How will static protection be organized?
Dangerous potentials of the static electricity are formed at the movement of neprovodyayoshchy liquids or dust on pipelines with the speed over 0,7 — 1 m/s at their draining filling.
The risk of explosion arises when at electrostatic discharge energy of the spark exceeds the minimum energy of ignition of vzryvoopasyony mix.
In order that on processing equipment not появлялись dangerous potentials of the static electricity, apply the following measures of protection. Metal parts of the equipment zayozemlyat. Increase conductivity of moving materials and materials of which it is made technology oborudovayony by the covering or additive to them of the carrying-out components. Humidify the environment filling devices for increase in its conductivity. Purify gases from the weighed liquid and tveryody particles, and liquids — from pollution with colloid particles. In rooms where the static elektriyochestvo can be formed, arrange electroconductive floors.
Protection against the drift of potential and lightning currents
On wires of transmission lines, pipelines, rails the drift of lightning currents and high atmospheric potentials to vzryvoopasyony rooms is possible. According to PUE, these rooms have to be protected from such danger. 3 categories of measures of protection are established.
- I - the category of measures is carried out for explosive rooms of the classes B-I, B-II and for productions of category A on fire danger. Buildings and constructions are protected from head-on impacts of the lightning and from its secondary manifestations, i.e. from potential, kotoyory is induced by the channel of the lightning on wires and metal designs. For this purpose establish separate molniyeyootvoda with separate grounding conductors (fig. 1 and). Grounding conductor resistance for protection against secondary manifestations of the lightning has to be 1 Ohm, and from its head-on impact - 10 Ohms. Conducting elements of lightning arresters isolate from the protected object and from the metal parts connected to it. Constructions up to 15 m high protect the lightning arresters established on the construction, but separately from it. For protection against the drift of the dangerous potenyotsial of the wire of overhead power transmission lines and communication do not enter into rooms;
- The II category of measures is carried out for rooms of the classes V-1a, V-16, B-IIa and productions of category B. These constructions protect lightning arresters which establish directly on the protected object (not separately) (fig. 1). As the interception rod use the metal roof. Descents from the roof to the grounding conductor establish on perimeter at least through 15 — 20 m. Protection against secondary manifestations of the lightning is osushcheyostvlyat as well as in case of the I category. Allow objedineyony the grounding conductor from head-on impacts of the lightning with the grounding conductor from its secondary manifestations. At the same time resistance of the lightning-protective grounding conductor should not exceed 10 Ohms;
- III - the category of measures is carried out for explosion and the fire-dangerous rooms which did not enter I and II categories and for the buildings and sooruyozheniye which are of economic value. Lightning protection of these buildings is obligatory only with their big height, special economic, scientific and cultural value and at big accumulation of people. The computational method of protection against lightning currents is considered in the special course.