First of all, tank entry is a dangerous task. We called it confined space entry. There is a danger of low oxygen level in the tank as well as hazardous gas inside it. As a precaution, the tank need to be ventilated properly with a blower for a day or so and check with oxygen meter before entering to ensure the oxygen level is sufficient and hazardous gas is at the minimal. Safety helmet, heavy duty glove, safety shoes and overall must be worn for safety reason. By the way, it is dark inside the tank, a good torch light is needed.
To enter a tank, one must enter via man hole as shown. It is pretty small and can fit a single body into it at a time. Big sized person will find it impossible or hard to even pass through it.
What I shown here are photos of ballast tanks of a 21 years old ship. Corrosion usually will happen in ballast tanks as the tanks are filled with sea water, which is salty and promote corrosion. Fuel oil tank and fresh water tank tend to be in better shape but for older ships, it is worth to check as I had seen badly corroded fresh water tank. When ships are newly built, all the tanks are properly coated. Coating will breakdown as the years goes by. Usually, by 15 years old or so, corrosion will be noticeable.
Zinc anode attached by M-clamp on top right
One way to combat continuous corrosion on older ship is using sacrificial zinc anode inside the tanks. For better results, the tank structure need to be fully sand blasted, wasted structures renewal and tank to be fully coated. This procedure however is costly and time consuming.
It is really uncomfortable when inside the tank. It is hot, dirty, smelly, rusty, cramped and dark. European ships tend to have a bigger tank for a person to navigate but Japanese and Korean ships tend to have small and tight tanks to navigate inside it. I know some ship/marine surveyor who died due to cancer. I suspect entering ballast tank on a continuous basis somehow contribute to this cancer. Imagine they have to enter tanks on average 2-5 times a month. A ship usually has a few tanks, so do the Maths. As for me, I have to follow the ship/marine survey whenever they enter the tank for inspection. For me, on average I probably have to do tank entry 3-5 ships per year. Let’s just hope I won’t die of cancer.
I will definitely get very dirty when coming out of the tanks. Just take a look at the gloves above. It could be sludge, mud or unknown substances to me. These stains are hard to be removed as can be seen on my nail after second wash. There a few stain mark on my nail.
I usually was nagged by my mother and wife after messing my overall. What you see here is just stain after entering 1 tank. For a ship, I need to enter 8-20++ tanks depending on the ship design and the amount of tanks the ship has. So, the end result of the overall is beyond my words. The stain will remain even after washing it many times with Clorox Bleach. A senior surveyor once advises me to boil the overall to get the best cleaning result. I never tried it as I usually throw the overall away once it is badly torn apart.
The tank can be small where it is impossible to walk and one needed to crawl to navigate around the tank. With so many stiffeners and structures around, one might get bruise on the knee or elbow. Great flexibility is also needed to pass through each stiffener with a round opening where a single normal size body can fit in at a time. Usually a tall guy will have a bit of difficulty due to the long feet, like me.