Seamless steel pipe dimensional inspection

Seamless steel pipe dimensional inspection

According to the standard requirements, the dimensional inspection of seamless steel pipes mainly includes the wall thickness, outer diameter, length, curvature, ovality and end face shape of the steel pipe.

(1) Wall thickness inspection of seamless pipes
The tools used for wall thickness detection are mainly micrometers. During inspection, use a micrometer to measure the wall thickness of the steel pipe one by one. Before inspection, first verify whether the micrometer's certificate is within the validity period, and check whether the micrometer is aligned with zero and whether it rotates flexibly. The measuring surface should be free of scratches and rust spots, and it can be used after passing the test. During inspection, hold the micrometer bracket with your left hand and turn the excitation wheel with your right hand. The diameter of the screw should coincide with the diameter of the measurement points, and the end face measurement should be no less than 6 points. If the wall thickness is found to be unqualified, it should be marked.

(2) Inspection of outer diameter and ovality of seamless pipes
The tools used for outer diameter and ovality inspection are mainly calipers and vernier calipers. During inspection, use qualified calipers to measure the outer diameter of the steel pipes one by one. Before inspection, first verify whether the caliper's certificate is within the validity period, calibrate the used caliper with a vernier caliper, and check whether there are scratches or rust on the measuring surface. During inspection, the vernier caliper should be perpendicular to the axis of the steel pipe, slowly rotate the steel pipe, and measure the maximum and minimum points of its section. If the outer diameter is found to be too large or too small, it should be marked.

(3) Seamless pipe length check
The main tool used for steel pipe length inspection is steel tape measure. When measuring the length, align the "O" point of the tape measure with one end of the steel pipe, and then tighten the tape measure so that the scale side of the tape measure is close to the surface of the steel pipe. Use a tape measure to measure the length of the other end of the steel pipe to determine the length of the steel pipe.

(4) Steel pipe bending inspection
The inspection of steel pipe curvature is mainly to check the curvature of the total length of the steel pipe and the curvature per meter. The main tools used are levels, feeler gauges and fishing lines.
When measuring the total bend of the steel pipe, align one end of the steel pipe with the fishing line, and then tighten the fishing line so that one side of the fishing line is close to the surface of the steel pipe. Then use a feeler gauge to measure the distance between the surface of the steel pipe and the maximum gap of the fishing line. The maximum distance measured is the total length of the steel pipe.
The bending of steel pipes per meter is mainly measured using a 1m or 1.83m level. When measuring, first attach the level to the surface of the steel pipe, place the level on the axis plane of the steel pipe, and then use a feeler gauge to measure the maximum gap distance between the level and the surface of the steel pipe.

(5) Check the shape of the end of the seamless pipe
Both ends of the steel pipe should be cut at specified angles and burrs removed. The inspection method is to use a square ruler, and pipe end beveling pliers are generally used on site.

After the inspection is completed and there are no problems, the shipment will be arranged. Next, let’s take a look at the packaging and transportation of seamless pipes.

Seamless pipes are transported on special trailers with a length of 18m. The trailer is covered with 100mm×200mm wooden squares, and the wooden squares are covered with rubber mats or straw bags. The thickness is not less than 10mm and the width is not less than 300mm. Rubber bands or fine earth bags are laid between the two layers of seamless pipes. During transportation, the pipes must be tied firmly to prevent pipe rolling and shooting, and special slings must be used for bundling.

During the entire process of hoisting, transportation, and stacking, the pipe openings should be kept intact and must not be damaged. Use a cross to secure and protect the nozzle to prevent deformation. The stacking site should be flat and solid, and two sleepers (section 300×300mm) 4 to 8m apart should be placed under the stack. Sandbags or fine soil bags should be placed between sleepers and anti-corrosion pipes. There should be fixed wedges on the sleepers at the edge of the pipe stack to prevent the pipes from slipping.

Before unloading seamless pipes, unloading pipe piers should be laid at the pre-unloading position. The lower surface of the seamless pipes should be 0.5~0.7m away from the ground. A straw mat should be placed on the fine soil pillow to protect the anti-corrosion layer. Three seamless pipes are removed from the bottom of each group of pipe piers. The distance between each seamless pipe is 0.2m to facilitate the hanging of slings. The distance between each group of pipe piers should be 6-8 meters, and the distance between two piles of pipe piers should be about 8 meters. The crane stands in the middle to facilitate the unloading of pipes on both sides. Both sides of the pipe pier should be covered with woven bags or compacted fine soil mounds; if multi-layer stacking is required, it should not exceed two layers, and the upper layer of pipes must fall between the lower two layers of pipes to prevent the pipes from collapsing. Rolling (it is strictly prohibited to spray and climb on the surface of the pipe). In general areas (except for storage yards), on-site unloading must be on one level, and two levels are strictly prohibited.

When unloading, check the integrity of the seamless pipe in a timely manner, record the damage to the pipe mouth and anti-corrosion layer in the seamless pipe receipt book, and the manufacturer will promptly arrange personnel to repair it. Seamless pipes with unqualified quality, such as serious damage or deformation, will not be accepted.

Note: Special pipe lifting tools such as iron rods, steel wire ropes, and 5T lifting straps should be used during loading and unloading. Four slings are wound around the seamless pipe at equal distances, and the iron rod is connected to the slings through wire ropes and hooks to lift the seamless pipe. It is absolutely not allowed to use the wire rope directly to avoid damaging the nozzle. When loading and unloading, care should be taken that the pipes cannot collide or be scratched.

According to the completion of the pipe trench excavation foundation, the pipes will be unloaded one by one along the pipes to the exact location of the construction site, and the pipes will be padded with soil-filled woven bags. Pay attention to controlling the arrangement length of seamless pipes and the length of pipe trenches to avoid leaking pipes and multiple pipes, which may lead to pipe replacement and pipe transfer. Pipeline transportation and pipe layout are completed in one step, avoiding secondary reverse transportation. Pipes are installed where roads, rivers, etc. pass.

At the stacking site, the pipes are lined with woven bags filled with soil. The uneven areas along the pipe trench should be leveled to facilitate on-site pipe routing and welding.