For chemical and oil tanker vessels with short and hectic trade patterns and limited crew, it may be difficult to prepare cargo tanks to load crude palm oil in a short period of time. As a result, the ideal choice is to allow for downtime in port and to clean all of the designated tanks before the start of the voyage.
Because my prior cargo was Gasoil, I’ll share my experience as well as the process we used to clean and prepare the tanks for loading crude palm oil.
We had a deck crew of eight people and three deck officers. So we held a meeting, reviewed the preparation, and accounted for the available resources. I was able to persuade the team that we had three days to prepare twenty-one cargo tanks. Following that, I had to declare the vessel ready to carry crude palm oil.
The bridge watchkeeping schedule at anchorage is six on and six off, which implies that just the duty officer will be on duty. Male’, Maldives anchorage is a secure location. There will be no possibility of piracy or pilferage. As an outcome, the deck watch was not kept. The deck crew of eight was divided among two groups. Each group will have four crew members doing six on six off. As both an end, each team will receive six hours of minimum rest in any 24-hour period, as required by MLC.
We began by gathering information and inventorying the necessary tools. Confirmed the number and condition of tank cleaning machinery onboard. Tank cleaning lines were fabricated and installed at the Thilafushi working anchorage. All of the Butterworth machines were tested to ensure that they worked properly. Some machines experienced minor water leaks and nozzle rotation issues. Prior to arriving at the task, I rectified the equipment as needed and observed that they were operating properly.
We were fortunate to have 0.05 percent tank cleaning detergent onboard, which came in handy. There was no need to wait for additional supplies.
Because the tanks I possessed were made of stainless steel, there was no need for coating. The book Tank cleaning guide by Dr.A.Verwey should be studied to get all the right tank cleaning procedures. The ISBN for this book is 978-90-800904-3-9. Cleaning charts for 413 products are included in this book.
However, we confirm whether or not the cargo may be carried by our vessel by checking the “International Certificate of Fitness for the Carriage of Dangerous Chemicals in Bulk.” Page 2 to 16 of this certificate demonstrates that the ship satisfies the criteria for the bulk carrying of the products listed therein, provided that the applicable operational provisions of the Code and Annex II of MARPOL 73/78 are followed.
Cleaning chart and practical use of the chart to load crude palm oil
The products have been listed on the left side of the cleaning chart (Table 1) and numbered.
The product numbers have also been listed across the top of the cleaning chart for cross reference.
Cleaning procedures have been registered by letter code A or BB etc.
A description of the cleaning procedures identified by the specific letter code has been given in Table 2 of the Tank cleaning guide.
For each letter code two procedures are given one for coated tanks and one for stainless steel tanks.
When cleaning from one product to another the cleaning chart (Table 1) should be used as follows: The product from which the tank has to be cleaned is found in the outer left hand column.
The number of the product to be removed can also be found in this column.
The number is noted down and next the code of the relevant cleaning procedure can be found at the intersection of the horizontal line against the product to be removed, and the vertical line under the number of the product to be cleaned for.
Let us now work through an example.
Product to be cleaned from: Gasoil
Product to be cleaned for: Palm Fatty Acid
Find the corresponding number of Gasoil in the column (190).
You can find Palm Fatty Acid in same column.
Then the letter code of the relevant cleaning procedure is found at the intersection of the horizontal Gasoil line with the vertical line under no.190
The letter code ‘J’ will be found.
The exact details for this cleaning procedure have been stated in Table 2.
Cleaning procedure I followed for Stainless Steel tanks to load crude palm oil
1. Butterworthing with abundant cold seawater 4 cycles.
2. Butterworthing with hot water (80° C) and 0.05% liquid detergent 2 cycles.
3. Butterworthing with hot freshwater 1 cycle;
5. Draining of tank, line, and pump;
Prewash procedures required by MARPOL 73/78 Annex II are not considered to have an important effect on the “commercial” cleaning procedure.
The procedures stated in the charts are applicable to coated and uncoated tanks; one has to consider however that tank coatings absorb a certain amount of the cargo loaded, depending on cargo and coating properties. Tank washing procedures will not remove all of this absorbed product; often prolonged ventilation at above ambient temperatures will remove most of the absorbing material. Organic coatings like epoxy and polyurethane coatings, which are applied in relative thick coats are known to show this absorption effect.