FLAME SPREAD AND SMOKE & TOXICITY TESTING INTERPRETATIONS FOR PLASTIC PIPES

Lightweight composite materials are increasingly used in the ship industry as a substitute to their heavier steel alternatives. These materials are often inherently flammable and require an assessment of the fire risk associated with their flame spread and smoke & toxicity in order to enable their safe usage. However, for plastic pipes there are contradictions within the IMO (International Maritime Organisation) guidelines which lead to different interpretations and different implementations. The goal of this work is to evaluate whether smoke and toxicity is adequately assessed for products currently approved for use and commercially available on the market. Testing according to standardised means given in the IMO code shows that the materials fail both flame spread and smoke & toxicity testing. This proves that there are different interpretations and illustrates the need for clarity in this area to enable safe and consistent use of these materials.

Modeling Transient Pipe Flow in Plastic Pipes with Modified Discrete Bubble Cavitation Model

Most of today’s water supply systems are based on plastic pipes. They are characterized by the retarded strain (RS) that takes place in the walls of these pipes. The occurrence of RS increases energy losses and leads to a different form of the basic equations describing the transient pipe flow. In this paper, the RS is calculated with the use of convolution integral of the local derivative of pressure and creep function that describes the viscoelastic behavior of the pipe-wall material. The main equations of a discrete bubble cavity model (DBCM) are based on a momentum equation of two-phase vaporous cavitating flow and continuity equations written initially separately for the gas and liquid phase. In transient flows, another important source of pressure damping is skin friction. Accordingly, the wall shear stress model also required necessary modifications. The final partial derivative set of equations was solved with the use of the method of characteristics (MOC), which transforms the original set of partial differential equations (PDE) into a set of ordinary differential equations (ODE). The developed numerical solutions along with the appropriate boundary conditions formed a basis to write a computer program that was used in comparison analysis. The comparisons between computed and measured results showed that the novel modified DBCM predicts pressure and velocity waveforms including cavitation and retarded strain effects with an acceptable accuracy. It was noticed that the influence of unsteady friction on damping of pressure waves was much smaller than the influence of retarded strain.

A Comprehensive Review on Failure Analysis of Electrofusion Joint For Plastic Pipes

Electrofusion joint plays an important role in connecting plastic pipes and composite pipes. The safety of electrofusion joint has been of major concern affecting the pipeline system. Existing researches reveal that the failure of electrofusion joints is influenced by intrinsic factors such as welding and installation qualities, and external factors such as various load conditions. The combination of these factors would result in different failure modes of electrofusion joints. This paper provided a comprehensive review of current publications on failure analysis of electrofusion joints focusing on both the intrinsic and external factors. The former summarized premature failure of joints caused by incorrect production procedure before service, while the latter addressed the relation between failure modes and load conditions. Key factors affecting the failure modes were subsequently listed. Ultimately, based on current researches and industry hotspots, prospects on the development of electrofusion joint were discussed.

Assessing Ground Support of Plastic Pipes Using Ultrasound

The ability to detect early signs of failure in buried pipe infrastructure is necessary to facilitate the continued use of ageing infrastructure for delivery of society’s essential services and move beyond disruptive and expensive reactive maintenance and repair. This paper reports detailed experiments on the use of in-pipe ultrasound techniques for assessment of ground conditions around buried plastic pipes. Two sets of ultrasonic experiment on the soil conditions are presented: (1) existence, shape, and dimension of void, and (2) water content in the soil. The ultrasound technique is shown to be capable for detecting water filled voids and assessing the soil support, critical early indicators of failure. The technique requires water as the transmission media hence is naturally suited to application in operational water distribution systems. The work represents an important advance in in-pipe condition assessment of plastic pipes, demonstrates the practical capability of the ultrasound technique, which is critical for progression towards proactive maintenance, offering cost and service improvements.

INVESTIGATION OF VIBRATIONS OF A LIGHTWEIGHT GRATE ON ELASTIC SUPPORTS OF A COARSE LITTER CLEANER WITH RANDOM DISTURBANCE FROM RAW COTTON

The article discusses the results of theoretical studies of vibrations of a plastic grate on elastic supports of a coarse litter cleaner under accidental exposure to raw cotton. Graphical dependences of changes in displacements and vibration rate of the grate on changes in the coefficients of stiffness, dissipation and on the disturbing load from raw cotton at various values of the grate mass are constructed. Based on the analysis of the obtained graphical dependencies, the values of the system parameters are recommended. KEYWORDS: plastic grates, elastic supports, raw cotton, plastic pipes, mass, polyethylene, stiffness coefficient.

Drinking water contamination from the thermal degradation of plastics: implications for wildfire and structure fire response

Plastic pipes are susceptible to thermal degradation which can produce volatile organic compounds such as benzene, toluene, ethylbenzene, and xylene that leach into drinking water.