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Machinery Industry Standard of the People's Republic of China
Method for calculating the strength of boiler suspension rods
This standard specifies the strength calculation method for suspension rods on pressure parts of boilers. JB/T6735-93
This standard is applicable to the strength calculation of suspension rods on pressure parts of fixed water tube boilers and pipelines in boiler models. It can be used as a reference for the strength calculation of suspension rods on non-pressure parts and other supporting structures. 2 Reference standards
GB1591
GB3077
GB3274
GB3323
GB9222
GB11251
GB10181
GB10182
JB/T6734
Basic dimensions of common threads (diameter 1~600mm)Tolerances and fits of common threads (diameter 1~355mm)Technical conditions for high-quality carbon structural steel
Carbon structural steel
Manufacturing carbon steel and low-alloy steel plates for boilersLow-alloy structural steel||tt| |Technical conditions for alloy structural steel
Radiographic quality classification of hot-rolled thick steel plates and steel strips for carbon structural steel and low-alloy structural steel Fusion welded butt joints Strength calculation of pressure components of water tube boilers
Hot-rolled thick steel plates for alloy structural steel
Constant force spring hanger
Variable spring hanger
Strength calculation method of boiler fillet welds
ZBJ74003 Ultrasonic flaw detection of steel plates for pressure vessels 3 General
3.1 Design principles
3.1.1 The suspension rod device should have sufficient strength to ensure the long-term safe and reliable operation of the boiler body and boiler fan pipes under various specified working conditions.
3.1.2 The setting of the suspension rod device should meet the requirements of the overall layout of the boiler and the layout of the supported and suspended pressure parts. 3.1.3 The suspension rod installation should strive to be simple and reasonable in structure, easy to manufacture and install, and it is advisable to select a mature, reliable and economical structural type. 3.1.4 The suspension rod device and its parts should be standardized, universal and serialized as much as possible. 3.2 Design requirements
3.2.1 The strength calculation of each load-bearing component should be carried out according to the load and displacement under various operating conditions, and the stiffness and stability calculation should also be carried out if necessary.
3.2.2 Each load-bearing weld in the suspension rod device should meet the requirements of JB/T6734. 3.2.3 The thickness of the load-bearing components (such as lifting ears, etc.) welded to the pressure-bearing parts such as boiler shells, headers and pipes with a nominal outer diameter greater than 133mm shall not be greater than the nominal thickness of the pressure-bearing parts.
Approved by the Ministry of Machinery Industry on August 21, 1993
Implementation on October 1, 1993
JB/T 673593
3.2.4 The diameter of the ordinary suspension rod on the top of the suspended boiler, whether with or without a sealed cover, should not be less than 16mm. 3.3 Categories and structural types
3.3.1 The suspension rod device is divided into two categories according to its use position: the sauce-through suspension rod device and the boiler shell suspension rod (frame) device. The ordinary suspension rod device is used to support the pressure-bearing parts of the boiler body except the shell and the pipelines within the boiler range. 3.3.2 The common structural types of ordinary suspension rod devices are shown in Figure 3-1. 3.3.3 The common structural types of boiler drum suspension rod (frame) devices are as follows: round key type boiler shell suspension rod device: see Figure 3-2; b.
Chain plate type boiler shell suspension rack device, which is further divided into full chain plate type (Figure 3-3) and composite chain plate type (round steel on the upper part and chain plate on the lower part, see Figure 3-4).
The one with only one U-shaped suspension rod (frame) at one end of the boiler drum is called a single suspension rod (frame), and the one with two is called a double suspension rod (frame). The specifications of fasteners (including nuts, nut blocks, spacers, pins, pin shafts, etc.) on the boom device should be selected in accordance with the relevant national standards. 3. 3. 4
Specifications not in the national standards can be designed by referring to the relevant standards. 3. 3. 5
The common types of threaded hangers are the following five: single-head threaded hanger;
double-head threaded hanger,
double-head left and right threaded hanger (generally not recommended): U-shaped hanger:
threaded connection hanger. The recommended values of thread and round steel nominal diameter of threaded hanger are shown in Appendix A1. 3. 3. 6
The structural types of the hanging plate and U-shaped clamp (both used to connect the hanger and the lifting ear) on the ordinary hanger device are shown in Figures 3-5 and 3-6. The U-shaped clamp is connected to the hanger by threads.
Single-hanging plate hanger
Double-hanging plate hanger
Connecting plate hanger
Single-head U-shaped clamp hanger
Variable elastic poor product rack
Transition beam hanger
1—explosion mother, 2-—heat enclosure, 3
JB/T 673593
e Double-headed U-shaped clamp hanger
h, constant force spring frame
k Inlaid hanger
Stud bolt hanger
iU-shaped hanger
Annular round steel welded hanger
Figure 3-1 Ordinary rod device
-Conventional rod, 4
One-pin plate,
9 Pin or cotter pin, 10-
Variable spring hanger, J3
Picking shaft, 6
Pin ear,? -
Connecting plate, solid
Constant force spring rear frame, 12-U-shaped rod, 13----through micro-recording, -nut, 2~
JE/T 673593
Screw part
Figure 3-2 Round steel boiler hanger device
Cylindrical pad, 3-pad, 4-strengthening rib, 5-heat-enough grid
Di Jie auxiliary load
Figure 3-3 Full-burning plate Wu boiler angle hanger device
U-shaped hanger, 6-boiler.
plate, 2 boiler plate, 3 support frame, 4-chain plate group, 5. Washer, double-head purchase inspection,? -ban,·Caution lock plate. 87
JB/T673593
After thermal expansion
Axis of hanger
Figure 34 Composite chain plate type boiler hanger device
—Spherical washer, 3—Conical washer, 4—Hanging rod, 5—A nut, 2-
A chain plate group,
6—Pin, 7——Pin shaft, 8-—Channel mother, 9—Interlocking plate, 10-Single hanging plate
Figure 3-5 Hanging plate
Figure 3-6 U-shaped clip
A connecting plate.
Double-side hanging plate
JB/T6735--93
3.3.7 The lifting lugs on the common hanger device (directly welded on the header, pipe, pipeline or beam) are divided into two types: transverse lifting lugs (Figure 3-7) and longitudinal lifting lugs (Figure 3-8).
Single product ear
Lifting lug under beam
Transverse lifting lug
Header lifting lug
Figure 3-8. Longitudinal lifting lug
The spring hanger mounted on the common hanger device shall meet the following requirements: 3.3.83
Constant force spring hanger: selected according to GB10181. a.
Variable spring hanger: selected according to GB10182. 3.3.9Www.bzxZ.net
When necessary, the hanger device can use a transition beam, and its type is shown in Figure 3-9. Steel combination type
Figure 3-9 Wave beam
3.4 Calculation position
Double normal ear
Bend pipe ear
5 Steel plate combination type
3.4.1 For the convenience of calculation, the temperature of each place on the suspension device shall be reduced in principle from the bottom. 3.4.2 Each type of suspension device shall be calculated according to the design requirements for all calculation parts specified in Table 3-1, and the positions shall meet the requirements. The strongest strength can also be used as the calculation basis. 39
Ordinary suspension rod
Ink pot suspension rod
Chain plate suspension bracket
Figure 3-1, 8
Figure 3-1, b
Figure 3-1 , c
Figure 3-1, d, e
Figure 3-1, f
Figure 3-1, 1
Figure 31,
Figure 3-1, k
Figure 3-1, 1
Figure 3-2
Figure 3-3
Figure 3-4
Material and allowable stress
Symbol explanation
JB/T6735-93
Table 3-1
Calculation parts of the suspension rod device
1. Suspension rod burst between No. 1 and No. 2, 2. Round pot at the junction of No. 3 and No. 4, 3. No. 4 suspension plate; 4. No. 5 pin, 5. No. 6 lifting ear. 1. Threaded rod No. 3, 2. Round pot at the junction of No. 3 and No. 4, 3. Hanging plate No. 4, 4. Pin No. 5.
1 Threaded rod No. 1 and No. 2, 2. Steel ring at the junction of No. 3 and No. 4, Hanging plate No. 4, 4. Pin No. 5
Threaded rod No. 3, 2. Pin No. 5. 1.
Thread of suspension rod between No. 1 and No. 2
1. Thread end of No. 12, 2. Transition beam of No. 13, 3. Thread at the bottom of suspension rod of No. 3. Thread of suspension rod near transition beam, 2. Transition frame of No. 13. 1.
1. Upper thread, 2. Lower suspension plate.
1. Upper thread, 2. Circular round steel welding.
Thread of suspension rod between No. 1 and No. 2, 2. Suspension rod at boiler end, 3, No. 3 pad, 1.
1. Stud bolt at boiler end of No. 6, 2. Chain plate at boiler end. 1. Thread of the suspension rod between No. 1 and No. 4, 2. Pin shaft at the end of No. 7 copper cylinder, 3. Chain plate at the end of the boiler shell The meanings and units of the symbols used in this chapter are as follows: o—tensile strength of the material at room temperature, N/mm\; c—yield point of the material at the calculated temperature, N/mm\, op-—endurance strength of the material at 10° at the calculated temperature, N/mm; [o]—allowable stress of the material at the calculated temperature, N/mm'—safety factor corresponding to tensile strength at room temperature; n—safety factor corresponding to yield point at the calculated temperature np—safety factor corresponding to endurance strength at 10° at the calculated temperature. 4.2 Material selection
4.2.1 The material should be selected according to the type and calculation temperature of each load-bearing component of the suspension rod device. When the calculation temperature is high, the material's anti-oxidation performance should be considered.
4.2.2 The load-bearing components connected by welding should use materials with good weldability and their heat treatment requirements should be considered. 4.2.3 To prevent threaded load-bearing components from seizing at the screw-in joint, the hardness of nuts and hangers should be different. Materials with different performance grades or different heat treatment specifications can be selected. 4.2.4 The belt materials and their maximum allowable wall temperatures of load-bearing components shall comply with the provisions of Tables 4-1 to 4-2. Q235A in Table 4-2 shall not be used to manufacture more important hangers and nuts. The maximum allowable wall temperature of forgings is the same as that of the same grade of steel plates, steel sections or round steels. 4.2.5 The materials of load-bearing components shall comply with the provisions of relevant national standards or industry standards. 4.3 Allowable stress
4.3.1 The allowable stress [o] of steel is calculated according to the following formula, and the minimum value is taken: [o]%
(4-—1)
JB/T6735-93
..0.00:
.+.......+
(4—2)
(4—3)
When calculating, % and c are the statistical lower limit values of a large number of steel test results; % is the average value of the 10h endurance strength of a large number of steel test results. The safety factor is selected according to the following formula: n=3
100008000
The allowable stress of common materials for load-bearing components can be referred to Appendix A2. Table 4-1
Types of steel
Low alloy steel
Types of steel
Low alloy steel
15MnVg
15CrMo
12Cr1Mo
20, 25
12Cr1MoV
30CrMoA
35CrMo
Standard code
GB1591, GB3274
GB1591, GB3274
GB3077, GB11251
GB3077, GB11251
Table 4-2 Steel and round steel
Standard number
GB1591
GB1591
GB3077
GB3077
Transition beam, nut
Frame, hanger
Beam, hanger
Hanger, pin, nut
Maximum allowable whole temperature
Maximum allowable wall temperature
(4—4)
(4—6)
2 For the load-bearing components arranged in the flue, when the flue gas temperature is not more than 600℃, the allowable stress shall be 4.3.1
95% of the value obtained according to 4.3.1; when it is greater than 600℃, it shall be 90%.
4.3.3 The allowable stress of forgings shall be 100% of the value obtained in accordance with 4.3.1 when the forged material is a rolled material, and 90% when the forged material is a steel material. 4.3.4 For materials not listed in Appendix A2 (including domestic and imported materials), as long as they meet the relevant requirements of 4.2, their allowable stresses may be determined in accordance with 4.3.1, and %, s and shall be the minimum guaranteed values of the corresponding steel grade. When there is no guaranteed value, a sampling test may be carried out, and the minimum value of the test results and the average value of p multiplied by 0.9 shall be used as the adopted value. The sampling test method shall comply with the requirements of the relevant standards. 4.3.5 For load-bearing members made of carbon steel or low alloy steel, if the calculation temperature is not more than 350℃, and for other alloy steels not more than 400℃, the endurance strength shall not be considered when determining the allowable stress.
5 Calculation load
3.1 Special symbol description
The meaning and units of the symbols used in this chapter are as follows: F total calculation load, N
F permanent load, N;
F individual load, N
F. Calculation load of member, N, mm;
Calculation load correction factor;
Load statistical correction factor;
%—load distribution unevenness coefficient.
JB/T6735-93
3.2 Load classification
5.2.1 During the use of the boiler, the value does not change with time or changes, and the change value is negligible compared with the average value is called a fixed load, and the value changes with time and the change value is not negligible compared with the average value is called a variable load. For the convenience of calculation, fixed loads and variable loads are combined and called permanent loads. 5.2.2 Loads that may not appear during the use of the boiler, but once they appear, although the duration is very short, the value is not negligible is called accidental loads.
5.3 Permanent loads
5.3.1 Permanent loads F, shall include the following loads on the pressure parts supported by the suspender device: a.
Metal weight of the pressure parts;
Medium weight in the pressure parts;
Insulation weight on the pressure parts;
Weight of other parts supported by the pressure parts (including the metal weight, medium weight and insulation weight of the parts); thermal load and other loads obtained from system stress analysis (including the thrust of the connecting pipes, cold drawing and pre-tightening force during installation, etc.); deadweight of the suspender device.
When calculating the permanent loads of ordinary suspender devices, the following variable loads shall also be added: slag and ash accumulation on the heating surface of the pulverized coal boiler; flue gas pressure of the steel furnace or flue.
The corresponding variable loads shall be determined according to the type and location of the suspender device and added to the pressure parts through allocation. 5.4 Occasional loads.
The accidental load F includes the following loads:
The instantaneous explosion pressure of the furnace or the explosion pressure in the furnace that the boiler is allowed to withstand during design, whichever has the larger absolute value; the reaction force of the safety valve or exhaust valve when exhausting steam; other short-term loads on the suspension rod device. The corresponding accidental loads should be determined according to the type and position of the suspension rod installation and added to the pressure parts through allocation. 5. 4.2
5.4.3 For open-air boilers and boilers in areas with a fortification intensity of 6 or above, the wind force and horizontal earthquake force should be checked for strength when necessary. 5.5 Calculation principles
5.5.1 For plates, the theoretical weight obtained by the nominal size is used as the metal weight, and for pipes, 1.1 times the theoretical weight obtained by the nominal size is used as the metal weight.
5.5.2 The calculation principle of medium weight is as follows: Gravity: According to the medium state under rated working conditions, the medium in the pressure parts is divided into three categories: water, steam-water mixture and steam. The a.
gravity of water and steam-water mixture is the gravity of water under atmospheric pressure, and the gravity of steam can be ignored. >. Volume: Except for the steel cylinder, which is calculated as half of the total volume, other pressure parts are calculated as total volume. 92
JB/T6735-93
5.5.3 The insulation weight is 1.2 times the design calculation weight. 5.5.4 The weight of slag is 12~14kN/m for liquid slag boilers and 10~12kN/m for solid slag boilers. The weight of ash accumulation is 8~10kN/m2.
The recommended values of slagging and ash accumulation locations and their average thickness in the boiler are shown in Appendix A3. 5.5.5 The flue gas pressure of the boiler furnace or flue is the design pressure of the furnace or flue. 5.5.6 The load statistical correction coefficient is used to consider the possible errors in the statistics of various loads. For ordinary hanger devices, =1.05, for boiler simple hanger (frame) devices, 1.10.
5.5.7 The load distribution unevenness coefficient is used to consider the uneven distribution of loads on each hanger. The value is specified as follows; when multiple hangers on the membrane wall tube panel header are uniformly loaded, =1.20; a.
Pipes and other headers (only 2 hangers, calculated as simply supported beams, more than 2 hangers, calculated by continuous beam static method), b.
Single U-shaped hanger (frame) of boiler, = 1.00, double U-shaped hanger (frame), n = 1.20. e
When the load distribution of the load-bearing component is obtained through stress analysis, = 1.00. Use the calculated load correction factor \ to consider the deviation between the calculated value and the actual value: 5.5.8
(5-1)
The larger value in the following formula should be taken as the total calculated load F of all hanger devices on a certain pressure-bearing member: 5.5.9
F=(F:+F,)
·（5-2)
When F,≥3F:, the total calculated load can be directly obtained according to formula (5-2). 5.3.10 When calculating the strength of the load-bearing component, the total calculated load F should be distributed according to the type and number of the hanger device to determine the calculated load Fc of each load-bearing component installed on the hanger. 5.5.11 If necessary, the strength of the suspension rod device under the water pressure test condition can be checked. For open-air boilers, snow load should be added during the check.
6 Calculation temperature
6.1 Explanation of symbols
The meaning and units of the symbols used in this chapter are as follows; l,---the calculated length of any point p on the suspension rod, mm;---the calculated temperature of the load-bearing component, °C;
t. The ambient temperature of the furnace top when there is no sealed cover, °C; td The ambient temperature of the furnace top when there is a sealed cover, C; t—Medium temperature, C.
t——The calculated temperature of the load-bearing component in the insulation layer, °C; ti. The calculated temperature of the load-bearing component on the surface of the insulation layer, C; t, The calculated temperature of any point p on the suspension rod, °C; At-the additional value of the calculated temperature, °C.
5.2 Overview
5.2.1 The calculation source temperature when calculating the strength of the hanger device should be determined according to the medium temperature and the ambient (or flue gas) temperature of the hanger device in the boiler.
6.2.2 When determining the elastic modulus, the material temperature is the arithmetic average of the calculated temperatures at the lower and upper ends of the hanger. 6.3 Ambient temperature
5.3.1 The ambient temperature of the furnace top without a sealed cover or outside the sealed cover is 100℃. 93
1B/673-93
6.3.2 The ambient temperature of the furnace top in the sealed cover is the maximum medium humidity of the top tube plus 55℃. 6.3.3 For the load-bearing components arranged in the flue, the calculation avoidance is determined by the flue gas temperature instead of the ambient temperature. The value of the flue gas temperature is based on the thermal calculation book of the boiler under rated working conditions.
6.4 Medium temperature
6.4.1 The medium temperature in the boiler shell shall be the saturated temperature corresponding to the boiler shell working pressure under rated conditions. 6.4.2 The medium temperature in other pressure-bearing parts except the boiler shell shall be based on the rated condition boiler thermal calculation book or refer to the strength calculation book of the pressure-bearing parts. 6.5 Calculation temperature of load-bearing components
6.5.1 The calculation temperature of the boiler drum hanger (rack) device shall be 20℃ at the threaded end or fixed end, and the saturation temperature under the working pressure of the boiler drum at the boiler shell end. 6.5.2 When the medium temperature t in the header, pipe or pipeline supported by the ordinary hanger device is lower than the ambient temperature, the ambient temperature shall be used as the calculation temperature of the hanger.
6.5.3 When the medium temperature t in the header, pipe or pipeline supported by the ordinary hanger device is not lower than the ambient temperature, the calculation temperature of the hanger shall be selected according to Table 6-1.
Table 6-1 Calculated temperature of hanger (t≥t, time) Serial number
Working conditions of hanger
Hanger without casing through insulated tube bundle or hanger in direct contact with nest box or tube bundleHanger with casing through insulated tube bundle or hanger close to header or tube bundle connecting pipeHanger passing through non-insulated tube bundle but not in contact with tube bundle or connecting pipeCalculated temperature
tr--100+At
t:-28+△t
The additional value △t of calculated temperature in Table 6-1 is related to the tightness of the sealing of the top through-the-wall pipe. When the through-the-wall pipe has a reliable seal, t=0. When there is no reliable seal, the value of △t is related to the position of the hanger on the upper part of the furnace neck. Please refer to Table 6-2 for selection. Table 6-2 Calculation of additional temperature value
Position of the suspension rod on the furnace roof
Calculation of additional temperature value
Top of the furnace brain
40~-50
Top of the turning flue
20--30
Top of the rear flue
6.5.4 When there is no sealed cover, the calculated temperature t, at any point p along the length of the suspension rod (see Figure 6-1) can be calculated according to the following formula: tr+t
When t, obtained by formula 6-1 is less than t, take t,=ta. ℃
(6-1)
Figure 6-1 Calculation of temperature at any point along the length of the suspension rod Calculation of the load-bearing component at the surface of the insulation layer. Take the arithmetic average of the medium temperature and the ambient temperature in the pressure-bearing part. In the moisture-retaining layer, 6.5.54 When there is no sealed cover, the calculated temperature t, at any point p along the length of the suspension rod (see Figure 6-1) can be calculated according to the following formula: tr+t
When t, obtained by formula 6-1 is less than t, take t,=ta. ℃
(6-1)
Figure 6-1 Calculated temperature at any point along the length of the suspension rod Calculated temperature of the load-bearing component at the surface of the insulation layer. Take the arithmetic mean of the medium temperature in the pressure-bearing part and the ambient temperature. In the moisture-retaining layer, 6.5.54 When there is no sealed cover, the calculated temperature t, at any point p along the length of the suspension rod (see Figure 6-1) can be calculated according to the following formula: tr+t
When t, obtained by formula 6-1 is less than t, take t,=ta. ℃
(6-1)
Figure 6-1 Calculated temperature at any point along the length of the suspension rod Calculated temperature of the load-bearing component at the surface of the insulation layer. Take the arithmetic mean of the medium temperature in the pressure-bearing part and the ambient temperature. In the moisture-retaining layer, 6.5.5
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