Some standard content:
Mechanical Industry Standard of the People's Republic of China
JB/T7837-1995
Heating Network Heater
Published on November 24, 1995
Ministry of Machinery Industry of the People's Republic of China
Implementation on July 1, 1996
Mechanical Industry Standard of the People's Republic of China
1 Subject Content and Scope of Application
JB/T7837—1995
1.1 This standard specifies the technical requirements for the performance, design, manufacture, testing, inspection, installation and maintenance of heating network heaters. 1.2 This standard applies to shell and tube heating network heaters used in thermal power plants or other types of centralized heating. Parameters of heating network heaters to which this standard applies: Design pressure PN tube side ≤ 3MPa
PN shell side ≤ 1.35MPa.
Design temperature t tube ≤ 200℃+
shell side ≤ 400℃.
Cited Standards
GB150—89
GB151-89
GB2270—80
GB3087-82
GB3323—87
GB8163-87
GB8890-88
GB/T13306-91
JB755-85
JB1152-81
JB2536-80
JB337591
JB3965—85
JB/T5862-91
3 Terminology
3.1 Heat network
Steel pressure vessel
Steel shell and tube heat exchanger
Stainless steel seamless steel pipe
Seamless steel pipe for low and medium pressure boilers
Radiography and quality classification of steel fusion welded butt jointsSeamless steel pipe for conveying fluids
Copper alloy pipe for heat exchanger
Technical conditions for pressure vessel forgings
Ultrasonic flaw detection of butt welds of boilers and steel pressure vesselsPainting, packaging and transportation of pressure vessels
Incoming inspection of boiler raw materials
Magnetic particle flaw detection of steel pressure vessels
Performance test procedures for surface feedwater heaters for steam turbinesThe heat medium distribution system composed of a regional heating steam pipe network or a hot water pipe network is collectively referred to as a heat network. 3.2 Heat network heater
The surface heat exchanger that uses steam or water at a higher temperature (heating medium) to heat the circulating water in the hot water heating system to provide hot water for the heat network is called a heat network heater (hereinafter referred to as a heat heater). There are basic heating and peak heating in heating. The heating that works continuously during the heating period and bears the basic heat load, that is, it meets the user's requirements for hot water temperature during most of the heating period, is called basic heating. During the coldest period in winter, the heating that is connected in series after the basic heating to increase the temperature of the hot water supplied to meet the user's requirements for higher water temperature is called peak heating. 3.3 Heat load
The total heat exchange amount between the heating medium and the heated medium per unit time, unit W. Approved by the Ministry of Machinery Industry on November 24, 1995
Implementation on July 1, 1996
3.4 Terminal temperature difference
For steam-water heating:
JB/T7837-1995
The difference between the saturated temperature of the heating steam at the steam pressure at the inlet of the heating and the outlet temperature of the heated water, unit ℃. For water-to-water heat treatment:
The difference between the outlet temperature of the heating water and the outlet temperature of the heated water (in downstream), unit: °C.
The difference between the inlet temperature of the heating water and the outlet temperature of the heated water (in downstream), unit: °C. 3.5 Shell pressure drop
The total pressure loss of the heating medium flowing through the shell side of the heat treatment is the shell side pressure drop, unit: MPa. 3.6 Tube side pressure drop
The pressure loss of the heated medium flowing through the tube side (including the pressure loss in and out of the water chamber) is the tube side pressure drop, unit: MPa. 3.7 Heat transfer coefficient
The amount of heat transferred from the heating medium to the heated medium per unit heat transfer area (surface area of the heat exchange tube), per unit temperature difference and per unit time, unit: W/m\C.
3.8 Total area
Refers to the total surface area of the heat exchange tubes in the heat treatment, unit: m. It includes the calculated area obtained by thermal calculation and the surplus area appropriately increased by considering some surfaces that cannot fully or do not participate in heat exchange.
The proportion of appropriate surplus shall be determined by the designer. 3.9 Effective heat exchange area
The area after deducting any tube surface area that is not exposed to the heating medium and does not participate in heat exchange from the total area, unit m. The area in the design general drawing should be the effective heat exchange area. 4 Product classification and others
4.1 Product classification
4.1.1 According to the structural form: three basic forms: fixed tube sheet type, U-tube type and floating head type (see Figure 1). 4.1.2 According to the layout form: vertical (upright and inverted) and horizontal. 4.1.3 According to the medium: steam-water type and water-water type. 4.1.4 According to the heat exchange form: steam-water type is condensation convection heat exchange; water-water type is convection convection heat exchange.
4.2 Product model
4.2.1 The product model consists of three parts, each separated by a line. The first part is the product code of the heat treatment, which is represented by the capital Chinese pinyin letter JR (basic heat treatment) or GR (peak heat treatment). The second part is the performance characteristic code: Arabic numerals are used to represent the effective heat exchange area (m\). The third part is Arabic numerals, indicating the number of modified designs. When it is the first design, there is no such part. 4.2.2 Model marking examples
Example 1 JR-1200 represents the basic heat treatment with an effective heat exchange area of 1200m2, the first design. Example 2: GR350-1 represents the effective heat exchange area of 350m, the first modified design of peak heat treatment. Example 3: JR-500-2 represents the basic heat treatment with an effective heat exchange area of 500m*, the second modified design. 4.3 Heat exchanger level
The heat treatment level shall not be lower than the requirements of Class II heat exchanger specified in GB151. When the design has other requirements, it shall be indicated on the product drawing. 2
5 Performance and design requirements
5.1 Performance requirements
5.1.1 Terminal temperature difference
JB/T 7837—1995
Fixed tube sheet heat network heater
(b) U-tube heat network heater
(ce) Floating head heat network heating system
Under rated conditions, the terminal temperature difference of heat treatment shall meet the design requirements. The designed terminal temperature difference is generally: steam-water heat treatment (when there is no superheated steam cooling section), not less than 5℃. Water-water heat treatment, not less than 10℃.
When the system has other requirements, the designed terminal temperature difference shall meet the requirements of the system. 5.1.2 Outlet temperature deviation of heated water
Under rated conditions, the outlet temperature deviation of heated water shall not be less than 10% of the designed outlet temperature and shall not be greater than 10°C. 5.1.3 Shell side pressure drop
When designed according to rated conditions, the total shell side pressure loss of the three sections in the heat treatment (i.e., superheated steam cooling section, condensation section, and drain cooling section) shall not exceed 0.1MPa, and the pressure loss of any section in the heat treatment: the condensation heat release section shall not exceed 0.02MPa; the convection heat release section shall not exceed 0.05MPa.
5.1.4 Tube side pressure drop
Total tube side pressure loss: for steam-water heat treatment, it shall generally not exceed 0.12MPa; for water-water heat treatment, it shall generally not exceed 0.029MPa. 5.2 Design requirements
Flow rate in tube
JB/T7837-1995
Under rated working conditions and average temperature of heated water (arithmetic mean of inlet and outlet temperatures), the design average flow rate of heated water through the heat exchange tube shall not exceed the requirements of Table 1,
Stainless steel
Pin-nickel alloy
Navy copper and copper
5.2.2 Pipe diameter, wall thickness and operating temperature
The commonly used pipe diameter and wall thickness of heat exchange tubes are shown in Table 2. The recommended upper limit of the operating temperature of the pipe is shown in Table 3. Table 2
Stainless steel
Copper nickel alloy
Navy copper and copper
Stainless steel
Copper nickel alloy
Navy copper and copper
Outside flow rate
Refers to the average flow rate of the heating medium outside the heat exchange tube in the shell. The recommended design value is:
Steam-water heating:
Superheated steam cooling section
Drain cooling section
Water-water heating:
5.2.4 Take-over flow rate
10~30m/s
0.3~1.5m/s
0.3~1.5m/s
Outer diameter of pipe
Under rated working conditions, the allowable flow rate of medium in the pipe shall be as specified in Table 4. Table 4
Name of pipe
Steam inlet
Heated water inlet and outlet
Vegetable water inlet and outlet
Fouling thermal resistance
Allowable flow rate
Limited flow rate in pipe
Pipe wall thickness
Upper limit of pipe material service temperature
High pressure takes the small value, low pressure takes the large value
Use the low value without water level, use the high value with water level
JB/T7837-1995
The heated water in the heat exchanger is softened and anti-corrosion treated water. When the scale thickness of the heat exchange tube is greater than or equal to 0.5mm, the heat exchanger should be cleaned. The recommended design value of the scale thermal resistance of the tube side water is 35.2×10-5m2℃/W. The recommended design value of the scale thermal resistance of water vapor is 8.8×10-5m2℃C/W. 5.2.6 Structural design requirements
5.2.6.1 The structural strength design shall comply with the provisions of GB150 and GB151. If the diameter of the heat exchanger exceeds the range of GB151, the heat strength and structural design shall be considered separately.
5.2.6.2 All types of heat treatment (Figure 1) should generally be designed to be disassembled, and the basic components for disassembly are the water chamber, tube bundle, and shell. For fully welded structures, a manhole should be provided in the water chamber, and the disassembly cutting position should also be indicated, and protective measures such as protective rings should be provided inside the shell. Safety relief devices should be provided on the shell side and tube side. For heat treatment that cannot use pipes (or interfaces) for venting and draining, vent ports should be provided at the highest point of the tube side and shell side, and drain ports should be provided at the lowest point. The recommended minimum nominal diameter is 20 mm. 5.2.6.3 The design of the tube bundle (including baffles, baffle rods and baffle rings, tie rods, spacer tubes, etc.) and shell side structure (including anti-collision plates, guide tubes, etc.) of heat treatment should comply with Articles 3.9, 3.10, and 3.11 of GB151 and the provisions of the design drawings. 6 Materials
6.1 General requirements for materials
The materials used for hot-addition shall have a quality certificate (or its copy) that meets the corresponding standards. The inspection department of the manufacturer shall conduct factory acceptance according to the certificate. If any of the following conditions are met, re-inspection shall be carried out according to JB3375. If the materials are not inspected or fail the inspection, they shall not be put into production. The content of the quality certificate is incomplete:
b. When the manufacturer has doubts about the performance and chemical composition of the materials; e
There are requirements on the design drawings.
6.2 Tube sheets, flat covers, and flanges
6.2.1 The selection of materials for tube sheets, flat covers, and flanges. Forgings shall comply with the provisions of Article 2.2.1 of GB151. When there are other requirements, they shall be in accordance with the drawings or relevant technical documents.
6.2.2 When steel plates are used for tube sheets, flat covers, and flanges, they shall comply with the provisions of Article 2.2 of GB150. When the plate material used is 16Mn, it shall also comply with the provisions of Article 2.2.2.2 of GB151. 6.3 Heat exchange tubes
Heat exchange tubes can be selected from the following standards for ordinary cold-drawn tubes. When the drawing specifies a level 1 heat exchanger, a higher level cold-drawn tube shall be selected. GB8163;
GB3087;
GB2270;
GB8890.
6.4 Bolts, studs and nuts
Bolts, studs and nuts shall comply with the provisions of Article 2.4 of GB151. 7 Manufacturing technical requirements
In addition to complying with the provisions of this standard, hot processing manufacturing shall also comply with the provisions of GB150GB151 and the requirements of the drawings. 7.1 Head
7.1.1 Welding arrangement of jointed head
7.1.1.1 Jointed head can be made by butt jointing several steel plates, or by butt jointing petals and top round plates. However, when it is made by butt jointing the top round plates of petals, the weld direction is only allowed to be radial and circumferential. 7.1.1.2 The minimum distance L between various non-intersecting welds shall not be less than 3 times the nominal thickness and not less than 100mm (as shown in Figure 2). 5
7.1.2 Minimum thickness
JB/T78371995
The minimum thickness of the head after stamping shall not be less than the nominal thickness minus the negative deviation of the copper plate thickness. 7.1.3 Inner surface shape deviation
The measurement and deviation of the inner surface shape of the head shall comply with the provisions of Article 10.2.2.3 of GB150. 7.1.4 Openings
Openings on the head shall comply with the requirements of Article 7.2.13. 7.2 Cylinders and shells
35.H2100m
7.21 When rolled from sheet metal, the allowable deviation of the inner diameter of the cylinder is controlled by the outer circumference. The upper allowable deviation of the outer circumference is: 5mm when the nominal diameter of the cylinder is DN≤1200, 10mm when DN>1200~2000mm, and 12mm when DN>2000. The lower deviation is zero
When the nominal diameter is DN≤400mm and seamless steel pipes are used as cylinders, the allowable deviation of the size shall comply with the provisions of GB3087, GB2270, or corresponding standards.
7.2.2 On the same section of the cylinder, the difference between the maximum inner diameter and the minimum inner diameter e≤0.5%DN, and shall not be greater than the provisions of Table 5. Table 5
Nominal diameter DN
e not larger
>1200~2000
7.2.3 The classification of hot press welds shall be in accordance with Article 4.1 of GB151. The misalignment of the weld ends of A and B welds (see Figure 3) shall comply with the provisions of Table 6.
Nominal thickness at the end
12<8mg20
20<8n40
Misalignment of the weld ends classified by weld type
≤25%8n
≤25%8n
≤25%8n
The misalignment requirements of the weld ends of Class A welds in the table do not include the circumferential welds connecting the spherical head and the sleeve and the welds connecting the embedded pipe and the cylinder or the head. Note, ①
.
JB/T 7837-1995
②The misalignment requirement for Class B welds in the table includes the circumferential welds connecting the spherical head and the cylinder. 7.2.4For Class B welds and Class A welds connecting the cylinder and the spherical head, when the thickness of the two plates is unequal, the edges of the thick plates shall be thinned in accordance with the requirements of Article 10.2.3.4 of GB150. 7.2.5The inspection and allowable value of the angle E formed by the axial direction of the butt annular seam and the circumferential direction of the butt longitudinal seam shall comply with the provisions of Article 10.2.3.3 of GB150.
7.2.6The allowable deviation of the straightness of the cylinder is L/1000 (L is the length of the cylinder). And: when L≤6000mm, its value shall not exceed 45mm; when L>6000mm, its value shall not exceed 8mm.
Straightness inspection should be carried out through the horizontal and vertical planes of the center line, that is, measurement along the circumference at 0°, 90°, 180°, and 270°. 7.2.7 The limit of longitudinal welds in each section of the simplified body is: when DN≤1400mm, no more than 1;
14001 General requirements for materials
The materials used for hot-addition shall have a quality certificate (or its copy) that meets the corresponding standards. The inspection department of the manufacturer shall conduct factory acceptance according to the certificate. If any of the following conditions are met, re-inspection shall be carried out according to JB3375. If the materials are not inspected or fail the inspection, they shall not be put into production. The content of the quality certificate is incomplete:
b. When the manufacturer has doubts about the performance and chemical composition of the materials; e
When there are requirements on the design drawings.
6.2 Tube sheets, flat covers, and flanges
6.2.1 The material selection of tube sheets, flat covers, and flanges shall comply with the provisions of Article 2.2.1 of GB151 when forgings are used. When there are other requirements, they shall be in accordance with the drawings or relevant technical documents.
6.2.2 When steel plates are used for tube sheets, flat covers, and flanges, they shall comply with the provisions of Article 2.2 of GB150. When the plate material used is 16Mn, it shall also comply with the provisions of Article 2.2.2.2 of GB151. 6.3 Heat exchange tubes
Heat exchange tubes can be selected from the following standards for ordinary cold-drawn tubes. When the drawing specifies a level 1 heat exchanger, a higher level cold-drawn tube shall be selected. GB8163;
GB3087;
GB2270;
GB8890.
6.4 Bolts, studs and nuts
Bolts, studs and nuts shall comply with the provisions of Article 2.4 of GB151. 7 Manufacturing technical requirements
In addition to complying with the provisions of this standard, hot processing manufacturing shall also comply with the provisions of GB150GB151 and the requirements of the drawings. 7.1 Head
7.1.1 Welding arrangement of jointed head
7.1.1.1 Jointed head can be made by butt jointing several steel plates, or by butt jointing petals and top round plates. However, when it is made by butt jointing the top round plates of petals, the weld direction is only allowed to be radial and circumferential. 7.1.1.2 The minimum distance L between various non-intersecting welds shall not be less than 3 times the nominal thickness and not less than 100mm (as shown in Figure 2). 5
7.1.2 Minimum thickness
JB/T78371995
The minimum thickness of the head after stamping shall not be less than the nominal thickness minus the negative deviation of the copper plate thickness. 7.1.3 Inner surface shape deviation
The measurement and deviation of the inner surface shape of the head shall comply with the provisions of Article 10.2.2.3 of GB150. 7.1.4 Openings
Openings on the head shall comply with the requirements of Article 7.2.13. 7.2 Cylinders and shells
35.H2100m
7.21 When rolled from sheet metal, the allowable deviation of the inner diameter of the cylinder is controlled by the outer circumference. The upper allowable deviation of the outer circumference is: 5mm when the nominal diameter of the cylinder is DN≤1200, 10mm when DN>1200~2000mm, and 12mm when DN>2000. The lower deviation is zero
When the nominal diameter is DN≤400mm and seamless steel pipes are used as cylinders, the allowable deviation of the size shall comply with the provisions of GB3087, GB2270, or corresponding standards.
7.2.2 On the same section of the cylinder, the difference between the maximum inner diameter and the minimum inner diameter e≤0.5%DN, and shall not be greater than the provisions of Table 5. Table 5
Nominal diameter DN
e not larger
>1200~2000
7.2.3 The classification of hot press welds shall be in accordance with Article 4.1 of GB151. The misalignment of the weld ends of A and B welds (see Figure 3) shall comply with the provisions of Table 6.
Nominal thickness at the end
12<8mg20
20<8n40
Misalignment of the weld ends classified by weld type
≤25%8n
≤25%8n
≤25%8n
The misalignment requirements of the weld ends of Class A welds in the table do not include the circumferential welds connecting the spherical head and the sleeve and the welds connecting the embedded pipe and the cylinder or the head. Note, ①
.
JB/T 7837-1995
②The misalignment requirement for Class B welds in the table includes the circumferential welds connecting the spherical head and the cylinder. 7.2.4For Class B welds and Class A welds connecting the cylinder and the spherical head, when the thickness of the two plates is unequal, the edges of the thick plates shall be thinned in accordance with the requirements of Article 10.2.3.4 of GB150. 7.2.5The inspection and allowable value of the angle E formed by the axial direction of the butt annular seam and the circumferential direction of the butt longitudinal seam shall comply with the provisions of Article 10.2.3.3 of GB150.
7.2.6The allowable deviation of the straightness of the cylinder is L/1000 (L is the length of the cylinder). And: when L≤6000mm, its value shall not exceed 45mm; when L>6000mm, its value shall not exceed 8mm.
Straightness inspection should be carried out through the horizontal and vertical planes of the center line, that is, measurement along the circumference at 0°, 90°, 180°, and 270°. 7.2.7 The limit of longitudinal welds in each section of the simplified body is: when DN≤1400mm, no more than 1;
14001 General requirements for materials
The materials used for hot-addition shall have a quality certificate (or its copy) that meets the corresponding standards. The inspection department of the manufacturer shall conduct factory acceptance according to the certificate. If any of the following conditions are met, re-inspection shall be carried out according to JB3375. If the materials are not inspected or fail the inspection, they shall not be put into production. The content of the quality certificate is incomplete:
b. When the manufacturer has doubts about the performance and chemical composition of the materials; e
When there are requirements on the design drawings.
6.2 Tube sheets, flat covers, and flanges
6.2.1 The material selection of tube sheets, flat covers, and flanges shall comply with the provisions of Article 2.2.1 of GB151 when forgings are used. When there are other requirements, they shall be in accordance with the drawings or relevant technical documents.
6.2.2 When steel plates are used for tube sheets, flat covers, and flanges, they shall comply with the provisions of Article 2.2 of GB150. When the plate material used is 16Mn, it shall also comply with the provisions of Article 2.2.2.2 of GB151. 6.3 Heat exchange tubes
Heat exchange tubes can be selected from the following standards for ordinary cold-drawn tubes. When the drawing specifies a level 1 heat exchanger, a higher level cold-drawn tube shall be selected. GB8163;
GB3087;
GB2270;
GB8890.
6.4 Bolts, studs and nuts
Bolts, studs and nuts shall comply with the provisions of Article 2.4 of GB151. 7 Manufacturing technical requirements
In addition to complying with the provisions of this standard, hot processing manufacturing shall also comply with the provisions of GB150GB151 and the requirements of the drawings. 7.1 Head
7.1.1 Welding arrangement of jointed head
7.1.1.1 Jointed head can be made by butt jointing several steel plates, or by butt jointing petals and top round plates. However, when it is made by butt jointing the top round plates of petals, the weld direction is only allowed to be radial and circumferential. 7.1.1.2 The minimum distance L between various non-intersecting welds shall not be less than 3 times the nominal thickness and not less than 100mm (as shown in Figure 2). 5
7.1.2 Minimum thickness
JB/T78371995
The minimum thickness of the head after stamping shall not be less than the nominal thickness minus the negative deviation of the copper plate thickness. 7.1.3 Inner surface shape deviation
The measurement and deviation of the inner surface shape of the head shall comply with the provisions of Article 10.2.2.3 of GB150. 7.1.4 OpeningsbZxz.net
Openings on the head shall comply with the requirements of Article 7.2.13. 7.2 Cylinders and shells
35.H2100m
7.21 When rolled from sheet metal, the allowable deviation of the inner diameter of the cylinder is controlled by the outer circumference. The upper allowable deviation of the outer circumference is: 5mm when the nominal diameter of the cylinder is DN≤1200, 10mm when DN>1200~2000mm, and 12mm when DN>2000. The lower deviation is zero
When the nominal diameter is DN≤400mm and seamless steel pipes are used as cylinders, the allowable deviation of the size shall comply with the provisions of GB3087, GB2270, or corresponding standards.
7.2.2 On the same section of the cylinder, the difference between the maximum inner diameter and the minimum inner diameter e≤0.5%DN, and shall not be greater than the provisions of Table 5. Table 5
Nominal diameter DN
e not larger
>1200~2000
7.2.3 The classification of hot press welds shall be in accordance with Article 4.1 of GB151. The misalignment of the weld ends of A and B welds (see Figure 3) shall comply with the provisions of Table 6.
Nominal thickness at the end
12<8mg20
20<8n40
Misalignment of the weld ends classified by weld type
≤25%8n
≤25%8n
≤25%8n
The misalignment requirements of the weld ends of Class A welds in the table do not include the circumferential welds connecting the spherical head and the sleeve and the welds connecting the embedded pipe and the cylinder or the head. Note, ①
.
JB/T 7837-1995
②The misalignment requirement for Class B welds in the table includes the circumferential welds connecting the spherical head and the cylinder. 7.2.4For Class B welds and Class A welds connecting the cylinder and the spherical head, when the thickness of the two plates is unequal, the edges of the thick plates shall be thinned in accordance with the requirements of Article 10.2.3.4 of GB150. 7.2.5The inspection and allowable value of the angle E formed by the axial direction of the butt annular seam and the circumferential direction of the butt longitudinal seam shall comply with the provisions of Article 10.2.3.3 of GB150.
7.2.6The allowable deviation of the straightness of the cylinder is L/1000 (L is the length of the cylinder). And: when L≤6000mm, its value shall not exceed 45mm; when L>6000mm, its value shall not exceed 8mm.
Straightness inspection should be carried out through the horizontal and vertical planes of the center line, that is, measurement along the circumference at 0°, 90°, 180°, and 270°. 7.2.7 The limit of longitudinal welds in each section of the simplified body is: when DN≤1400mm, no more than 1;
14001. The misalignment b of the welds of type A and B (see Figure 3) shall comply with the provisions of Table 6.
Nominal thickness at the joint
12<8mg20
20<8n40
Misalignment of the joints classified by weld type
≤25%8n
≤25%8n
≤25%8n
The misalignment requirements of the welds of type A in the table do not include the circumferential welds of the connection between the spherical head and the sleeve and the welds of the embedded pipe and the cylinder or the head. Note, ①
.
JB/T 7837-1995
②The misalignment requirements of the welds of type B in the table include the circumferential welds of the connection between the spherical head and the cylinder. 7.2.4 For Class B welds and Class A welds connecting the cylinder and the spherical head, when the thickness of the two plates is unequal, the edge of the thick plate shall be thinned according to the requirements of Article 10.2.3.4 of GB150. 7.2.5 The inspection and allowable value of the edge angle E formed by the butt annular seam in the axial direction and the butt longitudinal seam in the circumferential direction shall comply with the provisions of Article 10.2.3.3 of GB150.
7.2.6 The allowable deviation of the straightness of the cylinder is L/1000 (L is the length of the cylinder). And: when L≤6000mm, its value shall not exceed 45mm; when L>6000mm, its value shall not exceed 8mm.
The straightness inspection shall be carried out through the horizontal and vertical planes of the center line, that is, the measurement at four positions along the circumference of 0°, 90°, 180°, and 270°. 7.2.7 The limit of longitudinal welds in each section of the simplified body is: when DN≤1400mm, no more than 1;
14001. The misalignment b of the welds of type A and B (see Figure 3) shall comply with the provisions of Table 6.
Nominal thickness at the joint
12<8mg20
20<8n40
Misalignment of the joints classified by weld type
≤25%8n
≤25%8n
≤25%8n
The misalignment requirements of the welds of type A in the table do not include the circumferential welds of the connection between the spherical head and the sleeve and the welds of the embedded pipe and the cylinder or the head. Note, ①
.
JB/T 7837-1995
②The misalignment requirements of the welds of type B in the table include the circumferential welds of the connection between the spherical head and the cylinder. 7.2.4 For Class B welds and Class A welds connecting the cylinder and the spherical head, when the thickness of the two plates is unequal, the edge of the thick plate shall be thinned according to the requirements of Article 10.2.3.4 of GB150. 7.2.5 The inspection and allowable value of the edge angle E formed by the butt annular seam in the axial direction and the butt longitudinal seam in the circumferential direction shall comply with the provisions of Article 10.2.3.3 of GB150.
7.2.6 The allowable deviation of the straightness of the cylinder is L/1000 (L is the length of the cylinder). And: when L≤6000mm, its value shall not exceed 45mm; when L>6000mm, its value shall not exceed 8mm.
The straightness inspection shall be carried out through the horizontal and vertical planes of the center line, that is, the measurement at four positions along the circumference of 0°, 90°, 180°, and 270°. 7.2.7 The limit of longitudinal welds in each section of the simplified body is: when DN≤1400mm, no more than 1;
14002200mm, no more than 3.
The arc length between the center lines of two adjacent welds shall not be less than 300mm. 7.2.8The shortest section length of the cylinder shall not be less than 300mm. If there is a shroud, it shall be greater than three times the nominal thickness 8n and not less than 100mm. 7.2.9The verticality deviation △f (Figure 4) of the cylinder end face to the generatrix of the outer circle (Do); when Do≤1200mm, △f≤2mm;
When Do≥1200mm, △f≤3mm.
7.2.10When assembling the cylinder, the distance between the Class A welds of the adjacent cylinders or the distance between the end point of the Class A weld of the head and the Class A weld of the adjacent cylinder shall be greater than three times the nominal thickness n and not less than 100mm. 7.2.11The requirements of the flange surface for the center line of the main axis of the nozzle or cylinder shall comply with the provisions of Article 10.2.3.7 of GB150. 7.2.12 The weld edge of the hot-adding internal parts and shell welding shall comply with the existing weld and shall not be less than 50mm. 7.2.13 The hot-adding holes shall be avoided as much as possible on the welds, and the heat-affected zones of the pipe hole welds and the adjacent welds shall not overlap with each other. If it cannot be avoided, all welds within 60mm around the pipe hole (if the pipe hole diameter is greater than 60mm, the hole diameter value shall be taken) shall be subjected to radiographic inspection according to GB3323, and the weld quality shall not be lower than Grade I. In addition, there shall be no slag inclusions on the edge of the pipe hole, and the pipe joints shall be heat-treated after welding to eliminate stress before holes can be opened on the welds and their vicinity. 7.2.14 All welds on the shell covered by reinforcing rings, supports, pads, etc. and welds in the shell that affect the assembly of the tube bundle shall be polished to be flush with the parent material.
7.2.15 The treatment requirements for mechanical damage that cannot be avoided during manufacturing shall comply with the provisions of Article 10.2.3.13 of GB150. 7.2.16 Single-sided welding is allowed for the terminal annular seam of the fully welded fixed tube-sheet shell, and ultrasonic testing can be used instead of radiographic testing. The weld quality shall meet the requirements of Grade I of JB1152 to be qualified. 7.3 Flanges and flat covers
7.3.1 Pipe flanges and container flanges shall be processed in accordance with the requirements of the corresponding standards. 7
JB/T7837-1995
7.3.2 The processing of flat covers and cylinder end flanges shall comply with the provisions of Article 10.2.4.2 of GB150. 7.4 Bolts, studs, and nuts
The manufacture of bolts, studs, and nuts shall comply with the provisions of Article 10.2.5 of GB150. 7.5 Heat exchange tubes
7.5.1 The outer surface of the heat exchange tube end shall be derusted to a metallic luster. When used for welding, the derusting length of the tube end shall not be less than the tube diameter, and shall not be less than 25mm. When used for expansion, the length of the rust removal of the tube end should not be less than the thickness of the tube sheet plus 50mm. If the hardness of the expanded tube end is greater than the hardness of the tube sheet, or the tube hardness HB>170, the tube end should be annealed before expansion, and then the rust should be removed from the outer surface of the tube within the same length range until the metallic luster is revealed, and there should be no defects such as heavy skin, dents, cracks, and longitudinal or visible spiral notches. When there is a requirement for stress corrosion resistance, the method of local annealing of the tube head should not be used to reduce the hardness of the heat exchange tube. 7.5.2 When the heat exchange tube is a copper tube, splicing is not allowed. When the heat exchange tube is a steel tube, splicing is generally not allowed. If splicing is necessary, in addition to complying with the provisions of Article 4.3.3 of GB151, it should also meet the following requirements: a. When the butt-jointed tubes are subjected to water pressure test one by one, the pressure holding time shall not be less than 10s; b. The inner diameter of the heat exchange tube after butt joint shall not be less than 80% of the nominal diameter of the tube. 7.5.3 The roundness of the U-shaped pipe after bending is controlled by a steel ball, and the ball is qualified if it passes. Ball diameter: When dw≤R<2.5dw, dball=0.75d (dw-tube outer diameter, da-tube inner diameter, d-ball diameter, R-bend radius). Ball inspection must be carried out for pipes that are spliced one by one; for pipes that are not spliced, 5% of the number of bends can be randomly inspected, but for pipes with the smallest bending radius, no less than 2 pipes. The thickness reduction at the bend of the U-shaped pipe with the smallest bending radius shall not be greater than 17% of the wall thickness before bending. 7.5.4 When the drawing requires heat treatment or stress corrosion resistance, the bend section of the cold-bent U-shaped pipe and the straight section of at least 150mm should be heat treated.
a. Carbon steel and low alloy steel pipes are subjected to stress relief heat treatment; b. Austenitic stainless steel pipes can be heat treated according to the method agreed upon by the supply and demand parties or the drawing requirements. 7.5.5 When the heat exchange tube is a straight tube, 10% of it should be randomly checked for water pressure test before cutting. When the heat exchange tube is a U-shaped tube, it should be subjected to water pressure test from the beginning of the tube bending. The test pressure is 1.5 times the design pressure, and the pressure holding time under the test pressure is not less than 10S. After the test is passed, the water should be drained. When the heat exchange tube is butt-joined, it is allowed to conduct water pressure test one by one after butt-joining (straight tube) and bending (U-shaped tube), but the test pressure should be based on the water pressure test pressure value after butt-joining.
7.5 Tube sheet and baffle (baffle)
7.6.1 The diameter and allowable deviation requirements of the tube sheet and baffle holes shall be in accordance with Table 7(a) when the heat exchanger is a 1st stage heat exchanger; in accordance with Table 7(b) when the heat exchanger is a 1st stage heat exchanger and the heat exchange tubes of the heat exchanger are copper tubes. After drilling holes in the tube sheet, the tube holes in the plate center angle area of not less than 60° shall be randomly checked. The upper deviation of the tube holes is allowed to be 0.15mm larger than the value in Table 7, but the number of holes shall not exceed 4% and shall not exceed 5. After drilling holes in the partition (baffle), the tube holes in the plate center angle area of not less than 60° shall be randomly checked. The upper deviation of the tube holes is allowed to be 0.1mm larger than the value in Table 7, but the number of holes shall not exceed 4%.
7.6.2 On the surface of the tube sheet on one side of the final drilling, the hole bridge width B between two adjacent tube holes shall comply with the following provisions: a. When the heat exchanger is a Class I heat exchanger, it shall comply with Table 8 (a); b. When the heat exchanger is a Class 1 heat exchanger and the heat exchange tubes of the heat exchanger are copper tubes, they shall comply with Table 8 (b). 8
Nominal heat exchange tube
Nominal heat exchange tube
Table 7(a)
Table 7(b)
JB/T78371995
Partition hole diameter and allowable deviation
I-level heat exchanger tube sheet,
Allowable deviation
Partition (baffle) hole
Partition hole diameter and allowable deviation
1-level heat exchanger tube sheet,!
Table 8(a)
Allowable deviation
Hole bridge width of II-stage heat exchanger
Allowable deviation
Partition (baffle) hole
Allowable hole bridge width (≥96% of the hole bridge width shall not be less than the following value)8
Table 8(b)
Hole bridge width of tube sheet of II-stage heat exchanger
Allowable hole bridge width (≥96% of the hole bridge width shall not be less than the following value)B
The surface roughness of the tube hole of the tube sheet is:
The surface roughness Ra value of the tube hole is not greater than 25μm; when the heat exchange tube is welded to the tube sheet,
When the heat exchange tube is connected to the tube sheet by welding, the surface roughness Ra value of the tube hole is not greater than 12.5um. Allowable deviation
Minimum hole bridge width allowed
Degree (the number is ≤4% of
number of hole bridges, and not more than 5
Minimum hole bridge width allowed
Degree (the number is 4% of
number of hole bridges, and not more than 5
JB/T7837-1995
7.6.4 After drilling holes in tube sheets and partitions, burrs around the tube holes should be removed. 7.6.5 When expanding the connection, there should be no defects on the surface of the tube holes that affect the tightness of the expansion connection, such as longitudinal or Spiral notches, etc. The nominal outer diameter of the partition (baffle) shall be determined by the designer according to the structural requirements, but shall not be less than the specification of Article 3.9.2.4 of GB151. 7.6.6
The outer surface roughness Ra value of the partition (baffle) or baffle ring shall not be greater than 20μm. The sharp angles on both sides of the outer surface shall be blunted and any burrs shall be removed.
7.7 Welding requirements
7.7.1 Welding must be performed by welders who have passed the examination in accordance with the "Test Rules for Boiler Pressure Vessel Welders". 7.7. 2 The shape, size and appearance requirements of the weld surface shall comply with the provisions of Article 10.3.3 of GB151 and the following requirements: The coverage width of the weld on each side of the weld joint is 2~4mm: a.
b. The difference between the maximum width and the minimum width of the same butt weld shall not exceed 4mm. Weld repair shall comply with the provisions of Article 10.3.4 of GB150. 7.7.33
7.7.4 Other requirements for welds shall comply with the provisions of Article 10.3 of GB150. 7.8 Welds Flaw detection
Weld flaw detection inspection shall be carried out in accordance with the provisions of Article 10.8 of GB150. 7.9 Heat treatment
The heat treatment requirements shall comply with the provisions of Article 10.4 of GB150. 7.10 Other requirements
7.10.1 The sealing surface of heat treatment shall be protected after processing, and shall not be damaged by silicon scratches, arc damage, welding nodules and splashes, etc. 7.10.2 Sealing gaskets shall generally be integral gaskets. Splicing is allowed in special circumstances, but the splicing joints shall not affect the sealing performance. 7.10.3 The signal hole of the reinforcement diagram should be passed through 0.4-0.5MPa compressed air before the pressure test to check the weld quality. 7.10.4 The distance between the lap weld of the support pad, reinforcement ring and shell and any adjacent weld should not be less than 3 times the shell wall thickness, and not less than 50mm.
7.11 Component assembly
7.11.1 Connection between heat exchange tube and tube sheet
. The surface of the heat exchange tube and tube sheet hole at the connection part should be cleaned, and no burrs, iron filings, rust spots, oil stains, etc. that affect the expansion or welding quality should be left.
b. When expanding the connection, the expansion length shall not extend beyond the shell side on the back of the tube sheet). The minimum value of the expansion length L shall not be less than twice the outer diameter of the heat exchange tube; or 50mm; or not greater than the nominal thickness of the tube sheet minus 3mm, whichever is smaller. c. When expanding and connecting, the end of the heat exchange tube should be flush with the tube sheet or extend out of the tube sheet according to the design requirements, and should not be retracted into the tube sheet. When the heat exchange tube is a copper tube, its end should extend out of the tube sheet by 12mm, and the water inlet end should be flanged. d. The range of the expansion rate H is recommended to be 1% to 4%, and the larger value is taken for copper tubes. The calculation formula of the expansion rate is: H=dd-ax
Where: di—inner diameter of the tube before expansion, mmdz-inner diameter of the tube after expansion, mm;
d-—actual diameter of the tube hole on the tube sheet, mm;X100%
8—the gap between the actual diameter of the tube hole on the tube sheet and the outer diameter of the tube, mm. e. The expansion part and the non-expansion part of the heat exchange tube should have a smooth transition and no sharp edges or corners. ". When welding, after the heat exchange tube and tube sheet are welded, the weld and heat affected zone shall not have defects such as cracks, pores, slag inclusions, and incomplete fusion. The minimum diameter of the pipe mouth after welding shall not be less than 80% of the inner diameter of the tube. Welding slag and weld nodules protruding from the inner wall of the heat exchange tube shall be removed. For repair of weld defects, the defects shall be removed first and then repaired by welding. g.
h. The strength welded joints between the heat exchange tube and the tube sheet shall be evaluated for welding procedure according to Appendix C of GB151 before welding. 10
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