Predicting Service Life
The process for long-term service life prediction involves two assessments:
- The anticipated service conditions of the drainage pipe, including such factors as environmental conditions, soil and traffic loads, and the resulting long-term stresses and strains evident in the pipe, and
- The capacity of the material and the manufactured pipe product.
The service conditions of the pipe will vary by geographic location, based on temperature and soil and traffic loads. Deep installations may result in large compressive stresses on the pipe, while shallow installations are more subject to bending and tensile stresses. These bending and tensile stress levels are typically lower in magnitude than the compressive stresses associated with deep burial conditions, but they are considered a limiting condition as the material is more prone to failure in tension rather than compression.
The capacity of the material to resist failure is the second factor that must be addressed. Based on its wide use as a piping material (i.e. gas, water, industrial, oil field, etc.) polyethylene is a highly scrutinized material and its mechanisms of failure are well known. For corrugated drainage pipe, the primary mechanisms of material failure are slow crack growth and oxidation or chemical failure.