Polyvinyl Chloride Pipelines Research Articles

(Digital Presentation) Life Cycle Cost and Technical Analysis of Corrosion Control Methods to Prevent Failures in Water Service Systems

INTRODUCTION Water service systems, such as drinking/potable water and process water (e.g., cooling water), are undoubtedly strategic in any industrial installation. Their continuous, reliable and quality-controlled operation must be therefore guaranteed. The stable operation of a water supply system (and of other processes/areas) depends on many factors, namely: preventive maintenance, operation within the range of specific conditions and appropriate design, among others. In a petrochemical estate, especially in the Caribbean where all-year-round exposure to harsh environmental conditions aggressively enhances corrosion, high corrosion-related remediation costs are incurred if appropriate corrosion protection/minimization methods, such as corrosion control by materials selection and/or intervention corrosion control techniques, were not implemented during the design and construction phases and/or are not currently in place, respectively. The focus of this study is to perform a combined life cycle cost and technical aspects analysis in order to evaluate the feasibility of several corrosion prevention techniques for two important and strategic pieces of plant equipment: a potable water tank and a direct cooling water (DCW) pipeline, in use at several companies at a petrochemical estate located in the Caribbean. At least five (5) different construction materials for both pieces of equipment under study were selected for the analysis. Cost estimates from different sources (vendors, suppliers, providers) were obtained. All costs were discounted by applying an appropriate discount rate. For convenience and to facilitate the comparison in the cost analyses, normalization of all costs to those of the (total) initial costs of the two pieces of equipment to be evaluated was done. An adequate service life of 30 years was selected for this study. METHODOLOGY Corrosion prevention methods: materials selection - Potable water tank Five (05) different materials, some combined with different coatings and other corrosion protection techniques, are considered as replacements: Stainless Steel 304 grade tank (SS 304 Tank), Hot Dipped (Zinc) Galvanized Steel Tank (HDG STank), Chlorinated Rubber coated Steel Tank with Cathodic Protection (CRC STank CP:), Polyurethane coated Steel Tank with Cathodic Protection (PUC STank CP), and (inorganic)Zinc Silicate coated Steel Tank with Cathodic Protection (ZnSC STank CP). - Direct cooling water (DCW) pipeline Five (5) different alternatives(materials) are considered as DCW pipeline replacements, in addition to a new (inorganic)Zn-silicate coated steel pipeline (ZnSC SPipe): Polyvinyl Chloride pipeline (PVC Pipe), Ductile Iron Pipeline (DuctI Pipe), Hot Dipped (Zn) Galvanized Steel Pipeline (HDG SPipe), Fusion Bonded Epoxy coated Steel Pipeline (FBEC SPipe), and 3-Layer Polyethylene coated Steel Pipeline (3LPEC SPipe). Life Cycle Cost Analysis (LCCA) The LCCA was carried out in accordance with the appropriate ASTM standard [1]. A reasonable 30-years life cycle was taken into consideration, as in other studies [2]. After calculating costs and in order to standardize and facilitate the comparison among the different techniques under study, all the LCC results were normalized to the (total) initial costs of purchasing (new) current equipment, (potable water) mild steel tank and (DCW) Zn-silicate coated steel pipelines. CONCLUSIONS A combined life cycle cost(LCC) and technical feasibility analysis of several corrosion control methods to prevent failures in water service systems at a petrochemical complex was carried out. A potable water tank and a direct cooling water (DCW) pipeline were the equipment chosen in the study. For the potable water tank, using SS304 as the material of construction was proven to be the best option(Figure 1) to replace the current (mild) steel tank. In the case of the DCW pipeline, keeping a currently installed zinc-silicate coated steel pipeline was a suitable choice. This study highlights the imperative nature of managing corrosion by selection of fabrication materials in plant equipment to minimize maintenance activities and to avoid failures associated with corrosion. REFERENCES [1] "Life-cycle cost analysis of corrosion protection systems is focus of new ASTM iron and steel product standard", Anti-Corrosion Methods and Materials, Vol. 58 No. 4 (2011)[2] D. Kowalski, B. Grzyl & A. Kristowski, The Cost Analysis of Corrosion Protection Solutions for Steel Components in Terms of the Object Life Cycle Cost. CEER 26 (3): 005-013 (2017) FIGURE CAPTIONS Fig. 1. Cumulative discounted & normalized LCC for potable water tank alternatives. The even slighter increment that Zn Silicate coated steel tank with cathodic protection (CP) alternative exhibits every 12 years is due to cost of replacing the zinc coating; while the CRC and PUC options present slight increments (not noticeable) every 3 and 4 years, respectively, due to the need of their respective coating´s replacement. Also, every 20 years the CP for the ZnSC, PUC and CRC STanks is replaced (not noticeable in their respective lines). Figure 1

Deformation capacity of buried hybrid-segmented pipelines under longitudinal permanent ground deformation

Innovative hybrid-segmented pipeline systems are being used more frequently in practice to improve the performance of water distribution pipelines subjected to permanent ground deformation (PGD), such as seismic-induced landslides, soil lateral spreading, and fault rupture. These systems employ joints equipped with anti-pull-out restraints, providing the ability to displace axially before locking up and behaving as a continuous pipeline. To assess the seismic response of hazard-resistant pipeline systems equipped with enlarged joint restraints to longitudinal PGD, this study develops numerical and semi-analytical models considering the nonlinear properties of the system, calibrated from large-scale test data. The deformation capacities of two hybrid-segmented pipelines are investigated: (i) hazard-resilient ductile iron (DI) pipe and (ii) oriented polyvinylchloride (PVCO) pipe with joint restraints capable of axial deformation. The numerical analysis demonstrates that, for the conditions investigated, the maximum elongation capacity of the analyzed DI pipe system is greater than that of the PVCO pipeline. The implemented semi-analytical approach revealed that the pipeline performance improves strongly by increasing the allowable joint displacement. Comparison of the numerical results with analytical solutions reported in recent research publications showed excellent agreement between the two approaches, highlighting the importance of assigning appropriate axial friction parameters for these systems.

Pressure data-driven model for failure prediction of PVC pipelines

Polyvinyl chloride (PVC) pipes are used extensively in water infrastructure due to their lightweight, low cost, and ease of jointing. Failure occurrences in PVC pipes are attributed to poorly manufactured pipes, bad installation, excessive operating conditions, or third-party damage. Data-driven modeling techniques have been widely used in simulating and solving water infrastructure problems, specifically when the collected data are limited. The objective of this paper is to develop a data-driven modeling system that utilizes computational approaches and provides the analytical underpinnings to predict future PVC pipe failures. The system is based on data from El Pedregal City in Peru, simulation and regression algorithms, and supported by easy-to-perceive schematic representations. The hydraulic pressure and flow rate data are streamlined and fed to the regression machine. Subsequent to successive simulation iterations and various polynomial functions, the best fit model is selected. The efficacy of the model is investigated via different performance metrics, in tandem with a residual analysis scheme. The validation results revealed the robustness of the model with mean absolute error (MAE) of 0.35. The proposed model is a predictive tool that can be used by utility managers as a proactive measure against future pipeline bursts or leaks.

Bending behavior of glass fiber reinforced composite overwrapping pvc plastic pipes

The challenge associated with the use of polyvinyl chloride (PVC) plastic pipelines is to improve their structural integrity without increasing their cost. Currently, PVC pipelines are the most cost-effective method of transporting water and sewage drainage. However, their low deterioration and mechanical properties cause significant losses and sacrifice the structural integrity of pipelines. Therefore, this study proposes the glass fiber-reinforced polymer (GFRP) overwrapped system to strengthen the external surface of PVC pipes, which will improve pipes’ flexural load-carrying capacities. Accordingly, an extensive experimental program is developed and performed to examine the flexural behavior of GFRP composite overwrapped onto PVC plastic pipes. These phases include the fabrication process and different types of tests for evaluating the structural integrity of the GFRP/PVC pipes. The results showed that the proposed overwrapped system significantly improved the flexural carrying capability. The initial flexural failure load increased significantly, with an improvement from 64 to 1140 N. Also, the ultimate flexural load found to be improved by a factor of nine. The flexural behavior was significantly affected by changes in the fiber orientation angle. The results also revealed that as the pipe diameter increased, the flexural carrying load capacity increased. It is also important to note that the matrix cracking, fiber debonding, and fiber breakage were dominating the failure modes of GFRP/PVC pipes.

Segmented pipeline damage predictions using liquefaction vulnerability parameters

Past observations showed that pipeline damages in liquefaction zones are significantly higher than the damages in areas where there was no liquefaction. Existing vulnerability relationships for the pipelines in liquefaction zones utilize parameters such as ground displacement, horizontal ground strain, angular distortion or both. These relationships are particularly useful in performance or risk assessment of pipeline systems. However, prediction of these parameters for pipeline damage estimates is difficult to perform and highly variable with current procedures. This paper proposes new correlations of asbestos cement (AC), cast iron (CI) and polyvinyl chloride (PVC) pipeline damage, expressed as repairs/km, with three different liquefaction parameters: liquefaction severity number (LSN), one-dimensional volumetric reconsolidation settlement (SV1D), and liquefaction potential index (LPI). The pipeline damage data from 22 February 2011, Mw = 6.2 Christchurch earthquake and geotechnical information pertaining to liquefied area in Christchurch are utilized herein. Cone penetration test (CPT) based Boulanger and Idriss [1] liquefaction triggering procedure with 15th, 50th and 85th percentile cyclic resistance ratio (CRR) curves (corresponding to probabilities of liquefaction, PL, equal to 15%, 50%, and 85%) was used to calculate the parameters. It is shown that the relationships between AC, CI and PVC pipeline damages and LSN, SV1D and LPI are strong, except for the correlation for AC pipeline damage versus LPI. Considering CI and PVC pipelines, both LSN and LPI correlations are comparable and slightly better than SV1D correlations. Use of different probabilities of liquefaction triggering does not have significant effect on correlations with LSN and SV1D whereas the same is not true for LPI correlations. Regarding the resilience of pipelines, PVC and AC pipelines performed the best and worst, respectively in all cases with CI pipelines in the middle. The correlations have the potential for use with existing or new liquefaction hazard maps for prediction of pipeline damage from future earthquakes.

Pipeline deformation monitoring using distributed fiber optical sensor

Deformation of long distance pipeline takes place more easily under the various adverse factors such as freezing-thaw and earthquake, and oil and gas often leak from the broken pipeline once the deformation has exceeded a previously established threshold. In order to solve the hot issue on the pipeline deformation monitoring, this research was launched on the basis of the combination of distributed fiber optical sensor and conjugate beam method. One finite element model of a pipeline with the length of 50 m and one PVC (Polyvinyl Chloride) pipeline with the length of 4 m were constructed to validate the deformation method, respectively. The finite element pipeline model was loaded vertical displacement at different positions simultaneously, and the PVC pipeline was gradually applied different level of loads at the midspan. In the two tests, the continuous or distributed strain data and the discrete strain data were used to calculate the deformation of the pipeline based on the conjugate beam method. In order to validate the deformation monitoring method, a comparison between the displacement curve calculated by the distributed strain data and that calculated by the discrete strain data was conducted. The results of the two tests indicate that the deformation of the pipeline can be well monitored and the method can be applied to the field applications.

Distributed fibre optic sensing of strains on buried full-scale PVC pipelines crossing a normal fault

Seismic faulting is extremely detrimental to buried pipelines owing to bending moments and axial forces generated by the soil–pipe interaction. Pipe responses to ground rupture are usually evaluated by beam-on-spring analysis. However, the empirical data used to define the spring response were obtained for steel pipes with high flexural stiffness and the effectiveness of the resulting spring stiffness values for flexible pipes is questionable. This paper presents full-scale tests undertaken using a new split-box apparatus which permits the testing of pipes in dry sand subject to a normal fault with dip angle of 90°. Four polyvinyl chloride (PVC) pipes (various diameters), one instrumented with strain gauges and three instrumented with fibre optic sensors, were tested to provide experimental evidence for flexible pipes. The research includes confirmation of the effectiveness of fibre optic strain measurement, which has the advantage of providing much more data than the limited discrete values obtained from conventional strain gauges. However, the fibre optic strain sensing technique is limited to strain values below 1%. The prototype-scale testing permits assessment of the efficacy of the current design approaches, including the relative success of accounting for reduced spring stiffness or patterns of imposed deformation.

Evaluation of biofilm development on various pipelines in the domestic hot water system

Abstract Biological safety of hot water is important, and it is affected by pipeline material to a certain degree. Polypropylene random (PPR), polyvinyl chloride (PVC) and stainless steel (SS) are the common materials for pipelines in domestic hot water systems (DHWS), and biofilm growth characteristics, and biofilm microbial communities and biological diversity on the walls of pipelines are affected by the pipeline materials to a certain extent. In this paper, the effects of different materials on the growth characteristics and diversity of microbial communities were studied. The results showed that after about 60 days, the bacteria of the biofilm on the wall of pipelines completed a microbial growth cycle. Compared with PPR and SS, a greater amount of the total number of bacteria, Escherichia coli and heterotrophic plate count (HPC) attached to the PVC pipeline. Although the types of bacteria on the pipelines were similar, the proportions of species were different. Proteobacteria were the dominant bacteria at the phylum level on all the walls of the PPR, PVC and SS pipelines, and the dominant bacteria at the genus level changed before and after the exfoliation of biofilm. Some potential pathogens, such as Pseudomonas and Legionella, were detected in biofilm, so effective biofilm disinfection should be considered to ensure biological safety in DHWS.

Response of the Christchurch water distribution system to the 22 February 2011 earthquake

The effects of transient and permanent ground deformations during the 22 February 2011 earthquake on the Christchurch water distribution system are investigated through geospatial analysis with the most detailed and accurate databases currently available. Using the most recent repair records, ground motion records, high resolution Light Detection and Ranging (LiDAR) data collected before and after the earthquake, and improved screening criteria, repair rates, expressed as repairs/km, for different types of pipeline are correlated with 1) peak ground velocity outside liquefaction areas, and 2) differential ground surface lateral and vertical movements in liquefaction areas. The substantial influence of LiDAR resolution on the relationship between pipeline damage and lateral ground strain indicates sensitivity of repair regressions to the degree of data resolution. Repair regressions of different pipelines show that polyvinyl chloride pipelines are markedly more resilient to earthquake effects than other types of segmental pipelines in the Christchurch system. The analytical process is described in detail for assistance in future investigations with data sets of similar size and complexity.

PVCO Pipeline Performance Under Large Ground Deformation

Technological advances have improved pipeline capacity to accommodate large ground deformation associated with earthquakes, floods, landslides, tunneling, deep excavations, mining, and subsidence. The fabrication of polyvinyl chloride (PVC) piping, for example, can be modified by expanding PVC pipe stock to approximately twice its original diameter, thus causing PVC molecular chains to realign in the circumferential direction. This process yields biaxially oriented polyvinyl chloride (PVCO) pipe with increased circumferential strength, reduced pipe wall thickness, and enhanced cross-sectional flexibility. This paper reports on experiments performed at the Cornell University Large-Scale Lifelines Testing Facility characterizing PVCO pipeline performance in response to large ground deformation. The evaluation was performed on 150-mm (6-in.)-diameter PVCO pipelines with bell-and-spigot joints. The testing procedure included determination of fundamental PVCO material properties, axial joint tension and compression tests, four-point bending tests, and a full-scale fault rupture simulation. The test results show that the performance of segmental PVCO pipelines under large ground deformation is strongly influenced by the axial pullout and compressive load capacity of the joints, as well as their ability to accommodate deflection and joint rotation. The PVCO pipeline performance is quantified in terms of its capacity to accommodate horizontal ground strain, and compared with a statistical characterization of lateral ground strains caused by soil liquefaction during the Canterbury earthquake sequence in New Zealand.

Novel vibration-based technique for detecting water pipeline leakage

Exacerbating the imbalance between demand for freshwater and available water resources is the sub-optimal performance of water distribution systems, which are plagued with leaks that cause significant losses of treated freshwater. This paper presents an approach for leak detection that involves continuous monitoring of the changes in the correlation between surface acceleration measured at discrete locations along the pipeline length. A metric called leak detection index is formulated based on cross-spectral density of measured pipe surface accelerations for detecting the onset and assessing the severity of leaks. The proposed non-invasive approach requires minimal human intervention and works under normal operating conditions of the pipeline system without causing any operational disturbances. The approach is demonstrated on a 76 mm diameter polyvinyl chloride pipeline test system considering varying leak severities. The preliminary results presented in this paper seem promising and lead to several interesting questions that will require further research.

A physical probabilistic model to predict failure rates in buried PVC pipelines

For older water pipeline materials such as cast iron and asbestos cement, future pipe failure rates can be extrapolated from large volumes of existing historical failure data held by water utilities. However, for newer pipeline materials such as polyvinyl chloride (PVC), only limited failure data exists and confident forecasts of future pipe failures cannot be made from historical data alone. To solve this problem, this paper presents a physical probabilistic model, which has been developed to estimate failure rates in buried PVC pipelines as they age. The model assumes that under in-service operating conditions, crack initiation can occur from inherent defects located in the pipe wall. Linear elastic fracture mechanics theory is used to predict the time to brittle fracture for pipes with internal defects subjected to combined internal pressure and soil deflection loading together with through-wall residual stress. To include uncertainty in the failure process, inherent defect size is treated as a stochastic variable, and modelled with an appropriate probability distribution. Microscopic examination of fracture surfaces from field failures in Australian PVC pipes suggests that the 2-parameter Weibull distribution can be applied. Monte Carlo simulation is then used to estimate lifetime probability distributions for pipes with internal defects, subjected to typical operating conditions. As with inherent defect size, the 2-parameter Weibull distribution is shown to be appropriate to model uncertainty in predicted pipe lifetime. The Weibull hazard function for pipe lifetime is then used to estimate the expected failure rate (per pipe length/per year) as a function of pipe age. To validate the model, predicted failure rates are compared to aggregated failure data from 17 UK water utilities obtained from the United Kingdom Water Industry Research (UKWIR) National Mains Failure Database. In the absence of actual operating pressure data in the UKWIR database, typical values from Australian water utilities were assumed to apply. While the physical probabilistic failure model shows good agreement with data recorded by UK water utilities, actual operating pressures from the UK is required to complete the model validation.