Composed piece of seamless steel pressure pipes are generally standard, so the pressure piping components are primarily designed selection, pipeline pressure levels to determine their standard of its standard level is determined.

Pipe pressure rating: usually determined by a common pipe fittings standard nominal pressure rating and wall thickness of the pipe pressure rating that can reflects the parameters characteristic called pipe pressure rating. The customary to simplify the description, often to the pipe fittings nominal level called pipeline pressure rating. Pressure levels to determine the basis for the design pressure of the pipeline, but also the core design. It is the pressure piping, pressure piping design stress check preconditions pressure pipeline is an important factor in investment in infrastructure and pipeline reliability impact.

Different materials, the mechanical properties are different, the temperatures are in the standard - the corresponding value on the pressure gauge is not the same. Therefore, before determining nominal pipe material pipeline should first determine its components. It is determined by the choice of material design temperature, design and operation of the pressure medium. With forging material, while valve multi-cast material. No matter what material standard used, they should be the same level of material that has the same operating conditions, such as strength and adaptability; note pipe, plate, bar, cast material compatibility.

Allowable stress of the material refers to the material strength index value divided by the appropriate factor of safety obtained. Mechanical performance materials are yield limit, ultimate strength, creep limit, fatigue limit, these indicators reflect different states were failures limit. To ensure reliable operation of the pipe strength, the pipe element is often restricted to a value of stress at each intensity index, the value is the allowable stress. When the pipe element stress exceeds the allowable stress values, it believes its strength can not be guaranteed. So, to say, material allowable stress level is to determine the basic parameters of the pipe wall thickness.