Rice - Protection Materials

January 2004

 

This article is based on a report recently circulated by Allied Maritime Inc, Athens. In recent years Allied have transported substantial quantities of bagged rice and have made some very useful observations which they have kindly offered to share for the benefit of others. 

Background And Observations - Bamboo Mats and Sticks v Kraft Paper and Plastic

It has been common practice to protect rice cargoes using bamboo mats and sticks. These materials are still widely used today in the belief that they provide the best possible protection. Surveyors attending on behalf of Clubs in Thailand and/or Vietnam will almost certainly recommend bamboo mats and sticks as protection material for this cargo. However, Peru will not allow cargo protected by bamboo mats and sticks to be discharged at their Ports. A similar restriction applies in Chile, in the sense that disposal of protection materials like bamboo mats and sticks is not allowed. This has made it necessary for the rice cargoes destined for these countries to be transported with protection material consisting only of kraft paper and plastic sheets and nothing else. In addition, cargoes loaded in Japan and Taiwan have as the sole protection material kraft paper. Having been obliged to transport this cargo with this protection material, Allied observed that at the discharge ports the cargo was coming out in a better condition than when bamboo mats and sticks were used as protection material. 

The observations are based on cargo loaded in Japan, Taiwan, and China and discharged in West Africa and South America as well.

Trials and Results

As a result of these observations, Allied has carried out certain trials: Cargo loaded in Thailand and discharged in Chile had as protection material only kraft paper and plastic. The results were extremely good. In addition, good results were obtained for cargo loaded at Japan and discharged at Banjul and Pointe Noire which had only kraft paper as protection material*. A particularly interesting trial was also carried out on a vessel loading in Thailand, where bamboo mats and sticks were used in holds 2, 3, 4 and 5 but kraft paper and plastic were used in hold 1. The results of this transport were as follows: 

First discharge port - Lagos:

Hold

Number of Caked Bags

1 85 2 1,183 3 3,970 4 1,439 5 5,770

There were also had some 25 kgs bags in all holds. Whereas Hold 1 did not have any party caked bags, the other holds had, Hold 2 - 30 bags, Hold 3 - 228 bags, Hold 4 - 900 bags and Hold 5 - 1,160 bags. 

At the second discharge port, Port Harcourt, Hold 1 had 50 partly caked bags whereas in the other holds the figures  ranged from 150 to 750 bags. 

These results seem to be a clear indication that kraft paper and plastic give better results than bamboo mats and sticks.

Since then, in the vessels they manage, Allied are using kraft paper and plastic as protection material and the results are good. They have used these materials in other vessels with good results. 

The results appear to show that when there is condensation, bamboo mats tend to absorb the moisture and pass this onto the bag that rests on them. Depending on the percentage of moisture, this bag may then pass the moisture on to other bags in contact with it. The greater the condensation, the greater the damage. However, with kraft paper touching the steel places of the ship and plastic separating this from the cargo, the damage is always less. 

As a result of these observations Allied are extremely sceptical about the use of bamboo mats and sticks. They believe that such protection materials can cause damage to the cargo. The damaged bags are those that are in direct contact with bamboo mats. A report recently received from one of Allied's supercargoes attending a vessel chartered by Allied: 

"I have attended disch. operation of m/v ............ at cotonou. From the beginning of disch. until the end, we have experienced enormous quantity of mouldy bags. All of them were the ones who had direct contact with bamboo sticks  and mats. That is to say, 

a- ship side where frames are (port and strbd.). 

b- hoopers (port and strbd.). 

c- tanktops. 

In all holds at these areas, first tier of bags where had direct contact with bamboo + mats are mouldy. As far as I know, bamboo sticks and mats are there to protect the bags from eventual possible sweating of ship's + holds plating. However here we had the opposite. A little sweating of cargo makes mats wet and they damage the cargo."

Ventilation

Ventilation also plays an important role. Allied gives directions to every vessel in this regard however they cannot be sure that these are followed. As an example, one Allied-managed vessel left HCMC for Peru one day apart from another vessel which they had chartered. The vessels arrived half a day apart at Callao. While the managed vessel had less than 50 mouldy bags, the other vessel had 1000s of mouldy bags, even though the vessels had loaded at the same Port, had taken the same course and used the same protection material. The only difference appears to have been that the Allied crew members had followed fully the directions Allied had given; when the weather was good the crew had even slightly opened the hatch covers and the doors of the masthouses thereby allowing ample ventilation with dry air from the sunny surroundings. 

Styrofoam

Another protection material on trial is styrofoam (used in refrigerators and as insulating material in house building). Allied believe that styrofoam in contact with the steel sides of the vessel will protect the cargo from temperature differences and cause less condensation to be formed into the holds. 

Corrugated Bulkheads

Another point relates to the hold's corrugated bulkheads. Many of the local surveyors insist that no cargo is put into this space. In all vessels with corrugated bulkheads empty it has been noted that bags drop down and burst in large numbers. (Also, if the  top cargo is for the first port and that lower down for second or third port(s) then there are often shortages at the first port and surplus at the subsequent ports.) However where cargo is loaded in this space but protected from the plate with kraft paper (always included in Allied-managed ships)  no problems are encountered - no condensation damage, no burst bags or cargo shortage. Allied's experience also shows that engine room and No.1 forward bulkheads also need additional to kraft paper protection like plastic. With these efforts, it is believed that condensation and other damage can be reduced. 

***

The risk of other physical damage on discharge still remains and tallying should be monitored. However, by using these protection materials and ensuring that the cargo is well ventilated, damage arising from condensation can be substantially reduced. 

 

*Allied have made available the discharge surveys showing these results and these can be obtained from the Club