1、 General Guidelines Repairing Buried HDPE Potable Water Pressure Pipes TN35-2006 2/2006 iForeword 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
2、assisting independent standard-making and user organizations in the development of standards, 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 maintenan
3、ce of existing HDPE pipelines with suggested general guidelines for the repair of those lines that have been subjected to third party or other unforeseen damage. These guidelines constitute a set of basic operations that have been demonstrated by test and experience to produce satisfactory repairs w
4、ith commercially available materials. Each specific procedure must be acceptable to, and qualified by, the operator having legal responsibility for the performance of the piping system. This document was not intended to provide system design information. Go to the PPI website at www.plasticpipe.org
5、for different system design documents. The Plastics Pipe Institute, Inc. has prepared this technical note as a 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 im
6、plied. Additional information may be needed in some areas, especially with regard to unusual or special applications. 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 pr
7、ocesses of any manufacturer, and assumes no responsibility for compliance with applicable laws and regulations. PPI intends to revise this report form time to time, in response to comments and suggestions from users of this note. Please send suggestions for improvements to PPI. Information on other
8、publications can be obtained by contacting PPI directly or visiting the web site. The Plastics Pipe Institute, Inc. 202 462-9607 www.plasticpipe.org iiTable of Content Section: 1 Introduction 1 Section: 2 Temporary Field Repairs 2 2.1 Full Circle Band Clamps Section: 3 Permanent Field Repairs 3 3.1
9、Small Field Repairs 3.1.1 Saddle Fusion Repair 3.1.2 Electrofusion Patch Repair 3.1.3 Mechanical Fitting Repair 3.2 Large Field Repairs 3.2.1 Mechanical Fittings Repair 3.2.2 Repairs with Solid Sleeves 3.2.3 Flange Adapter Spool Repair 3.2.4 Electrofusion Spool Repair Section: 4 Stiffener Installati
10、on Guidelines 14 Section: 5 Restraints Methods 16 5.1 Mechanical Repair Fittings Restraint 5.2 Mechanical Coupling Restraint Section: 6 References 18 SECTION 1 1Introduction Traditional piping systems have gasket sealed bell and spigot joints every 20, which can be a potential maintenance and repair
11、 point at each connection. Metallic pipes are subject to corrosion which can require constant maintenance over the life of the pipes. A heat fused high density polyethylene (HDPE) pipeline is not only corrosion and chemical resistant but the leak free joints at 40 50 intervals are as strong as the p
12、ipe itself which provides a maintenance free system except for infrequent unforeseen third party damage. If HDPE is damaged by a third party, repair methods may be required to bring the piping system back into service as soon as possible. This document will provide general guidelines for repairing H
13、DPE. They should be useful in establishing procedures and/or specifications for various repair methods to HDPE piping systems. For above ground repairs, when the pipe can be moved, the damage can be cut out and replacement pipe can be butt fused or electrofused into the system. Figure 1 Above Ground
14、 Repair with Fusion Machine However constrained installations, such as buried pipes, may not allow such movement. Permanent repairs of constrained pipes may require techniques and fittings that do not require longitudinal movement such as spool or flanged assemblies, mechanical or electrofusion coup
15、lings, etc. Caution: Be sure to follow OSHA safety guidelines when uncovering and repairing buried pipelines. SECTION 2 2Temporary Field Repairs 2.1 Full Circle Band Clamp Many system operators will have full circle band clamps in their specifications as a repair option. In general these types of re
16、pair clamps have proven to be a great method of temporary repair, especially in emergency situations. Some general design considerations for the successful use of full circle band clamps are as follows: Full Circle Band Clamps are recommended for repairs only where the pipe is able to maintain its s
17、tructural integrity. Consider repairs only to a clean-cut round hole or deep scratches or gouges of maximum dimension, less than the nominal diameter of the pipe divided by three. Do not use band clamps when the pipe has cracks, jagged punctures, long tears, or deep scratches or gouges which could p
18、ropagate outside the clamp under anticipated field loads. Do not exceed the manufacturers recommended maximum operating parameters such as temperature and pressure. The installer should always follow the clamp manufacturers recommend installation guidelines. Whenever possible, use a product that has
19、 been specifically designed for use with polyethylene pipe. The manufacturer should always be consulted on the use of their product on polyethylene pipe if the clamp was not manufactured specifically for use with polyethylene pipe. Pipe movement due to thermal expansion, thermal contraction and cree
20、p, as well as, surge events must be considered when repairing polyethylene pipe with a full circle band clamp. Generally, full circle band clamps are intended for use in underground applications. If your application is of a different nature, contact the manufacturer of the band clamp. If the band cl
21、amp is to be used as a permanent repair, contact the fitting manufacturer for the suitability of use as a permanent repair. Figure 2 Full Circle Band Clamps SECTION 3 3Permanent Field Repairs 3.1 Small Field Repairs 3.1.1 Saddle Fusion Repair If the size of the puncture damage is very small (1” or s
22、maller puncture on one pipe wall), a capped off Tapping Tee or High Volume Tapping Tee or patch can be saddle fused to the main over the damaged area, provided the water flow can be stopped and the repair area kept dry during the repair process. Before adding the patch or fitting, drill a small hole
23、 at each end of the damage to prevent the crack from propagating further. Then, butt fuse a cap on the service outlet of the Tapping Tee selected for the repair. Turn off the water and prepare the surface area around the damage for the saddle fusion process (see PPI Generic Saddle Fusion Procedure T
24、R-41). Saddle fuse the fitting over the damaged area using the Generic Procedure and allow the joint to cool. Wait 30 minutes and turn the water back on. Figure 3 Saddle Fusion Repair SECTION 3 43.1.2 Electrofusion Patch Repair An electrofusion patch can also be used to repair small puncture damage
25、in the pipe (3” or smaller puncture in one wall of the pipe) as long as the water flow can be stopped and the repair area kept dry during the repair process. Use the manufacturers recommended electrofusion procedure and equipment for saddle fusion. Figure 4 Electrofusion Patch Repair 3.1.3 Mechanica
26、l Fitting Repair In some cases where the damage is slight but has severed the pipe, the line can be shut off and a small section of the pipe cut out to install a mechanical coupling in the damaged area (see Figures 5, 6, & 7). Contact the coupling manufacturer for the size of damage that can be repa
27、ired. A certain amount of the piping system will need to be exposed to allow the pipe to be bent for the installation of the coupling. Some couplings are self restrained and others are not. Some require a stainless steel stiffener inside the HDPE pipe and some do not. It is recommended that all coup
28、lings used with HDPE should have a stiffener installed to increase the sealing capability of the coupling by minimizing the effects of creep and dimensional changes due to temperature variations (see Section 4). It is also recommended that, if the coupling does not provide its own restraint, then ex
29、ternal restraints should be utilized on each side of the fitting to prevent pullout due to the thermal expansion or the poisson effect of the pipe SECTION 3 5(see Section 5). Mechanical fittings have different design advantages and accommodate different sizes. Contact the mechanical fitting manufact
30、urer for more information. Several manufacturers make mechanical fittings specifically for use with HDPE, including Mueller, Victaulic, Dresser, JCM, Ford, Romac, Cascade Water Works and Smith-Blair. Figure 5 Mechanical Couplings Figure 6 Mechanical Couplings SECTION 3 6Figure 7 Mechanical Couplings
31、 3.2 Large Field Repairs 3.2.1 Mechanical Fitting Repair If the damage to the pipeline cannot be repaired with a single mechanical coupling as described above, two mechanical fittings can be used by cutting out the damaged pipe (figure 8 & 9) and making up an assembly with two mechanical fittings an
32、d a properly sized and length of polyethylene pipe in the middle. Again, install per the fitting manufacturers instructions. (Figure 10) A repair to larger pipes requires joining devices for the size of pipe being repaired. However, the various types of joining devices discussed in this section may
33、not be available for all pipe sizes. Contact the joining device manufacturer or supplier for availability and applicability with polyethylene pipe. + Figure 8 Damaged Pipe SECTION 3 7Figure 9 Cut out Damaged Section of Pipe A saw is needed to cut out the damaged pipe and to cut the replacement secti
34、on between the cut ends. A wrench is also needed to tighten the bolts. After the damaged section is examined, it can be removed. Damaged HDPE pipe is usually cut using a dry chain saw. Measure the distance between the cut pipe ends and cut an HDPE replacement section approximately ” shorter than tha
35、t length. Install the insert stiffeners in both ends of the existing HDPE pipes and in both ends of the replacement section. Figure 10 Mechanical Coupling Repair Assembly Slide the couplings over the replacement section of the pipe and drop the assembly between two cut ends. Then slide the couplings
36、 between the replacement section and the cut ends and tighten the bolts using the manufacturers procedures. SECTION 3 8Caution: Make sure to provide restraints or anchors for the HDPE pipe if the mechanical couplings are not self restrained. Failure to follow this procedure could result in the pipe
37、pulling out of the coupling (see Section 5). As noted above, it is recommended that all HDPE pipe ends used with mechanical couplings have a stiffener installed to increase the sealing capability of the coupling by minimizing the effects of creep and dimensional changes due to temperature variations
38、 (see Section 4). 3.2.2 Repairs with Solid Sleeves Repairs can be made using a mechanical joint (MJ) solid sleeve along with insert stiffeners, restraint device, gasket and tee bolts. A saw is needed to cut out the damaged pipe and to cut the replacement section of HDPE pipe. A wrench is also needed
39、 to tighten bolts. The pipe, gasket and solid sleeve must be cleaned before final tightening of the bolts. The benefit of this repair method is that it can be made in a wet environment with no special equipment. This is basically the same repair method used for PVC and ductile iron pipe with the add
40、ition of insert stiffeners used with HDPE pipe. The parts are MJ sleeve or sleeves, glands, restraint ring, gasket, extra pipe if large area is damaged, gaskets and tee bolts. Figure 11 Restraint fitting placed on HDPE pipe After cleaning the contact surfaces, and installing a stiffener in existing
41、HDPE pipe ends and in the ends of the replacement HPDE pipe section, slide the restraint ring and gland over pipe followed by a gasket as shown above. The drawing below shows a typical layout of parts needed to make a repair. SECTION 3 9In a repair situation, the MJ sleeve is connected on both ends
42、to HDPE pipe. The solid sleeve can make up small sections of pipe. If the damaged pipe is longer than the span of a single sleeve, two solid sleeves are used to replace damaged pipe. Figure 12 Solid Sleeve Repair Assembly SECTION 3 103.2.3 Flange Adapter Spool Repair Once pipeline damage has been re
43、ported, the size of the pipeline and the DR needs to be established. The correct flange adapter and backup ring size is selected and (4) are required for the repair (see Table 1). The water valve is then shut off and the area excavated and planking installed. Cut the damaged pipe from the piping sys
44、tem. Make sure that the length removed is long enough for the flange adapter spool assembly to be installed. (see Table 1) Caution: Make sure the water valve shuts the water flow off 100% with no water flowing. Butt or Electro-fusion joints cannot be made with water flowing through the pipes. If a s
45、mall amount of water is flowing, a towel or pneumatic bladder can be inserted in the valve end to dam up the water long enough to make the butt fusion joint. Be sure to remove this item before making the final connection. A butt fusion machine capable of fusing the pipe size is installed in the ditc
46、h on planking and clamped to the main pipe. A proper sized flange adapter/back-up ring assembly is installed in the movable jaw. Face the pipe and the flange adapter end to mechanical stops. Remove the pipe chips from the area and align the pipe ends. Using the pipe manufacturers recommended butt fu
47、sion procedures, fuse the pipe to the flange adapter/back-up ring assembly and allow the joint to cool under pressure. When this joint is cool, remove the fusion machine from the pipe and install the fusion machines fixed end on the other end of the pipe. Install the proper sized flange adapter/back
48、-up ring assembly in the movable jaw. Face the pipe and the flange adapter end to mechanical stops. Remove the pipe chips from the area and align the pipe ends. Using the pipe manufacturers recommended butt fusion procedures, fuse the pipe to the flange adapter/back-up ring assembly and allow the jo
49、int to cool under pressure. Once the flange adapters have been fused to the existing pipe ends, measure the inside distance between the flanges. Using the pipe manufacturers recommended butt fusion procedures, fuse the other two flange adapter/back-up ring assemblies to a piece of pipe with the same OD, DR and specification as the existing pipe to produce an assembly that matches the inside distance between the flanges on the existing pipe. Install the spool piece between the two flanged pipe ends. Bolt the assembly together using the manufac
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