Basic knowledge of pressure pipeline inspection

1. Industrial pipeline on-line inspection, what parts should be focused on inspection?
(1) the outlet parts of the compressor and pump;
(2), compensator, three links, elbow (elbow), big head, branch pipe connection and dead angle of medium flow.
(3) piping components and welded joints near the damaged part of the support hanger;
(4) there have been parts of the problem that affect the safe operation of pipelines.
(5) the pipe section at the key part of the production process and the pipe section connected with the important device or equipment;
(6) severe working conditions or pipe sections subjected to alternating loads.
Industrial pipeline on-line inspection, what parts should be focused on inspection
2. why does the pipe stress analysis be carried out? What does it contain mainly? What are the purposes of various analyses?
Ensure the safety of the piping system, ensure the safety of the connected equipment, and ensure the safety of the civil structure.
Mainly including static analysis and dynamic analysis
Static analysis includes:
The primary stress calculation of pipelines under pressure and gravity loads prevents plastic deformation and failure.
The two stress calculation under the action of thermal expansion, cold contraction and additional load at end point – to prevent fatigue damage;
The calculation of the force acting on the machine and equipment by the pipeline prevents the excessive force and ensures the normal operation of the machine and equipment.
The force calculation of pipe hangers and hangers provides the basis for the design of supports and hangers.
Force calculation of flange on pipe to prevent flange leakage;
Displacement calculation of piping system to prevent pipeline collision and excessive displacement of supporting points.
Dynamic analysis includes:
Analysis of natural frequency of gas (liquid) column in reciprocating compressor (pump) pipeline to prevent resonance of gas (liquid) column;
Pressure pulsation analysis of reciprocating compressor (pump) piping — control pressure pulsation value;
Natural frequency analysis of pipelines to prevent piping system resonance;
Seismic analysis of pipelines to prevent excessive seismic stress of pipelines;
Stress analysis of pipelines under impact load – to prevent pipe vibration and stress is too large.
Displacement calculation of piping system to prevent pipeline collision and excessive displacement of supporting points
3. what is a stress? The two stress? Which loads are produced separately? What are the characteristics of these two stresses?
The primary stress is the stress generated by the interaction of pressure and gravity with other external loads. It is the stress required to balance external loads and increases with the increase of external loads. Features: there is no self limit.
The two time stress is caused by the constraint of pipeline deformation, which is caused by thermal expansion, cold shrinkage and endpoint displacement. It is necessary to meet the continuous requirements of constraints or the deformation of the pipeline itself. Features: self limiting.
4. what is pipe flexibility? How to carry out the flexible pipe design?
It is a concept reflecting the difficulty degree of pipeline deformation, which indicates that the pipeline absorbs heat accounts, cold shrinkage and other displacement deformation capacity through its own deformation.
In the design, the pipeline should be flexible enough to absorb the displacement and strain, so that the length of the pipeline should be as short as possible or the investment as little as possible.
Generally, the following methods are used to increase the flexibility of pipes:
Change the direction of the pipe;
Add wave compensator;
A spring hanger is used.
5. what is the purpose of flexible pipe design?
Ensure that the pressure pipeline has sufficient flexibility under the design conditions to prevent the following problems caused by the cold contraction of the heat account, the additional displacement of the endpoint, the improper installation of the pipe support and so on.
Pipeline failure caused by excessive stress or metal fatigue.
Leakage at the pipe junction;
Excessive thrust or torque of the pipeline will cause excessive stress and deformation to the equipment connected with it, which will affect the normal operation of the equipment.
Excessive pipe thrust or torque causes failure of pipe support.
6. generally speaking, which point of stress on the pipe is larger? Why?
Generally speaking, the stress on the three way and elbow pipe is larger. Because, compared with straight pipe, the stress increasing coefficient of the three way and elbow pipe is larger.
7. hangers? Can the fixed bracket, the guide bracket and the supporting bracket limit the displacement?
There are three functions of the pipe support and hanger.
To bear the weight load of the pipeline (including self weight, medium weight, etc.);
The function of the limiting position prevents the pipeline from moving in an unexpected direction.
Control vibration to control swing, vibration or impact.
Fixed frame: limiting the linear displacement in three directions and the angular displacement in three directions;
Guide frame: the displacement of two directions is limited.
The bracket (or one-way thrust frame) restricts the linear displacement in one direction.
 hangers? Can the fixed bracket, the guide bracket and the supporting bracket limit the displacement
8. what problems should we pay attention to when designing vibrating pipe supports?
The following questions should be paid attention to:
The bracket should adopt anti vibration pipe card, not simply supported.
The spacing of the support should be determined by the vibration analysis.
The support structure and the root of the scaffold should have enough stiffness.
An independent foundation should be set up to avoid rooting in the beam column of the workshop.
When the medium temperature in the tube is high and thermal expansion occurs, the flexibility requirement should be satisfied.
The support should be arranged along the ground.
Source: China Stainless Steel Pipelines Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)

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