A new method to calculate hydraulic transients in HDPE pipes using the standard solid model to represent the HDPE viscoelastic behaviour

Abstract

In this paper, a method for the calculation of hydraulic transients for pressurized flow in high density polyethylene (HDPE) pipes is developed. The proposed method incorporates the Standard Solid Model in the Method of Characteristics (MOC) to represent the viscoelastic behaviour of the pipe material. The Standard Solid Model is able to represent both a short-term elastic response and a long-term viscoelastic response. This model only requires the calibration of two parameters in a test facility, what is an advantage over other methods reported in the literature. The paper present how these parameters are calibrated. Keeping constant the wave velocity and the friction factor, the method estimates with high precision both the extreme values and the damping time of the pressure due to a water hammer in HDPE pipes. The results are compared against the data gathered over tubes with PPI 4710 resin (equivalent to PE100) in the test facility of a HDPE pipe producing plant, located in San Luis Potosí, México. The same procedure can be used to collect data of pipes made with other viscoelastic material. The main contribution of the paper is to avoid the need to perform calibration measurements during the start-up of the hydraulic systems.