Energy Limitation nL

Previously, Zone 1 applications predominated, and a series of ignition protection methods was available especially for these areas. These methods could also be used in Zone 2, but the requirements for a Zone 1 application are more costly than those for Zone 2. The demand for Zone 2 ignition protection methods increased.

EN 60079-15 provided a solution with a single standard for the design of apparatus in Zone 2. Ignition protection methods were not completely reinvented, but modified from pre-existing Zone 1 methods. Reduced requirements for equipment in Zone 2, netted a 20 - 30% savings, making Zone 2 more attractive.

While intrinsic safety was never part of the original Zone 2 protection method, it did exist in a limited manner under the guise of energy limitation, nL. But this, led to missing or unclear requirements in installation standard EN 60079-14. EN 60079-14 requires intrinsically safe circuits to be separated from other circuits to prevent possible spark ignition. This led to increased cable costs.

Unfortunately, EN 60079-15 for Zone 2 apparatus virtually replaced the hazardous location installation standard EN 60079-14, which required intrinsically safe circuits to be separated from other circuits to prevent possible spark ignition. And, the energy limitation protection method nL was not clearly described in the installation standard. The section about the installation of intrinsically safe cables stated that they should not be subject to any interference from non-intrinsically safe circuits. Users were tempted to lay energy limited cables without the required shielding or separation.

The current edition of EN 60079-14 clears up this misunderstanding. Now, nL cables must go through a risk assessment, as to whether an impermissibly high electromagnetic energy input is possible. If so, protective measures must be taken, such as shielding, twisting or appropriate spatial separation, just as with intrinsic safety.

The intended simplifications led to many discussions about what is not described in the standard have no relevance or conversely that the fulfillment of the requirements in the standard guarantees the safety of current circuits or plants.

The existing protection levels will be expanded to ic for Zone 2 in EN 60079-11, and in the medium term, nL will disappear from EN 60079-15. Manufacturers must now become familiar with the requirements of intrinsic safety in respect to the nature of the apparatus, which sometimes places higher demands on energy limitation. Because nL will no longer exist, manufacturers will revert to use EN 60079-11 as a reference to bring their products to the market in accordance with the requirements of RL 94/9/EC.