Mechanical
- Home
- Mechanical
The Mechanical Service encompasses all process and power piping, buried or above ground piping / pipeline, pressure vessels, boilers, tanks and many more. The piping may be subject to a feasibility study or studies during the design phase, but even more challenging are those piping systems that are part of the revamp of an existing plant (brown field) to maximize output. Flow-related problems such as slugging, surge-related phenomena and cavitation can also put severe loads on the piping. Pressure vessels, boilers, tanks, etc. can be, apart from the common pressure and thermal loads, subject to severe thermal gradients during start-up conditions, high cyclic loads giving rise to fatigue, and dynamic environmental loads such as wind and seismic activity. Sunrise has a good experience in solving these multidisciplinary mechanical problems. The most suitable software will be selected from a wide range of available software packages. Code calculations and finite element analyses (FEA) can be performed for Code compliance.
Piping / Pipeline Systems
Static analysis/piping flexibility study
Sunrise Engineering team conducts piping flexibility assessments of piping / Pipeline systems using the software Caesar II. The code stress is of course not the only criteria that should be considered to clear the piping & Pipeline systems, in our studies attention is paid to pipe stress, nozzle loads, flange loads and support loads. Special attention will be paid to the support configuration and supporting structure should large loads be unavoidable. The code stress should be within design envelope.
Sunrise Engineering team conducts assessments in conformance with industry standard American ASME B31 design codes. ISO 14692 for fiberglass.
Our engineers are adopt at taking special conditions into account, such as when piping is buried or on an offshore plant or FPSO, or when cold service means that the risk for brittle fracture needs to be evaluated. The recent code improvements in Stress Intensifications Factors (SIFs) and flexibilities for tees and bends as per ASME B31 J (2017) are also considered in our approach, which is especially applicable for thin walled piping.
Piping / Pipeline Systems
Static analysis/piping flexibility study
Sunrise Engineering team conducts piping flexibility assessments of piping / Pipeline systems using the software Caesar II. The code stress is of course not the only criteria that should be considered to clear the piping & Pipeline systems, in our studies attention is paid to pipe stress, nozzle loads, flange loads and support loads. Special attention will be paid to the support configuration and supporting structure should large loads be unavoidable. The code stress should be within design envelope.
Sunrise Engineering team conducts assessments in conformance with industry standard American ASME B31 design codes. ISO 14692 for fiberglass.
Our engineers are adopt at taking special conditions into account, such as when piping is buried or on an offshore plant or FPSO, or when cold service means that the risk for brittle fracture needs to be evaluated. The recent code improvements in Stress Intensifications Factors (SIFs) and flexibilities for tees and bends as per ASME B31 J (2017) are also considered in our approach, which is especially applicable for thin walled piping.
Dynamic analysis
Engineering does not always stop after the static analysis of your piping system. If there is a risk of dynamic forces on the piping, then these should also be considered at the design stage. Dynamic excitation can be either mechanical, such as direct forcing by vibrating equipment or seismic activity, or fluid driven such as pulsations or water hammer within the pipe.
Option 1: Model analysis This is the starting point for a dynamic analysis and here the mechanical eigenmodes (resonance modes) can be determined. This gives an insight into how susceptible a system is to excitation by a dynamic loading.
Option 2 : Cyclic Loading, fatigue failure is a risk When a loading is periodic, for example when a forced excitation by equipment is present, the possibility of fatigue failure needs to be considered. In this type of analysis, the loads will be applied periodically at a given frequency. It will then be calculated by how much a given mechanical resonance frequency will be excited. The arising code stresses will be checked for the conformance with the design fatigue curve such as those in ASME B31.3 section 302.3.5 (d).
Option 3 : Single event worst case loading, pipe rupture is a risk In the case of water hammer/pressure surges, the excitation force is not periodic (frequency of events is much lower that typical Eigenfrequency of piping system) and instead the risk to the piping is a large magnitude single event. In the analysis we will apply the dynamic loading as a function of time in a time history analysis. The arising stresses, and flange and nozzle loadings will be evaluated against occasional loading limits from the appropriate design code.
Pressure Vessels
Most pressure vessels will be designed using Design by Formula (DBF) according to ASME VIII Boiler & Pressure Vessel Code or EN 13445. However, not all loads and geometries can be considered with these standard design rules. For example, think of cyclic thermal loading, where the metal temperature distribution needs to be calculated, or the design of a nozzle with gussets or a nozzle close to a discontinuity in the shell geometry.
we regularly perform Finite Element Analyses (FEA) and assessments according to ASME VIII-2 Part 5 or EN 13445-3. For these analyses we use the software packages PV-Elite, ANSYS and FEA Pipe.
The most common use of FEA for pressure vessel design is for a cyclic loading assessment. Such an analysis is required if the vessel does not conform to the fatigue screening criteria in ASME VIII-2 Part 5.5 or EN 13445-3 5.4. Cyclic loading can lead to the accumulation of micro strain, crack initiation and crack growth. A crack will typically reach macroscopic dimensions and cause failure after a high number of cycles (typically in the order of thousands, but there is no fixed limit).
On the other hand, there is cyclic failure due to a limited number of cycles. This type of failure results from crack growth due to the buildup of plastic strain (ratcheting).
Pressure Vessels
Most pressure vessels will be designed using Design by Formula (DBF) according to ASME VIII Boiler & Pressure Vessel Code or EN 13445. However, not all loads and geometries can be considered with these standard design rules. For example, think of cyclic thermal loading, where the metal temperature distribution needs to be calculated, or the design of a nozzle with gussets or a nozzle close to a discontinuity in the shell geometry.
we regularly perform Finite Element Analyses (FEA) and assessments according to ASME VIII-2 Part 5 or EN 13445-3. For these analyses we use the software packages PV-Elite, ANSYS and FEA Pipe.
The most common use of FEA for pressure vessel design is for a cyclic loading assessment. Such an analysis is required if the vessel does not conform to the fatigue screening criteria in ASME VIII-2 Part 5.5 or EN 13445-3 5.4. Cyclic loading can lead to the accumulation of micro strain, crack initiation and crack growth. A crack will typically reach macroscopic dimensions and cause failure after a high number of cycles (typically in the order of thousands, but there is no fixed limit).
On the other hand, there is cyclic failure due to a limited number of cycles. This type of failure results from crack growth due to the buildup of plastic strain (ratcheting).
Steps in an FEA assessment
Step 1 : Thermal loading What is the temperature distribution within the vessel? Do significant local thermal gradients occur or are there large differences between components? Determining the (transient) heat transfer boundary conditions, and thereby the actual temperature distribution is a key part of most FEA analyses. Here we take care to ensure a conservative but credible case, which is either based on flow calculations with CFD, analytical formulas or HTRI results.
Step 2 : Calculate the stresses The calculated temperature distribution is used as a boundary condition in the FEA model, together with the other loadings such as pressure and nozzle loads. With an elastic material model, the calculated stresses need to be categorized, it needs to be considered which load is primary (or weight driven) or secondary (displacement limited). It is important to consider which loads should be combined, for instance what is the range for the startup/shut down, or the operating cycle, or does the pressure load always act simultaneously with the thermal loading.
Step 3 : Results and recommendations for the client The results from analysis will always be documented in a detailed technical report. This will include all the boundary conditions, details of the model setup and the analysis approach, and will be suitable for a rigorous review by a notified body. The report will also make sure that the results are explained to the client in a concise manner to build up to conclusions and practical recommendations.
Components & Specials
Detailed assessment of a flange connection Flanges are either standard ASME B16.5 or B16.47 flanges or custom flanges. However, neither of these design approaches provide a measure on the gasket sealing that is achieved or consider temperature gradients between the inner surface of the flange and the bolt.
Detailed analysis of a flange using FEA can provide an understanding of whether a flange will leak. For instance, how does thermal expansion in a heat exchanger affect the gasket sealing around a tube sheet circumference, will the gasket be crushed or lose contact? Or could a bolt be plastically deformed due to a radial thermal gradient.
Components & Specials
Detailed assessment of a flange connection Flanges are either standard ASME B16.5 or B16.47 flanges or custom flanges. However, neither of these design approaches provide a measure on the gasket sealing that is achieved or consider temperature gradients between the inner surface of the flange and the bolt.
Detailed analysis of a flange using FEA can provide an understanding of whether a flange will leak. For instance, how does thermal expansion in a heat exchanger affect the gasket sealing around a tube sheet circumference, will the gasket be crushed or lose contact? Or could a bolt be plastically deformed due to a radial thermal gradient.