Pipa HDPE (high density polyethylene) adalah pipa plastik bertekanan yang saat ini merupakan pilihan utama untuk pipa air. Beberapa faktor yang menyebabkan dipilihnya pipa HDPE karena:
- Pipa HDPE dapat digunakan hingga 50 tahun lebih.
- Pipa HDPE bebas karat karena terbuat dari plastik poly ethylene.
- Pipa HDPE mudah dan cepat dalam pemasangan.
Untuk specifikasi pipa HDPE serta designnya mengacu pada research dibawah ini:
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM
Systematic, well-designed research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local
interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation
develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research.
In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research
program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation.
The Transportation Research Board of the National Research Council was requested by the Association to administer the research program because of the Board’s recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them.
The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific
areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials.
Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board.
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because they are considered essential to the object of this report.
SUMMARY
HDPE PIPE: RECOMMENDED MATERIAL SPECIFICATIONS AND DESIGN REQUIREMENTS
The objective of this study was to evaluate the stress crack resistance (SCR) of high density polyethylene (HDPE) corrugated pipes and correlate it with o bserved field performance.HDPE PIPE: RECOMMENDED MATERIAL SPECIFICATIONS AND DESIGN REQUIREMENTS
Because of the limitation of the current environmental stress crack resistance (ESCR) tests (ASTM D 1693), an alternative test, the single-point notched constant tensile load (SP-NCTL) test (ASTM D 5397-Appendix), was used in the study. The research further explored the specific conditions of the SP-NCTL test to evaluate HDPE corrugated pipes and to establish the minimum SCR requirements by calibrating the test with the field performance of the pipe.
The following steps were taken to accomplish the research objectives:
- Discussing the modification of cell classification in different AASHTO specifications and the recent adoption of a new SCR test (ASTM F 1473) in ASTM D 3350.
- Compiling information on the overall performance of HDPE corrugated pipes through a questionnaire.
- Identifying sites with cracked pipes through a second questionnaire developed specifically for that purpose.
- Performing field investigations at identified sites and collecting data on the pipe conditions and retrieving cracked pipe samples.
- Conducting laboratory testing to evaluate material properties and the SCR of both commercially available new pipe samples and retrieved field samples.
- Investigating the effects of orientation, bending, and residual stress on the SCR of finished pipes.
- Identifying the appropriate test condition for the SP-NCTL test to be used in HDPE corrugated materials.
- Establishing the minimum criteria for the SP-NCTL test to quality HDPE corrugated pipe resins.
The majority of the responses from the questionnaire expressed a good or satisfactory experience with the overall performance of the HDPE corrugated pipe. The information
provided by the second questionnaire indicated 62 sites with problems associated with deflection, buckling, cracking, and joints. Twenty-nine of these sites were visited, and pipes at twenty sites showed cracking. Cracking occurred in pipe with profile Types C-helical and C-annular, S-helical and S-annular, and S-honeycomb, and with diameters ranging from 300 mm to 1,050 mm. Circumferential cracking was the dominant type, indicating longitudinal stresses. The circumferential cracks in Type S pipes mostly occurred at the junction of the liner and corrugation. The crack grew from the outer surface (interior of the void in the corrugation) through the thickness of the liner. In contrast, longitudinal cracks propagated through both the liner and the corrugation, potentially allowing infiltration of soil into the pipe. Much of the cracking was associated with installation problems that led to excessive deflection and buckling or longitudinal bending. However, there were sufficient cases of cracking under moderate deflection levels to warrant attention to the material quality and product design, as well as to the
installation procedure and detailing of pipe junctions with rigid structures. Nineteen pipe samples retrieved from the field were evaluated in various laboratory tests.
LABORATORY TESTING
Fourteen commercially available new pipes and nineteen retrieved field samples were
evaluated for their material properties and SCR. The material properties were assessed
according to the latest AASHTO M 294 Specification. The majority of the tested samples
conformed to the specified values for density, melt index (MI), flexural modulus, and tensile yield strength. However, one-half of the new pipes and one-half of the retrieved pipes failed to pass the current ESCR test, that is, the ASTM D 1693 test. The results indicate materials that comply with the basic property requirements, such as density and melt index, do not necessarily meet the SCR criteria. Thus, the SCR of corrugated pipe materials must be evaluated independently.
The SP-NCTL test was performed on the thirty-three pipe samples. The specific applied stress for the proposed AASHTO recommendations was investigated and a 15% yield stress was determined to distinguish various resin qualities and to produce a reasonable testing time. The results of the SP-NCTL test, that is, the failure time at 15% yield stress, ranged from 0.5 to 1,800 hours, indicating a large variation in SCR behavior of the tested materials. Materials with longer failure times have a greater SCR than those with shorter failure times. Data from retrieved field pipe samples indicated that pipes made from high SCR resins have not exhibited cracking even under a large deflection. This indicates that the SCR of the pipe resin is an important parameter in preventing cracking in the field.
A proposal for minimum failure time of the SP-NCTL test for HDPE resins used in corrugated pipes was established on the basis of data obtained from retrieved pipe samples as well as on the pipe condition and pipe profile. The specific value is defined according to the type of pipe profile:
- For Type C- and S-helical pipes, the minimum average failure time is 400 hr;
- For Type C- and S-annular pipes and Type S-honeycomb pipes, the minimum average failure time is 24 hr; and
- For all types of pipe profiles, statistical variability is accounted for by setting lower minimum test times for individual tests.
Meskipun tulisan diatas belum secara gamblang membahas spesifikasi pipa HDPE, tapi sudah menggambarkan betapa pipa HDPE memiliki standard yang baik dan dapat dipertanggung jawabkan.
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