Chemical Tankers / Day 3 / Day 3 Topic 6 Tank Cleaning Chemicals & Best Industry Practi

6.2 Cleaning chemicals compatibility with tank coatings

The following cleaning agents are prohibited to use in certain coatings:

oAcid based or Metal Bright cleaning chemicals in zinc coated tanks;

oCaustic Soda or Alkaline cleaners in zinc coated tanks;

oChlorinated solvents in phenolic and epoxy coated tanks. Epoxy coated tanks depend on manufacturer’s resistance list;

oMixing of chlorinated solvents with water in any coated tanks;

6.3 Use of cleaning chemicals

The cleaning of cargo tanks is achieved by the use of tank cleaning chemicals in conjunction with tank cleaning systems or when necessary with other forms of cleaning equipment. The most widely used cleaning methods with tank cleaning chemicals can be listed as follows:

6.3 Use of cleaning chemicals

•Direct injection into tank cleaning system during washing process;

•Re-circulation with tank cleaning machines;

•Hand spraying;

•Steaming;

•Special methods;

6.3 Use of cleaning chemicals

In some cases more than of the above methods may be used to complete a cleaning operation, for example the direct injection method may be followed by hand spraying.

6.3 Use of cleaning chemicals

The selection of the appropriate cleaning method will of course depend on the equipment available and the circumstances at the time of cleaning, but a description of each of the basic cleaning methods is follows.

6.3 Use of cleaning chemicals

Direct injection into tank cleaning system during washing process

Direct injection of chemicals into the tank cleaning system is a widely used tank cleaning method, as it is least time consuming and requires a minimum of labor. This method involves injection of undiluted chemical directly into the tank cleaning system pipeline, before the fixed or portable tank cleaning machines.

6.3 Use of cleaning chemicals

Direct injection into tank cleaning system during washing process

Injection is achieved in either of the following ways: air-operated pump or gravity feed.

By air-operated pump a tank cleaning chemical is injected directly into the wash water line. The pump is positioned on top of a drum of tank cleaning chemical and connected to the air line on deck by hosing.

6.3 Use of cleaning chemicals

Direct injection into tank cleaning system during washing process

A regulating valve on the chemical feed line controls the chemical injection at a pre-determinate rate into wash water supply line. This is the preferred method of direct injection, as the correct dosage of chemical can be controlled at any location.

6.3 Use of cleaning chemicals

Direct injection into tank cleaning system during washing process

6.3 Use of cleaning chemicals

Direct injection into tank cleaning system during washing process

By gravity feed a drum of cleaning chemical is located in a high position in or near the tank and chemical is fed by gravity at a rate controlled by a regulating valve to the suction side.