Well as a 1st mate working on a tanker, I would say if you adopted the practice of pumping the water overboard, you will likely see yourself in jail.hayhugh wrote:I have never seen hot water used to clean a tankers tanks. the Butterworth machine is put in access opening and lowered as tank is cleaned (usually around 15/20 minnets) and then lowered about ten feet. Water is pumped overboard and whatever was in the tank (crude,etc) is stored in separate tank for later disposal.
Washing cargo tanks can be done with hot or cold water. Hot water with a cargo tank that contained a waxy cargo like diesel, and warm water if it is with a tank which carried gasoline. (Always consult the ISGOT prior to operations)
Butterworth machines are employed to impart a high velocity stream of water to the cargo tank sides. This machine will rotate to create a washing pattern in the tank. The water is always sent back to the refinery in the coastal and great lakes trade. In deep sea trades you are to have this wash water settle or decant in slop tanks, then should you need to you can pump clean water over the side bu utalizing an onboard ODME system, which will stop pumping water over the side when an oily water mix of 15 ppm is detected.
Onboard a tanker there are plates which open into the cargo tank called butterworth plates, this is the entry point for the machine into the cargo tank.
Modern tankers, usually have fixed butterworth machines in the tanks, making the washing process some what simpler, but maintenance wise more complicated.