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Research on Inner Polishing Technology of Pipeline in Construction Site

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1 work tool

(1) Three-phase planetary concrete vibrator. Model Z3N-100, power 3.0kw, voltage 380V, current 6.6A.

(2) Flexible shaft polishing rod (Figure 1, Figure 2). Model ZNP50 can choose 4m, 6m and other specifications according to the length of the pipeline. It should not be too long, and it is difficult to operate if it is too long.

(3) Spiral cone for abrasive installation and jig for abrasive installation (Figure 3). Choose one of the two.


2 polishing material

(1) Iron abrasive cloth roll (applicable to the flexible shaft polishing rod in Figure 1). Width 200mm: Mesh 80#, 120#, 180#, 240#. Fold the emery cloth roll in the same direction to a thickness of about 15mm, and fold it into a rectangular parallelepiped of about 150mmĂ—200mm. The number of folded layers should not be too small. If it is too small, it will be easily torn by the spiral cone during polishing. After folding and compacting, use 6~8 iron nails to punch through the abrasive cloth layer in an arc shape near the center position, bend the part of the iron nails penetrating the abrasive cloth and stick it to the abrasive cloth, so that each layer of abrasive cloth is tightly fixed together: Drill a small 16mm hole in the middle of the arc formed by the iron nail.

(2) Thousand impeller (applicable to flexible shaft polishing rod in Figure 2). Thickness 25mm: Diameter 200mm, 250mm: Aperture 25mm: Mesh 80#, 120#, 180#, 240#.

(3) Nylon fiber polishing wheel. Hardness 7P, 9P, 12P: Thickness 25mm: Diameter 200mm, 250mm: Mesh 120#, 180#, 240#, 320#.

According to the roughness requirements of equipment or pipelines, we can choose the corresponding mesh cloth, flap wheel, nylon fiber polishing wheel, if the mesh number is too high, the production efficiency will be low, otherwise, the roughness will reduce the efficiency of the next process.

3 scope of application

Use this tool to internally polish pipes or tubular equipment. It is suitable for straight pipes, elbows, tees, and reducers with a diameter of 300~1600mm: if the diameter is too small, there is no way to operate it; if the diameter is too large, the work efficiency is low. The length of straight pipes or tubular equipment should not be too large, preferably less than 6m; if the length is large, flanges should be added to reduce the length of a single pipe section: the pipe section must be longer, and the length should not exceed 8m, and the operation at both ends should be used. If the pipe section has pipe fittings such as elbows, tees, and reducers, the pipe fittings should be arranged at the end of the pipe section, and there can only be one elbow: try to polish the pipe fittings and straight pipe sections separately first, and then weld them together , After butt welding, only the weld seam needs to be polished to reduce the difficulty of operation.

4 Selection of equipment manufacturing materials

In order to reduce the polishing workload and improve efficiency, when selecting pipes that require internal polishing equipment, pipes with thicker pipe wall thickness or smaller negative deviation should be selected; and the inner wall of the pipe should be checked, the inner wall should be smooth, free of interlayers, slag inclusions, Cracks, pits, bumps. When using welded steel pipes, try to choose pipes with smaller weld reinforcement and fewer welds on the inner wall.

When using steel plate coiled tubes, steel plates with thicker tube sheets or smaller negative deviations should be selected: the inner wall after rolling should be smooth, without interlayers, slag inclusions, cracks, pits, and bumps. Welding seams should be reduced as much as possible when the steel plate is unloaded and arranged: when rolling, the sundries on the roller of the plate rolling machine should be cleaned to avoid scars during the rolling process: the roundness should be corrected as much as possible during the rolling process. When welding, the inner wall should be welded by argon arc welding, and the weld seam should be smooth and full: the fillet reinforcement should not be too large, and the weld seam and the base metal weld seam should have a smooth transition: there must be no defects such as slag inclusions, cracks, undercuts, etc.

5 operating procedures

(1) Choose a relatively open site and transport the pipeline to be polished there. Both sides of the pipe are padded with wood or straw mats, and the operating end is properly raised to a comfortable height for operation.

(2) The power box, concrete vibrator, and flexible shaft polishing rod are arranged at the operation end of the pipeline. The power box and concrete vibrator should be well grounded and grounded. The power switch of the power box should be set at a comfortable position convenient for the operator to operate.

(3) The other end of the pipeline should not be aligned with the road or places where people gather: it should not be aligned with equipment and facilities that require dust and pollution prevention. At the same time, an axial flow fan is arranged to extract dust, and a canvas enclosure is set behind the axial flow fan to reduce the overflow of the extracted dust.

(4) For pipes with larger diameters that people can enter, use an angle grinder to smooth the weld fillet reinforcement, weld bumps, spatter, etc., so as to reduce the polishing workload and improve the polishing quality.

(5) The power box is connected to the concrete vibrator, and the flexible shaft polishing rod is connected to the concrete vibrator and stuck. Insert the spiral cone at the end of the flexible shaft polishing rod into the iron abrasive cloth cuboid (nylon fiber polishing wheel), and tighten it properly (Figure 4): or install the flap wheel (nylon fiber polishing wheel) on the abrasive installation fixture (Figure 5). According to the operator’s feedback after several uses, the efficiency and quality of polishing with a spiral cone fixed abrasive is better.

(6) Insert the flexible shaft polishing rod into the pipe. If the method shown in Figure 4 is used, the length of the flexible shaft polishing rod initially inserted into the pipe shall not be less than 1m, because it will bounce when the four corners of the iron sand cloth cuboid are not ground into circular arcs: after the iron sand cloth cuboid is ground into rounded corners, then polish the pipe mouth area.

(7) The operator is located in front of the nozzle, holds the flexible shaft polishing rod firmly, and turns on the power. After the rotational speed of the abrasive is stable, drag the flexible shaft polishing rod, and the dragging stroke should be based on the swing of the operator’s arm. When dragging the flexible shaft polishing rod, drag it to the left and right properly, so that the front abrasive can cover a larger polishing area at one time.

(8) When the polishing effect of one dragging stroke meets the requirements, extend the flexible shaft polishing rod into the other dragging stroke, and the overlapping length of the two strokes should not be less than 100mm, until the longitudinal direction of the entire included angle is polished.

(9) When the pipe is placed once, it can only be thrown at a certain angle. When one angle is thrown, the pipe needs to be turned to throw another angle. The overlap between the two angles should not be less than 100mm.

(10) During the polishing process, the abrasive mesh number is changed from low to high. After the iron abrasive cloth or thousand impellers are polished, replace them with nylon fiber polishing wheels. All levels of abrasives can be replaced in one operation stroke, or the first-level abrasive can be used to polish the entire pipe, and then a higher-level abrasive can be replaced to start polishing again until the roughness requirements are met.

(11) For the polished pipeline or equipment, the sundries and tools in the pipeline must be removed to prevent the pipeline or equipment from being damaged when the pipeline or equipment is hoisted or moved. If the polished pipeline or equipment is not installed temporarily, all openings must be closed. Closed to prevent debris from entering and damaging the polished surface.

(12) During the polishing process, it is necessary to frequently use a thickness gauge to detect the wall thickness of the pipe, especially on both sides of the longitudinal weld. Excessive polishing should be avoided, so that the pipe wall is too thin to meet the requirements of design and standard specifications.

6 Inspection method

(1) When the primary abrasive is polished, the inner wall of the tube is visually covered, and there is no original surface color of the tube wall.

(2) When polishing with abrasives at all levels, each level of polishing must be fully covered, and no missed polishing is allowed. The level of abrasives used can be judged by visually measuring the thickness of the grinding marks.

(3) The inspection methods after the last abrasive polishing include visual inspection, finger touch, cotton ball wiping, and instrument inspection. When there is no inspection instrument or the operator self-inspects, visual inspection or cotton ball wiping can be used. When the light is irradiated on the polished parts, they are all smooth surfaces, and there is no visible wear marks when the angle is adjusted: touch the polished parts back and forth with the fingertips, and feel smooth without scratches; wipe the polished parts with cotton balls, and the cotton threads will not stick to them, which can basically meet or exceed Roughness Ra=0.8um requirement. The final detection is mainly carried out by the instrument (Fig. 6, Fig. 7), and the detection is carried out by contacting the polished part with the contact of the detection instrument. When testing, multi-point testing is required, especially for rough parts with visual inspection, and the testing density should be increased.


(4) During the polishing process, frequent inspections should be carried out, and the abrasive and polishing time should be adjusted in time according to the inspection results: it can also avoid excessive polishing, reduce efficiency, and waste time.

7 occupational health and safety measures

The operating conditions and safety production conditions on the construction site are limited. During the on-site polishing operation, in addition to the conventional safety and occupational health protection measures on the construction site, the operators and personnel in the affected area need to take the following safety and occupational health protection measures :

(1) A safety warning area should be set up around the on-site polishing operation, and non-operating personnel are not allowed to enter to prevent the pipeline from rolling or the abrasive from damaging people.

(2) The power box and concrete vibrator should be grounded and zero-connected. The switch of the power box must be set at a position where the operator can switch immediately, so that the power can be cut off quickly when an accident occurs: hand-held electric tools with reinforced insulation signs must be used and equipment.

(3) The pipes or equipment to be polished should be padded with sleepers and straw mats, or other measures to prevent rolling should be taken.

(4) When the operator needs to enter the pipeline or equipment for operation, the power supply used must be a safe voltage level power supply: corresponding safety measures must be taken in accordance with the regulations for confined space operations, and guardians must be set up: the time for entering the pipeline should not be too long .

(5) Install an axial flow fan at the non-operating end of the pipeline to extract dust to reduce the impact and harm of dust on the operator; at the same time, set a canvas enclosure behind the axial flow fan to reduce dust overflow: the axial flow fan draws air against the mouth of the pipe, The air velocity at the operating end is high, and the operator should wear appropriate clothes to prevent catching a cold.

(6) Operators must wear dust caps, dust masks, and goggles to reduce dust damage.

(7) When polishing the end, the hand should be held on the metal handle of the flexible shaft polishing rod, and both hands should be held tightly to prevent the abrasive from bouncing and hurting the operator.

Research on Inner Polishing Technology of Pipeline in Construction Site

8 Apply Effects

Figure 6 and Figure 7 show the roughness detection data of two engineering pipelines and equipment after polishing. Figure 6 uses the tool in Figure 1, and Figure 7 uses the tool in Figure 2. Both tools can meet the roughness requirements well. Since they have been put into production for many years, they have not received feedback that production is affected by unqualified roughness. According to the detection data in Figure 6 and Figure 7 and the feedback from the operator, the tool in Figure 1 is easier to operate, and the effect and efficiency are higher. 3 sets of internal polishing tubular equipment mixers in a project, consult foreign equipment manufacturers, the quotation is about 5 times the construction cost of on-site production; consult domestic equipment manufacturers, the quotation is about 2 times the construction cost of on-site production: use on-site production and polishing The unit saves a lot of investment and greatly reduces the cost for the construction unit.

9 Epilogue

The above-mentioned tools and operation methods have been used in many projects. The equipment is simple, the operation method is simple, and the operators are easy to master. At the same time, good quality effects have been achieved. If you need to meet higher or lower requirements, you only need to increase or decrease the level of abrasive, and increase or decrease the polishing time.

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