1、 1General Guidelines for Butt, Saddle, and Socket Fusion of Unlike Polyethylene Pipes and Fittings TN-13/2007 105 Decker Court, Suite 825, Irving, TX 75062 P: 469-499-1044 F: 469-499-1063 www.plasticpipe.org 2GENERAL GUIDELINES FOR BUTT, SADDLE AND SOCKET FUSION OF UNLIKE POLYETHYLENE PIPES AND FITT
2、INGS FOREWORD This technical note was developed and published with the technical help and financial support of the members of the Plastics Pipe Institute. The members have shown their interest in quality products by assisting independent standard-making and user organizations in the development of s
3、tandards, and also by developing reports on an industry-wide basis to help engineers, code officials, specifying groups, and users. This technical note has been prepared to provide those responsible for the joining of polyethylene (PE) piping for fuel gas and other applications with suggested genera
4、l guidelines for the heat fusion of components made from PEs that exhibit unlike (i.e., significantly different) melt flow properties. These guidelines constitute a set of basic operations that have been demonstrated by test and experience to produce satisfactory joints with commercially available m
5、aterials. Upon this framework may be developed the specific procedures for the joining of a particular combination of unlike PE piping products. Each specific procedure must be acceptable to, and qualified by, the operator having legal responsibility for the performance of the piping system. These g
6、uidelines are intended only for making heat fusion joints with unlike materials under specific conditions. It is recommended that there be no indiscriminate mixing in a PE piping system of components made from unlike materials. The Plastics Pipe Institute, Inc. has prepared this technical note as a
7、service to the industry. The information in this note is offered in good faith and believed to be accurate at the time of its preparation, but is offered without any warranty, express or implied. Additional information may be needed in some areas, especially with regard to unusual or special applica
8、tions. Consult the manufacturer or material supplier for more detailed Information. A list of member manufacturers is available from PPI. PPI does not endorse the proprietary products or processes of any manufacturer, and assumes no responsibility for compliance with applicable laws and regulations.
9、 PPI intends to revise this report from time to time, in response to comments and suggestions from users of this note. Please send suggestions for improvements to PPI. Information on other publications can be obtained by contacting PPI directly or visiting the web site. The Plastics Pipe Institute,
10、Inc. (469) 499-1044 www.plasticpipe.org This technical note was first issued in January 1981 and was revised in October 1989, June 2001, and June 2007. 3GENERAL GUIDELINES FOR BUTT, SADDLE AND SOCKET FUSION OF UNLIKE POLYETHYLENE PIPES AND FITTINGS 1.0 INTRODUCTION On occasion it may be necessary fo
11、r an installer of a polyethylene (PE) piping system to heat fuse to each other piping components that are made from unlike PE materials. Recognizing this, the Plastics Pipe Institute first issued in April of 1974 Statement E, “Criteria for Joining Various Polyethylene Materials to One Another by Hea
12、t Fusion Techniques“, which includes some general guidelines for this operation. Since the publishing of this statement, additional laboratory and field evaluations have been conducted by PPI members and independent testing laboratories, and new information has become available from the literature a
13、nd other sources. Upon this background have been developed the general guidelines presented in this technical note. These should be useful in establishing the procedures for the heat fusion joining of specific combinations of unlike PE materials. In its previously issued Statement E the Plastics Pip
14、e Institute warned that “indiscriminate mixing without consideration of inherent differences between polyethylenes can produce faulty joints subject to failure in service“. PPI continues to hold to this position against indiscriminate mixing. If the application is for butt fusion of gas distribution
15、 pipe, refer to TR - 33, “Generic Butt Fusion Joining Procedure for Polyethylene Gas Pipe”. In general, if the materials to be butt fused meet ASTM D2513 and have a melt index between 0.05 and 0.25 g/10 min inclusive, the generic procedure defined in TR - 33 apply. This melt index range represents t
16、he melt index extremes of the polyethylene materials that were joined and evaluated in the development of TR-33. The procedure defined in TR-33 may apply to materials with melt indices outside of this range, but appropriate testing would be required to determine the applicability of TR-33 to these m
17、aterials. A number of PPI member manufacturers made successful fusions between the various manufacturers products using the TR-33 generic procedure then tested the fusions per DOT requirements. The manufacturers then prepared letters of endorsement that identify the combinations of products that wer
18、e successfully fused using the TR-33 generic procedure, and tested under DOT requirements. The manufacturers letters of endorsement are published in Appendix B of TR-33 for gas piping applications, and Appendix C for municipal and industrial applications. TR-33 also states, “The results further indi
19、cate that there is strong likelihood that the generic fusion procedure used in this testing (see Appendix A) could be qualified by gas pipeline operators under DOTs regulations in Part 192 for use with most of these PE piping products.” Current United States and Canadian PE 2406 and PE 3408 gas pipe
20、 materials fall in the 0.05 to 0.25 g/10 min range used in TR-33. Materials no longer commercially available, but which may be encountered in the ground for extension and/or service connections, such as Driscopipe 8000, 8600, and DuPont/Uponor Aldyl A, fall outside of the TR-33 4melt index range. Fo
21、r fusing to materials outside of the TR-33 range, the guidelines in this Technical Note may apply and the user should contact the manufacturers of the components to be fused. Materials that have been pre-qualified to be joined by the TR-33 generic fusion procedure are within the nominal melt index r
22、ange of 0.05 to 0.25 gm/10 minutes (190C/ 2.16 Kg), or a high load melt flow of 6 to 17 gm/10 minutes (190C/21.6 Kg), and have a nominal base resin (non-pigmented) density range of 0.936 to 0.955 gm/cc. 2.0 HEAT FUSION JOINING AND EVALUATION OF JOINTS In the heat fusion joining process, joining of t
23、he two components occurs by melting two aligned interfaces; merging the melts, and solidifying the unified melt by cooling under pressure. A fundamental factor for the efficient merger of the two materials is the development, in the interfaces to be joined, of melts that are uniform. Another factor
24、is for the merger to take place evenly and under positive pressure over the entire interface. Parameters affecting melt quality are heating temperature, heating time, fusion pressure, polymer melt flow behavior, ambient temperature, and wind conditions. The melt flow behavior of polyethylene may dif
25、fer significantly from one material to another according to polymer structure characteristics such as the degree of branching, molecular weight and molecular weight distribution. An indicator of the comparative melt flow behavior of polyethylene materials is the Melt Index as determined in accordanc
26、e with ASTM D 1238, “Standard Test Method for Flow Rates of Thermoplastics by Extrusion Plastometer“ 1. ASTM D 3350, “Standard Specification for Polyethylene Plastic Pipe and Fittings Materials“, includes Melt Index as a classification criterion. When heat fusing similar materials, the development o
27、f uniform melts may readily be accomplished with currently available equipment. This is a little more difficult when fusing materials that have different melting characteristics. One technique intended to compensate for this difference and produce uniform melt qualities in different materials is to
28、heat both materials under the same thermal driving force (i.e., heater temperature) but start the heating of the higher melt viscosity (lower Melt Index - see Note 1) material earlier than that of the lower melt viscosity (higher Melt Index) material so that both materials simultaneously emerge from
29、 the heating tool with relatively uniform depth of melt. This technique, which usually employs a heat shield, is used by some installers of PE piping, and has been the subject of an evaluation by PPI. Results obtained indicate that this heat fusion technique yields satisfactory joints. The operator
30、joining piping components made of unlike PE materials should consider that requirements on fused joints imposed by the regulations of the Department of 1The Melt Index per ASTM D-1238 is a measure of the amount of molten material that extrudes during a given period of time through a die of specified
31、 diameter and length and under prescribed conditions of temperature and extrusion pressures. Materials of higher melt viscosity extrude more slowly and exhibit, therefore, lower Melt Indexes. 5Transportation are essentially quality control tests keyed on the performance characteristics of monolithic
32、 joints that have been validated by both long term successful experience and long term pressure testing in accordance with ASTM D 2837, “Standard Method for Obtaining Hydrostatic Design Basis for Thermoplastic Pipe Materials. A similarly extensive background of information is not available for combi
33、nations of fusions of mixed PEs. The operator is, therefore, advised to not only rely on quality control type tests for evaluating mixed joints, but to also consider their longer term pressure testing performance which is a more reliable indicator of ultimate joint quality. 3.0 PPI EVALUATION OF FUS
34、ION OF UNLIKE PE PIPING COMPONENTS PPI member producers of PE pipe and fittings and of the materials from which they are made have been evaluating various methods for the heat fusion joining of unlike PE components. This work has led to the development of the guidelines herein presented. By using th
35、ese guidelines, socket, butt, and saddle fusions of many combinations of piping components made from the following materials have been produced: Pipe and Fittings Materials Evaluated Coded Materials Material Classification 2Tested By ASTM D 2513 By D 3350-02a A PE 2306 PE 214333 B PE 3406 PE 335433
36、C PE 2306 PE 234333 D PE 3408/3406 PE 355434 E PE 2306 PE 234333 F PE 3408/3406 PE 345434 The resultant joints have been evaluated for compliance to the 73.4F burst pressure and sustained (1,000 hours) pressure requirements imposed by ASTM D 2513, “Standard Specification for Thermoplastic Gas Pressu
37、re Piping Systems“ on the less demanding component. The short-term test was conducted in accordance with ASTM D 1599, “Standard Test Method for Short-Time Hydraulic Failure Pressure of Plastic Pipe, Tubing, and Fittings“; the sustained pressure test in accordance with ASTM D 1598, “Standard Test Met
38、hod for Time-to-Failure of Plastic Pipe under Constant Internal Pressure“. A large number of specimens containing heat fusions of the above materials in various pipe diameters and wall thicknesses, and fittings types and sizes, have been evaluated by these tests. In every case the requirements of AS
39、TM D 2513 for the less demanding component have been satisfied. 2In both of the shown classification systems the second digit codes the Melt Index Category. The lower the value of the Melt Index the more viscous is the melt at a given melt temperature. The system of ASTM D-3350 covers more Melt Inde
40、x categories and is, therefore, more useful for making comparisons of the melt flow properties of PE materials. 6The following are recommendations for basic operations that need to be complemented by the addition of detailed requirements reflecting melt characteristics and other properties of the sp
41、ecific materials being joined. The developer of a procedure designed to fuse two specific unlike materials is responsible for ensuring that the resultant joints qualify to all applicable code and regulatory requirements. It is not to be assumed that the use of these basic recommended operations auto
42、matically ensures the qualification, or compliance, of the resultant joint to any standard or code requirement. 4.0 SUGGESTED GUIDELINES FOR THE JOINING OF UNLIKE MATERIALS 4.1 Guidelines for Socket Fusion 4.1.1 Joining Conditions: (1) Heater surface temperature: 500 10F. (2) Heating times for pipe
43、and fitting as recommended by the manufacturer of each component. 4.1.2 Guidelines: (1) Attach the proper size heater adapters and bring the temperature of the heating surface to 500 10F. Be sure that the heating surfaces are clean and free of water, dirt, or plastic. (2) Cut the pipe end squarely a
44、nd remove any burrs. (3) Clean the pipe end and the fitting, both inside and outside, by wiping with a clean, lint free cloth. (4) Place the cold ring clamp3around the pipe at the location determined by the depth gauge. (5) Using even pressure, bring the preheated tool into full contact with the out
45、side surface of the end of the pipe and the inside surface of the socket in such a time sequence that the recommended heating time for each component is satisfied.4The lead time for the component with the longer heating time should be predetermined by subtracting the shorter form the longer heating
46、times. If the recommended heating times are within 10 percent of each other, the longer time may be used for both components. As with socket fusion of like components, the fusion time count down begins when pipe and fitting are fully inserted. 3The cold ring clamp is a fixture placed on the pipe tha
47、t limits pipe heating to only a specific section. 4Heating times required to achieve proper melt conditions may be affected by ambient working conditions such as temperature and wind. Appropriate compensation for these may be required and should be considered. Some manufacturers provide helpful guid
48、elines. 7(6) At the completion of the heating cycle, simultaneously pull, with a snap action, pipe and fitting from the heater. Quickly check visually to confirm that there is complete melt around the entire pipe and fitting socket surfaces. If satisfactory, immediately insert the pipe squarely and
49、fully into the socket. Hold or block the fresh joint in place until the mating surfaces have solidified. If an incomplete melt pattern is observed, the joint is not to be completed. A new joint should then be made with slightly longer heating times 4.2 Guidelines for Butt Fusion 4.2.1 Joining Conditions: (1) Set the heater surface temperature at the higher of the two values that are recommended by the manufacturers of the piping components that are to be joined to each other. Temperatures in the range of 340 to 450F tend to be preferred for butt fusion of pipe
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