Home >> Industry Knowledge >> Nitrogen Generator (Nitrogen equipment) Stress Analysis and Design
With modern low-temperature storage and transportation equipment (hereinafter referred to as: tank) in
Development, and tank sandwich pipe (referred to as: Pipeline) is designed to rise to
Related manufacturers widespread attention. Proper sandwich piping design, will
Have a reasonable stress distribution pipe to avoid stress concentration; and pipeline
During its use, it will not happen abnormal sound or even tear, resulting in something
So. Therefore, the sandwich piping design is good or bad, will directly affect the storage
Trough the quality and life expectancy, and even the use of security.
l tank piping stress analysis of sandwich
In order to design the best channel. Often the need for pipes to be
Force analysis. The use of analysis software for stress analysis. Can be solved out
Pipeline took a little stress and displacement can also be derived for supporting the anti -
Force and torque, the design of the pipeline has an important role. Pipe should
Force analysis of a variety of software, where the use of CAESAR II piping should be
Power analysis software, calculation and analysis.
CAESAR I1 analysis software is currently imported from abroad in various
The field is widely used pipe stress analysis software, which is the pass
Over pairs of consecutive simple tube sections and pipe sections on each node of the load input is indeed
Fixed pipe model, then the constraints of the various nodes, analysis and calculation
The pipe on each node of the displacement, load, stress and pipeline right of all
Bearing (including vessel wall) in the summer of force and torque. Analytical knot
Fruit can be exported in text or graphics. CAESAR I1 analysis
Software output are generally three kinds of load combination states: operation (work
To) state, bearing (bearing) state and the endpoint displacement and temperature-like
State. Analysts can also be based on actual needs, determine their own load
CAESAR I1 analysis software is used on a typical two tank
Sandwich piping analysis description for reference.
1.1 tankers into the liquid pipe stress analysis
1.1.1 Analysis of hazardous conditions and boundary input
Tankers into the drain pipe as shown in Figure 1, the pipeline directly from within the head
Citation to the outer head. Diameter: 45mm x 3mm, operating temperature:
1 196 oC, operating pressure: 0.8MPa, Material: A312 TP304
(B31.3, with 0Crl8Ni9). Tankers in the preliminary into the liquid, the content
Devices, pipelines have dramatically from hot to cold state of the transition state, therefore, keep
A large thermal stress is the most dangerous working conditions. According
CAESAR I1 analysis software requirements for the input boundary conditions
Entry: gratuitous point displacement at both ends of the pipeline to connect with internal and external head office in accordance
BS 5500 standard to establish nozzle model does not consider interlayer insulation material
Figure 1 arm through the car into the liquid
1.1.2 Pipe Stress Analysis Results
CAESAR I1 analysis software according to the given conditions on the tank car into the liquid
Pipe automatic analysis and the results are as follows:
(1) The maximum stress in the pipe and the outer head junction, and its value
To 498MPa, far more than the allowable stress range pipeline. Actual
On the production of pipeline in Figure 1 have been broken.
(2) Head in the pipeline with internal and external connections are linear displacement and angular
(3) in the pipeline connections with the outer head in the Y direction reaction force
To 13701N, moments in the z direction for the 1942N · in, moments too large.
With results from the analysis, pipeline junction with the outer head bending over
Large, eventually leading to where the stress is too large may have reached a pull pipeline
Split level. Therefore, this a serious shortage of flexible pipes. Design,
Should refer to Figure 2 (a), (b) the structure to determine the pipeline structure.
1.2 large-scale cryogenic liquid storage tank bottom liquid discharge pipe stress analysis
1.2.1 Analysis of hazardous conditions and boundary input
The bottom row of large-scale cryogenic liquid storage tank liquid pipe as shown in Figure 3, the
Pipeline directly from the device backplane cited the contents of the container to the outer cylinder of the problem is a kind of
Commonly used liquid discharge pipe structure. Pipe diameter: 159mm X 5mm,
Operating temperature: a 196 ~ C, operating pressure: 0.2MPa, Material:
A312 TP304 (B31.3, with 0Crl8Ni9). Pipeline of the most dangerous
Draining the tank usage when the device filled with liquid contents at this time, and
Carried out a full shrink, shrink the amount of take 13.2mm (in 1000 Ⅱ l3 storage
Figure 2 The improved tank car into the liquid pipe
CAESAR · I1 analysis software according to the requirements for the boundary input
Entry: Pipeline and content according to device backplane connections clamped (with endpoint position
Shift) the establishment of model junctions with the outer packaging according to standard WRC297
The establishment of nozzles model does not consider the impact of sandwich insulation materials.
Figure 3 bottom row of large-scale cryogenic liquid storage tank liquid pipe
1.2.2 Pipe Stress Analysis Results
CAESAR I1 analysis software based on the input, under the conditions of the tank
The Ministry of liquid discharge tubes automatically analyzed, analytical results are as follows:
(1) The maximum stress is located at the third bend, and its value is
297MPa, the pipe is less than the allowable stress range, but more than the material
Material yield limit.
(2) The liquid discharge tube and outer container is connected to the line at large displacement,
For a 3.6mm, this is the case in practice there have been consistent.
(3) The fulcrum constraint forces too great. The direction of counter-force to
To see from the above analysis, pipeline junction with the outer container, some
Line displacement is too large deformation of the outer packaging large, does not meet the requirements. Because
Therefore, this lack of flexible pipes. According to the channel characteristics, the current design of
The pipeline has been connected with the outer container at an increase of bellows.
2 tank sandwich piping design principles
Tank on the face of two typical sandwich piping stress analysis done
Shows that the reasons for the limited space, it is impossible for all tank pipe
The stress analysis is for illustration. In fact, I use CAESAR
Ⅱ analysis software, for many have carried out tank pipe stress analysis,
Some find that the existing pipeline design is obviously unreasonable. Here, the sum
Out of six tanks sandwich piping design principles, for reference.
(1) tank sandwich piping design, we should try to increase the pipeline
Flexibility, to improve the stress distribution pipelines. Such as changes in pipe direction, by
Canadian elbow and bellows and so on.
(2) For tankers, due to structural reasons, into the fluid control and safety
Venting tube from the inside leads to head office, the need to use the knot as shown in Figure 2
Structure, and to improve the pipeline flexibility, reduce stress pipelines. Horizontal Vacuum Storage
Trough similar situations, we should also adopt this structure.
(3) For vertical vacuum tank, since the content of fixed-point devices
Is located in the drop-down belt and the outer packaging of the junction, fluid-filled device in the content, the
The drop-down zone will shrink, driving up the bottom of the content of devices, which led to the next
The Ministry of liquid discharge pipe with a larger secondary stress, especially for more than 50m
Tank of large diameter pipes (DN ≥ 65mm), the stress values will be very
Great. For this pipeline should look for ways to increase the flexible pipe or kapa patterns
(4) For large-scale cryogenic liquid storage tank bottom row of catheters, because of
Large in diameter, while the content of device backplane (or cylinder) has a great beginning
Start (endpoint) displacement, therefore, x ~ ~ t-Vessel great pull
Force would often pull deformation of the outer packaging. The pipeline is difficult to rely on pipelines to increase self -
Flexible body to change the stress state, therefore, only the outer container is connected to
Add the corrugated compensator.
(5) For the upper part of a large cryogenic liquid tank into the liquid pipe and pump
After the return pipe, due to longer pipelines require a lot of support hanger (branch
Cheng). Analysis software CAESAR Ⅱ analysis showed that the pipeline
Should only be installed on a fixed bearing, the other should be a sliding bearing.
In this way, flexible pipe increases, stress less. In determining the installation of sliding
Bearing Department, should not adopt the form of packets hoop supports, because such support
Bearing, it is difficult to judge is a sliding bearing or fixed bearing.
(6), bearing mezzanine within the pipeline should be minimal. Non-bearing position
Often important, supported properly, will substantially increase the stress level of the tube.
ROC examples in this regard.
3 Conclusion
Tank sandwich piping design is an important tank design
One, it is designed properly, will lead to security incidents. And tank
Are double-vessel, with a hidden, maintenance is also very inconvenient. Because
Of this, the tank should be designed to sandwich the pipe caused by the designer sufficient weight
TV, making piping design, stress analysis should be carried out. When
Really can not stress analysis, pipeline design should be above the original
The design.