The Solution: Explosion Protection

For more than 30 years, Will & Hahnenstein has been a leading supplier of explosion-protected heating chambers and your expert partner for systems used in potentially explosive atmospheres.

Benefit from our experience. We will be pleased to advise you on all matters relating to explosion protection.

• Heating chambers
• Drum heaters
• Cylinder heaters
• Heating jackets
• Heated containers
• Melting vessels
• Workplace extraction systems
• Custom heating systems

Due to changes in legislation resulting from the mandatory introduction of the ATEX Directives, the following applies to systems installed in potentially explosive atmospheres:

• The operator may only operate the heating chamber if the explosion protection document required under Directive 99/92/EC (ATEX 137) is available.
• The required ignition hazard assessment filed with the PTB and the inspection of the heating chamber in accordance with EN 13463, “Non-electrical equipment for use in potentially explosive atmospheres”, are included in the scope of supply.
• All installed electrical equipment is type-tested in accordance with Directive 2014/34/EU (ATEX). The corresponding declarations of conformity are included in the documentation.

When submitting an enquiry, please specify whether explosion protection is required for gas or dust:

• For gas, please specify the required temperature class.
• For dust, please specify the required zone (21 or 22) and the maximum permissible surface temperature.

Zone classification of heating chambers and drum heaters
Potentially explosive areas in workplaces are classified as Zone 1, Zone 2, Zone 21 or Zone 22. Zones 0 and 20 are generally restricted to the interiors of process equipment or very small, inaccessible areas within workplaces.

Will & Hahnenstein designs its heating chambers and drum heaters for gas atmospheres as standard for Zone 1, which automatically also covers Zone 2. This provides the highest practicable level of gas explosion protection, as a heating chamber for Zone 0 is generally not feasible. For dust atmospheres, you can choose between Zone 21 and Zone 22. Here too, Zone 20 is generally not feasible.

General information about explosion protection
Wherever a mixture of fuel—such as flammable gases, liquids or dusts—and oxidising substances such as atmospheric oxygen can occur, there is a risk of explosion. Explosive mixtures may be ignited by:

• High surface temperatures
• Incendive sparks, for example when electrical circuits are interrupted or through electrostatic discharge
• Mechanical impact and friction sparks

Primary explosion protection
Primary explosion protection aims to replace flammable substances or atmospheric oxygen, or to reduce their quantities sufficiently to prevent the formation of an explosive mixture—for example, by increasing the air supply.

The concentration of the mixture can be monitored using gas detection systems. When the lower explosion limit is reached, a warning is issued and the system is shut down.

Secondary explosion protection
Ignition sources such as high surface temperatures, incendive sparks, and mechanical friction or impact sparks are eliminated through design measures and suitable electrical equipment.

The conditions under which the equipment is to be used are decisive. These are defined by specifying the zone, explosion group and temperature class.

Explosion groups for the classification of gases and vapours
Flammable gases and vapours are classified into explosion subgroups IIA, IIB and IIC. An explosive atmosphere classified as IIC is the easiest to ignite, while one classified as IIA is the most difficult.

Will & Hahnenstein designs its heating chambers and drum heaters as standard for the highest explosion subgroup, IIC, which also covers subgroups IIB and IIA.

Temperature class—for gases and vapours only
Every gas-air mixture has a different ignition temperature. The temperature class of a piece of equipment indicates its maximum surface temperature.

This surface temperature must be selected according to the ignition temperature of the gas-air mixture. For example, if a mixture ignites at approximately 280°C, the equipment must have a maximum permissible surface temperature of 200°C, corresponding to temperature class T3.

If you have any further questions about explosion protection, please contact Mr Stöcker on +49 (0) 2744 9317-15.