【Daily Question 20090211】Are flameproof electrical devices also waterproof?

Many people believe that explosion-proof electrical equipment is able to prevent explosions because its enclosure prevents explosive gases from entering it; its sealing performance must be excellent, allowing it to block rainwater as well, so it should work fine when installed outdoors. In fact, this confuses two concepts: the explosion protection type of explosion-proof electrical equipment and the enclosure protection rating. Explosion-proof electrical equipment is classified into different explosion-proof types based on their respective explosion-proof principles. Flameproof electrical equipment is electrical equipment that has a casing capable of withstanding the explosive pressure of internal explosive gas mixtures, and that prevents the spread of an internal explosion to the explosive mixtures surrounding the casing. Obviously, its explosion-proof performance is unrelated to the protection rating of its enclosure; **the standards do not impose any specific requirements regarding the protection rating of the enclosure – it is sufficient that the requirements for the protection rating of motor and low-voltage electrical equipment are met. However, strict regulations exist regarding the material and mechanical strength of the enclosure. Increased safety type explosion-proof electrical equipment is electrical equipment whose design prevents the occurrence of arcs, sparks, or high temperatures that could ignite explosive mixtures under normal operating conditions; measures are taken to enhance its safety level in order to avoid such phenomena under normal and permitted overload conditions. In contrast, intrinsically safe explosion-proof electrical equipment (commonly found in small low-voltage devices) is such equipment whose entire circuit ensures that neither the electric sparks nor the thermal effects generated under specified fault conditions can ignite the specified explosive mixture. These two types of explosion-proof electrical equipment either do not generate sparks or high temperatures, or the sparks and heat generated are not sufficient to ignite explosive mixtures; clearly, their explosion-proof properties are also unrelated to the enclosure protection rating, and therefore **the standards do not impose any specific requirements regarding the enclosure protection rating. It can be seen that the vast majority of explosion-proof electrical equipment cannot prevent gases or water from entering its interior; therefore, such equipment cannot be installed directly in outdoor areas, nor can their enclosures be washed with water. In fact, the water resistance of a device is entirely determined by its enclosure protection rating. The protection rating of the enclosures for electrical devices used outdoors, which need to be protected from rain, should be at least IPX5 (meaning they can withstand water coming from all directions without allowing water to enter). Therefore, when purchasing explosion-proof electrical devices, it is necessary to specify the required enclosure protection rating as well. Another point to keep in mind is that explosion-proof electrical devices used outdoors must be resistant to corrosion.

It can’t be generalized; some provide protection while others don’t, and the corresponding instructions explain this.

Generally, it can be made explosion-proof or waterproof, or both explosion-proof and waterproof, depending on the customer’s requirements

Ordinary explosion-proof equipment does not have such requirements; in other words, it is basically not waterproof. However, in cases where the application environment is special, it is possible to request that the equipment be designed with a higher protection level when customizing it :)

There is a significant conceptual difference between explosion-proof performance and waterproof performance. Flameproof electrical equipment is electrical equipment that has a casing capable of withstanding the explosion pressure of explosive gas mixtures inside, and preventing the explosion from spreading to the explosive mixtures surrounding the casing. The waterproof performance is primarily determined by the protection rating of the enclosure.

It can’t be generalized; some provide protection while others don’t, and the corresponding instructions explain this.

Yes, explosion-proofing does not necessarily mean water resistance; they are not the same concept. Therefore, the materials used by manufacturers during production, as well as the measures taken for water resistance or explosion protection, vary

Explosion-proof electrical equipment is classified into different explosion-proof types based on their respective explosion-proof principles. Flameproof electrical equipment is electrical equipment that has a casing capable of withstanding the explosive pressure of internal explosive gas mixtures, and that prevents the spread of an internal explosion to the explosive mixtures surrounding the casing. Obviously, its explosion-proof performance is unrelated to the protection rating of its enclosure; **the standards do not impose any specific requirements regarding the protection rating of the enclosure – it is sufficient that the requirements for the protection rating of motor and low-voltage electrical equipment are met. However, strict regulations exist regarding the material and mechanical strength of the enclosure. Increased safety type explosion-proof electrical equipment is electrical equipment whose design prevents the occurrence of arcs, sparks, or high temperatures that could ignite explosive mixtures under normal operating conditions; measures are taken to enhance its safety level in order to avoid such phenomena under normal and permitted overload conditions. In contrast, intrinsically safe explosion-proof electrical equipment (commonly found in small low-voltage devices) is such equipment whose entire circuit ensures that neither the electric sparks nor the thermal effects generated under specified fault conditions can ignite the specified explosive mixture. These two types of explosion-proof electrical equipment either do not generate sparks or high temperatures, or the sparks and heat generated are not sufficient to ignite explosive mixtures; clearly, their explosion-proof properties are also unrelated to the enclosure protection rating, and therefore **the standards do not impose any specific requirements regarding the enclosure protection rating. 　　 　　It can be seen that the vast majority of explosion-proof electrical equipment cannot prevent gases or water from entering its interior; therefore, such equipment cannot be installed directly in outdoor areas, nor can their enclosures be washed with water. In fact, the water resistance of a device is entirely determined by its enclosure protection rating. The protection rating of the enclosures for electrical devices used outdoors, which need to be protected from rain, should be at least IPX5 (meaning they can withstand water coming from all directions without allowing water to enter). Therefore, when purchasing explosion-proof electrical devices, it is necessary to specify the required enclosure protection rating as well. Another point to keep in mind is that explosion-proof electrical devices used outdoors must be resistant to corrosion.

Explosion protection refers to electrical explosion protection, which defines the grade of electrical equipment used in hazardous areas, while water resistance refers to the protection rating. The differences between the two are as follows:

I. Explosion Protection: The meaning of the explosion protection mark Ex(ia)ⅡC T6 for instruments:
- Mark elements: Symbol – Meaning
- Explosion protection declaration: “Ex” indicates compliance with certain explosion protection standards, such as China’s relevant standards.
- Explosion protection method: “ia” denotes the use of an intrinsically safe explosion protection method, allowing installation in Zone 0.
- Gas category: “ⅡC” means that the instrument can be used in environments with ⅡC class explosive gases.
- Temperature group: “T6” indicates that the surface temperature of the instrument does not exceed 85°C.

Classification of hazardous areas, explosion protection classification for electrical components, and allowable temperature ranges:
1. Classification of hazardous areas:
- Zone 0: Explosive gases are present all the time or for extended periods.
- Zone 1: Flammable gases may occur or be present during the normal operation of the instrument.
- Zone 2: Under normal conditions, no flammable gases are present; even if they do appear occasionally, their presence is brief.

Comparison of international and American standards for classification of explosive areas:
I.E.C. N.E.C.:
- Gases: Zone 0 – Class I, Division I; Zone 1 – Class I, Division I; Zone 2 – Class I, Division II.
- Dusts: Zone 10 – Class II, Division I; Zone 11 – Class II, Division II.
I.E.C.: International Electrotechnical Commission.
N.E.C.: National Electrical Code, U.S.A.

2. Explosion protection classification for electrical components:
1. General protection: EN50.014
2. Protection by immersion in oil: 0 EN50.015
3. Protection using pressurized gas: p EN50.016
4. Protection using filled powder: q EN50.017
5. Flame-retardant housing: d EN50.018
6. Increased safety factor: e EN50.019
7. Intrinsically safe protection: i EN50.0120
8. Airtight protection: h – No standard specified.
9. Pressure relief protection: n – No standard specified.
10. Special measures: s – No standard specified.

II. Classification of protection ratings for instrument housings:
For instruments used in explosive hazardous areas, it is also necessary to specify the protection rating of their housings, which is represented by a code, namely the IP rating. The enclosure protection rating specified by IEC144 is represented by a code that corresponds to its resistance to impacts and punctures from external objects, as well as its waterproofing capability. For example: Intrinsic safety instruments used for measuring circuit boards should not be removed from their enclosures, as this would violate the minimum requirements specified by IP40. The protection rating consists of two digits, preceded by the word IP. IP1 2: First digit, second digit – Resistance to impact by external objects, waterproofing capability. 0: No resistance to penetration; 0: No waterproofing capability. 1: External objects larger than 50 mm (very large); 1: Water droplets falling vertically. 2: External objects larger than 120 mm (medium); 2: Water droplets at an angle of -15°. 3: External objects larger than 2.5 mm (small); 3: Water sprayed at a 60° angle. 4: Granular external objects with a particle size greater than 1 mm; 4: Spraying from all directions. 5: Hazardous dust; 5: Water jet of 50 liters per minute. 6: Penetrating dust (applicable only to special enclosures); 6: Water jet of 100 liters per minute. 7: Submersion in water at a speed of 1 meter per minute. 8: Submersion in water in a pre-agreed manner

Normally, flameproof electrical devices are not waterproof; they can be customized if needed.

Explosion resistance does not necessarily imply water resistance. These are not the same concepts; therefore, the materials used by manufacturers during production, as well as the measures taken to ensure water resistance and explosion resistance, differ.

Water resistance rating and explosion protection rating are two distinct concepts. Water resistance is indicated by the IPXX rating system, while explosion protection is determined using the IP protection rating standards for hazardous environments. The IP protection category is denoted by two digits: for example, the IP4 rating consists of a first digit and a second digit. The first digit indicates the level of protection against contact and foreign objects; the second digit indicates the level of water resistance. The first digit also represents the range of protection, while the second digit specifies the name of that protection level. Explanation: 0 – no protection; 1 – protection against foreign objects with a diameter of 50 mm or more. A sphere with a diameter of 50 mm should not be able to enter completely. 1 – protection against vertically falling water droplets; such droplets should not cause any damage. 2 Protection against foreign objects with a diameter of 12.5 mm and larger: the sphere has a diameter of 12.5 mm and must not be able to enter completely. When the enclosure is tilted at 15º, water droplets falling vertically from either side, even at an angle of 15º, should not cause any damage. 3 Protection: Detector for foreign objects with a diameter of 2.5 mm and larger; the sphere has a diameter of 2.5 mm. Water splashing out under 3 protection should not allow such objects to enter completely. Water splashing out at an angle of 60º from either side of the vertical line should not cause damage. 4 Protection: Detectors for foreign objects with a diameter of 1.0 mm or larger; the sphere has a diameter of 1.0 mm and shall not be able to enter completely within the 4 protection area. **Water jets directed at the container from any direction shall not cause damage. 5 Dust protection: It is not possible to completely prevent dust from entering, but the amount of dust that enters should not be enough to cause damage to the device or its safety features. 5 Water jet protection: Water jets directed at the enclosure from any direction should not cause any damage. 6. Dust sealing: Dust should not penetrate when the internal pressure is at 20 millibars. 6. Protection against high-pressure water jets: High-pressure water jets directed at the enclosure from any direction should not cause damage. 7 Protection against short-term immersion: When the enclosure is submerged in water for a short period of time at standard pressure, no amount of water that could cause harmful effects should penetrate inside. 8 Protection against long-term immersion: The enclosure must be able to withstand prolonged immersion in water under conditions agreed upon between the manufacturer and the user; no amount of water that could cause harmful effects should penetrate inside during such immersion. But these conditions must be more complex than those specified by marker number 7. Electrical Explosion Protection Knowledge I. Classification of Hazardous Areas The meaning of hazardous area classification is a measure of the actual risk present in that area, which determines the appropriate type of explosion protection to be used there. The explosion-proof zones classified by the International Electrotechnical Commission/European Committee for Electrotechnical Standardization are as follows: Zone 0: Areas where the hazard level is present continuously for more than 1,000 hours per year ； Zone 1: Areas with intermittent hazard of 10–1000 hours per year ； Zone 2: Areas with a hazard level of 0.1~10 hours per year under accident conditions ； The valid regions divided in China are the same as those mentioned above. II. Explanation of explosion protection markings ① Typical hazards of gas groups: Gas, European Committee for Standardization in Electrotechnics EN50014/EC, North America NEC Article 500, CLASS1 table. China: GB-3836-1. Minimum ignition energy (microjoules): Acetylene – II C A, II C 20; Hydrogen – II C A, II C 20; Ethylene – II B C, II B 60; Propane – II A D, II A 180. Note: According to China’s GB3836 standard, the minimum ignition energy for Class II C is 19 microjoules, while that for Class II A is 200 microjoules. Gas grouping and ignition temperature are related to the mixing concentration of flammable gases with air under certain ambient temperature and pressure conditions. ②Temperature category (Group T): This refers to the maximum surface temperature of electrical equipment related to the ignition temperature of the gas (under the assumption that the ambient temperature is 40°C); the ignition energy is independent of the ignition temperature. All flammable gases and their groups are listed in Part 1 of the standard BS5345. Maximum surface temperature (°C) Temperature Category IEC79-8 GB3836-1 450°C T1 T1 300°C T2 T2 200°C T3 T3 135°C T4 T4 100°C T5 T5 85°C T6 T6 ③ Explosion protection marking: Taking the CENELEC explosion protection marking for hydrogen as an example: E E*a ⅡC T4E: Approved according to the CENELEC marking; Ex: General explosion protection marking; ia: Explosion protection type (intrinsic safety); Ⅱ: Equipment category; C: Gas category; T4: Temperature category. ④ Terminology explanation: Flameproof electrical equipment (d): Refers to electrical equipment in which the components that could ignite explosive mixtures are enclosed within a housing capable of withstanding the explosion pressure from such mixtures and preventing the spread of explosion to surrounding areas. Increased safety electrical equipment (e): Electrical equipment that, under normal operating conditions, does not generate sparks or dangerous temperatures that could ignite explosive mixtures, and which incorporates structural measures to enhance its safety level in order to prevent ignition under normal conditions as well as under specified overload conditions. Intrinsically safe electrical equipment (i): Electrical equipment whose sparks or heat generated under normal operation or under standard test conditions cannot ignite explosive mixtures. Spark-free electrical equipment (n): Electrical equipment that does not generate arcs or sparks under normal operating conditions, nor does it produce hot surfaces or ignition points that could ignite the surrounding explosive mixture, and generally does not experience faults that could lead to ignition. Explosion-proof special type (s): When electrical equipment or components use an explosion-proof design not covered by GB3836-83, provisional regulations are established by the competent authorities. It shall be submitted to the Ministry of Labor and Personnel for record-keeping, and after inspection by a designated appraisal agency, it shall be treated as a special electrical equipment of type “s”. III. Explosion-proof standards and selection ① Standards corresponding to various explosion-proof types. Explosion-proof types, locations where they are permitted in the UK, Chinese standard GB3836, explosion-proof type codes: IEC standards, CENELEC standards EN50. Increased safety type: 1 or 2, 3 e, 7 019; Intrinsically safe type: 0, 1 or 2, 4 ia or ib, 11 020 (for equipment). Flameproof type: d, 2, d, 1, 018; Special type: s, none, s, none, none. ② Table for selecting explosion-proof types of electrical equipment for areas at risk of gas explosions. Explosion hazard zone, appropriate protection types, types of electrical equipment and their codes: Zone 0: 1. Intrinsically safe type (class ia), ia; 2. Other electrical equipment specifically designed for Zone 0 (special type), s. Zone 1: 1. Protection types suitable for Zone 0; 2. Flameproof type, d; 3. Increased safety type, e; 4. Intrinsically safe type, ib; 5. Oil-filled type, o; 6. Positive pressure type, p; 7. Sand-filled type, q. Zone 2: 1. Protection types suitable for Zone 0 or Zone 1; 2. Spark-free type, n. I hope the moderator can give me some points so that I can upload the materials

Explosion protection refers to electrical explosion prevention, while water resistance denotes the protection rating; these are two distinct concepts that should not be confused