HG/T 20544-1992 Technical requirements for the installation of chemical industrial furnace structures
Some standard content:
Industry Standard of the People's Republic of China
Technical Specification on Erection of Structure Parts for Chemical Furnace
20544-92
Editor: Sixth Design Institute of the Ministry of Chemical Industry
Approval Department: Ministry of Chemical Industry
Effective Date: July 1, 1993
Editorial Center of Engineering Construction Standards of the Ministry of Chemical Industry
1993 Beijing
Standard Authorization Network w.bzaoeo.com Free Download of Various Standard Industry Information 1 General Provisions
1.0.1 This technical specification specifies the manufacturing and installation requirements of the steel structure, furnace tube, furnace tube support and furnace lining support, burner, soot blower, door and flue damper of the industrial furnace in the chemical plant. : This technical specification is applicable to general chemical industrial furnaces. 1.0.2 In addition to the requirements specified in this technical condition, when there are special requirements in the drawings, they shall also be implemented in accordance with the drawings. 1.0.3 Design modification or material substitution must obtain the written consent of the original design unit. 1.0.4 The equipment, materials and processed order parts included in this technical condition shall have factory certificates and quality certificates.
1.0.5 In addition to complying with this technical condition, it shall also comply with the provisions of the relevant current national standards (specifications). 1.0.6 Standards cited in this technical condition: GBJ205 "Steel Structure Engineering Construction and Acceptance Code" SHJ
1037 "Technical Conditions for Steel Structure Engineering and Accessories Installation Engineering of Tubular Heating Furnace in Refinery" (Trial) 226
HGJ230
"Technical Conditions for Construction and Acceptance of Tubular Furnace Installation Engineering" "Technical Regulations for Construction of Cracking Furnaces in Ethylene Plants" "Technical Conditions for Construction and Acceptance of Special Steel Structure Engineering in Petrochemical Industry" 507
1620 "Technical Conditions for Boiler Steel Structure Manufacturing" 2880 "Technical Conditions for Steel Welded Atmospheric Pressure Vessels" 3301 "Welded H-beam" (Trial)
1041 "Tubular Heating Furnace in Refinery" Engineering Technical Conditions for Furnace Cr25N12 Alloy Steel Castings (Trial) 1043 Engineering Technical Conditions for Heat-resistant Ductile Iron Castings for Tubular Heating Furnaces in Oil Refineries (Trial) 6414 Dimensional Tolerances of Castings
GB/T11351 Weight Tolerances of Castings
20545 Technical Conditions for Manufacturing Pressure Components of Chemical Industrial Furnaces HG
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2.1 General Provisions
2.1.1 When the working environment temperature of ordinary carbon steel is lower than -16°C or the working environment temperature of low alloy steel is lower than -12°C, cold straightening and cold bending shall not be carried out.
The surface of the steel after straightening shall have no obvious concave surface and damage, and the depth of the scratch shall not be greater than 0.5mm. 2.1.2 The allowable deviation of steel after correction shall comply with the following provisions: 2.1.2.1 The local flexural height deviation of steel plates and fan steel within 1m shall be less than or equal to 1.5mm when the plate thickness is less than or equal to 14mm, and less than or equal to 1mm when the plate thickness is greater than 14mm. 2.1.2.2 The flexural height deviation of angle steel, channel steel and I-beam shall not be greater than 1/1000 of its length, and shall not be greater than 5mm.
2.1.2.3 The verticality deviation of the angle steel limb shall not be greater than 1/100 of the angle steel width. 2.1.2.4 The inclination deviation of the flange of channel steel and I-beam shall not be greater than 1/80 of the flange width. 2.1.3 Ordinary carbon steel or low alloy steel can be heated and corrected, but the heating temperature is strictly prohibited to exceed the normalizing temperature (900℃). Low alloy steel must be cooled slowly after heating and correction. 2.1.4 The minimum curvature radius and maximum bending height loss of bending shall not exceed the requirements of the drawings or technical specifications to avoid loss of plasticity or cracks in the steel.
2.1.5 The steel material shall leave processing allowances such as cutting, planing and milling, as well as welding shrinkage allowances. 2.1.6 The deviations of steel material and cutting shall comply with the following provisions: 2.1.6.1 The allowable deviation of the size of the steel material is ±2mm. 2.1.6.2 The allowable deviation of the length and width of the steel plate material is ±2mm, and the difference in the length of the two diagonals should not be greater than 3mm. bzxZ.net
2.1.6.3 The node plate and reinforcement plate should use a 1:1 sample material, and the allowable deviation of the sample size is ±0.5mm. 2.1.6.4 The allowable deviation between the edge after cutting and the material line is ±2mm. 2.1.7 When the working environment temperature of ordinary carbon steel is lower than 20℃ or the working environment temperature of low alloy steel is lower than 15℃, shearing or punching shall not be carried out.
2.1.8 The marking of the number of the bent member or the hole should be carried out after the bending process of the member is completed and the inspection is qualified. 2.1.9 Before cutting, the rust and oil stains in the cutting area of the steel surface should be removed. After cutting, there should be no macro defects such as cracks, delamination and slag inclusions on the fracture.
2.1.10 The groove type and size of the welding joint, when there is no requirement in the drawing, should be selected according to the provisions of GB985 "Basic Types and Sizes of Gas Welding, Manual Arc Welding and Gas Shielded Welding Welding Bevel" or GB986 "Basic Types and Sizes of Submerged Arc Welding Weld Bevel".
Standard Technology Exchange Network o.bzuoso.com2.2 Component Prefabrication
2.2.1 Steel sections are allowed to be extended by welding, and the type of splicing joints should comply with the provisions of relevant steel structure standards. The position of the steel section splicing joints should be staggered by more than 300mm from the node area. However, the main load-bearing beams and columns should be made of whole materials. If splicing is required, the written consent of the original design unit must be obtained, and the position and type of the splicing joints must be determined according to the stress conditions of the components. The surface quality of the welds shall comply with the provisions of 2.4.7 of this standard, and the flaw detection requirements shall comply with the provisions of 2.4.8 of this standard. 2.2.2 The surface flatness deviation of the flat end cover and the conical head after prefabrication shall not be greater than 4mm. 2.2.3 Circular or arc-shaped steel components, whether hot-bent or cold-bent, shall be inspected with an arc-shaped template. When the chord length of the component is greater than or equal to 1500mm, an arc-shaped template with a chord length of not less than 1500mm shall be used for inspection; when the chord length of the component is less than 1500mm, an arc-shaped template with a chord length equal to the component shall be used for inspection, and the gap shall not be greater than 2mm. When placed on a platform for inspection, the flatness deviation shall not be greater than 1/1000 of the component length, and shall not be greater than 5mm. 2.2.4 The allowable deviation of the processed dimensions of angle steel and flat steel flanges (see Figure 2.2.4) shall comply with the provisions of Table 2.2.4. The surface of the flange butt weld shall be polished smooth.
b±Ab
(a) Angle steel flange
Allowable deviation
Diameter tolerance AD
Nominal diameter
Surface flatness deviation
Difference between maximum and minimum diameters
Vertical deviation of angle steel limb AC
Width tolerance
Thickness tolerance
h≤100
Figure 2.2.4 Dimensional deviation of angle steel and flat steel flanges Allowable deviation of angle steel and flat steel flange processing
(b) Flat steel flange
≤0.18 and not more than 3
Note: ① The surface flatness of angle steel and fan steel shall be checked with a ruler of not less than 300mm in length. Straightness deviation Am is the gap between the ruler and the plane being inspected.
Standard microgrid mo.bzaoro.com2.2.5 Components formed by hot annealing shall not be overburned or deteriorated. The thickness reduction shall not be greater than 1mm. 2.2.6 When annealing components, the heating temperature shall be controlled at 1000~1100℃. The processing shall be terminated when the temperature of ordinary carbon steel drops to 500~550℃ or the temperature of low alloy steel drops to 800~850℃, and the components shall be cooled slowly. 2.2.7 The roundness deviation of circular components shall not be greater than 1/100 of the diameter and shall not be greater than 20mm. The section with opening reinforcement shall be measured 100mm away from the edge of the reinforcement ring. 2.2.8 The circumference deviation of circular components shall not be greater than 2.5/1000 of the circumference and shall not be greater than 18mm. 2.2.9 The misalignment of the longitudinal weld joint of the cylinder section b (see Figure 2.2.9) shall not be greater than 1/10ga, and shall not be greater than 3mim. Figure 2.2.9 The misalignment of the longitudinal weld joint of the cylinder section
The edge angle E formed by welding in the circumferential direction of the cylinder section shall be checked with an inner or outer sample with a chord length equal to 1/6 of the designed inner diameter D and not less than 300mm (see Figure 2.2.10). The E value shall not be greater than 5mm.
VD and not less than 300
(a) External edge angle of longitudinal seam
+2) mm, and should not be greater than
%D and not less than 300
(b) Internal correction angle of longitudinal seam
Figure 2.2.10 The edge angle formed by the welding of cylinder section in the circumferential direction 2.2.11
The allowable deviation of the cross-sectional dimensions of the channel steel assembly (see Figure 2.2.11) shall comply with the following provisions: Figure 2.2.11
Channel steel assembly cross-sectional dimension deviation
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2.2.11.1 The allowable deviation of the cross-sectional width of the channel steel assembly is +mm when the cross-sectional width is less than or equal to 250mm; when the cross-sectional width is greater than 250mm, the allowable deviation is +3mm. 2.2.11.2 The position deviation in the height direction between the two channels of the cross-sectional area of the channel steel assembly is less than or equal to 2mm when the channel steel height is less than or equal to 300mm; when the channel steel height is greater than 300mm, the △ value is less than or equal to 3mm. 2.2.12 The prefabrication of welded H-shaped steel components shall meet the following requirements: 2.2.12.1 For the blanking of flanges and webs, when the plate thickness is less than or equal to 8mm, mechanical shearing shall be adopted; when the plate thickness is greater than 8mm, gas precision cutting may be adopted. The surface roughness of the flange plate edge after cutting is Ra12.5μm. 2.2.12.2 The allowable deviation of the flange and web after cutting is ±2mm for the flange width and +2mm for the web width. The verticality deviation of the cut end face is 1/10 of the plate thickness and should not be greater than 2mm. 2.2.12.3 The welding of welded H-shaped steel should be done by submerged arc automatic welding. 2.2.12.4 The flange and web should be made of whole material as much as possible. If splicing is required, only one splicing joint is allowed, and the rolling direction should be consistent with the length direction. The flange and web splicing are both welded by 45° bevel welding. The butt weld should be welded by groove arc penetration welding, and the groove type and size shall comply with the provisions of GB985. 2.2.12.5 The misalignment of the butt thickness of the flange and web splicing weld should not be greater than 1/10 of the plate thickness, and should not be greater than 1mm.
2.2.12.6 The misalignment of the butt joint width of the flange and web welds shall not be greater than 1mm for the web and 2mm for the flange.
2.2.12.7 The allowable deviation of lateral bending after the flange and web are spliced shall not be greater than 2mm when the plate length is less than or equal to 6m; and shall not be greater than 3mm when the plate length is greater than 6m. 2.2.12.8 When welding H-shaped steel, the splicing lines of the two flanges and the web shall be staggered, and the projection distance of the closest point shall be within the range of 0.5m~1m (the lower limit shall be taken when the height of the H-shaped steel is equal to or greater than 600mm, and the upper limit shall be taken when the height is less than 600mm). The distance between the end of the H-shaped steel and the closest point of the splicing line shall not be less than 1m, and shall be kept at a distance of more than 1m from the main nodes of the frame.
2.2.12.9 The fillet welds between the two wing plates and the web plate shall be welded by submerged arc automatic welding. When the web plate thickness is less than 20mm, no groove is required; when the web plate thickness is equal to or greater than 20mm, the web plate shall be grooved. The groove type and size shall comply with the provisions of GB986.
2.2.12.10 The allowable deviation of the outer dimensions of welded H-shaped steel components shall comply with the following provisions: (1) The allowable deviation of the web plate width shall not be greater than ±2mm; (2) The web plate inclination deviation shall not be greater than 1/10 of the web plate width when the web plate width is less than or equal to 200mm, and shall not be greater than 5mm when the web plate width is greater than 200mm; (3) The offset between the web plate center and the H-shaped steel section axis shall not be greater than 2mm; (4) The allowable deviation of the H-shaped steel height shall be ±2mm when the height is less than or equal to 400mm, and ±3mm when the height is greater than 400mm; |tt||(5) The deviation of the sagittal height of the vertical deflection and lateral bending over the entire length shall not be greater than 1/1000 of the length, and shall not be greater than 5mm. 2.2.12.11 The welds of welded H-beams shall be visually inspected. Cracks, slag inclusions, pores and other defects are not allowed. If the above defects are found, they shall be removed and then re-welded.
2.2.12.12 The quality inspection of the butt welds of the wing plates and web plates and the fillet welds of the H-beams shall be carried out. The surface quality of the welds shall comply with the provisions of 2.4.7 of this standard, and the non-destructive testing shall comply with the provisions of 2.4.8 of this standard. 2.2.13 The straightness deviation of the prefabricated column shall not be greater than the length 1/1000 of the length, and when the column length is less than or equal to 16m, the 45
standard should not be greater than 10mm according to the search network ms.btoso.com, and when the column length is greater than 16m, it should not be greater than 15mm. 2.2.14 The straightness deviation of the beam after prefabrication should not be greater than 1/1000 of the length, and should not be greater than 8mm. 2.2.15 All bolt holes on the components should be machined. After drilling, the allowable deviation of the distance between any two adjacent holes in the same group of holes is ±1mm; the allowable deviation of the distance between any two holes is ±1.5mm. 2.2.16 Openings for all doors, instruments and pipes It should meet the requirements of the drawings. During prefabrication, the position deviation should not be greater than 10mm.
2.3 Assembly
2.3.1 The misalignment of the joint of the cylinder girth weld b (see Figure 2.3.1) should not be greater than 2.5/1000 of the wall thickness when the wall thickness is less than or equal to 20mm.
Figure 2.3.1 Misalignment of the joint of the cylinder girth weld
2.3.2 The angle E (see Figure 2.3.2) formed by the cylinder in the axial direction due to welding should be checked with a ruler of not less than 300mm in length. The E value should not be greater than.
+2) mm, and should not be greater than 5mm.
(a) Circumferential seam outer angle
(b) Circumferential seam inner angle
Figure 2.3.2 When assembling and butting the edges formed by the axial direction of the cylinder welding, the distance between the longitudinal welds of adjacent sections should not be less than 100mm, and the length of the cylinder section should not be less than 2.3.3
300mm.
2.3.4 For the cylinder section or box with flange, the flange surface should be perpendicular to the axis of the cylinder section or box, and the allowable deviation is 1/100 of the outer diameter of the flange and should not be greater than 3mm.
2.3.5 The deviation of the cylinder of the cylindrical furnace after assembly shall comply with the following provisions: 2.3.5.1 The allowable deviation of the cylinder height is ±5mm. 2.3.5.2 The allowable deviation of the cylinder circumference should not be greater than 2.5/1000 of the circumference, and should not be greater than 18mm. The cylinder roundness deviation should not be greater than 1/100, and should not be greater than 20mm. 2.3.5.3
The straightness deviation of the simplified body should not be greater than 2/1000 of its length and should not be greater than 20mm. 2.3.5.4
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oso.cam Various standards industry information free download 2.3.6 The straightness deviation of the smoke box should not be greater than 2/1000 of its height and should not be greater than 20mm when the height of the smoke box is less than or equal to 20m; when the height of the smoke box is greater than 20m, it should not be greater than 1/1000 of its height and should not be greater than 30mm. 2.3.7 The length and width of the welded tube sheet shall not be allowed to deviate by more than 5mm, and the maximum flatness deviation of the whole tube sheet shall not be more than 10mm; the distance between two adjacent tube holes on the tube sheet shall not be allowed to deviate by more than 2mm, and the distance between any two tube holes shall not be allowed to deviate by more than 5mm
2.3.8 The height of the convection chamber frame shall not be allowed to deviate by more than 4mm, and the width shall not be allowed to deviate by more than 3mm. The verticality deviation shall not be more than 1/1000 of its height, and shall not be more than 5mm; the difference between the two diagonal lengths of the convection chamber frame of the circular furnace shall not be more than 1/1000 of the diagonal length, and shall not be more than 10mm: the difference between the two diagonal lengths of the convection chamber frame of the box furnace shall not be more than 1/1000 of the diagonal length, and shall not be more than 15mm; the allowable deviation of the column spacing is ±5mm when the column spacing is greater than or equal to 5m; it is ±3mm when the column spacing is less than 5m, and the horizontality deviation of the beam shall not be more than 1/1000 of the length of the beam, and shall not be more than 5mm.
2.3.9 The bottom beam of the convection chamber and the top beam of the furnace should be straight, and the horizontal deviation at both ends should not be greater than 3mm. 2.3.10 The length and width allowable deviation of the elbow box door and the furnace top cover plate should not be greater than 5mm; the flatness deviation of each elbow box door or cover plate should not be greater than 10mm.
2.3.11 The height allowable deviation of the bottom steel structure of the round cylinder furnace should not be greater than 2mm, and the vertical deviation should not be greater than 3mm. The diameter and roundness should be consistent with the actual size and shape of the lower end of the cylinder. The allowable deviation of the center circle diameter of the column foot bolt hole should not be greater than 5mm, and the position deviation of the bolt hole on each column foot plate should not be greater than 2mm. 2.3.12 The size and shape deviation of the saddle support of the horizontal round cylinder furnace after assembly shall comply with the following provisions: 2.3.12.1 The allowable deviation of the distance from the center line of the saddle to the reference plane and between the two saddles shall comply with the provisions of Table 2.3.12 (the reference plane is the geometric joint surface of the cylinder and the head). Allowable deviation of saddle position
Spacing between the center line of saddle bolt hole to the reference plane and the center of two saddle bolt holes, m
Allowable deviation, mm
>4~≤7
2.3.12.2 The allowable deviation of the center position of the anchor bolt hole on the saddle base plate is ±3mm. 2.3.12.3 The horizontal deviation of the saddle base plate along the length direction is 3mm. Table 2.3.12
>7~≤10
2.3.12.4 The horizontal deviation of the saddle base plate along the width direction is 1.5mm. 2.3.13 The bolt holes on the flange of the cylinder and the anchor bolt holes on the bottom plate of the base ring of the floor-standing smoke window should be evenly distributed in the middle of the span. The allowable deviation of the center circle diameter of the bolt holes, the allowable deviation of the chord length of two adjacent holes, and the allowable deviation of the chord length of any two holes should not be greater than 2mm.
2.3.14 The deviation requirements of the frame of the box-type furnace after the pieces are assembled should meet the following requirements: 2.3.14.1 The parallelism deviation between the beams is 1/1000 of the length and should not be greater than 5mm. 2.3.14.2 The allowable deviation of the distance between the axes of the two columns is ±3mm. 2.3.14.3 The parallelism deviation between the two columns is 1/1000 of the length and should not be greater than 5mm. 2.3.14.4 The difference between the two diagonals of the frame is 1/1000 of the length of the diagonal and should not be greater than 12mm. 2.3.14.5 The allowable deviation of the position of the beam is ±5mm. 2.3.14.6 The straightness deviation of the column is 1/1000 of the column length and should be less than or equal to 10mm. 47
Standard Technology Network m, basono:com2.3:15 The dimensional deviation of the furnace wall panel after assembly shall comply with the following provisions: 2.3.15.1 The allowable deviation of the length and width of the wall panel is ±3mm. 2.3.15.2 The straightness deviation of each side of the wall panel is 1.5/1000 of the length or width and should not be greater than 5mm. 2.3.15.3 The straightness deviation of the wall panel surface is checked with a 1m ruler and should not be greater than 5mm. 2.3.15.4 The difference between the two diagonals of the wall panel should not be greater than 1/1000 of the diagonal length and should not be greater than 10mm. 2.3.16 The dimensional deviation of the platform and ladder after assembly shall comply with the following provisions: 2.3.16.1 The allowable deviation of the platform length per meter is _gmm, and the allowable deviation of the total length is _10mm. 2.3.16.2 The allowable deviation of the platform width is ±3mm. 2.3.16.3 The deviation of the flexural height of each side of the platform is less than or equal to 6mm when the platform length is less than or equal to 6m, and less than or equal to 10mm when the platform length is greater than 6m and less than or equal to 10m. 2.3.16.4 The difference between the lengths of the two diagonals of the platform should not be greater than 6mm. 2.3.16.5 The allowable deviation of the width of the ladder is ±3mm. 2.3.16.6 The allowable deviation of the inclination angle of the inclined ladder is ±5°. 2.3.16.7 The longitudinal flexural height deviation of the ladder should not be greater than 1/1000 of the length. 2.3.16.8 The allowable deviation of the ladder step spacing is ±5mm. 2.4 Welding
2.4.1 Pre-welding preparation and welding environment shall comply with the following provisions: 2.4.1.1 Storage of welding rods, flux and other welding materials shall be kept dry, and the relative humidity shall not exceed 60%. 2.4.1.2 Welding is prohibited when any of the following conditions occur in the welding environment and there are no effective protective measures. (1) Wind speed is greater than 10m/s during manual welding;
(2) Wind speed is greater than 2m/s3 during gas shielded welding (3) Relative humidity is greater than 90%;
(4) Rain or snow environment.
2.4.1.3 When the temperature of the weldment is lower than 0℃, it shall be preheated to about 15℃ within 100mm of the welding location. 2.4.2 Welding of steel structures must be performed by welders who have passed the examination. The welder examination shall be conducted in accordance with the provisions of Chapter 6 of GBI236 "Construction and Acceptance Specifications for Field Equipment and Process Pipeline Welding Engineering". 2.4.3 The welding procedure of steel structure shall be formulated according to the technical requirements of the drawings and the qualified welding process. 2.4.4 Welding shall be carried out after the prefabrication and assembly dimensions of the components are inspected and qualified. Before welding, the oil, rust and other debris on the groove surface and near its edge shall be removed. Slag and spatter shall be removed in time after welding. 2.4.5 For welds that are required to undergo non-destructive testing according to the drawings, the welder shall stamp their code in a conspicuous position near the weld.
2.4.6 After ordinary carbon steel welds are cooled to the working environment temperature, and low alloy steel welds are inspected for appearance 24 hours after welding is completed.
2.4.7 The surface quality of welds shall comply with the following provisions: 2.4.7.1 The weld metal surface and heat-affected zone shall not have defects such as cracks, pinholes, slag inclusions and arc pits, and slag and spatter shall not be retained.
2.4.7.2 The allowable deviation of the length of intermittent welds shall be +10mm, and the allowable deviation of the height of the weld leg of fillet welds shall be 48
Standard Technology Network m, basono:com2.4.7.3 The depth of the undercut on the weld surface shall not be greater than 0.5mm, the continuous length of the undercut shall not be greater than 100mm, and the total length of the undercut on both sides of the weld shall not exceed 1/10 of the length of the weld. The weld and the parent material shall have a smooth transition without obvious irregular shapes. 2.4.7.4
The reinforcement height of the butt weld shall comply with the provisions of Table 2.4.7: Butt
12≤25
Reinforcement height of the butt weld
Reinforcement height of the butt weld
2.4.8 The radiographic inspection of the weld shall be carried out in accordance with GB3323 "Radiographic Photography and Quality Grading of Steel Fusion Welded Butt Joints", and the straight grade shall be qualified. Fillet welds can be inspected by penetration or magnetic particle inspection. Penetrant inspection shall be carried out in accordance with Appendix H "Penetrating Inspection of Steel Pressure Vessels" in GB150 "Steel Pressure Vessels", and magnetic particle inspection shall be carried out in accordance with JB3965 "Magnetic Particle Inspection of Steel Pressure Vessels". 49
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3.1 Allowable Deviations and Defects of Castings
3.1.1 The chemical composition and mechanical properties of castings shall comply with the requirements of the drawings and relevant standards. 3.1.2 The dimensional deviation and weight deviation of castings shall comply with the following provisions: 3.1.2.1 The outer shape tolerance of castings shall comply with CT13 in GB6414 "Dimensional Tolerances of Castings"; the dimensional tolerance of wall thickness or rib thickness of castings shall comply with CT14.|| tt||3.1.2.2 The weight tolerance of castings shall comply with MT13 grade in GB/T11351 "Weight Tolerance of Castings". 3.1.2.3 The maximum misalignment value during casting is 1.5mm. 3.1.2.4 The thickness uniformity and surface flatness deviation of castings shall be within the allowable deviation range. 3.1.2.5 The straightness deviation of castings shall not be greater than 5/1000 of the length and shall not be greater than 10mm. 3.1.3 Castings shall be cleaned, including removal of risers, gates, flash, burrs and chills. 3.1.4 There shall be no sharp angles and sharp transitions on castings. Unless otherwise specified in the drawings, all corners shall be rounded, with an inner fillet radius of not less than 6mm and an outer fillet radius of not less than 4mm. 3.1.5 There shall be no cracks or chills on castings that seriously affect the mechanical properties. Defects such as separation, shrinkage and insufficient casting. 3.1.6 Castings need to be heat treated. Machining should be carried out after heat treatment. 3.1.7 The allowable deviation of the center distance between two adjacent tube holes in the tube sheet or tube rack should not be greater than 3mm, the allowable deviation of the center distance or the center distance between any two tube holes should not be greater than 5mm, and the deviation of the tube hole diameter should not be greater than 2mm. 3.1.8, It is allowed that there are minor defects such as pores, slag inclusions and sand holes with a diameter not greater than 5mm and a depth not greater than 20% of the wall thickness at that place on the surface of the casting that do not affect or basically affect the appearance, strength and performance of the casting. However, there should be no more than 3 defects on a surface of 100cm, and the distance between the edges of any adjacent defects should not be less than 20mm. There should be no more than 10 defects on a tube rack or hanger, and there should be no obvious defects at the hooks and hanging legs. Defects on a tube sheet are not There should be more than 20. 3.1.9 Defects that exceed 3.1.5 and 3.1.8 of this standard but are not serious and can be repaired must be inspected and approved by the manufacturer's inspection department before repair welding, but repair welding should be carried out before the final heat treatment. 3.1.10 Except as indicated in the drawings, the tolerance grade of the machined surface without tolerance dimensions shall be IT14 in GB1804 "Limit Deviation of Tolerances and Fits Without Tolerance Dimensions", and the surface roughness shall not be less than Ra12.5μm. 3.1.11 All bolt holes shall be machined by mechanical methods. 3.2 Inspection of Heat-resistant Cast Steel Tube Plate and Tube Rack Castings 3.2.1 The analysis sample of the chemical composition of the casting shall be based on the sampling in the ladle. Each furnace shall be inspected. The inspection and analysis methods shall be carried out according to GB223 "Chemical Analysis Methods for Steel and Alloys" according to different components. 3.2.2 Each batch of castings (castings from the same casting furnace and the same heat treatment furnace) shall be tested for mechanical properties. The sample selection and test methods adopted shall comply with the provisions of GB11352 "Classification and Technical Conditions for Carbon Steel Castings". 3.2.3 During the inspection of each batch of castings, if one item fails, double the number of samples shall be taken for re-inspection. If one item still fails, the batch of castings shall be scrapped.
3.3 Inspection of heat-resistant cast iron tube plates and brick frame castings 3.3.1 Each package of molten iron shall be subjected to chemical composition analysis and metallographic structure inspection. The sample selection and analysis method for chemical composition analysis shall comply with the provisions of GB9437 "Heat-resistant Cast Iron Parts". The sample selection and test method for metallographic structure inspection shall comply with the provisions of GB9441 "Metallographic Inspection of Ductile Iron". 3.3.2 At least one package of molten iron shall be sampled for mechanical properties in each furnace or every 10 packages. The selection and test methods of the samples shall comply with the provisions of GB9437.
3.3.3 After the inspection, if one item fails, double the number of samples shall be taken for re-inspection. If one item still fails, the batch of castings shall be scrapped.
3.4 Quality Assurance
3.4.1 Castings must be inspected and accepted piece by piece by the technical inspection department of the manufacturer. After passing the inspection, they must be accompanied by a certificate of conformity and a product quality certificate before they can leave the factory. The ordering unit may re-inspect the quality of the castings when it deems it necessary. 3.4.2 The factory certificate and product quality certificate shall include the following items: manufacturer name; product name and drawing number; casting material brand and chemical composition; casting mechanical properties; casting metallographic structure; heat treatment specifications; furnace number and manufacturing date; other acceptance items specified in the order technical conditions.
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