Explosion-proof solenoid valve selection and Explosion-proof knowledge
1. Category, level and temperature group
1.1、Explosive Gas Atmospheres dangerous zone division Zone 0: consecutive or long-term explosive gas mixture environmental Region 1: when in normal operation it may occur an explosive gas mixture environment Zone 2: In the normal operation it can not be an explosive gas mixture in the environment or even if there is also only a short-term presence of explosive gas mixture the environment Zone 0: general exists only in sealed containers, tanks and other internal gas space, in the actual design process, zone 1 rarely exists, in most cases belong to zone 2.
1.2、Explosion-proof electrical equipment is divided into two categories: Class I underground coal mine electrical equipment class II electrical equipment used except mine sites
1.3 class II electrical equipments, according to its biggest test security clearance or minimum igniting current ratio in explosive gas mixture, it is divided into IIA, IIB, IIC three classes; according to their maximum surface temperature is divided into T1-T6six groups. (IIC is the highest level in explosion-proof type, can covers over IIA, IIB applicable range.
1.4、Explosive gas mixtures are divided by ignition temperature, shown in Table 1.
1.5, explosive gas mixtures, according to their maximum test security gaps (MESG) or minimum igniting current ratio (MICR) classification, shown in Table 2.
| group | ignition temperature T(℃) | ||
| T1 | ＜450 | ||
| T2 | ＜300 | ||
| T3 | ＜200 | ||
| T4 | ＜135 | ||
| T5 | ＜100 | ||
| T6 | ＜85 | ||
| class | maximum test security gaps （MESG）(mm) |
minimum igniting current ratio (MICR) | |
| II A | ≥0.9 | ＞0.8 | |
| II B | 0.5＜MESG＜0.9 | 0.45≤MICR≤0.8 | |
| II C | ≤0.5 | ＜0.45 | |
2.Terminology
2.1、Flameproof electrical equipment explosion pressure that withstands the internal explosive gas mixtures and prevent internal explosion to spread external shell around the explosive mixture electrical equipment, marked by "d".
2.2、Increased Safety electrical equipment under normal operating conditions it will not produce arcing, sparks or is likely to ignite an explosive mixture high-temperature, structural measures to increase the safety margin, in order to avoid in normal and recognized overload conditions occur arcing, sparks, or high-temperature electrical equipment, it is marked as "e"
| explosion-proof type | marks | explosion-proof principle |
| Flameproof type | d | Take components of equipment that can produce sparks arc inside the flameproof shell when it is in normal operation, explosion-proof shell can withstand the internal explosion pressure without damage, and can ensure that the internal flames gas spread through the gap, reducing energy, and not enough to detonate outside shell gases. |
| Increased Safety | e | Under the normal operation it will not produce arcing, sparks and dangerous high temperatures, about the structure further to take protective measures to improve equipment safety and reliability. |
| Pressure-type | p | Keep the internal protection gas pressure is higher than the surrounding pressure so as to avoid an explosive mixture entering into the shell or the full amount of shielding gas through the shell, so let the explosive mixture concentration fall below the explosive lower limit. |
| Intrinsically Safety | i | The equipment internal circuits under specified conditions, normal work or the set fault condition produce electric spark and thermal effects can not ignite an explosive mixture. |
| Poured seal-type | m | It pours sealing arc, spark or high temperature part that may ignite an explosive mixture, so that it can not ignite the surrounding explosive mixture. |
