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The safe use of explosion-proof electrical products from the beginning the correct classification of hazardous areas

Published:2010-10-20 9:57:46 |

1 explosion-proof safe use of electrical products and product safety issues as important as

A long time, involving the national electrical safety standards for explosion-proof, explosion-proof electrical mainly based standard (National Standard GB 3836 series-based manufacturing test), and explosion-proof electrical product standards. The implementation of these standards is the main explosion-proof electrical products, manufacturers and product quality inspection institutions. But the explosion-proof electrical products used in hazardous locations explosion can ensure the safety not only depends on the design, manufacturing and inspection department to provide high security, explosion-proof products, but on the product's safe use of user departments. Even the best quality performance of explosion-proof electrical products, if used improperly, not only can not play the role of proof and may even endanger the safety of a terrible killer. Many tragic explosion prove this point. For example, explosion-proof electrical products cable into the device on the rubber seal to maintain product explosion-proof performance is an important component, the part in use is often neglected by people, can not be the correct selection, installation and maintenance. For example, some users do not be pressed after repair, and some use the ring size and material does not meet the standard requirements, and some simply do not install the ring after repair. Results for the dangerous places in the combustible gas can be unhindered access to junction box cavity. Once the wiring connections inside the terminal at the arc appear. Sparks, it could ignite flammable gas, causing an explosion. This is not the safe use of similar products, explosion-proof electrical explosion caused by explosion of examples in the statistics of the total account for a large proportion.

Thus, the safe use of explosion-proof electrical products and to reflect the safety performance of explosion-proof electrical products manufacturing quality are equally important. This, as we are ill, often need a doctor in the symptoms of our body carefully diagnosed, and then correct medication guide us for the same reason. Of acceptable quality and the correct use of drugs must be combined in order to play the role of the safety of symptomatic treatment, or it may be counterproductive - not only drugs of acceptable quality can not safely treat and may even endanger the physical safety.

We are talking about the safe use of explosion-proof electrical products, generally include the following aspects: the right to divide the type of explosion danger; proper selection, installation of explosion-proof electrical products; proper maintenance and repair explosion-proof electrical products.

Seen from the above, explosion-proof electrical safety is a systematic project, which includes the design of explosion-proof electrical products, manufacturing, testing, Classification of hazardous areas, explosion-proof electrical product selection installation, maintenance and overhaul, and the related quality management, personnel training and other links. The negligence of any part of the explosion could be hidden.

Indeed, many user departments also recognize that the safe use of explosion-proof electrical products to ensure proof of the importance of security, but suffer from a long time without a complete set of national standards to follow, therefore, can only be based on experience and some incomplete information formulated a number of departments standards and specifications to implement the safe use of explosion-proof electrical products, technical production management. Therefore, to formulate a set of complete, and with the international standards of national standards, has been pressing concerns in all aspects.

In recent years, with the explosion-proof electrical standardization of development and strengthen the need for international standards, standards of proof electrical product manufacturing from the previous state-based test, and gradually evolved to include manufacturing testing, areas are classified, Selection criteria such as installation and maintenance of the composition of the complete overhaul of safety standards for explosion-proof electrical system. "Classification of hazardous areas (GB 3836  14-2000)", "hazardous areas electrical installation (GB 3836  15-2000)", an explosive gas atmospheres Electrical equipment maintenance (GB 3836  13-1997) "the three criteria the first time in the form of national standards, provides the user complete the safe use of explosion-proof electrical products sector of the technology and management requirements of the safe production explosion danger of great significance. In addition, the three standards and international standards implementation of the standards, and thus also for China's petrochemical unit to enter the international market and make the introduction of explosion-proof equipment and technical management of production safety to create favorable conditions.

2 Classification of hazardous areas is to achieve the safe use of explosion-proof electrical products based on the work of the most important

User departments of the three criteria, the first and most basic work is involved in the sector classification of explosion danger. It is like a doctor's patients, the first comprehensive examination and doctors through the analysis of the symptoms diagnosed as post-judgment. Accurate diagnosis and symptomatic treatment is the basis for safe use. Aiming at the national standard, "Classification of hazardous areas" (GB 3836  14-2000) introduces some analysis.

The purpose of 1 Classification of hazardous areas

Classification of hazardous areas is likely to place an explosive gas environment for analysis and classification methods. The purpose of site classification is to be used in place of such explosion proof electrical equipment selection and installation of sufficient security and a good economy. Because the use of flammable substances in dangerous places, to ensure that there is explosive gas atmospheres never difficult. Similarly, to ensure that electrical equipment in hazardous locations as light source is never difficult. Therefore, the risk of large sites (that is, the possibility of an explosive gas atmospheres large sites) should be selected high safety type explosion-proof electrical equipment. On the contrary, the risk of smaller sites (ie, the possibility of an explosive gas atmospheres smaller place), select the security lower (but still has enough security), the price is relatively inexpensive type of explosion-proof electrical equipment.

2.2 Classification of hazardous areas the main content of the work

Classification of hazardous areas work has two main aspects:

(1) According to the explosive gas environment the frequency and duration of the hazardous area is classified into three regions

Zone 0: explosive atmosphere is present continuously or for long periods;

Zone 1: In normal operation, you may place an explosive gas environment;

Zone 2: In normal operation, not the explosive gas environment, if there is occasional, and there is only a short time the place.

(2) to determine the number of hazardous locations and extent of existing

Because the only sure somewhere in the regional category of dangerous places is not enough, we must also determine the type of dangerous places in and around the device number exists, and to determine risk areas for each type of spatial extent, that is to be conducted on the premises of the spatial extent accurate quantification.

2.3 Classification of hazardous areas of basic safety principles

(1) the handling or storage of flammable substances in the design of equipment and devices should be as much as possible the type of dangerous places as the least dangerous category, in particular the Zone 0 and Zone 1 areas and scope of the number of places have become the minimum , that is, as far as possible have become the most dangerous places in Area 2 places.

(2) for the process equipment should be the main source for the two releases, if not meet this requirement, it should make the source to a very limited release and release rate of the amount released into the air.

(3) determined the type of dangerous places, are not free to make changes. After the process equipment for the repair, you must carefully check and confirm whether it can guarantee the safety level of the original design.

2.4 Classification of hazardous areas of thought

We can see from the definition of dangerous places, dangerous places is an explosive gas atmospheres or anticipated number of possible enough to require the structure of electrical equipment, installation and use of special safety precautions taken by the region.

By definition can be seen as a dangerous place to determine whether establishments, mainly based on whether the site may be explosive gas environment, and conditions for the formation of explosive gas environment, the range is the concentration of flammable gas is in the explosive limit range. Combustible gas concentrations in the air in the explosive limit (that is, the lower explosion limit and upper explosive limit) within the light source can form explosive event; if outside this range, using a strong light source can not be excited explosion. In other words, any concentration below the lower explosion limit or above the upper explosive limit of the mixture in contact with the light source itself will not lead to flame propagation. Concentrations below the lower limit of explosion due to excessive air as inert medium in the combustion reaction, consuming part of the reaction heat from the cooling effect, impede the flame spread themselves; the contrary, the concentration is higher than the upper limit of explosion due to excess fuel, the air volume insufficient, leading to incomplete chemical reaction, the reaction heat released is less than the heat loss, and thus hinder the spread of flame.

Seen from the above site appears in the number of flammable gases is to determine the key risk areas, and places the emergence of flammable gas, flammable gas release depends on the source and impact of the accumulation of flammable gas ventilation. Therefore, we can sort out the idea of such a problem: the size of establishments classified according to their risk - the risk of workplace depends on the explosive gas environment that places the number of - for explosive gas atmospheres there is a number of flammable gases, the explosion limit of decision - depending on the number of flammable gas was present in the source and places the release ventilation.

2.5 Classification method places

Places the core issue of classification is the place for explosive gas atmospheres may occur in the basic probability analysis, which requires experienced professionals and participate in the research, while places to accumulate and collect operational status of each device and place of environmental factors and other information. Thus, classification places should be familiar with the properties of flammable materials, equipment and technology professionals and engage in safe condition, electrical and other engineering and technical personnel to discuss identified. Specific methods are as follows:

(1) Find and determine the sources of release

Places only the presence of flammable gases or vapors may form explosive gas atmospheres. Therefore, we must first look for places containing flammable material storage equipment, processing equipment and pipelines in the possibility of release to place flammable gas or vapor, or air into the container and the possibility of flammable gas or vapor to form an explosive mixture mixture.

Each piece of equipment (such as tanks, pipelines, pumps, compressors, etc.), if its internal containing flammable substances should be considered as a potential source of release. If they can not contain combustible material, then it is obvious they will not be around to form an explosive mixture. If such equipment, although containing flammable substances, but can not escape or leak into the place, you can not be deemed to release the source (for example: setting the space in a seamless pipe).

If the device has confirmed the release of flammable substances in the workplace, you should first determine the frequency and duration of release, and thus determine the level of the release of the source:

1) Continuous-level emission sources: continuous release, or is expected to release the long-term release of the source.

For example, the upper part of the fixed roof of the tank space and exhaust ports; open containers of flammable liquid near the surface at the other, should be regarded as a continuous order release source.

2) one source of release: In normal operation, is expected to be released periodically or occasionally release source.

For example, normal operation, is expected to place around the release of flammable material to the pump, compressor or the valve seals; container containing flammable liquid at the outlet; normal working hours, is expected to be released into the combustible material places around the sampling point; normal operation, the release of flammable substances is expected to pressure relief valve, vent or other openings shall be deemed a release of such source.

3) 2 emission sources: In normal operation, is expected to not release if the release is only occasional and short-term release is the release of the source.

For example, normal operation, the compressor can not leak or the valve seals; normal operation, not leaking flanges, fittings or pipe joints; normal operation, it is impossible to place the release of flammable material around the sampling points, and so the release should be considered as two sources.

(2) determine the type of hazardous area locations

Regional division of the main types of hazardous locations based on the source of the release site level and ventilation conditions.

In general, the formation of a continuous order release the source zone 0 hazardous areas; one release source area to form a dangerous place; two sources on the release of Zone 2 dangerous places.

Should also be determined according to geographic division of ventilation. Such as ventilation, can reduce the dangerous places of the regional categories. On the contrary, such as ventilation, can improve the regional categories of dangerous places. This is because the release into the surrounding areas of flammable gases or vapors, the ventilation will be formed by means of air flow or spread, making it less dilution to the explosion limit.

(3) identify the risk areas of the region-wide

Region-wide effects are dangerous places flammable gas or vapor release rate, the gas explosion limit, the relative density, ventilation and other factors, and therefore the impact on their comprehensive analysis to determine the dangerous places in the regional context.

2.6 The impact of regional factors dangerous places

(1) the release rate of combustible materials

Release rate increases, per unit time in release into the surrounding areas the more the amount of flammable material, the corresponding range of hazardous area the greater.

(2) explosion limit

For a given release, lower explosive limit, the concentration above the lower explosion limit the amount of explosive gas mixture to a corresponding increase in the range of hazardous area will be a corresponding larger.

(3) the relative density of gas or vapor

If the relative density of gas or vapor than air is small, then the lighter than air gases and vapors flowing upward, so that the release of the source of the danger zone above the vertical range of the relative density decreases with the increase; if the gas or vapor relative density than air, so heavy in the air of the gas or vapor will tend to deposit on the ground, so near the ground, the level of the range danger area will decrease with the relative density increase.

(4) Ventilation

Increase ventilation, can reduce the range of hazardous area. That is because air leaks can be places of flammable gases or vapors disperse or dilute the hazardous area narrowed down. If good ventilation, air ventilation is large enough, and continuous existence of ventilation, for example, have a spare fan, then we can reduce the dangerous places of the regional categories.

In addition, the release of the source can affect the ventilation around the obstacle effect, expanded the scope of the danger zone. On the other hand, if the obstacle (such as dams, walls, ceilings, etc.) can stop the flammable gas or vapor to the further spread around, then barriers can limit the range of hazardous area extended further to the periphery.

Different ventilation conditions on the range of hazardous area can be analyzed as follows:

1) Natural ventilation and forced ventilation when the overall

As mentioned above, although usually release the source to form a continuous level 0 area sites, a source of the formation of a zone free sites, two sources on the release of Zone 2 areas. However, the actual production site since the effects of ventilation, the situation is more complicated. For example, a well-ventilated, may cause dangerous places in the regional small to negligible, may become less dangerous regional categories. Particularly if ventilation is good, may become non-dangerous places. Conversely, if ventilation is poor, and perhaps dangerous places in the region will expand the scope, might become a higher risk of regional categories.

2) When the local forced ventilation

Under normal circumstances, the use of local ventilation and dilution of explosive mixtures, the overall force than natural ventilation and better ventilation. As a result, the area will reduce the scope of dangerous places, and even reduced to a negligible level. May become less dangerous area categories. Even a non-dangerous places.

3) When no ventilation

There is no place for the release of the ventilation source, the continuous release of the source level would certainly place the formation of Zone 0, 1 release of the source may also be formed in Zone 0 areas, two sources of release sites may also form a zone. However, under special circumstances, such as monitoring the release of little or release, they may make it less dangerous category.

4) when obstructions restrict ventilation

If there are obstacles within the hazardous areas of ventilation, then will expand the scope of dangerous places, or make it a higher risk category. Consider the impact of obstacles, should pay particular attention to the hollow pit, and the relative density of gas or vapor.

5) ventilation failure

Classification of hazardous places to work based on ventilation as the prerequisite. If the risk of failure of the ventilation device is negligible (such as another set of automatic standby system), there is no need to change to the ventilation device to work as a precondition Classification of hazardous areas identified. However, if the risk of failure of the ventilation device can not be ignored, no forced ventilation should be predicted when the explosive expansion of the scope of the mixture level of ventilation should also predicted failure frequency and duration, and accordingly to determine the type of place.

If ventilation is not a fault or failure is very short even if there should be the result of a malfunction of the ventilation device extended Zone 2 hazardous locations as places.

If the ventilation fails, to take measures to prevent the release of flammable substances (such as: process flow automatically stops), you do not change the original classification of certain places.

6) other conditions

Climatic conditions, topography and other factors can also affect the range of explosion hazardous area. In summary, in determining the danger zone should pay attention to the following:

Heavier than air gases or vapors may flow into the space below ground, such as grooves and groove; lighter than air, gases or vapors may be stuck in the height of the space, such as the roof space; if the release of the source is located near the plant or place outside should take measures to prevent a large number of flammable gases or vapors into the shop or place; ventilation conditions on the range of explosion danger great influence during the zoning should be great attention.

2.7 The Classification of hazardous areas and hazardous areas are classified diagram of an example to determine type and extent of workplace

Based only on the scene in the production of complete sets of equipment or equipment designed for cursory review, put the device around the various parts identified as Zone 0, Zone 1 or 2 places is almost impossible, but must be carefully analyzed the formation of explosive mixtures of various possibilities.

To determine the frequency of release of flammable substances, the release time, release rate, concentration, ventilation and other types of hazardous locations, range of elements, it must release the source of the possible formation of flammable material for the process to accommodate devices one by one Study careful analysis. National Standard GB 3836.14-2000 "Electrical equipment for explosive atmospheres Part 14: Classification of hazardous areas," given the "Classification of hazardous areas diagram" and "dangerous places by example" prompt appendix, these data place the master principles and classification methods provide practical help. However, given some of the standard range of examples of hazardous areas are classified under certain conditions, the use should pay attention to their qualification. The example given in the standard guidance is only an example, the example to the standard place for the actual classification, must take into account the special circumstances of the actual situation and a variety of special details, such as the division of oil facilities is a danger zone that determined under normal circumstances. If the hydraulic oil or air pressure is very high, then the corresponding range of hazardous area will be expanded. In addition, each example shows only some impact parameter, but not all, under normal circumstances, taking into account the special requirements of these factors, and some are qualitative rather than quantitative, so the classification results more conservative. That is, if the regulations may be more closely operating parameters, the place will be more accurate classification results. IR3Y31M is the number for products that is related with integrated circuit.

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