The Oil-tanker is designed for the bulk transportation of crude oil or petro-chemical products, and broadly there are two types of tankers, Product carrier and Crude oil carrier. In case of Product Carrier, every compartment shall be cleaned because different kinds of consignments are being stored in, otherwise they could contaminate each other. The remaining oil and oil sludge inside of oil tanker also shall be removed after unloading, because other kinds of oil might be stored in. For this work, S.W or F.W is needed to be heated above 70 ~ 80 ℃, by using Tank Cleaning Heater.