Frequently asked questions (FAQs)

What is ATEX?

ATEX consists of two European directives:

Directive 1999/92/EC, also known as the ‘ATEX Workplace Directive’, deals with the safety and health of workers potentially at risk from exposure to explosive atmosphere. The directive has been in force from 30th of June 2003 but the deadline for enforcement is 30th of June 2006.

Directive 94/9/EC, or the ‘ATEX Equipment Directive’ deals with equipment intended for use in potentially explosive atmosphere. The Directive has also been in force since 30th of June 2003.

What is the purpose of the ATEX directive?

The main purpose of the ATEX directive is to minimise, or completely eliminate, the risk of ignition in explosive areas and to limit the harmful effects in case of an explosion.

ATEX was introduced to harmonise the national regulations within the EU and to introduce a new common directive for materials in explosive atmospheres.

The present ATEX directive 94/9/EC replaces all previous ATEX directives. The new directive deals with both electrical and mechanical equipment, whereas the previous directives only dealt with electrical equipment. Hence, it is an enforcement of safety regulations. The present ATEX directive, 94/9/EC, replaces previous ATEX directives about electrical equipment.

What does “ATEX” stand for?

ATEX is named after the French ‘ATmosphère EXplosif’, which mean explosive atmosphere.

In which countries is ATEX in force?

All the 24 member countries of the European Union (plus Norway, Iceland and Liechtenstein) are subject to the directives. Manufacturers, who comply with its provisions and affix the CE and EX marking, are able to sell their equipment anywhere in the European Union.

In which areas is ATEX in force?

ATEX is in force in all areas where explosive atmosphere is present. An explosive atmosphere for the purposes of directive 94/9/EC is defined as a mixture

  • of flammable substances in the form of gases, vapors, mists or dusts;
    with air;
  • under atmospheric conditions;
  • in which, after ignition, the combustion spreads to the entire unburned mixture (it has to be noted that in the presence of dust not always the whole quantity of dust is consumed by the combustion).

What does ATEX mean for the oil tank cleaning industry?

The new ATEX directive means that both service providers, offering tank cleaning services, as well as tank owners must prepare and carry out procedures for performing safe work in areas where a potentially explosive atmosphere can occur. This is done by identifying these areas (zones) and consequently prepare ‘workplace assessments’ for the affected zones.

Before estimating the probability of an explosion, all potential sources of ignition must be identified. Possible sources of ignition can be:

  • Electrical generated sparks, i.e. from headlights
  • Electrostatic discharge sparks, i.e. from personnel not wearing anti-static clothing or materials such as plastic hoses etc.
  • Flames from smoking
  • Hot surfaces, i.e. from malfunctioning pumps
  • Mechanically generated sparks, i.e. a metal object hitting a hard surface with high impact

Which equipment must comply with ATEX?

In very broad terms, there are three pre-conditions for the Directive to apply:

  • the equipment must have its own source of ignition;
  • be intended for use in a potentially explosive atmosphere (air mixtures); and
  • be under normal atmospheric conditions.

Why choose automated oil tank cleaning instead of manual?

Automated oil tank cleaning offers numerous benefits and advantages compared to conventional manual cleaning.

More effective
Simultaneous desludging, tank cleaning, hydrocarbon separation and hydrocarbon recovery

Saves time
Reduce tank cleaning time by up to 80%
Shorter overall down-time of tanks

Protects the environment
Recover nearly all hydrocarbons
Minimise need for waste disposal
Minimise hydrocarbon emissions to atmosphere
Lower utility consumption (water, electricity, etc)

Better cleaning
Unique indexed washing pattern covers complete interior tank surface area
Tank desludging re-circulates cleaning media

Safer work environment
No staff inside tank during cleaning process (Non-man entry system)
Continuous monitoring of process and automatic shutdown features
No risk of explosion
Minimal injury risk to staff

Easier maintenance
Easier maintenance of tanks following the cleaning process

Follows legislation
Complies with present and future environmental, health and safety legislation

Highly flexible
Modular system tailored to customer needs
Expandable, as customer’s needs change

Lower costs
Reduce overall cost of cleaning process – see the cost/benefit analysis

What kind of tanks can be cleaned using Oreco tank cleaning systems?

In principle, Oreco’s systems can clean any oil storage tank regardless of its dimension and contents. The BLABO® and MoClean® systems are especially designed to clean the following tank types and sizes:

Tank type, For difficult to clean tanks such as:

  • Crude oil
  • Heavy fuel oil / heavy gas oil
  • Ballast water
  • Catalytic cracker residue
  • Slop oil
  • Rail tanker

Tank capacity:

  • 10,000 – 120,000 m³
  • 62,000 – 744,000 bbl

Tank diameter:

  • 30 – 100+ m
  • 98 – 308+ ft

Tank type, For oil product tanks such as:

  • Gasoline
  • Diesel oil
  • Kerosene / jet fuel
  • Edible oils
  • Chemicals / petrochemicals

Tank capacity:

  • Up to 30,000 m³
  • Up to 186,000 bbl

Tank diameter:

  • Up to 35 m
  • Up to 115 ft

How do Oreco oil tank cleaning systems ensure high safety standards?

The Oreco systems are among the safest tank cleaning systems available today. We continuously improve our systems to comply with the strictest safety standards. Potential hazards and risks:

Staff health and safety issues

  • Exposure to hydrocarbons and toxic substances.
  • Respiratory problems or oxygen deficiency.
  • Injuries caused by falls, inadequate lighting or structural tank failure.

How our systems reduce risks

  • Staff don’t need to enter tanks during cleaning.
  • No scaffolding is required.
  • Our systems normally clean in an inert atmosphere.

What HSE features have Oreco taken into account in its tank cleaning and oil recovery systems?

Every aspect of Oreco’s non-man entry tank cleaning systems have been designed with Health, Safety and Environment (HSE) in mind.

The BLABO® and MoClean® systems’ fully automated process contains a range of safety features and procedures. Thanks to these, hazardous risks commonly associated with manual cleaning are significantly reduced.

The following factors ensure that the cleaning operation is performed under the safest possible conditions and without harming our environment:

Non-man entry system: Eliminates the need for personnel to enter the tank during cleaning. This means that personnel are not exposed to hazardous substances.

Monitoring: Built-in warning systems for hydrocarbon vapours minimises exposure to hazardous substances.

Procedures: The operating procedures guarantee that the tank cleaning is performed according to refinery safety codes and that uniform procedures are used all over the world.

Inert atmosphere: Continuous oxygen monitoring is an integral part of the systems. The cleaning operation is automatically shut down if oxygen content is too high.

Mechanical safety: The systems are build according to EN 13480, including 3.1.b certificates on all piping. Only certified welders are used.

Electrical safety: The BLABO® system is constructed to operate in explosive areas and meets the highest international standards, including ATEX or CSA/UL.

Monitoring: Constant monitoring and progress reporting keeps the process safe.

Training: Thorough process training for operators and systematic safety procedures are standard.

Sludge separation: Separation of the cleaned-out sludge is part of the Oreco systems. The advanced separation module of the BLABO® system allows for near 100% recovery of hydrocarbons from sludge.

Media recirculation: The recirculation of the cleaning media reduces energy and water consumption, as well as the need for cleaning chemicals.

Emissions: The closed loop process eliminates the risk of oil spillage and ensures that hydrocarbon emissions to the atmosphere are limited.

Who offers automated oil tank cleaning?

A network of service providers using Oreco non-man entry tank cleaning technologies offers cleaning of both black oil and white all tanks.

The partners are specifically trained by Oreco A/S to ensure that the process complies with Oreco’s highest standards and with increasingly demanding legal and safety requirements.

In case you are looking for a service provider, please contact Oreco at

Back to FAQs

When you convert from manual to automated cleaning methods, you reduce tank cleaning by weeks or even months …

What is the most effective oil tank cleaning method – high pressure or low pressure jetting?

Studies show that low pressure jetting methods (5-15 bar) using high re-circulated cleaning fluid flow rates clean tanks more efficiently than traditional high pressure methods (100-2,500 bar). This is measured in terms of time and cleaning fluid consumption.

Low pressure versus high pressure jetting methods

The graph below illustrates the effect of jetting distance (from nozzle tip to tank wall) on the jet impact pressure on the tank wall (measured in mm water) for high pressure (HP) and low pressure (LP) jetting methods.

At short jetting distances, a high pressure jet exerts greater jet impact pressure on the tank wall. However, this higher impact pressure is quickly lost as jetting distance increases, because the kinetic energy of the HP jet is absorbed by the acceleration of the air molecules surrounding the jet.

As a result, the wall impact pressure of the HP jet drops off very rapidly as it gets further away from the tank wall. Already at a distance of 30 cm (12 inches) from the nozzle, the impact pressure of a LP jet with a fluid flow rate in the range of 250-5000 l/min (60-120 GPM) is 100 times greater than that of HP jet with a fluid flow rate in the range of 75-125 l/min (20-30 GPM).

Note: This graph is a double logaritmic projection.

HP jetting systems are effective for short-distance hydro-blasting applications. Long-distance jetting used for the internal cleaning of larger tanks, such as oil storage tanks, is most effectively accomplished using LP jetting methods.

Benefits of using LP jetting methods for tank cleaning (compared to HP methods)

  • Faster cleaning provided by higher impact pressures and higher cleaning fluid flow rates.
  • Lower consumption of cleaning fluid resulting as cleaning fluid is re-circulated. (HP systems normally cannot operate with re-circulated cleaning fluid).
  • Lower investment costs for cleaning system.
  • Lower total operating costs for the cleaning job, due to reduced cleaning time and lower utility consumption.
  • Safer cleaning operation, because staff don´t need to enter tanks, eliminating exposure to a hazardous environment.


Is it safe to use the SafeTap® tool in hazardous areas (zone 0)?

Yes – cold tapping is safe.

Cutting holes in tank roof, e.g in connection with preparations for tank cleaning operations, often pose great concern from tank owners and operators. However, with the Oreco cold tapping tool, the SafeTap®, holes in tank roof is cut in a safe and quick manner.

Cold tapping methods cool the equipment so that heat build-ups, fires and explosions are prevented. However, many conventional methods are slow, inconvenient and leave a desire for a safer method. For this purpose Oreco has developed the cold-tapping tool, the SafeTap®. Design features and procedures make the SafeTap considerably safer than most traditional cold tapping methods:

  • Before the SafeTap® is fixed to the roof, an inert tank atmosphere below 8% oxygen is produced as an extra precaution to eliminate the dangers of cutting in an explosive atmosphere.
  • There is no frictional heat build-up from mounting and operating the SafeTap®, as cutting oil added throughout this stage is cooling the equipment and prevents dangerous heat build-ups.
  • A gasket ensures that the operators are not exposed to hydrocarbon or H2s steam.
  • A powerful magnet placed on the bottom of the cutting head ensures that the cut-out roof plate does not fall in the tank, but is removed along with the cutting instrument – thereby eliminating the risk of the roof to to cause sparks.

Will use of the SafeTap® tool have an impact on the strength of the tank roof?

In general the negative effect to the mechanical integrity of the tank roof, when circular perforations with the SafeTap® are made, is so minute that it in praxis can simply be regarded as negligible.

Test performed by independent notified body
Tests and reference tests performed with and without any load show that the maximum calculated stress levels never reached critical values. This is the conclusion that can be drawn from an analysis performed by FORCE Technology in Denmark, independent certifying body providing advanced technical consultancy on an international basis.

The analysis consists of tests measuring the stresses on a tank roof with circular perforations executed with the Oreco SafeTap®. The method used to calculate the stresses is the Finite Element Method (FEM) which is suitable for calculation of complex elasticity and structural analysis problems. The work considers stress analysis of a representative steel plate (S235) used as a sample and simulation of conditions of loads with and without circular perforations.

In the following some of the tests and the respective results obtained are described in order to give you insight into the test method. If you wish to see the full report, please contact Oreco.

The test results
One test determines the stresses in case of a worst case scenario on the tank roof section where the SafeTap has been used. Here the worst case scenario is an exaggerated load of 100 kg acting on the flanged steel trunk and applied as a compression load evenly distributed on the flange of the steel trunk. Furthermore, it was applied an extra load on account of equipment and personal of 300 kg which was distributed on the centre squared area of 1.0 mt. X 1.0 mt. The maximum stress around the circular perforation was found to be 21 MPa (see graph to the right) – a value far below the critical level of 235.

Graph showing test results

Conclusion of the test
Even in the test with the most extreme condition stimulated with exaggerated loads but perforation, the stress levels reach only 42 % of the critical yield stress level. It should be noted that additional findings in the test shows that, whenever some of the support legs are removed, there is a potential risk of reaching critical stress levels if the tank roof is overloaded (without circular perforations performed).

Oreco A/S . Oldvej 1A . DK-3540 Lynge . Denmark . TEL. +45 4332 0200 .

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