Proper materials selection provides safety against brittle fracturing of piping. Important considerations in the selection of construction material for a safe piping system include:
- Material compatibility with process fluids under all operating and accidental pressure and temperature parameters
- Changes in concentration and/or content of the fluids carried in piping and the surrounding environment
- Erosion and corrosion mechanisms that may be present
- Past experience from similar operating plants.
Piping material specifications (PMS) are developed in line with ASME B 31.3 fluid service categorization, with an emphasis on standardizing all piping commodities for use on a project. A well-defined PMS in an automated engineering environment eliminates any chance of casual or unintended errors and helps ensure that intended safety procedures at the PMS design stage will be translated to construction deliverables.
For non-metallic piping materials, various limitations such as temperature, pressure, sensitivity to ultraviolet light, surge, impact loads, vibration and higher thermal expansion coefficient must be carefully accounted for when determining material specifications. The weaknesses of these materials usually require closer pipe supports and, in many cases, a continuous structural support is considered a more viable solution.
Underground piping must withstand external loads in addition to internal fluid pressure. Underground piping must be capable of bearing the soil load above it, groundwater buoyancy, traffic loads from the surface and loads caused by potential earthquakes. Leakage detection and repair are inherently difficult in underground piping, so it must be limited to non-hazardous services and requires cathodic protection, coating, wrapping and encasing.
