Service

In the field of strength calculations and assessments of high pressure equipment we offer a comprehensive services based on standard procedures and also nonstandard approach in cases where assessment of the equipment is beyond the standards (due to design or application conditions).

References in this field we have gained during solutions for energy and petrochemical industry. We benefit from over 20 years of experience with nonlinear finite element analyses and participation in expertises which require multi-disciplinary cooperation (material science, measurement and test).

Fig.1 Cross section of high pressure polyethylene reactor

Procedure by standard

Standard assessments of high pressure equipment are based on calculation procedures in according to standards, for example ASME BPVC Sec.VIII Div.3, which allows and in some cases requires the use of elastic-plastic FEM analyses.

Fig.2   Distribution of plastic deformation near radial holes, polyethylene reactor

Fig.3   Temperature field, normal operating conditions, polyethylene reactor

Integration of FEM calculations into standards allows comprehensive assessment not only principal dimensions, but also complex shapes of equipment including their interactions with surrounding systems.

Calculations procedures in according to standards are focused to assessment of all relevant damage mechanisms. Strength calculations address static strength, ratcheting and fatigue. Due to thick walls of assessed equipment resistance against crack growth (fracture mechanics) is also included.

Nonstandard approach

Current possibilities of nonlinear FEM analyses are far beyond approaches incorporated into standards. To describe the phenomena in material during cyclic loading beyond yield strength respectively creep temperatures were developed a wide variety of material models. A lot of them are also available in commercial software (e.g. Ansys).

Fig.4   Material model parameters set based on low cycle fatigue test

Nonstandard approach is the choice in cases, if assessment of atypical design / load condition is required. Usually experimental program dedicated to measurement of special material properties is the part of the solution. In such cases we offer research and development type services:

• problem analysis, solution methodology elaboration, coordination of specialist from the fields of material science and welding technology,
• ensure the experimental part of the solution (e.g. low cycle fatigue or creep tests),
• evaluation of the experimental program and material model parameters set,
• computational analyses focused on different aspects of design (selection of autofrettage pressure, optimization tasks, lifetime maximization, limit states of design).

Fig.5   Illustration of the calculation results evaluation, cumulation of plastic deformation in evaluated points, combined pressure and thermal load

Fig.6   Temperature field and creep deformation in thick walled vessel at partial melting of inner surface

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