose cement from hardening if exposed to seawater or rainwater during the vessel’s journey


Carriage

After completion of loading of this cargo, the hatches of the cargo spaces shall be sealed as necessary. All vents and access ways to the cargo spaces shall shut during the voyage. Bilges in the cargo spaces carrying this cargo shall not be pumped unless special precautions are taken.


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, 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.


Clean up

In the case that the residues of this cargo are to be washed out, the cargo spaces and the other structures and equipment which may have been in contact with this cargo or its dust shall be thoroughly swept prior to washing out. Particular attention shall be paid to bilge wells and framework in the cargo spaces. The fixed bilge pumps shall not be used to pump the cargo spaces, because this cargo may make the bilge system inoperative.

Example
Loading port: – Kanda - Japan

Discharging port : -Kwinana-Australia


Facing problems

A wide variety of problems can exist when carrying cement. When vessels have sailed around the Cape, the cement cargo stored underneath other cargoes is often damaged in the bad weather as it has not been adequately protected or packed. Cement cargoes also run the risk of becoming caked due to water ingress.

One of the major causes of cargo damage in some ports is due to improper handling of the cargo by stevedores; this results in torn cement bags spilling cargo in the hold. Problems often occur due to mismanagement of the cranes and machinery, meaning bags are dropped, which could be very dangerous and can result in cargo being lost over the side. Additionally, theft is a noticeable problem and reminded to remain vigilant.


Things to do
  1. masters should confirm that weather routing advice takes account of the water-sensitive nature of the cargo carried. Masters should let it be known when they have reservations
  2. stevedores and charterers should be approached when incorrect loading equipment is used
  3. before loading cement or other dusty cargoes, the coaming drain holes should be taped over to prevent the entry of dust. Tape should be removed before blowing down
  4. after a closed loading operation, the trackways should be cleaned if possible and cleared to free the drain holes, (if the weather allows). Masters should advise their owners and charterers of this requirement
  5. Make sure the holds are clean and dry before loading
  6. Be extremely careful if the vessel has previously carried a cargo of sugar
  7. Conduct an ultrasonic test before loading to ensure hatch covers are weather tight
  8. Discourage loading and unloading during periods of bad weather
  9. Discourage loading cargo at very high temperatures as this could produce water vapor in the holds
  10. After loading, ensure all cement dust is swept away from all exposed surfaces to prevent it from hardening on contact with rainwater or seawater
  11. Always ensure crew dealing with cement are provided and trained in using the appropriate PPE
  12. Consider carefully the cleaning method to be employed from the very start in the event of hardened cement on the hold surface. A wrong approach can exacerbate the situation, increase cleaning costs and cause significant delays
  13. Aim to include extremely specific clauses regarding delivery, re-delivery and cleaning obligations in the charterparty
  14. Know your obligations and liabilities under the charterparty



Read more on Bulk cement & clinker handling



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Operation of sea going bulk carriers involved numerous hazards . Careful planning and exercising due caution for all critical shipboard matters are important . This site is a quick reference to international shipping community with guidance and information on the loading and discharging of modern bulk carriers so as to remain within the limitations as specified by the classification society.
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