Overview of metal glue reinforcing plates for reciprocating compressor body cracks
Our company was founded in the 1900s and is a medium-sized nitrogen fertilizer enterprise mainly producing synthetic ammonia urea. Nitrogen-hydrogen compressors are one of the key equipment in ammonia production systems. Our company has a nitrogen and hydrogen compressor station, including two nitrogen-hydrogen compressors. This machine is a horizontal double-row six-stage large-scale reciprocating piston manufactured by the former Soviet Union designing Taiyuan Heavy Machinery Factory in the 1960s. Nitrogen hydrogen compressor. The overall structure of the first two-stage cylinder is a column called the low-pressure column of the third four-five-six-stage cylinders, which is called a high-pressure column.
The two rows of cylinders are symmetrically arranged on both sides of the motor, driven by the crankshafts of each column, and the stroke is the suction pressure of the continent. The maximum displacement of the piston pressure is 74. The original design of the exhaust volume is modified by our company. The blade lining its synchronous motor power is the speed. At present, our two compressors are the main models in the production system. The machine is characterized by large displacement and stable operation, but the mass and inertia force of the reciprocating components are also large, and the dynamic balance performance is poor. The crosshead slide and the crankcase main bearing seat are integrally molded into a fuselage.
At the beginning of the year, the equipment management personnel found that there was a long crack near the joint between the lower part of the fuselage and the secondary cylinder of the low-pressure train of a compressor, and the crack continued to move with the movement of the unit, and further development The trend, if not taken as soon as possible, the consequences will be unimaginable. At present, there are many defects such as loose sand holes and shrinkage holes in the crack of the fuselage. We think this is one of the main causes of cracks in the fuselage. Moreover, due to the existence of these defects, the welding performance of the base metal is very poor. If the repair welding is performed, the carbon tetrasulfide content of the cast iron is high, which is prone to thermal deformation and residual stress, which may cause serious consequences that cannot be repaired. The risk is considerable. Later on the Internet, we found a metal glue produced by Belzona in the United States to repair such cracks, and there have been similar successful precedents.
Immediately we got in touch with Belzona's domestic agents and learned some knowledge about the adhesion repair cracks. At the same time, we also obtained detailed specifications and technical parameters of Belzona metal glue. According to the instructions, the maximum bonding strength of the metal glue is a. Two is far less than the strength of the base material itself and the welding strength. Therefore, the bonding by light is far from ensuring the safe operation of the unit. Therefore, it is proposed to add steel plate reinforcement on the crack sidewall of the fuselage to bear part of the load. For the selection of the reinforcing plate, we adopt the principle of strong strength with the base material of the fuselage. By calculation, we choose 16 thick steel plate as the reinforcing plate.
Because the cracks of the fuselage are distributed on two sides and the two sides form the first phase of the Ningxia Petrochemical Year. Therefore, two reinforcing plates are respectively attached to the two sides with cracks, fixed by screws, and then the reinforcing plates are welded together by electric welding to improve the safety and reliability of the body. In order to demonstrate the feasibility of the fuselage crack bonding reinforcement repair program, we reviewed some relevant information, and calculated the strength of the material thickness of the reinforcing plate and the number of screws, and all of them met the operation of the unit. Strength requirements. The surface treatment of the bonding and reinforcing construction scheme firstly stains the crack to confirm the exact position of the crack, and at the same time, the crack is drilled at both ends of the crack. Then grind the groove along the crack until the crack is completely eliminated.
A small hole is drilled every 75 times on the crack and the thread is tapped, and then the screw is used to make the crack become a shorter series. The surface to be bonded and its four regions are burned with an oxygen-acetylene flame, and the temperature is controlled to remove oil stains that penetrate into the shrinkage holes or loose tissues of the sand in the base material of the body. Wash the surface to be ablated and its surrounding area with acetone, and then clean and degrease the surface to be bonded with Belzona cleaning agent to make it clean and dry. After detecting the bonding and reaching the time specified in the Belzona Technical Operation Manual, the bonding joints were inspected by visual method, such as the solvent method, and the next step was carried out without any obvious defects.
According to the specific position and shape of the crack, the steel plate with the thickness is selected, and two reinforcing plates are prefabricated. And the surface to be bonded to the body is ground and flattened to make it fit. In addition, a 50-point crack at the two sides of the crack of the fuselage is drilled according to the specific conditions of the site. The depth is the same as that of the fuselage wall (35). The spacing of each threaded hole is 40 and then compensated in two blocks. The corresponding hole is drilled on the strong plate (the diameter is called and fixed on the fuselage wall plate, and then the joints of the two reinforcing plates are welded firmly and the weld is qualified by the penetration test.
(2) Remove the welded reinforcing plate, grind the dead surface to a metallic luster and rough it, and clean the degreas according to the bonding requirements of the metal glue. Apply a thin layer of metal evenly on the bonding surface of the reinforcing plate and the fuselage. Glue, then install the reinforcing plate in place and evenly tighten all the coupling screws.
At least later, all the joint screws and the steel plate are welded together, and all the bonding repair work is completed.
Conclusion The selection of the plastic plate of the gold-plated rubber body and the various factors of the rubber compounding, the type of the metal glue, we choose a (super metal) cleaning agent, and the ratio of the rubber compound according to the specification requires the solidification of the base material according to the volume ratio. The second amount of the base material and the curing agent are poured on the plastic plate and mixed uniformly to make it a dark gray rubber material, and the mixing unevenness may not occur.
Before applying the glue, use a hair dryer or an infrared light bulb to preheat the surface to be bonded. Apply glue to the crack according to the requirements and regulations of the Belzona Technical Operation Manual, and use a plastic scraper in a favorable direction toward the exhaust. The metal glue is filled in multiple layers on the surface to be bonded, taking care to remove the air bubbles and ensure that the metal glue is in full contact with the cast iron. Curing After the sizing, if the indoor temperature is lower than 20, the bonding joint can be heated by the infrared bulb to continue to increase the degree of curing, effectively eliminating the internal stress and improving the bonding strength. If the indoor temperature is higher, it can be naturally solidified, and then the next step can be carried out on the low-pressure side of the compressor. After the construction of the fuselage crack is completed, the production will be started on the next day, and then our company will organize Special personnel conducted key monitoring of the unit.
During the operation of the unit, the dial indicator was inspected once a week between the reinforcing plate and the fuselage, and no relative distortion was observed. The commissioning of the unit has been safely operated for more than a month, indicating that the application of the bonding reinforcement technology for the fuselage crack is successful. In addition, due to the successful application of this technology, we have accumulated invaluable experience in the crack repair technology of cast iron components of large equipment subjected to huge alternating loads. At the same time, it also saved a lot of maintenance funds for our company, and its economic and social benefits are very considerable.
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