HG/T 20645.5-1998 Technical Specification for Mechanical Design of Pipelines for Chemical Plants HG/T20645.5-1998 Standard download decompression password: www.bzxz.net

Chemical plant pipeline mechanical design technical regulations HG/T20645.5-1998
Steam jacket pipe end plate strength calculation
1.1 Scope of application
This regulation applies to the verification calculation of the steam jacket pipe end plate strength. 1.2
Symbol explanation
Calculation method
Figure 1.2.1 Schematic diagram of steam jacket pipe end plate
Outer diameter of the outer casing;
Dp——outer diameter of the inner casing;
E. Elastic modulus of the outer casing;
E. Elastic modulus of the inner casing;
EElastic modulus of the end plate;
F.--Cross-sectional area of ​​the outer casing;
-Cross-sectional area of ​​the inner casing:
Reaction force on the outer edge caused by the internal pressure;-Media pressure in the jacket;
Reaction force on the inner edge caused by the internal pressure;-Outer radius of the end plate;
Inner radius of the end plate;
-Temperature of the outer casing;
T,—Temperature of the inner casing;
T. Temperature of the end plate;
tm Wall thickness of the outer sleeve;
——Wall thickness of the inner sleeve;
Wo(AL)
Deformation;
Maximum deformation of the inner and outer edges of the end plate; Deformation of the end plate caused by thermal expansion:
Deformation of the end plate caused by internal pressure;
p/r, at the inner radius of the end plate, X=1, at the outer radius of the end plate, X=R/r=α; Thickness of the end plate;
Angle;
Poisson's ratio;
Coefficient of thermal expansion of the outer sleeve;
Coefficient of thermal expansion of the inner sleeve;
Coefficient of thermal expansion of the end plate;
Op(AL)|| tt||Gt(AL)
Radial stress;
-Longitudinal stress;
Composite stress;
Radial stress of end plate caused by thermal expansion; Longitudinal stress of end plate caused by thermal expansion; Composite stress of end plate caused by thermal expansion;-Radial stress of end plate caused by internal pressure; Longitudinal stress of end plate caused by internal pressure;
Composite stress of end plate caused by internal pressure;
-Outer edge (or inner edge) stress caused by edge load F(P);Gvp-Comprehensive stress of inner edge (or outer edge) of end plate caused by internal pressure;Oumax
Maximum stress of inner (outer) edge of end plate caused by thermal expansion and internal pressure. 1.2.2 Calculation formula
The deformation of end plate is mainly caused by the different thermal expansion of inner tube and outer tube and the internal pressure in jacket. When checking the strength of end plate, these two forces can be calculated separately, and then the total stress of end plate can be obtained by superposition. According to the stress, the calculated stress of the end plate must be less than or equal to the allowable stress. Based on this condition, determine whether the end plate thickness (assumed) can meet the design requirements.
1 Calculate the stress and deformation caused by thermal expansion
1) Radial stress p(AL)
2) Longitudinal stress (AL)
Gt(AL)
3) Composite stress (AL)
3P(AL)
2元02
3P(AL)
2元82
Ot(AL)=μOp(AL)
4) Deformation W)Ov[F(P)=
6)Comprehensive stress at the inner (outer) edge of the end plate caused by internal pressure 6P(P)[F(P)
(1.2.2—5)
(1.2.2—6)
(1.2.2-7)
(1.2.2—8)
(1.2.2-9)
(1.2.2--10)
3Due to thermal expansion and internal The maximum stress vmx at the inner (outer) edge of the end plate caused by the combined pressure (the larger stress value of the two is selected as the basis for verification and judgment)
Omax=ov(AL)+eP
(1.2.2--11)
1.3.1 Original data required for calculation
1.3 Calculation requirements
1 Outer diameter of outer casing Dm; wall thickness tm; temperature Tm, thermal expansion coefficient αm; elastic modulus Em. Inner casing outer diameter Dp; wall thickness tp; temperature Tp thermal expansion coefficient αp; elastic modulus E,; jacket length L; jacket pressure P.
1.3.2 Calculation of auxiliary data
1 Coefficient α
2 Cross-sectional area of ​​outer casing Fm
D.—2tm.
Dm-2tm
Fm=(Dmtm）·元·tm
3 Cross-sectional area of ​​inner casing F
F,=(D,—t,)·元·tp
The load on the edge of the outer casing caused by the thermal expansion difference between the inner and outer casings P(AL)P(AL)
L(a At,-am△tm)
Outer edge load F(P) caused by internal pressure
Em·Fm
F(P)=P.R2
(1.3.2-1)
(1.3.2-2)
(1.3.2-3)
(1.3.2-4)
(1.3.2-5)
5Inner edge load Q(P
Q(P)=P(R2—r2) Yuan—F(P)
Coefficient e
e=(1+μ)lnX
Coefficient t
t=(1+μ)InX
Coefficient β
10Coefficient λ
()[(1+μ)X+(1-μ)]+1
)[(1+μ)X2-(1-μ)+μ
0.21702—0.434+0.217
λ=1# +(1+)lnX
-μaina
11 coefficient 9
0=μ+(1 十μ)lnX
12 coefficient u
0.868ln2a
2αlnα
a'lna+1+±.a+1
(1.3.2-6)
(1 .3.2-7)
(1.3.2-8)
(1. 3.2—9)
(1.3.2—10)
(1.3.2—11)
13 Coefficient e
14 Coefficient ?
15 Coefficient n
0.512α2-1.195+0.683lna—273ln2αa2
1.3.3 Calculation result processing
(1.3.212)
(1.3.2—13)
(1.3.2 -14)
(1.3.2—15)
1 The maximum calculated stress in the inner edge (or outer edge) of the end plate is vmax and is compared with the allowable stress []. 1) If the maximum calculated stress avnax is less than or equal to the allowable stress [, the selected end plate thickness meets the design requirements.
2) If the maximum calculated stress avmax is greater than the allowable stress [, the selected end plate thickness cannot meet the design requirements, so the end plate thickness value is increased and the calculation is repeated until it passes. 83
2 Standard flange grade verification regulations
2.1 Scope of application
In addition to bearing internal pressure, the pipeline flanges of chemical plants must also withstand the axial force and bending moment caused by pipeline quality, thermal expansion, vibration, etc. In order to prevent leakage and possible damage under operating conditions, if necessary, the reliability of the selected standard flange grade shall be verified to determine whether further safety measures need to be taken.
This regulation applies to the grade verification calculation of standard flanges. 2.2 Calculation method
The method of converting external loads into equivalent internal pressure is used to finally verify and judge the flange grade. Explanation of symbols
Effective sealing width of gasket;
Basic sealing width of gasket;
Effective sealing width of gasket in operating state:
Diameter of center circle of bolt;
Diameter of center circle of gasket pressing force;
Diameter of bolt hole;
Axial force;
Bending moment;
M—Bending moment in direction of x;
M,—Bending moment in direction of y;
PDesign pressure;
P1—Equivalent pressure caused by axial force; P2Equivalent pressure caused by bending moment;
P—Equivalent total pressure acting on flange
Allowable working pressure of flange at operating temperature (t). 2.2.2 Calculation formula
1 Equivalent pressure calculation
1) Calculation of axial force converted to equivalent pressure
(2.2.2-1)
- axial force, N; F-force that makes the flange tensile is (+), F-force that makes the flange compressive is (-);
Dc-diameter of the center circle of the gasket clamping force, mm. 2) Calculation of moment converted to equivalent pressure
Pg=±16M
Where M-bending moment, N·m.
2 Calculation of equivalent total pressure
P=P+Pi+P,=P
2.3 Calculation requirements
2.3.1 Input data
1 Moment M
(2.2.2—2)
The moment on the flange has three directions, two of which are bending moments and the other is torque. The torque mainly affects the cross-sectional area of ​​the bolts, and the effect on the flange strength can be ignored. The two bending moments play a key role in the flange strength and leakage. Therefore, the moment M should be the composite bending moment. That is, M=VM+M
In the formula, the bending moment in the M direction, N·m;
(2.3.1—1)
The bending moment in the My direction, N·m.
2 Gasket DG value
The determination of the center circle diameter DG of the gasket clamping force depends on the flange form and sealing width. 1) Narrow face flange
For loose flange, the gasket Do value is the average diameter of the contact surface between the flange and the flange. a
bFor other types of flanges, it is calculated according to the following provisions a) When b<6.4mm,
b) When b. >6.4mm,
Dc-average diameter of the gasket contact surface;
DG=outer diameter of the gasket contact surface minus 2b.
Among them, the effective sealing width 6 is determined according to the following provisions: When b≤6.4mm, b=b.
When b. >6.4mm, b=2.53b.
2) Wide face flange
DG=D—(d+26\)
Where Db—bolt center circle diameter, mm; db-—bolt hole diameter, mm;
26\—operating state gasket effective sealing width, mm, 3 Allowable working pressure Pma
The allowable working pressure of the flange without impact at the working temperature is an important indicator to measure the reliability of the flange, and the flange is used to limit the working conditions. The allowable working pressure Ptmax should be obtained in accordance with the pressure-temperature grade regulations in the flange standard.
2.3.2 Output data
Equivalent pressure P. is the total equivalent pressure of the flange at the working temperature, that is, it takes into account the effect of external loads and is an important basis for determining whether the flange is safe to operate. P. The value should be taken as an absolute value. 2.3.3 Processing of calculation resultsbZxz.net
Grade verification should satisfy the following formula
P≤Pma
If P. >Ptax, the flange may leak at the working temperature. In order to ensure the safe operation of the flange, the following measures can be taken:
1) Reduce the axial force and bending moment (change the flexibility of the pipeline); 2) Improve the material grade of the flange;
3) Improve the pressure rating of the flange.
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