Alarm And automatic control of the flammable gas concentration in the steel Drum Painting and Drying Line

The coated coating liquid or powder state into an amorphous solid thin film coating process known as a film forming process (or referred to as the curing of the paint). In the electric furnace, for example, electrically heated paint curing radiation generally refers to the generated energy to the emitting far infrared quartz heating tube energized the convection curing on the object to be coated. This is one monomer / oligomer mixture is quickly obtained by polymerization of a technique can also be crosslinked coating film of steel drum painting and drying production line.

First, the Preface

Such as the use of far-infrared electric heating drying method, because there is no the outer heating system hot air circulation, there is no dust in the outside hot air heating the workpiece, performance film bright. In addition, far-infrared heating and rapid heating rate, the higher the quality of the product, at the same time also smaller footprint of the device and to maintain a high heating efficiency, low cost conditions, these are far-infrared heating than traditional heating, heating methods such as gas, resistors and other advantages. In addition, this heating method also has precise temperature control, good stability, belongs to the paint and so on.

Using fuel gas heating, the presence of increasingly higher costs and difficult to control features, and the transportation of flammable and explosive materials management risky and cumbersome procedures. China's tariff is lower, more stable, trough time electricity more affordable cost. Comparison, the running costs of the electric heating is lower than the oil, gas heated to 200 liter steel drums, for example, only a single inner and outer coating, of heating temperature 180c ° for 16 minutes under ambient conditions at room temperature 20C °, the average power consumption 1.5 degrees. Peak of about 1.65 yuan, about 0.65 yuan trough, and are environmentally friendly low-carbon run in line with international trends. Under the same conditions of diesel fuel heating, fuel costs of $ 3.3 obvious economic benefits.

Security risks, paint drying oven

Closely related to the security problems of the drying furnace with temperature, and is particularly dangerous in the case of the explosion of combustible materials, such as, pay attention to this problem in normal operation.

(1) explosion of combustible and explosive concentration limit

Combustible substances (including combustible gases, dust, etc.) and the concentration of the oxidizing substances mixed within a certain range, and mixed uniformly, the event of the fire source, it may explode, this concentration is the earlier explosion limit, or called explosive concentration limit. Combustible explosion limit is also divided into explosive upper and lower limits to the highest concentration and the lowest concentration of a potentially explosive fuel combustion enhancer mixed, both also known upper explosive limit concentration and lower explosion limit concentration. When the combustible and the comburent mixture concentration higher than the explosion limit, the explosion does not occur, this is because of the lack of combustion and the combustion flame spread comburent limit restricted; when a mixed concentration below the lower explosion limit concentration , not enough to cause an explosion or burning due to the concentration of combustible material, a large number of supporters of combustion also played a certain cooling effect, also prevents the spread of flame. Only when the concentration of combustible material with equivalent concentration in the reaction is quite, it may explode.

(2) the security risks of the drying oven

Security incidents such as occurred in the drying oven explosion, deflagration, most of all because of the lack of understanding of the equipment, paint safety production process do not know do not know, this coating production line may have a serious impact to production, threatening personal safety accidents. Coating containing an organic solvent, an organic solvent may be released in the curing oven, and left in a high temperature furnace, resulting in a drying furnace explosion safety hazards may exist, as long as the release of the organic solvent concentration in the high-temperature furnace to achievethe limit concentration at any time and may cause an explosion. The way to avoid this is often used to supplement the fresh air to the furnace, remove the dissolved air of a solvent to dilute the organic solvent, to maintain the concentration in the furnace below the explosion limit.

Third, the combustible gas in the drying oven super-concentration alarm and automatic control

(1) Description of the problem

Although the use of far-infrared drying oven built-in electric heating compared to other heating method has many advantages, but not perfect. Inadequate heat curing furnace temperature, gas evaporation increased, resulting in flammable gas benzene, xylene concentration, easy to reach the flash point of concentration encounter heating element electrode in contact with the wire false spark, it will explode and cause accidents. Such events have occurred, to personal safety and property loss. Increase the pipeline gas emissions is common practice to solve this problem, but this approach is difficult to control, resulting in a large number of waste heat. Thus, it is necessary to develop a set of automatic control system, to resolve these contradictions.

(2) solutions

Benefited from Shenzhen Suo Fuda years of experience and in-depth thinking and research, Suo Fuda successful design and production of electricity (gas) heating paint curing oven when the concentration of combustible gas super automatic alarm and control system.

The entire system works as follows: First, the combustible gas detector to detect gas concentrations. The ordinary combustible gas sensor (electronic nose) operating temperature not higher than 70 ° C, paint curing oven operating temperature is generally in the range of 130-180 ° C, special coatings and even up to 280 ° C. Ordinary sensing probe can not be directly furnace detection. Currently, the majority of manufacturers in the market high temperature gas sensors, Japan Figaro However, its high temperature limit is only 160 ° C, it is difficult to meet most of the needs of ultra-high temperature customers. I developed in cooperation with the institutes of the Chinese Academy of Sciences, the high temperature limit of 250 ° C the sensor, the successful solution of this problem. The second step in the detection and alarm system set up micro-relay. The miniature relay normally open usually do not start oven combustible gas concentration exceeds the alarm set point, the control system in miniature relay normally open to closed, driven by the implementation of the contactor is closed, connected to the mainthe exhaust system fan start circuit, increasing the amount of exhaust, reducing furnace gas concentration. The furnace even if the lines were poor contact spark, it will not cause an explosion, so as to ensure the safe operation.

(3) Application Examples

My company's full range of high temperature products. Both temperature range below 160 ℃ SFD-600 (BAK) T-GW series, another temperature range up to 250 ° C the SFD-300 II-GW series, SFD-600 "chameleon"-GW series, and successfully applied Cummins Generator (China) Co., Ltd., Shenzhen BYD, China South Locomotive Mechanical and Electrical Equipment Co., Ltd., Shandong jungle Aluminium Company, CIMC Group Co., Ltd., the equipment put into operation over the years, the application of good, to achieve that energy saving, safe reliable development purposes. In particular, it is noted that the coating operating areas shall be arranged in the the plant perennial minimum frequency wind windward side, with the front area, crowded at the plant cleanliness requirements aside adequate safe distance, in principle, should be independent The plant set basis having GB50016-2006 "architectural design code for fire protection with the relevant provisions set fire exits to ensure the smooth import and export of more than two.Coating operatives within the large plant with entrance security door emergency evacuation distance does not exceed 25m. When coating operations closed painting process and to maintain a negative pressure within the closed painting space, at the same time set the concentration of combustible gas alarm system or automatic explosion suppression systems (including qualified explosion venting devices), and the painting section fire district accounted for painting workshop area less than 20% D, E, fire hazard classification according to production plant in the production plant to determine the fire protection requirements. Spraying equipment and other mobile electrical equipment should be equipped with dust cover, the power cable to the stent struts care; relaxation laying prevent insulation for wear and loose patch port. Used in the powder coating operation area lighting and switch must meet the requirements of explosion-proof dust. Must be tested periodically check the power source for electrical interlock system between the powder system and fan. Equipment conductor area of ​​the coating operations, including the transmission chain, spray tanks, duct, recovery unit must be securely grounded to prevent electrostatic spray gun near ground insulated conductors arc discharge charge accumulation can produce.

Of which, to ensure the safety of the curing oven is safe coating line the most important.The proposed electric heating paint curing oven combustible gas super-concentration alarm and automatic steel drums control system, to achieve the purpose of safety and fuel economy.However, advances in technology there is no end, hope this article efficient control of the security of the curing oven, to provide some reference.