Cause Analysis and Countermeasure of Compressed Air Dryer Drum Pack

Ke Hao, Dong Guozhen, Jia Chaohua, Zhang Xiaowei, Sun Tao, Hebei Province Electric Power Research Institute, Shijiazhuang 050021, Hebei Province, China, through the analysis of the material of the heater, to understand the impact of the container drum package on safe operation, and combined with the operation, find The reason for the drum kit is to propose corresponding countermeasures. In the actual production process, the pressure vessel of the heater type should strictly control its temperature operation range and strengthen the temperature control system. Foreword According to the special equipment safety supervision regulations, 2 sets of instruments for a power plant The compressed air drying electric heater is referred to as the heater for comprehensive inspection. During the inspection, it was found that there were serious bulgings in the two heater cylinders. The bulge was the long-term pressure in the environment where the pressure vessel was working under the pressure of the local temperature. The material deformation and the analysis of the operation of the drum package were analyzed. Looking for the reason of the drum kit, it is proposed that in the future operation inspection, 1 inspection should be carried out by Dong Zhaoqing Global Purification Equipment Co., Ltd., which was installed by Hebei Electric Power Construction Company. It was put into operation on April 20, 2001. The design pressure is designed to be 300 feet. The medium is air. The cylinder size is ¢307mmxtmmxl445mm, and the material is 20g. The heating device is installed inside. The compressed air passes through the heater to achieve the effect of drying and heating. The heating system adopts automatic temperature control, that is, after the specified temperature is reached, the heater stops heating.

Then 6 the heater is fully inspected and found that the heater is in, 8 there is a serious bulging phenomenon, there is obvious high temperature oxidation corrosion outside, the shape of the heater 4 has been deformed, the shape is like a spindle, the bulge is very serious, 13. The bulge is the most serious The diameter is 368mm, which is 6mnl thicker than the original diameter W07mrll, and the expansion and contraction amount is 19.8. There is severe high-temperature oxidation corrosion on the outside of the drum, the peeling of the skin is serious, and the wall thickness is thinned. The wall thickness of the drum is only 7.4. There is also a bulging phenomenon, but the degree of lighter bulging is the most serious diameter of 345, which is 38 thicker than the original diameter towel 307, the expansion and contraction amount is 12, and the wall thickness of the bulge is the smallest. 1 In view of the severity of the bulge, the container is required to stop running. replace. Analyze the operation of the bulge material to find out the cause of the bulge and avoid similar problems.

2Material analysis 2.1 Macroscopic analysis From the outside, the skin condition can be seen as the overheating failure of the cylinder material due to the excessive heating temperature. The actual measured roughness rate has reached 20, close to the minimum elongation of the material 208 after the breakage of 26, the material is produced. The design of the pressure vessel for the obvious plastic deformation power station is based on the elastic failure criterion, that is, the container is plastically deformed, and the pressure vessel is considered to be invalid.

In terms of strength, the minimum wall thickness is 7.40, and according to 135, the strength calculation formula can meet the requirements.

The heart is the inner diameter of the cylinder, 1; the allowable stress of 20 at the design temperature, 13; the coefficient of welded joint; 6 is the corrosion of 2.2 metallographic analysis, the metallographic examination of the long-term sampling of the heater, respectively, in the drum and the non-drum Sampling, the metallographic structure is ferrite + pearlite, the pearlite in the bulging part is significantly reduced than the pearl in the non-bulging part, the carbide in the bulge part has been dispersed, the pearlite received date 2010 7543; revised draft received date 2010641 There are fewer areas, and the organization has deteriorated. Metallographic photographs such as heater into drum kit photo high temperature oxidation corrosion partial enlargement 3 non-drum portion bulge part 2.3 mechanical properties analysis The heater is sampled for room temperature mechanical performance test, respectively, in the drum and non-drum parts, the test results are as follows 1. The tensile strength of the material at the bulge is significantly lower than that of the metallographic structure, and is lower than the 87134997 standard.

3 Operation analysis According to the above analysis, the root cause of the bulging of the heater is over-temperature operation. Through the understanding of the use of the site, it is found that the sample number yield strength is broken, the elongation is sampled, the position is bulging, the container is lower, the lower part of the container is not bulged, the container is in the middle, the bulge is in the middle, the bulge is in the middle, the bulge is in the middle, the upper part is not in the bulge, the upper part is not in the upper part of the barrel. The standard heater has the following problems in use. 20, 7 years ago, the heater temperature control system is a domestic single-board machine. It often crashes and crashes. If it is in the heating state, it will not stop heating, and all the doors can not be controlled. , causing the heater to overheat.

The temperature measuring point is located on the outlet pipe of the dryer. When the equipment is put into operation incorrectly, no air circulation is formed in the dryer. The temperature measuring point does not feel the temperature rise and the heater is continuously heated and overheated, causing the dryer to dry. burn.

At present, when the temperature-controlled thyristor fails, there is a possibility that the heater power supply cannot be turned off, and the heater is overheated.

The design temperature of the heater is 300 ft. However, due to the above problem of the heater temperature control system, the heater has frequent over-temperature operation, and the heater is insulated during operation, and cannot dissipate heat. The metal wall of the container The temperature is much higher than 300. In the general case, for carbon steel, the temperature is greater than 350 400, the material will creep under the action of external load and the package will be insulated due to the running condition. The container can not be found in the inspection and annual inspection. The temperature phenomenon causes the heater to deteriorate after 7 years of operation, resulting in a drum kit, which seriously affects the operation safety.

4 Conclusions and countermeasures Through comprehensive inspection of material analysis and operation analysis, the following conclusions were obtained. The comprehensive test found that the container produced obvious plastic deformation, the wall thickness was thinned, and there was obvious over-burning phenomenon. The surface oxidation corrosion was seriously based on material analysis. The metallographic structure of the bulge part is degraded, the pearlite morphology is obviously reduced, the carbide is dispersed, and the mechanical properties are obviously reduced. Below the standard, the root cause of the bulging of the equipment is over-temperature operation.

Many of the problems with heater temperature control systems are the main cause of overheating.

In Article 47 of Rule 1, it is determined that the safety status of the two heaters is level 5, and the operation is immediately stopped and replaced.

At present, the temperature control system has been gradually reformed, and the relevant control logic has been improved. However, due to the inevitable control component itself, it is necessary to strengthen regular inspections in the future to prevent the heater from over-temperature operation. The heater is over-temperature operated for 7 years without It is found that because the comprehensive inspection is not carried out as early as possible, the pressure vessel should be fully inspected according to the requirements of the regulations. All the insulation outside the container should be stripped during the inspection to prevent the leakage inspection of the bulge corrosion and thinning defects.

For the pressure vessel of the heater type, the temperature operation range should be strictly controlled, and the inspection of the temperature control system should be strengthened. State Council Order No. 373, Special Equipment Safety Supervision Regulations.

Fantasy 30 feet 70014004, pressure vessel periodic inspection rules 6.

Magic; order 13+17, boiler steel plate right.

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