Quality control requirements for rail installation

2022-07-25
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Quality control requirements for crane rail installation

the quality of crane rail installation directly affects the operation quality of cranes. Only by grasping the quality control from the source can the quality of crane rail installation be guaranteed

1. Crane rail

crane running rail includes crane rail, railway rail and square steel. The top of the rail is convex, and the bottom is a flat plate with a certain width, which increases the contact surface with the foundation; The track section is mostly I-shaped, with good bending strength. Square steel can be regarded as a flat top rail. Due to the large wheel wear, it is generally only used for cranes with small lifting capacity, slow running speed and infrequent work. The rail is usually rolled from steel with high carbon and manganese content (c=015% ~ 018%, mn=016% ~ 115%). The typical material of crane rail is U71Mn steel. Square steel is mainly made of Q275 square steel or flat steel

crane rails are special cross-section rails used for crane trolleys and trolleys. The standard lengths are 9, 915, 10, 1015, 11, 1115, 12, 1215, etc. The common specifications are qu70, QU80, qu100 and qu120. The number behind Qu indicates the width of the track head. Railway rails are divided into heavy rail and light rail. Rail specifications are expressed in nominal weight per meter of length. Steel rails weighing more than 30kg/m are heavy rails. There are 12150m and 25100m2 standard rail lengths. The length of the light rail is usually 5 ~ 12m for the rail with the quantity not more than 30kg/m. Light rail steels are mostly killed and semi killed steels of ordinary carbon structural steels. In order to improve the wear resistance and corrosion resistance of rails, low alloy structural steels with Mn, Si, P and other alloy elements have been used in recent years

2. Installation method of crane rail

there are two kinds of rail beams commonly used for rail installation: one is steel structure beam and the other is concrete precast beam. Precast concrete beams must be provided with embedded holes for bolts to be inserted during installation, or bolts must be embedded in precast concrete beams. The installation methods of crane rail include pressing plate fixation, hook screw fixation, welding and bolt joint fixation, etc. In order to adjust the horizontal direction, the hole on the track pressing plate is usually made into a long hole, and the vertical direction adjustment can be padded under the rail. The track pressing plate shall be designed with sufficient rigidity. Each pressing plate can be made into single hole or double hole according to the force. Only when the track is connected with the track beam or the steel base plate fixed on the track beam by welding, the car stop can be welded on the track

3. Installation requirements for track beam before track laying

3.1 requirements for concrete track beam:

(1) during track beam fabrication, it must be ensured that the position deviation of reserved bolt holes along the transverse and longitudinal direction of the beam is ≤ 5mm, the bolt hole diameter is 2 ~ 7mm larger than the bolt diameter, and the top surface of the beam shall be flat, but shall not be plastered smooth

(2) the current development status of the domestic plastic machinery industry is that the installation deviation of the track beam with low independent innovation ability and few advanced and personalized special varieties must meet the following requirements, otherwise the track beam can be leveled with concrete only after it is adjusted

① deviation of beam center position from design positioning axis ≤ 5mm

② deviation of beam top elevation from design elevation +10mm-5mm

③ whether the reserved bolt @5 on the beam and the panel display function are normal@ 6. Whether the panel key function is normal; The displacement deviation of the hole and reserved bolt to the beam center shall be ≤ 5mm

(3) construction requirements for concrete leveling course

① the strength grade of concrete leveling course is C30 and the thickness is 30 ~ 50mm

② before the construction of concrete leveling layer, the installation deviation of track beam shall be checked as required. If it does not meet the requirements, the track beam shall be adjusted

③ according to the measured elevation of the track beam surface, determine a suitable control elevation of the top surface of the concrete leveling layer, and set a datum point for the control elevation every 214 ~ 310m on the track beam

④ measure with instruments, adjust the elevation of the datum point, determine the datum line of the elevation of the top surface of the leveling layer, then install the formwork, remove the sundries on the top surface of the track beam and the bolt hole, block the upper opening of the bolt hole, and pour concrete after watering

⑤ the top surface of the leveling layer must be leveled and polished without exposed stones and unevenness. It is not allowed to use the method of paving cement mortar on the surface

⑥ instruments shall be used for measurement and inspection at any time during construction. The top surface of the leveling layer must meet the following requirements: the non levelness of the top surface within the 400mm width at the bolt shall be ≤ 5mm; The elevation difference of the top surface at any 610m length housekeeping bolt is ± 3mm; The elevation difference of the top surface of each bolt along the whole length is ± 5m

⑦ the concrete shall be mechanically mixed, and the curing shall be strengthened during construction. When the concrete test block reaches 75% of the strength design value, the track installation can be carried out

3.2 requirements for steel structure track beam

(1) the mid span perpendicularity of track beam is ≤ h/500, and H is the beam height of track beam

(2) horizontal side bending of track beam ≤ l/1500, and net 10mm, l is the beam length of track beam

(3) the vertical camber of the next beam of the track shall be ≤ 10mm

(4) the deviation of the center position of the track beam from the design positioning axis shall be ≤ 5mm. If it does not meet the requirements, the track can be installed only after the track beam positioning is adjusted

(5) the height difference of the top surface of the track beam with the same cross section in the same span is ≤ 10mm at the support and ≤ 15m at other places

(6) the height difference of the top surface of the track beam between two adjacent columns in the same column is ≤ l/1500, and ≯ 10mm. L is the beam length of the track beam

(7) at the joint of adjacent 2 track beams, the height difference of the top surface of 2 track beams shall be ≤ 1mm, and the center lateral dislocation shall be ≤ 3mm

4. Crane rail joint

4.1 preparation before welding

before welding the crane rail joint, carefully clean the groove and nearby dirt such as oil and rust until the metal luster is exposed. Welding materials shall be matched with alkaline electrodes according to the principle of equal strength, Its brand j857 (national standard 4.2 control of track welding deformation: the height of the pre cushioned rail end depends on the type, length, fixing condition, ambient temperature and other factors of the rail. The pre cushioned rail end shall be cushioned for 30 ~ 40mm with red copper backing plate and carbon steel plate. The fabricated bolts, pressing plates and other connectors shall be used to tighten the nuts to fix the rail on the track beam. At least 4 fixing points shall be set near each rail joint. When the rail bottom is welded, the Open the pressing plate, lower the cushioned part of the rail end to 20mm, and then tighten the pressing plate nut. When welding the rail waist part, gradually reduce the height of the base plate. When the rail waist part is welded, remove all the base plates and loosen the pressing plate. At this time, there should be a small upturning value at the rail joint. During the welding of the rail head, decide whether to tighten the pressing plate nut again according to the flatness of the rail. During the whole welding process, the deformation of the rail joint must be checked with a straight steel ruler at any time, and the height of the joint and the pressing plate must be adjusted at any time to control the deformation of the rail joint. When fixing the rail joint before welding, the gap between the ends of the two rails shall be wide at the top and narrow at the bottom, subject to the rail bottom gap, which shall not be less than 12mm or too wide, and generally controlled within the range of 15 ~ 18mm. When adjusting the fixed rail joint, in addition to ensuring the size of the end gap, the ends of the two rails must be aligned without distortion and staggering. Before and during welding, it is required to strictly check and ensure that the center lines of the two rails are on the same line, so as to prevent the track from bending and unbending after welding. When welding the rail joint of the rail fixed with hook bolts, temporary fixtures can be set to fix the rail for welding according to the specific conditions and with reference to the above methods

4.3 welding

the sequence of welding rail joints is from bottom to top, from rail bottom to rail waist and rail head, surfacing layer by layer, and finally repairing the surrounding. The range of two rail ends is 40mm respectively, and preheating shall be conducted at the same time. The preheating and interlayer temperature shall be controlled at 300 ℃ ~ 350 ℃. Welding of the first layer (priming): the current is 120a ~ 130a to prevent the permanent carbon steel base plate from burning through and melting the red copper base plate, so as to reduce the difficulty of removing the red copper base plate and shorten the track air cooling time, so as to maintain the interlayer temperature and prevent quenching; (130 ± 15) a can be used for each layer later. After each layer is welded, the welding slag must be removed before continuing welding

rail waist welding: the current is 130 ~ 140A. Weld from the lower part of the waist upward. Pay attention to slag removal

rail head welding: the current is 130 ~ 140A. The welding shall be started after the red copper support plate is installed, and the slag shall be removed once for each layer; Finally, repair welding shall be carried out for the parts not fully welded around the weld

4.4 precautions during track welding

when welding each layer of wave, especially when welding each layer of wave at the bottom of the rail, one welding rod shall be used to complete the welding, and the arc breaking caused by welding rod shall be avoided in the middle. The welding direction of the front and rear two layers of wave shall be opposite; Each rail joint shall be welded continuously to keep the rail end welded at a high temperature (300 ℃ ~ 350 ℃). After welding, before cooling after stress relief heat treatment, it is necessary to prevent rain and other wetting; The heated copper plate can be removed and cooled with water for reuse next time

4.5 stress relief heat treatment (flame heating method)

in terms of cost performance, the stress relief heat treatment of the rail end after welding is an important measure to improve the welding quality. This measure must be adopted for the track welded at relatively low temperature, such as winter construction; For stress relief heat treatment, gas welding nozzles are used to heat the rail head, rail waist and rail bottom repeatedly. The full section of the rail shall be heated evenly as much as possible, and special attention shall be paid to the heating quality of the rail bottom. The stress relief heat treatment temperature is 620 ℃ ~ 650 ℃, 40mm on both sides from the weld center as the range of stress relief heat treatment; After the temperature of stress relief heat treatment is reached, the constant temperature heating must be ensured to be more than 20 ~ 30min, wrapped with needled blanket insulation cotton, and kept warm and cooled slowly until normal temperature

4.6 grinding treatment of rail joints

after the rail welded joints have been stress relieved and cooled to the atmospheric temperature, the welds on the top and both sides of the rail shall be ground. When the welding bulge is too large, grind it with a grinding wheel grinder until it is flush with the rail head, and finally polish the surface

rail joint treatment at the expansion joint of the plant

there are usually two kinds of rail joint treatment at the expansion joint of the plant: one is connected by plywood or fishplate, and the rail is connected by 45 ° inclined joint with a gap of 10mm. The other is connected by splicing splints processed according to the rail head shape, with a gap of 50mm

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