Tank cleaning safety hazards

A Hazard is a physical situation with a potential for human injury, damage to property, damage to the environment, to capital investment or some combination of these. Hazards can be identified through a review of the Physical Properties and Product Characteristics of the product to be cleaned. Typical hazards that exist during Tank Cleaning and related activities are: 

Fire & Explosion Three elements are necessary to create a fire: Fuel, an Oxidiser (usually air) and a Source of Ignition (energy). In theory, ignition is not possible, if any one of the 3 is eliminated. Most cleaning operations will be carried out in tanks that are filled with air, thus the oxidiser is present in most cases, unless the tank is inerted. Fuel as far as tank cleaning is concerned could be the product itself, if this product has a low flash point, or a flammable cleaning solvent. Under certain circumstances even substances with a high flash point can be ignited and must thus be considered as a fuel (mist). During many tank cleaning operations the atmosphere in the tank must be considered as flammable because the product to be cleaned is flammable and inertisation is not possible. Under these circumstances the only way to guarantee that an explosion cannot occur during cleaning is to make certain that there is no source of ignition. A potential source of ignition during tank cleaning is Electrostatic discharge. Especially during water spraying electrostatic charges could be induced.

Undesired reactions Polymerization (Depletion of inhibitor or excessively high temperature) Saponification (Creation of hard soap forming a layer on the tank requiring acid cleaning or even removal by Hydroblasting) Drying/Hardening (Formation of hard debris that is no longer soluble, requiring treatment with a Solvent) Reaction with water (Violent reaction of an Isocyanate after Pre-Cleaning with water)

Corrosion – Corrosive substances destroy human tissue on contact (e.g. skin, eyes and mucous membranes in the mouth and respiratory tract) Metal or other material used in ship construction could be corroded at an excessive rate.

Overexposure to toxic substances (Death of operator after wiping Phenol residues by tank entry without wearing a full chemical suit and SCBA [self-contained breathing apparatus])

Asphyxiation -Oxygen deficiency (Entry into a tank with an inert gas atmosphere)


  • To the air: As always when ventilating, special care must be taken to prevent the risk of explosion (flammable products) or with regard to toxic vapors. All normal safety precautions must be taken. (No smoking, accommodation ventilation on recirculation etc.) The wind strength and wind direction must also be a decisive parameter for the Master to allow ventilation. To avoid a buildup of explosive or toxic vapors on deck the amount of gas to be escaped from the tanks should be limited. Never open and ventilate several tanks at the same time
  • To the water: Emissions to the water should be reduced to the absolute minimum. All on-board facilities must be operated carefully according to the P&A Manual to reduce the residues during unloading. All regulations, especially MARPOL I and II, must be followed strictly.