Cold Shoe Simulation

INSTRUCTIONS FOR USING ABAQUSCAE IN ANALYZING PIPE WITH A CRACK

Slug Flow "Sample Slug Problem"

"10 points to keep in mind while using project specific pressure vessel nozzle load tables during stress analysis."

Every EPC company must have project specific pressure vessel nozzle loading tables which are used for comparing allowable nozzle loads for vessels, columns or towers, heat exchangers, Drums or any similar type of equipments. Normally forces and moments at the nozzle and shell interconnection are provided in a tabulate format. These force and moment values are decided based on the following major factors:
1. Nozzle diameter
2. Connected flange rating
3. Equipment and nozzle thicknesses.
4. Equipment diameter etc.


Using these tables are quite simple. However we must keep in mind few points while using those tables. This article will list out few important points for using these tables easily.
1. Before checking the tables, find out the load and moment directional drawing from which we have to correlate the Caesar II axis.
2. Each nozzle, including those designated “spare” but with the exception of man-holes and instrument nozzles shall be designed to withstand the forces and moments specified herein. The indicated loads are to be considered to act at the shell/head to nozzle intersection.
3. For nozzles matching with any global direction (other than head nozzles) compare the values mentioned on the tables with global force values in CAESAR II output.
4. For inclined nozzles in horizontal plane (with respect to any global direction) there are 2 options
a) Compare loads mentioned on the tables above with local element forces in CAESAR II output. On that case local X force will be radial force, compare other directions to get proper forces.
b) Otherwise rotate the CAESAR II input model to match the nozzle axis with any global Caesar II axis and compare the loads and moments.


5. For Head nozzles (nozzle axis and equipment axis same direction) compare Mx and Mz as per √[{(Mx)2+(Mz)2}] ≤ √[{(ML)2+(MC)2}]
6. In case of any vessels in packaged area, these values shall not be applicable and nozzle loading shall be coordinated with vendor.
7. In case of any licensor / proprietary item, these values shall not be applicable and nozzle loading shall be confirmed by them.
8. Allowable for self reinforced nozzle shall be more than as mentioned in above table. In that case allowable shall be exercised from vendor.
9. For jacketed nozzles loads are to be confirmed from vendor.
10. This tables are not applicable for checking loads at flange faces.

نرم افزار اندرویدی Pipe data pro جهت محاسبات کلیه اقلام پایپینگ

Fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. Continued cycling of high stress concentrations may eventually cause a crack which propagates and results in leakages. This failure mechanism is called fatigue. Damage once done during the fatigue process is cumulative and normally unrecoverable.
Fatigue can be grouped in two classes; High cycle fatigue and low cycle fatigue.
High cycle fatigue involves little or no plastic action. Therefore, it is stress-governed. Normally, a fatigue curve (also called the S–N curve) is generated for every material by experimental tests which correlates applied stress with the number of cycles to cause failure. For high-cycle fatigue, the analysis is performed to determine the endurance limit, which is actually a stress level that can be applied for an infinite number of times without showing any failure. As a general rule no of cycles 10^5 is considered as demarcation point for high and low cycle fatigue.

The loading cycles applied in piping design are normally very few in the order of a few thousands. This type of fatigue is identified as low-cycle fatigue. For low-cycle fatigue, the applied stress normally exceeds the yield strength of the material, which causes plastic instability in the specimen under test. But when strain is used as the controlled variable, the results in low-cycle region are reliable as well as reproducible.
Sources of Fatigue:
For piping system, cyclic loadings are primarily due to:
• Thermal Expansion & Contraction
• Vibration due to Occasional loading
• Pressure variation within Piping system
• Motion wave.
• Due to Flow induced Vibration
The fatigue process is divided into three stages: crack initiation from the continued cycling of high stress concentrations, crack propagation to critical size, and unstable rupture of the section.
Factors Affecting the Fatigue Behavior:
The factors which affect the fatigue behavior are listed below:
• Type and Nature of Loading.
• Size of Component and stress or strain Distribution.
• Surface finish and Directional Properties.
• Stress or Strain Concentration.
• Mean stress or Strain.
• Environmental Effects.
• Metallurgical Factors and Material Properties.
• Strain Rate and Frequency Effects.

spring support failure

SAFETY ALERT FOR INSTALLATION
OF SPRING SUPPORTS

BASICS OF PIPE STRESS ANALYSIS

Structural Integrity:
• Design adequacy for the pressure of the carrying fluid.
• Failure against various loading in the life cycle. Limiting stresses below code allowable.

Operational Integrity:
• Limiting nozzle loads of the connected equipment within allowable values.
• Avoiding leakage at joints.
• Limiting sagging & displacement within allowable values.

Optimal Design:
• Avoiding excessive flexibility and also high loads on supporting structures. Aim towards an optimal design for both piping and structure.