If there is no influence of factors such as the extrusion thickness of the forming vertical roll on the shape of the edge of the plate, the ideal forming seam state 3, but due to the extrusion of the forming roll or the improper pressure of the crimping roll, the disc shear blade is not perpendicular to the edge of the steel strip. Influenced by forming process factors such as cutting and welding rolls too large or inappropriate planing angles, it is easy to form a 4-shaped forming seam. If the narrow gap is slightly larger or the position of the raw material changes when the opposite end enters the pinch machine, the edge of the strip will be thickened or the crimping roller will be damaged. These conditions will aggravate the narrow gap phenomenon and the thicker the raw material, the more obvious the narrow gap phenomenon will be. The existence of this narrow gap phenomenon is extremely unfavorable to welding, and it causes continuous pores in the inner welding part. Iron Bean 24 welding metallurgical analysis Let’s take a look at the welding characteristics under the condition of this forming seam. The internal welding penetration of double-sided spiral submerged arc welding is composed of two parts.
Part of it is formed by the mountain electric arc blowing and burning the mother village, and part is formed by the superheated molten pool gold, melting the mother village, and the welding molten pool is crystallized in a moving state because the welding arc cannot be blown directly to the narrow gap of the inner welding root. The root of the groove depends on the superheated molten pool metal to melt. In this way, when the superheated molten pool metal melts the base material, when the above-mentioned narrow gap is encountered, due to lack of sufficient support, part of the liquid molten pool metal is narrowed at the root. gap. Furthermore, because the formed occlusal seam has strong magnetism, the narrow gap at the root often entrains flux particles and flux iron oxide powder above the superheated liquid soldering pool gold. It will be partially or completely melted into the liquid molten pool. The formation of compound inclusions, and the reduction reaction with the molten pool, the reaction product 1 partially floats to the surface of the molten pool, and part of it remain in the molten pool. At 6, when it is close to the crystallization temperature, the iron oxide in the molten pool metal undergoes a violent redox reaction with carbon, and a large number of inclusions that dissolve into the molten pool but do not float out become the nucleation particles of carbon oxide pores. Carbon dioxide bubbles nucleate and gather together, which is bound to happen. During the floating process, the position of 1 is relatively deep, lacking arc stirring, and the viscosity of the pool increases continuously. Float out of the molten pool. There is also a part of 1 remaining in the inner weld and the root of the inner weld, forming 2 pores and pore cavities. When the gas nucleates and grows on the inclusions, the phenomenon of 2 pores wrapping inclusions will appear, which is what we call iron. When this kind of defect passes through the external welder, if the mining position is shallow, it will be burned and emerge from the external welding pool after external welding; if the position is deep, continuous air holes will even be formed in the penetrating seam to change this. This is the source of the porosity of iron beans 1. The penetration depth formed by the arc directly blowing the base metal 2 The penetration depth formed by the overheated molten pool metal melting the base metal For the narrow gap phenomenon, firstly adjust the forming equipment such as vertical roll, crimping roller, disc shear, welding pad roller, etc., so that the edge of the strip steel is smooth, no extrusion thickening occurs or minimizes extrusion thickness, no scratches, no flats, and reaches or It is close to the ideal forming seam state. Secondly, strengthen the internal welding or evening welding planing edge to weaken the narrow gap phenomenon at the root of the internal welding, to stabilize the joint quality of the forming seam, 3.3 adjust the welding parameters according to the edge shape of the forming seam. Appropriately increase the internal welding current and reduce the external welding current or appropriately reduce the internal welding current and increase the external welding current to reduce defects such as porosity and iron beans at the welding root. ability.
For single-entrance and single-exit steel pipelines, the calculation formula of the dynamic mass balance method is the method, that is, when the leakage exceeds a certain set threshold, the steel pipeline leaks. This method is not very reasonable for guiding the development of the steel pipeline leak detection system, because it is very difficult to set a suitable steel pipeline leakage threshold, and if the threshold is set too low, the steel pipeline leak detection system is prone to false alarms. It has been determined that the sensitivity and accuracy of the leak detection system for steel pipelines are very low, and often relatively large steel pipeline leakage has occurred but the leak detection system still will not alarm. To more effectively and sensitively detect whether the steel pipeline leaks and reduce mistakes, Document 2 uses the 5-foot-ding method of the circle to judge. After the leak is determined at the entrance and exit of the steel pipeline, the size of the leak is estimated by measuring the flow and pressure and the statistical average. This method has been verified by many on-site leak detection tests of steel pipelines, and its reliability is strong. 3. Wt time 1> Factors affecting the accuracy of leak detection of steel pipelines during the process of quality imbalance If the flow rate remains the same, that is, without considering the estimation error of, the lower limit of the leakage sensitivity of the steel pipeline in Eq. In this way, the accuracy of the flow meter determines the accuracy of the leak detection of the steel pipeline.
However, the flow in steel pipelines is not constant, especially in multi-batch operations and large-diameter steel pipelines, the hydraulic pressure changes caused by temperature and pressure changes must be considered, and volume adjustment is used to correct the balance of steel pipeline flow. For example, in a steel pipeline with a diameter of 1016mm, a temperature change of 10 will produce a volume change of 0.8 and a pressure change of 0.0%, which makes a volume change of about 10% in a section of a steel pipeline of 99,758km. Even with a steel pipeline simulation software with complete functions, it is difficult to accurately predict the long-term oil volume of the two measurement points of the steel pipeline. Therefore, the estimation error of steel pipeline oil product reserve also affects the accuracy of steel pipeline leak detection.
If the leakage of the steel pipeline is greater than or equal to the comprehensive error of the flow measurement result and the change value of the oil product reserve of the steel pipeline within a period, the leakage of the steel pipeline can be detected. Document 4 gives the minimum detectable leakage, the comprehensive error of 1dQm flow measurement results; dV, the estimation error of steel pipeline stock; At measurement time intervals.
For a given 1, the measurement error can be reduced by extending the measurement time interval, so that smaller leaks can be detected. For a large 17, or a shorter measurement time interval, the minimum detectable leak is larger and may reduce the influence of flow measurement errors on the accuracy of steel pipeline leak detection.
Conclusions and Suggestions The above analysis results show that the accuracy of the flowmeter and the estimation error of the steel pipeline oil reserve are two key factors in the dynamic mass balance steel pipeline leak detection technology, and these two factors affect the dynamic mass balance principle Accuracy of steel pipeline leak detection.
The reduction of the flow measurement error of the flowmeter can significantly improve the accuracy of leak detection of steel pipelines using the principle of dynamic mass balance. Calibration accuracy of the meter.
The method of fitting the flow error curve of the flowmeter can be used to compensate for the accuracy of the flowmeter and perform real-time online correction of the measurement accuracy of the flowmeter, thereby improving the principle of dynamic mass balance. Steel pipeline leak detection In the operation and management of steel pipelines, should be avoided Accidental Transient Phenomena To ensure the accuracy of the prediction of the oil product reserve in the steel pipeline between the two flowmeters, the distance between the two flowmeters should not be set too long. In fixed-length steel pipelines, under consideration of the principle of economy, the number of flowmeters should be appropriately increased
Post time: Jun-29-2023