Wall thickness is the first consideration in the piping system design. Once the design conditions (e.g., pressure, temperature, flow, and geometry) are determined, the pipe size as well as wall thickness could be selected. The wall thickness is also subjected to the material selections, the corrosion, errosion, welding procedure and inspection. For high pressure design, the wall thickness need to be determined by different rules and requirements.

Pipe flexibility analysis is the first important detail analysis to perform when designing pipe system. Flexibility analysis determines the piping system's capability to tolerate the possible thermal expansion/contraction or other movements of supports and terminal points. Flexibility is important to ensure the piping system not being over-stressed or fatigue under the secondary load conditions. Flexibility analysis also determines pipe layout and pipe supports locations. It can output the design loads for pipe supports and pipe joints (e.g., flange, expansion joint).

Dynamic analysis includes modal analysis, response spectrum analysis, hormonic analysis, and earthquake analysis. Dynamic analysis determines the response of the system under dynamical loads in a short duration. Natural frequency and model shapes are properties of the piping structure and are dependent on the mass the stiffness. For subsea piping system, added mass is another factor determining frequency. The free span of the subsea pipe is determined by the modal analysis.

Response spectrum analysis is used to determine the dynamical response of the pipe structure due to external load, mainly earthquake loading in piping system. This is also called earthquake analysis or seismic analysis. Earthquake loading is a low frequency phenomenon and usually modes with a frequency up to 33Hz are considered. An earthquake response spectrum normally vary depending on the location.

Harmonic analysis is normally used to analyze the effect of vibration due to oscillation loads, such as pumps, acoustics, pulsation flow, etc. A regular periodic force which oscillates from a maximum value to a minim value at a regular interval, is normally as a input to the harmonic analysis. If the harmonic frequency is near the natural frequency of the piping system, resonance of the pipe might happen, which will cause disaster failure. Therefore, it is important to perform harmonic analysis if the system has out-of-banance pump/compressors.

Other loads that also require dynamic analysis include, time history loads and impact loads. Dynamic load might also be replaced by dynamic load factor, and a static analysis could be used to replace the cost-comsuming dyanmic analysis. This is the normal practice in old time. For the modern piping system design, a detailed dyanmic analysis could be performed with the powerful computer system.

A fluid transient analysis is the dynamic analysis which handles the response of the piping system from the dynamic load resulting from fluid loads, such as, water hammer (sudden open/close of valve), steam relief, and slug flow. Other time-history fluid loads can also be handled by fluid transient analysis.

Water hammer is resulted from fast open/close of valves, pump shutdown/startup, or pipe rupture. The shock wave induced by the sudden change of the flow results pressure increase/decrease, which causes unbalanced force in pipe bends. The pressure change can be determined by the famouse Joukowski formula. The pipe span length decides the traveling time of the shock wave and therefore determines the magnitude of the unbalanced force. Therefore, water hammer can be optimized by reducing the length of a pipe span.

Other fluid transient analysis include steam relief valve analysis and slug flow analysis. They are basically a time-history analysis which determines the response of the piping system under time history loads. The thrust load at the valve exit piping due to discharge of the relief valve is the main time-history load in a steam relief valve analysis. Slug force in a two phase gas-liquid flow is the main load in a slug flow analysis.

The thermal and displacement loads require the piping system to be flexible enough, however, the dynamical and time history load require the piping system to be rigid. If the piping system is under both displacement and dyanmical loads, a balance between flexibiliby and rigidity need to be attained to meet the strength requirment of the codes and system. In this case, pipe support design is very critical and important, nonlinear pipe supports might be required.

Piping erosion relates the pipe wall thickness and flow design. Erosive wear is determined by flow velocity, impact angle, material, and particle in flow. DNV-RP-O501 and API 14E are the two widely used codes in pipe erosion analysis. DNV-RP-O501 gives detailed procedure for the corrosion rate of pipe. Tau Enginneering has successfully analyzed the erosion analysis in complex pipes for drilling manifold. Our analysis leads to the successful certification from DNV and deployment of the managed pressure drilling control piping system.