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Liu Huasheng Oilfield Branch Marine Oil Production Plant Maintenance Brigade Team Shandong Dongying 257237 In the process of stainless steel pipeline renovation in the oil plant swimming pool, our team successfully applied air plasma cutting technology, the application effect is good, the cutting quality is better than the previous arc cutting quality. The efficiency has been greatly improved and the construction efficiency has been greatly improved. At the same time, the air plasma arc cutting process applied to low carbon steel cutting can also obtain good cutting quality and high cutting efficiency.
Comparison point stainless steel tube arc cutting process stainless steel tube air plasma cutting process slow cutting speed (10cm / min) fast (40cm / min) slit width wide (10-15mm) narrow (3-5mm) cutting current large (150-200A) small (45A) Large energy consumption for cutting (6KW-8KW) Small (4KW) The straightness of the kerf is very poor. The verticality of the kerf is very poor. It is flat. Table 1 Advantages Table 1 Methods and problems of material cutting in the past stainless steel pipeline construction In the construction of the project, in the case of stainless steel pipeline construction, the cutting and cutting pipelines are processed by arc cutting. Cuts often stick to welds, slag, etc., oxidation is serious and the quality is very poor, flatness, verticality, etc. can not be effectively guaranteed, which brings great difficulties to the next construction process - electric welding, often caused by the mouth The gap between the welds is narrow and the surface of the groove is uneven. If you want to re-grind the cut with a sander, the amount of sanding work is very large.
The air plasma arc cutting process utilizes a high energy density plasma arc and a high speed plasma stream to blow the molten metal away from the cutting edge to form a continuous cut. The plasma arc cutting speed is fast, and there is no metal burning effect on the workpiece when the oxygen acetylene is cut. Therefore, the heat input obtained by the workpiece is small, the deformation of the workpiece is relatively small, and the carbon steel, stainless steel, copper, aluminum, cast iron, etc. can be cut and processed. Kind of metal. Therefore, in view of the wide variety of maintenance industries and the diversity of work tasks, the application prospect of this process is very optimistic.
2 Air plasma arc cutting principle and characteristics The principle of air plasma arc cutting is shown as the principle of air plasma arc cutting. The cutting method directly passes the compressed air into the nozzle, and decomposes the oxygen through the arc heating, and the undecomposed air washes the cutting mouth at a high speed, and the decomposed oxygen generates a strong chemical exothermic reaction with the cutting metal, thereby accelerating the cutting speed. The fully ionized air plasma arc has a high thermal enthalpy value and energy concentration (energy density up to 105-106 W/cm2), so the arc has a large heat and a high temperature (the center of the arc column can reach 18000-24000 K or more), and the flame flow speed Large (up to 3m / s or more), good arc stiffness and so on. Therefore, the cutting speed is high, the cutting quality is good (the slit is straight, the deformation is small, and the heat affected zone is small), and it is particularly suitable for cutting carbon steel of 30 mm or less, and can also cut stainless steel, copper, aluminum and other materials.
The team has one air plasma cutting equipment, the model is Ruiling RILcut70, the power supply uses FET-type inverter power supply, and the air supply system is air compressed air pump or high pressure oxygen cylinder.
3 Air plasma cutting technology applied to stainless steel pipeline construction In October 2011, during the reconstruction process of stainless steel pipeline in the swimming pool of the oil production plant, our team successfully applied air plasma cutting technology to the austenitic stainless steel tube of 2998 (material is 1Cr18Ni9Ti) The cutting process is carried out and the application effect is very good. The cutting quality is very good, the quality of the arc cutting is doubled, and the cutting speed is fast, so the construction efficiency is also greatly improved. The following are the advantages and disadvantages of arc cutting and air plasma cutting process: Compared with arc cutting 8mm stainless steel tube, air plasma arc cutting has the following advantages (Table 1): In summary, in the past, the use of electric welding machine arc cutting stainless steel pipe defects: can not get high quality The incision makes it difficult for the next group to work.
Advantages of using the plasma cutting process: Since the high current cutting is very serious for the loss of equipment life, the use of moderate current can also effectively extend the service life of the equipment. The cutting gas source can be compressed air or compressed oxygen (using oxygen for the electrode and cutting nozzle life), relatively easy to obtain, and cheap, low cost of use. During the construction, each DN250 weld is about 1 hour from cutting to welding, and the weld appearance is greatly improved. Compared with arc cutting, it saves more than half of the processing time. The overall construction efficiency has been doubled and the construction period has been greatly shortened.
4 air plasma cutting process in the daily maintenance of the application prospects often work, the engineering maintenance team is generally cutting carbon steel, the main varieties are: Q235A / B type low carbon steel, 20 low carbon steel these two most Common low carbon steel. The most common types of processing steels are: 1.5mm-10mm steel plate; 6mm-219mm steel pipe; 3mm-6mm angle steel. It is very convenient to use the air plasma cutting process when prefabricating the workpiece in the workshop. Because the 1.5mm-4mm steel plate is processed by oxyacetylene gas, the heat is not concentrated, and the heat input is very large, which causes the deformation of the cutting mouth to be large, which affects the processing precision and the appearance. When the thin steel plate is processed by the air plasma cutting process, the heat input of the cutting arc is small, the heat input area is small, and the heat affected zone is small, so the cutting deformation is small, the cutting speed is fast, the processing precision is high, and the slit is straight and easy to process. And the appearance is good.
In the long run, the economic benefits of cutting low carbon steel using air plasma technology are also better: each set of oxygen acetylene gas is about 86 yuan (73 + 13 = 86 yuan), a shift cuts the same amount of steel, using air plasma cutting The power consumption of the machine is about 12.46 yuan (0.623 yuan / KWh) 4.0KW5h = 12.46 yuan, and the cost per day is about 73 yuan. According to the calculation of 3 classes (three classes, 10 days for each team) in the monthly construction of the workshop, The annual saving of oxygen acetylene costs 73 yuan 360 = 26280 yuan, the entire brigade can save oxygen acetylene gas costs 52560 yuan, the efficiency of cost reduction and efficiency is more significant, the application prospects are more optimistic.
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