Chlorinated Polyvinyl Chloride Pipe Research Articles

Evaluation of damage and failure analysis of CPVC pipes

In this paper, the work we have carried out has focused on the failure analysis of CPVC (chlorinated polyvinyl chloride) pipes. We stimulated the damage by notch effect and evaluated its properties using models available in the literature, specifically, the linear damage of Miner, the normalized damage and the unified theory. Burst tests allowed us to obtain ultimate pressure and time parameters for the virgin specimens and the residual parameters for the damaged ones. Then, we analyzed the effect of defect on the mechanical behavior of the studied structures; we found that the mechanical properties of the material were lost as defects increased. An observation and analysis of the pressure drop and thereafter the residual ultimate resistance brings out acceleration from it around the critical depth. Then, an evaluation of the static damage of the studied CPVC pipes was made according to model based on the experimental results of the burst tests and on the modification of the unified theory concepts and the static damage. Indeed, we evaluated the static damage of blank and notched tubes using mainly burst pressure parameters.

Study of defects influence on chlorinated polyvinyl chloride pipes damage and analysis of their fracture

In several industrial applications, plastic, composites and ceramics replace a number of metallic structures such as copper, aluminum and steel. Most recently installed piping water and gas systems in the world are made of thermoplastic due to its advantages, for example, low cost, ease of fabrication and corrosion resistance. In this work, the chosen material is chlorinated polyvinyl chloride (CPVC); the best one used to transport cold and hot water beside simplicity of installation. Notwithstanding, the pipes in service are submitted to different loads, related to environmental, thermal and mechanical effects which procure to mechanisms of degradation. The aim of this article is to assess the effect of the defect on CPVC pipes, through a study of the defect criticality in the form of semi-elliptical, then the ability to predict defected pipes residual life. Therefore unexpected and sudden failure caused by pipes accelerated damage. Therefore, we performed burst tests on both pre-damaged CPVC pipes and virgin ones. To lead our work in this paper, interested in the damage modeling and the failure analysis of CPVC pipes, we adapted the model of unified theory static damage, originally developed in fatigue. We used burst pressure tests to identify the limits of three damage progression phases and, in turn, to calculate the critical life fraction at which these flaws become harmful. Furthermore, we identify the critical depth for the studied defect. These results and techniques enable industrialist s to anticipate this structures service life under these conditions after that set up a robust system of maintenance to ensure a reliable and safe functioning of the structure.

Energy and Exergy Analyses of Plastic Solar Air Heater Developed from Chlorinated Polyvinyl Chloride Pipes

Energy and Exergy Analyses of Plastic Solar Air Heater Developed from Chlorinated Polyvinyl Chloride Pipes

Fracture analysis of defect Chlorinated Poly Vinyl Chloride pipes based on burst pressure and prediction their fraction of life

Most Chlorinated Poly Vinyl Chloride (CPVC) resins contain 63-69 % chlorine, in particular those used for the extrusion of plumbing tubes, due to this chlorination of basic PVC, CPVC offers a mixture of corrosion resistance and low installation costs for its main applications requiring service in non-ambient conditions. CPVC replaces copper owing to its economic gain and by virtue of its pressure resistance characteristics. In this article, we have been interested in fracture analysis and damage modeling of CPVC tubes by subject CPVC samples to burst pressure tests. We performed a set of burst tests on virgin and artificially damaged CPVC pipe at different notch lengths, then submitted the specimens to burst pressure tests, in addition to recording the pressure and time during these tests for use in conducting the study. The results of the burst tests were exploited to estimate the damage and reliability of the material, these two parameters allow us to follow the degradation of the pipes used; subsequently, we determined a new relationship between these two parameters through the fraction life. This makes it possible to predict the moment of damage acceleration and to intervene at the right time for engaging predictive maintenance.

Experimental Study on Performance Parameters of Power Cable Conduits of Chlorinated Polyvinyl Chloride

Chlorinated polyvinyl chloride (CPVC) pipes are used more and more widely as protective conduits in the field of power cables. According to the application characteristics in the field of cables, there are special requirements for the performance parameters of CPVC pipes. In this paper, several key performance parameters such as CPVC pipe size inspection, ring stiffness, longitudinal retraction rate, vicat softening temperature, density and flattening test are selected, and the theoretical research of the test method is carried out. On the basis of theoretical research, the difference between the dimensional inspection, the ring stiffness, the longitudinal retraction rate, the density and the vicat softening temperature parameters of the unqualified sample and the qualified sample are compared. It is found that the unqualified samples of the flattening test have relatively poor compressive performance, and the longitudinal plasticity stability under the influence of the heat source is also relatively poor. Moreover, when the sample size is unqualified, it directly affects the compressive performance of the sample. Through the research results, it provides the necessary reference for the application of CPVC pipes in the field of power cables.

Damage Prediction of CPVC Based on Energy Method at Different Temperatures

The Chlorinated Polyvinyl Chloride pipes used for the supply of cold and hot water are designed and manufactured for a 50 years predictive life, but defects and harmfulness may occur during the transport process, storage and operation of tubes that significantly affect these forecasts. This work deals with the study of the mechanical behavior of Chlorinated Polyvinyl Chloride (CVPC) specimens subjected to tensile tests under the effect of temperature. Moreover, a study of damage evolution by the ultimate energy makes it possible to determine the three stages of the lifetime of the test pieces studied. On the basis of the stress-strain variation curves plotted from the experimental results, the critical value of the fraction of life corresponding to the acceleration of the damage was determined.

Experimental Study of Thermal Effect on Performance of PVC Pipes Using ANOVA Analysis

In this study thermal effect at high pressure on Chlorinated Polyvinyl Chloride (CPVC) pipes studied where a test rig is built and the pipe has a diameter (d=0.5 in). The temperatures of water are varied (40, 60 and 80 co) and the pressure is raised by using tester to reach (700 psi). The relationship between pressure and Reynolds number is discussed for the pipe used in this study with another pipe has a dimension (d= 0.75 in). ANOVA Analysis used to find the correlation of parameters effect the performance of CPVC pipes. The experimental results showed that the pressure drop increases with discharge increased at different values of temperature, when the pressure increased at constant temperature the friction losses is increased, where the values of friction losses were 4.8 ×10-4 , 8×10-4 and 2.4×10-3 mm at 100, 300 and 500 psi respectively. Thus the pipe is damage at pressure (500 psi) and temperature (80 Co) when the thickness is (3.1 mm).

A Refined One‐Slit‐Ring Method to Quantify Residual Hoop Stress in Chlorinated Polyvinyl Chloride Pipe—Application to Specimens After Immersion in Primer

A refined one‐slit‐ring method is presented to characterize residual hoop stress distribution in pipe ring specimens of inhomogeneous cross section. Although the original one‐slit‐ring method enables determination of residual hoop stress distribution through slitting single ring specimen in the axial direction, its use is limited to specimens of uniform material properties. This work is to extend applicability of the method to ring specimens with a cross section of core–shell structure. Chlorinated polyvinyl chloride (CPVC) pipe is used in the study, and core–shell structure in its ring specimens is introduced through immersion in primer for 30 min. Analytical expression for the residual hoop stress distribution in these specimens is derived, and verified using finite element (FE) simulation which uses a temperature gradient field to generate stress so that diametrical change by the slitting is same as that measured experimentally. Results from the analytical expression agree well with those from the FE simulation, showing decrease of the residual hoop stress by the exposure to primer, and the extent of decrease depends on the drying time after the immersion in primer, to about half of its original value after 30 days of drying, and then remains relatively constant afterwards. POLYM. ENG. SCI., 59:E296–E309, 2019. © 2019 Society of Plastics Engineers

The Impact of Mounting Method on the Flammability Testing of Chlorinated Poly Vinyl Chloride (CPVC) Pipe Type Certification for Maritime Applications

A series of tests was performed to elucidate the impact of the mounting methods on the performance of chlorinated poly vinyl chloride (CPVC) pipe in accordance with International Maritime Organization Fire Test Procedures Annex 1 Part 5. Also assessed, was the determination whether the current practice in type approval for the certification of all CPVC pipe sizes between smallest diameters, thinnest pipe tested and largest diameters, thickest pipe tested is a valid practice. Whole diameter pipe and pipe cut in half longitudinally were tested in the Lateral Ignition and Flame-Spread Test apparatus to determine if the different configurations of the pipe induced variability. A total of 42 tests were performed to look at sizes 12.7-mm copper tube size (CTS) through 38.1-mm Schedule 80 CPVC pipes. The following factors produced statistically different data at the 99% confidence limit: longitudinally half cut, versus whole, of the same pipe size and type, and thickness of the pipe for both total heat release and peak heat release rate (PHRR). Thickness is important with thicker pipe performing better in the testing. Whole pipe of the thinner material, CTS, versus the same pipe produced from longitudinally cut pipe, increased the heat produced significantly by holding the pipe in the combustion zone longer. Thin cut pipe appeared to melt and char, and fall out of the sample holder and the combustion zone, effectively reducing the mass consumed and energy produced. For Schedule 40 pipe of whole smaller pipe diameters, 12.7 mm, performed significantly better for both PHRR and total heat release than the longitudinally cut pipe. For diameters of 19.1 and 38.1-mm Schedule 40, the same trend was noted with the whole pipe performing significantly better. Thicker materials, such as Schedule 80, develop a thick char layer that stayed in place reducing combustion of CPVC.

Burst behavior of CPVC compared to HDPE thermoplastic polymer under a controlled internal pressure

Abstract: The HDPE (High Density Polyethylene) and CPVC (Chlorinated Polyvinyl Chloride) are extremely used in water piping systems. The CPVC have the particularity to support high temperatures of water. Those two materials are known for their different characteristics toward the internal pressure. To quantify their behavior we exposed pipe specimens, prepared according to ASTM 1599, to an increasing internal pressure and we registered the burst and the time of each specimen. To push further our analysis, we created groove notches over the same category of specimens and we exposed them to the same conditions. Then, we have noticed a drop of the internal pressure in function of the time and the life fraction which is the ratio of thickness and its fluctuation (Δe/e). Indeed, the burst pressure, and the time of failure are drastically dropping according to the notch depth. Besides, one important consequence is noticeable over the mechanical behavior which shift from a ductile one, for neat pipes, to a brittle one for the other HDPE pipes. Meanwhile, The CPVC pipes have a brittle behavior for both of the specimen's categories. The discrepancies can be explained by the nature of the two materials, the first one is an original polymer while the second is a Chlorinated PVC material. Furthermore, the comparison of the failure mode of the two polymers are slightly different compared to the linear damage of Miner. For HDPE pipes, the static damage is evaluating nearby the Miner one until getting to the critical life fraction (βc) of 52% and then get over it. However, the CPVC damage has a very weak evolution bellow the βc of 60% from which we notice a drastic increasing and an acceleration of the damage. The CPVC show good performances toward the supported internal pressure, support up to 160 bars, and a brittle behavior. Meanwhile, the HDPE pipe can support up to 70 bars and show a ductile behavior. Finally, this paper can be considered as a window to understand the difference between HDPE and CPVC polymers under burst pressure and the severity of the groove defects for researchers and industrials.

Investigation of factors affecting the accumulation of vinyl chloride in polyvinyl chloride piping used in drinking water distribution systems

Plastic piping made of polyvinyl chloride (PVC), and chlorinated PVC (CPVC), is being increasingly used for drinking water distribution lines. Given the formulation of the material from vinyl chloride (VC), there has been concern that the VC (a confirmed human carcinogen) can leach from the plastic piping into drinking water. PVC/CPVC pipe reactors in the laboratory and tap samples collected from consumers homes ( n = 15) revealed vinyl chloride accumulation in the tens of ng/L range after a few days and hundreds of ng/L after two years. While these levels did not exceed the EPA’s maximum contaminant level (MCL) of 2 μg/L, many readings that simulated stagnation times in homes (overnight) exceeded the MCL-Goal of 0 μg/L. Considerable differences in VC levels were seen across different manufacturers, while aging and biofilm effects were generally small. Preliminary evidence suggests that VC may accumulate not only via chemical leaching from the plastic piping, but also as a disinfection byproduct (DBP) via a chlorine-dependent reaction. This is supported from studies with CPVC pipe reactors where chlorinated reactors accumulated more VC than dechlorinated reactors, copper pipe reactors that accumulated VC in chlorinated reactors and not in dechlorinated reactors, and field samples where VC levels were the same before and after flushing the lines where PVC/CPVC fittings were contributing. Free chlorine residual tests suggest that VC may be formed as a secondary, rather than primary, DBP. Further research and additional studies need to be conducted in order to elucidate reaction mechanisms and tease apart relative contributions of VC accumulation from PVC/CPVC piping and chlorine-dependent reactions.

Challenges in Investigating Chlorinated Polyvinyl Chloride Pipe Failures

Abstract Chlorinated polyvinyl chloride (CPVC) is increasingly replacing steel pipe in fire protection systems due to lower cost and ease of installation. However, CPVC is susceptible to failure by mechanisms other than those typically experienced with steel pipe. The losses and remediation costs associated with a simple pipe failure can be extraordinary, as a failed pipe can cause significant water damage to a high-rise building. Identifying the cause(s) of pipe failure can be challenging for a number of reasons. First, CPVC pipes can fail by several mechanisms, including high pressure, impact, environmental stress cracking (ESC), and manufacturing defects. ESC can be particularly vexing during a failure investigation. Potential ESC agents include many lower molecular weight and highly mobile compounds, which are soluble in the polymer. Common construction compounds such as adhesives, plumber’s putty, fire barrier caulks, cutting oils, and glycol-based antifreezes are potential ESC agents. Second, the situation is complicated by the fact that only trace amounts of a contaminant may be necessary to cause ESC. The pipe failure event also tends to flush out the contaminants, further reducing their concentration on the pipe surface. What little contaminant remains can be difficult to identify or “fingerprint.” In addition, pipe defects including incomplete fusion, thermal damage, excessive residual stresses, or irregular molecular weight distributions may also contribute to ESC failures. Yet, they are not always apparent or easy to detect. This paper explores the challenges encountered during numerous failure investigations and reviews the state of the art in testing and analysis as applied to ESC in CPVC pipes.

Combined effects of termiticides and mechanical stress on chlorinated polyvinyl chloride (CPVC) pipe

CPVC pipe failures have recently been reported beneath structures as a result of termiticide soil treatments. To determine whether these CPVC failures were actually caused by termiticides, CPVC tubes were filled with 50 mL of either termiticide concentrate, dilutions or treated builder's sand and sealed. Mechanical stress was added to these sealed tubes by hanging bricks from their ends. As concentrates, eight of nine emulsifiable concentrates tested caused failure within 8 weeks. None of the three suspensible concentrates tested caused failure over this period. Dilution of emulsifiable concentrates caused progressively fewer CPVC tube failures. No treated soils caused tube failures. Excessive CPVC glue applications in combination with chlorpyrifos 440 g kg(-1) EC (Dursban(trade mark) TC) degraded the CPVC. All volatile organic compounds (VOCs) found in the termiticide formulations caused CPVC tube failure within 1 week as pure chemicals. The VOC 1,3,5-trimethylbenzene caused CPVC tube failure within minutes of exposure. This VOC was found in all termiticides that caused failures as concentrates. It is highly improbable that a properly conducted preconstruction soil treatment, where termiticide is completely adsorbed to the soil, would be solely responsible for CPVC pipe failure. Manufacturers should consider removing 1,3,5-trimethylbenzene from termiticide formulations to minimize the risk of CPVC pipe failure.

Fatigue Crack Growth Process in CPVC Pipe Couplings

AbstractAn investigation of the influence of temperature and loading frequencies on the morphological features found on the fatigue fractured surface of chlorinated polyvinyl chloride (CPVC) has been conducted. Single edge notched rectangular coupons obtained by flattening schedule 80 CPVC pipe couplings were subjected to fatigue loading at different temperatures of 0, 23, 40, and 70 °C and frequencies of 0.1, 1, and 50 Hz. Crack growth in CPVC, involved a combination of shear yielding and crazing processes. At the test temperature of 0 °C and 23 °C, the fatigue crack growth was noted to occur predominantly by shear yielding while crazing played a secondary role. On the other hand at 40 °C and 70 °C, the fatigue crack growth process appeared to predominantly involve a crazing process while shear yielding played a less significant role. Filler material particles played a major role as brittle second phase stress-raiser particles and facilitated craze initiation. iDiscontinuous crack growth bands (DGBs) indicating repeated crack arrests were also noted on the fracture surface.

Fire tests to evaluate CPVC pipe sprinkler systems without fire resistance barriers

Nine full-scale fire tests were conducted to assess the adequacy of exposed chlorinated poly vinyl chloride (CPVC) pipe and fitting sprinkler systems installed in light hazard occupancies. The tests were conducted in an enclosure using six different types of automatic sprinklers including QREC pendent and sidewall sprinklers, a pendent residential sprinkler, and a sidewall residential sprinkler. Two types of fires, fast growing and slow growing, were used as test fires. The sprinkler in each test was operated with the normal operation pressure until the test fire was almost completely suppressed. Next, to assess the integrity of piping systems after fire exposure, the water pressure was increased to 12.1 bar and maintained for 10 min and then were visually inspected for any leakage while hydrostatic pressure was maintained at 12.1 bar. No leakage was detected in any of the tests. The results of the tests indicate that sprinkler systems based on exposed CPVC pipe and fittings can be safely installed in light hazard occupancies and will provide adequate protection when installed to all the relevant standards.

A pilot study of bacteriological population changes through potable water treatment and distribution.

This pilot study compares the compositions of bacterial biofilms in pipe networks supplied with water containing either high levels of biodegradable organic matter (BOM) or low levels of BOM (conventionally or biologically treated, respectively). The Microbial Identification System for fatty acid analysis was utilized in this study to identify a large number of organisms (>1,400) to determine population changes in both conventionally and biologically treated water and biofilms. Data generated during this study indicated that suspended bacteria have little impact on biofilms, and despite treatment (conventional or biological), suspended microbial populations were similar following disinfection. Prechlorination with free chlorine resulted not only in reduced plate count values but also in a dramatic shift in the composition of the bacterial population to predominately gram-positive bacteria. Chlorination of biologically treated water produced the same shifts toward gram-positive bacteria. Removal of assimilable organic carbon by the biologically active filters slowed the rate of biofilm accumulation, but biofilm levels were similar to those found in conventionally treated water within several weeks. Iron pipes stimulated the rate of biofilm development, and bacterial levels on disinfected iron pipes exceeded those for chlorinated polyvinyl chloride pipes. The study showed that the iron pipe surface dramatically influenced the composition, activity, and disinfection resistance of biofilm bacteria.