Routine maintenance is required when thick-walled steel pipes are used:
Thick-walled steel pipes are widely used steel varieties. It directly affects the economic benefit and personnel's life. All countries in the world attach great importance to the inspection of thick-walled steel pipes and adopt various non-destructive testing (NDT) methods to carry out strict inspections on thick-walled steel pipes. To a certain extent, the corresponding maintenance and maintenance should be paid attention to during the use of thick-walled steel pipes. In general, a special person should be assigned to inspect the thick-walled steel pipes every day to check whether the vertical poles and backing plates are sinking or loose, whether all the fasteners of the frame are slippery or loose, and whether the components of the frame are complete; The foundation of the thick-walled steel pipe should be well drained. After the rain, the foundation of the thick-walled steel pipe frame should be fully inspected. It is strictly forbidden for the base of the thick-walled steel pipe to sink under water; The wind rope, etc. are fixed on the thick-walled steel pipe, and it is strictly forbidden to hang heavy objects on the thick-walled steel pipe; it is strictly forbidden for anyone to dismantle any parts on the thick-walled steel pipe; in case of strong wind, heavy fog, heavy rain, and heavy snow above grade 6, the thick-walled steel pipe should be suspended For steel pipe operations, the operation can only be continued after checking that there is no problem before resuming work.
Thick-wall steel pipe performance and economy:
In addition to the above-mentioned structural types of pipe fittings used in actual piping engineering, there are other structural forms of pipe fittings to meet the requirements of various working conditions, especially special working conditions. In engineering design or selection, the higher the strength grade of the pipe fittings, the higher the safety, but the greater the cost of the project, it will cause waste. From the perspective of economic benefits, while meeting the requirements of engineering design and reducing costs as much as possible, it is often easy to result in a small number of selected pipe fittings as a whole, which is not conducive to the management, regulation, and design of construction materials on site. material substitution etc. Therefore, the selection of pipe fittings should be comprehensive and economical, and it is advisable to reduce the variety of pipe fittings as much as possible. In addition, factors such as the conditions of on-site construction, the level of construction, and the procurement cycle of pipe fittings should also be paid attention to in the selection of pipe fittings. In specific cases, the possibility of adopting reinforced pipe joints, mitered elbows, and on-site bending of small-diameter pipes should also be considered. At the same time, we also have a good understanding of the production capacity, products, and market supply of pipe fittings manufacturers.
Causes and adjustments of the uneven wall thickness of steel pipes:
1. The reason for the uneven wall thickness of the spiral shape is: the uneven wall thickness caused by the adjustment of the rolling center line of the piercing machine, the inclination angle of the two rolls, or the small amount of reduction in front of the plug, etc., generally along the entire length of the steel pipe. Spiral distribution. During the rolling process, the uneven wall thickness caused by the premature opening of the centering roller, improper adjustment of the centering roller, and shaking of the ejector rod are generally distributed in a spiral shape along the entire length of the steel pipe.
Measures: Adjust the rolling center line of the piercing machine so that the inclination angles of the two rolls are equal, and adjust the pipe rolling machine according to the given parameters in the rolling table. For this situation, adjust the opening time of the centering roller according to the exit speed of the capillary tube. During the rolling process, the centering roller should not be opened too early to prevent the ejector rod from shaking and causing uneven wall thickness. The opening of the centering roller needs to be properly adjusted according to the change in capillary diameter, and the beating amount of the capillary should be taken into consideration.
2. Causes of linear uneven wall thickness: the height adjustment of the mandrel pre-piercing saddle is not appropriate, and the mandrel is pre-piercing when it touches the capillary on one side, causing the capillary to drop too quickly on the contact surface, resulting in uneven wall thickness or even Pull concave defects. The continuous rolling roll gap is too small or too large. Piping mill centerline deviation. The uneven reduction of the single and double racks will cause the linear symmetrical deviation of the steel pipe in the direction of the single rack (super thick) and the direction of the double rack (extra thick). If the socket breaks and the difference between the inner and outer roll gaps is large, it will cause asymmetric deviation of the straight line of the steel pipe. Improper adjustment of continuous rolling, piled steel, and drawn steel rolling will cause uneven wall thickness in a straight line.
Measures: Adjust the height of the mandrel pre-piercing saddle to ensure the centering of the mandrel and capillary. When changing the pass type and rolling specifications, the roll gap should be measured so that the actual roll gap is consistent with the rolling table. Adjust the center line of rolling with the optical centering device, and correct the center line of the rolling mill during the annual overhaul. Replace the broken frame in time, measure the inner and outer roll gaps of continuous rolls, and replace them in time if there is a problem. During continuous rolling, steel drawing and stacking should be avoided.
3. The cause of uneven wall thickness at the head and tail: the front end of the tube blank has a large inclination and curvature, and the centering hole of the tube blank is not correct, which can easily cause the wall thickness of the steel pipe head to be uneven. When piercing, the elongation coefficient is too large, the roll speed is too high, and the rolling is unstable. Unstable steel thrown by the piercer can easily cause uneven wall thickness at the end of the capillary tube.
Measures: Check the tube blank to prevent the front end of the tube blank from cutting inclination and large reduction, and the centering hole should be corrected when changing the hole type or overhauling. A lower piercing speed is used to ensure the stability of rolling and the uniformity of capillary wall thickness. When the roll speed is adjusted, the matching guide plate is also adjusted accordingly. Pay attention to the use status of the guide plate and increase the inspection of the guide plate bolts, reduce the range of movement of the guide plate during steel rolling, and ensure the stability of steel throwing.