Crack speeds up to 200 msec 600 ftsec have been measured. Vanspeybroeck, rapid crack propagation in polyethylene gas pipes correlation factor between smallscale and fullscale testing, 15th plastic fuel gas pipe symposium, 1997. Ppi claimed that fusible pvc had experienced a number of recent water pipeline failures as a result of rapid crack propagation, radoszewski said. Endot announces the immediate availability of pe100pe4710 gas pipe produced from the new, high performance bimodal resin, dgda 2490bk from dow chemical. The plastics pipe institute has retracted its news release dated june 11, 2008 and the contents therein. Underground water pipes include ductile iron pipe, highdensity polyethylene hdpe pipe, and polyvinyl chloride pvc pipe. Pdf the effect of air pockets on rapid crack propagation. Having outlined some of the potential issues that cause pipe weaknesses, it should be noted that pipe failures which are directly attributable to poor quality materials or poor extrusion are not commonly observed. Measurement of rapid crack propagation in pressure pipes. The most important property of pe pipes is its resistance to hydrostatic pressure. The pipe showed indications of rapid crack propagation that would be consistent with a highpressure event.
Among other things, ppi alleged that fused pvc pipe is subject to rapid crack propagation rcp, questions the integrity of joints of pvc pipe joined by fusion, and said the pvc pipe fused in the field does not comply with awwa standards. Such an event is referred to as rapid crack propagation rcp 14. This phenomenon has been recognized as rapid crack propagation rcp. The 50minute webinar offers a comparison between polyvinylchloride pvc pipe and highdensity polyethylene hdpe pipe while emphasizing the importance of a proper design basis to prevent rapid crack propagation rcp in fused, monolithic pipelines.
A method for creating rapid crack propagation in pressurized pipes under slow static loading using modified s4 apparatus is described. So, with all of the similarities between pe and pvc what truly differentiates the two pipe types. Very occasionally pvc u water pipes suddenly fail due to a long brittle crack with a length of many meters which propagates with the speed of sound along the pipe and causes extensive water loss. The majority of field failures in piping are attributable to slow crack growth scg fractures. These fractures are characterized by the stable growth of a crack with little deformation in the plastic material. On june 11, the plastics pipe institute ppi issued what it called a cautionary advisory read a copy here regarding the integrity of fusible polyvinyl chloride pvc pipe. A classical analysis of irwin and corten relates the minimum pressure to sustain crack propagation along a pipeline to the dimensions, elastic modulus and.
Because rapid crack propagation rcp failures in plastic pipe are so rare, the regime of standards and test methods which made them so has. A preliminary numerical analysis of the rapid crack propagation rcp in polymer pipe is firstly realised. They are a safe choice for transportation of drinking water, light and easy to handle and affordable. Increasing importance of rapid crack propagation rcp. Description jm eagles highdensity polyethylene irrigation and water pipe is made from premium. Thermoplastics pipes for the conveyance of fluids determination of resistance to rapid crack propagation rcp smallscale steadystate test s4 test en iso. Arrest of rapid crack propagation in polymer pipes springerlink.
A method for creating rapid crack propagation in pressurized pipes under slow static loading using. Pvc pipe can be used for most any drain, water, or ventilation application. Rapid crack propagation in pe pipes studied by modified. The increased working stress rating of highperformance pe 4710 resin material makes it a superior choice over steel or ductile iron pipe, especially for the large diameter pipe. Rapid decompression ahead of the propagating crack is retarded by internal baffles and by an external cage which restricts flaring of the test pipe at the edges of the fracture. Many homeowners believe pvc to be a maintenancefree product, however, which may or may not be accurate depending on its application. Resistance to rapid crack propagation rcp is a critical property for fusion joined thermoplastic pipes. The pipe was excavated and later examined in the laboratory.
In the middle east, more than 85% of the pvc consumption is in the construction industry and further growth is forecast in sewage, drainage and telecommunication pipes in most countries. Rcp has been connected to a number of recent water pipeline failures, such as the may collapse of a 36inch water main in naples, fla. At lower temperatures the crack speed is higher, and hence, the possibility of rcp increases. The nature of polyethylene pipe failure plasticstoday.
Hdpe pipes from lombardy hdpe pipe manufacturer in nigeria. Rcp can be caused by various reasons including defects in. In the development of the method a complexity involved with. Ppi said that fusible pvc pipe is susceptible to rapid crack propagation rcp and that this characteristic has led to a number of recent water pipeline failures. Pvc is a lightweight, inexpensive, rigid thermoplastic that requires a twin screw pipe extruder. Cracking of glass plates and frozen lakes is an example of rcp. Rcp is sometimes referred to as a fast brittle fracture and, by the construction industry, as a linear split. Each type of pipe exhibits varying degrees of resistance to puncture, cracking, and other types of pipe failure. Pvc o is the result of reorganizing the amorphous structure of pvc u into a layered structured, providing unbeatable mechanical properties in plastic pipes, such as. The elongation at break of hdpe pipes is generally above 500%. Rcp or rapid crack propagation in pressure pipe is where a fast running crack splits the pipe lengthwise.
Steel backing ringspe pipes and fittings, pvc pipes and. Cracks are thought to initiate at internal defects on an impact of impulse event and can travel long distances quickly. The focus is the pipe s susceptibility to rapid crack propagation rcp, which has led to a number of recent water pipeline failures. Determination of resistance to rapid crack propagation. Jan 24, 2014 used for rapid crack propagation test of polymer pipes. Rapid crack propagation in pressurised plastic pipeii. Rapid crack propagation an overview sciencedirect topics. Cast iron pipes and plastic pipes under certain conditions may also experience this phenomenon. Variation of final crack length with pressure for mdpe1 180 sdr 17. Very occasionally pvcu water pipes suddenly fail due to a long brittle crack with a length of many meters which propagates with the speed of sound along the pipe and causes extensive water loss. It was found that the lower the residual stress, the lower the s4 critical temperature t cs4 for rcp. Its highstrength walls give it the highest pe pressure rating, outstanding resistance to scg and increased resistance to rapid crack propagation. When a pressurized pe pipe is subjected to a high velocity impact, a preexisting or consequently initiated crack or flaw can propagate axially for many diameters at speeds in excess of 100 ms.
Fusible pvc pipe has not experienced a single inservice failure due to rapid crack propagation rcp. This failure mode is also termed rapid crack propagation rcp or is sometimes referred to as a stage one mechanical failure. Scg testing involves accelerating the growth mechanism and can be done through elevated temperature, concentrated stress, constrained geometry, surfactants or some. Rapid crack propagation rcp is a fast fracture type of failure. Sseniso478 thermoplastics pipes for the conveyance of fluids determination of resistance to rapid crack propagation rcp fullscale test fst iso 478. Rapid crack propagation tester for sale fyi factory.
Rapid crack propagation rcp is pretty much what it sounds and can occur up to several hundred feet per second. Both pe and pvc pipes can be used over long periods of time and serve as a cost effective piping solution for any application. It is especially designed for the production of larger diameter, thick wall pipe, but can be processed for the whole range of diameters. Rapid crack propagation rcp tester qtrcp series is designed to determine the. Plastics pipe institute issues cautionary advisory on. Iso 477 specifies a test method also known as the smallscale steadystate test s4 test for determination of arrest or propagation of a crack initiated in a thermoplastic pipe at a specified temperature and internal pressure. For all applications and standards within pressure test, impact test, leak tightness test, rapid crack propagation test, compression test, tensile test.
Thermoplastics pipes for the conveyance of fluids determination of resistance to rapid crack propagation rcp fullscale test fst. Traditionally, pvc pipe sections have been joined by using a bell and spigot. Pvc pipe is a popular construction material for its low cost and durability. Supplying 100% reliable test results our products sciteq. Detailed main standards for pvc piping systems list. Sseniso478 thermoplastics pipes for the conveyance.
The increased working stress rating of highperformance pe 4710 resin material makes it a superior choice over steel or ductile iron pipe, especially for the large diameter pipe sizes. Designing against rapid crack propagation in pvc water pipes. Ppi states that rcp has plagued fusible pvc pipe installations, yet the only fusible pvc pipeline failure mentioned by ppi is a project in naples, fl which did not involve rcp a. Excellent resistance to rapid crack propagation rcp. Rapid crack propagation rcp is a phenomenon in which a crack runs at a very high speed in the order of some hundreds of metres a second in axial direction over great distances along the pipe. Dynamic fracture mechanism in polyamide 11 pa11 material has been described at laboratory scale to access to an intrinsic material parameter. Resistant to rapid crack propagation highly resistant to scale build up that can reduce flow capacities installed by open cut or trenchless method high fluid flow coefficient c 150 over the life of the piping systems applications. Ppi states that rcp has plagued fusible pvc pipe installations, yet the only fusible pvc pipeline failure mentioned by ppi is a project in naples, fl which did not involve rcp a fact confirmed by the contractor. Particularly from the viewpoint of safety this is an undesirable situation. Hence this technique achieves steadystate rapid crack propagation rcp in a short pipe specimen at a lower pressure than in a fullscale test.
The irving, texasbased plastic pipe institute ppi has issued a warning on rapid crack propagation rcp in fusible pvc pipes. Pvc o is also well suited for buried nonpotable applications such as irrigation and sewer pumping mains. Rapid crack propagation rcp is a phenomenon in which a long fastmoving brittle crack can propagate in a material body. How to design against long running cracks in plastic pipe. Pdf rapid crack propagation in pressurised plastic pipeii. For the uneven settlement of the foundation, it has strong adaptability and good seismic performance. Technical note pp838tn preventing rapid crack propagation in. Slow crack growthrapid crack propagation nsf international. Hdpe pipes have been deployed in waterworks for several decades and have developed a proven track record of quality reliability and durability. Determination of resistance to rapid crack propagation rcp iso 477, s4test. Qualitest offers drop weight impact testers, hydrostatic pressure tester, and more to come. The effect of air pockets on rapid crack propagation in pvc. Results for three commonly used water pipe grade polymers agree well with the predictions of the thermal decohesion model, and with other experimental data where available. Pipes made of pvc o are especially advantageous when it comes to hydraulic capacity, ductility, crack propagation and impact and fatigue resistance.
Exposure to the elements, chemicals and bacteria is the enemy of pipes everywhere municipal, commercial or residential. Annealing of pe pipes at 80 c strongly improves the resistance to rcp. Plastic testing instruments,equipments,machines manufacturer. The majority of field failures in piping are attributable to slow. Establishing the correlation between s4 and full scale rapid crack propagation testing for polyamide11 pa11 pipe. This means that pvc o is an excellent choice for pressure pipes for drinking water. Pdf a new smallscale test method has been developed for generating steady state rapid crack propagation in plastic pipe. Pvc is a lightweight, inexpensive, rigid thermoplastic that requires a twin screw pipe extruder because of the harshness of the material in its raw state. Why pvco sizabantu plastic pipe systems plastic pipe. Technical note pp838tn preventing rapid crack propagation. These test methods are applicable to polyethylene pe, polypropylene pp and polybutylene pb piping. Leevers, a new small scale pipe test for rapid crack propagation, 11th plastic fuel gas pipe symposium, 1989. Rapid crack propagation, as its name implies, is a very fast fracture.
The increased working stress rating of highperformance pe 4710 resin material makes it a superior choice over steel or ductile iron pipe, especially for the largediameter pipe sizes. An engineering model for rapid crack propagation along fluid. Jan 12, 2016 this animation provides a description of the pariserdogan law equation for crack propagation. We can provide training about how to measure pvc pipe property. As plastic pipe became more prominent, researchers applied similar methodologies used for metal pipe on the newer plastic pipe materials, and particularly. Pvc pipes do not have the toughness and resistance to rcp that. Ahp rcp tester rapid crack propagation of plastic pipes. Infrastructure boom in the middle east drives growth of. Pvc pipes pvc is an amorphous plastic material that is below its glass transition temperature, and thus is in a glassy or brittle state. Further, rcp failures can be initiated at pressures well below the design stress of the pipe. The dupont company had two rcp incidents with its highdensity pe pipe, one that traveled. Endot pe100pe 4710 gas pipe is produced in black with three yellow stripes for easy identification as gas service pipe and tubing. Rcp tube fast crack extension test host, rcp low temperature state control.
Pipes and fittings made of pvcu have many benefits. Excellent resistance to rapid crack propagation rcp high temperaturepressure performance. A liquid transportation application is considered with polymer pipes. Nov 27, 2012 pipe extruded from polyethylene of strength class pe100 was tested using the iso 477 small scale steady state s4 method, to investigate the effect of frozen. Low system cost and reduced maintenance costs can greatly reduce project costs. Pe 100 is the best choice for water distribution networks due to its lowest weight per unit lenght among all hdpe, highest flow area for same pipe od, highest hydrostatic strength hs, resistance to slow crack growth scg and rapid crack propagation rcp. A simple intrinsic measure for rapid crack propagation in bimodal.
The rapid crack propagation behavior in pressurized plastic pipes was investigated to establish the criteria for onset of rapid crack propagation in terms of the relationship between decompression wave speed and crack velocity. Rapid crack propagation behaviour, in both test and service pipeline configurations, is dominated by the ratio of crack speed to fluid decompression wave speed. Rapid crack propagation rcp is exactly what it sounds like and can happen up to several hundred feet per second. Pipes made of pvc are less sensitive to thermal expansion elongation than pe pipe. Pvc and hdpe pipe are inarguably the two most popular pipes used in underground construction. Rapid crack propagation in pressurised plastic pipei 679 fig. Most of this research was done in europe and through the iso community. Scg and increased resistance to rapid crack propagation. Historically, pvc pipe is noncontinuous pipe connected by gasket joints. Hence this technique achieves steadystate rapid crack propagation rcp in a short pipe specimen at. Increasing importance of rapid crack propagation rcp for gas. Rather large variations in rapid crack propagation rcp behaviour of different pe types have been found. Institute issues warning about pvc pipes texasbased. Pdf the smallscale steadystate s4 test, evaluating rapid crack propagation rcp performance, is now an international standard for the.
Increasing importance of rapid crack propagation rcp for. Thesis, department of mechanical engineering, imperial college, london, january, 1991. Rapid crack propagation rcp is a rapidly traveling longitudinal crack that can pass through fused joints and destroy a pipeline in seconds. While rcp failures in pe pipes have been very rare, their potential consequences are very significant. Pvcu is the most common pvc type for pipes and fittings including transportation of drinking water, soil and waste, sewage and underground drainage and industrial applications. Rapid crack propagation tester rcp, also named rapid crack propagation rcp tester or rcp rapid crack propagation tester, which is used for performance test of critical pressure and critical temperature for fast crack propagation of thermoplastic pipes for conveying gas or liquid. The crack origin was located a few inches outside of the bell and spigot connection. In the us, there have been rapid crack propagation. It also shows excellent resistance to rapid crack propagation and slow crack. A simple intrinsic measure for rapid crack propagation in bimodal polyethylene pipe grades validated by elasticplastic fracture mechanics.
These fast cracks can also travel very long distances, even hundreds of feet. Among other things, ppi alleged that fused pvc pipe is subject to rapid crack propagation rcp, questions the integrity of joints of pvc pipe joined by fusion, and said the pvc pipe fused in. The hdpe pipes offer resistance to slow and rapid crack propagation, increased hydrostatic pressure resistance and performance at elevated temperature, broadening the range of its applications. The june 11 press release was labeled by ppi as a cautionary advisory regarding the integrity of fusible pvc pipe. Rcp can be initiated by impact, improper tapping, faulty fusion, fatigue, or other forms of failure. Increased toughness especially at low temperatures. The effect of air pockets on rapid crack propagation in pvc and polyethylene water pipe. Hdpe electrofusion couplingpe pipes and fittings, pvc pipes.1452 157 1365 244 114 1456 248 837 1147 407 917 109 970 71 900 480 1646 223 901 270 503 60 1083 209 1547 1480 295 644 1649 977 1364 1392 329 512 276 395 491 629 134 449 1290 351