Compressor Design Studies

Along with choosing a DA2 or DA3 study for your reciprocating compressor design, here are four more useful studies to consider.

• Small Bore Piping Analysis
• Dynamic and Static Stress Calculation on Pulsation Bottle Internals (formerly M.8)
• Compressor Valve Dynamic REsponse Study (formerly M.9)
• Pulsation Bottle Low Cycle Fatigue Anlaysis (formerly M.10) 

Small Bore Piping Analysis
API 618 Studies address the acoustical and mechanical interaction in the main piping but do not address high cycle fatigue in small bore piping or attachments. Our standard analysis will provide recommendations with regard to small bore piping based on good design practices; however a detailed analysis is not included in the scope.

There are three common methods to avoid vibration on Small Bore Piping:

• Likelihood of Failure assessment. This level considers the attachment service, location and geometry to arrive to a Likelihood of Failure as per the "MTD Ltd. Guidelines for the Avoidance of Vibration Induced Fatigue in Process Pipework. Publication 99/100. 1999". The outcome of the analysis is recommendations on whether the attachment should be modified, braced or monitored at commissioning.
• Finite Element Modeling. This approach is available, but may not be a practical solution.
• Field Test: Onsite measurements and recommendations to fix small bore vibration problems. 

Dynamic and  Static Stress Calculation on Pulsation Bottle Internals (formerly called M.8)
This analysis applies pulsation-induced shaking forces and pressure-induced static forces to the shell and vessel internals and computes stress levels to met API 618 guidelines.

The primary dynamic load acting on the baffle is the unbalanced force resulting from the pressure pulsations. The overall unbalanced force is calculated by the acoustical simulation. The overall unbalanced force is applied as a pressure firstly to the concave then the convex side of the baffle to calculate the alternating stress. The vessel design pressure is also applied to the inside of the shell.

This loading is applied to an axisymmetric finite element model of the baffle and pulsation bottle shell. The model is created using the ANSYS 11.0 analysis software. The model uses 3D solid elements or 2D plane axysmmetric to simulate the baffle and shell deflection.

Compressor Valve Dynamic Response Study (formerly called M.9)
This analysis predicts compressor valve behavior and, if required, recommends modifications to the proposed valves or selects alternate valves.

Pulsation Bottle Low Cycle Fatigue Analysis (formerly called M.10)
When required by Division 2 of the ASME code, this analysis is used to predict the stresses from thermal gradients, thermal transients, and pressure cycles on the pulsation-suppression devices and internal components. The stresses are compared to ASME-code allowable.