NEMA PRP 3-2009 Expansion Epoxy Based Fittings for RTRC Rigid Nonmetallic Conduit.pdf
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1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA PRP 3-2009 (R2016)Expansion Epoxy Based Fittings for RTRC Rigid Nonmetallic ConduitNEMA PRP 3-2009 (R2016) Page 1 2016 National Electrical Manufacturers Association A NEMA Polymer Raceway Products Document PRP 3-2009 (R2016)
2、 Expansion Epoxy Based Fittings for RTRC Rigid Nonmetallic Conduit Published by National Electrical Manufacturers Association 1300 North 17thStreet, Suite 900 Rosslyn, Virginia 22209 www.nema.org 2016 National Electrical Manufacturers Association. All rights, including translation into other languag
3、es, reserved under the Universal Copyright Convention, the Berne Convention for the Protection of Literary and Artistic Works, and the International and Pan American copyright conventions. NEMA PRP 3-2009 (R2016) Page 2 2016 National Electrical Manufacturers Association NOTICE AND DISCLAIMER The inf
4、ormation in this publication was considered technically sound by the consensus of persons engaged in the development and approval of the document at the time it was developed. Consensus does not necessarily mean that there is unanimous agreement among every person participating in the development of
5、 this document. NEMA standards and guideline publications, of which the document contained herein is one, are developed through a voluntary consensus standards development process. This process brings together volunteers and/or seeks out the views of persons who have an interest in the topic covered
6、 by this publication. While NEMA administers the process and establishes rules to promote fairness in the development of consensus, it does not write the document and it does not independently test, evaluate, or verify the accuracy or completeness of any information or the soundness of any judgments
7、 contained in its standards and guideline publications. NEMA disclaims liability for any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, application, or rel
8、iance on this document. NEMA disclaims and makes no guaranty or warranty, expressed or implied, as to the accuracy or completeness of any information published herein, and disclaims and makes no warranty that the information in this document will fulfill any of your particular purposes or needs. NEM
9、A does not undertake to guarantee the performance of any individual manufacturer or sellers products or services by virtue of this standard or guide. In publishing and making this document available, NEMA is not undertaking to render professional or other services for or on behalf of any person or e
10、ntity, nor is NEMA undertaking to perform any duty owed by any person or entity to someone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given c
11、ircumstances. Information and other standards on the topic covered by this publication may be available from other sources, which the user may wish to consult for additional views or information not covered by this publication. NEMA has no power, nor does it undertake to police or enforce compliance
12、 with the contents of this document. NEMA does not certify, test, or inspect products, designs, or installations for safety or health purposes. Any certification or other statement of compliance with any health or safety-related information in this document shall not be attributable to NEMA and is s
13、olely the responsibility of the certifier or maker of the statement.NEMA PRP 3-2009 (R2016) Page 1 2016 National Electrical Manufacturers Association Thermal expansion and contraction have a significant effect on long straight runs of conduit. For this application, O-ring expansion fittings are used
14、 to accommodate changes in length. This prevents potentially harmful thermal stresses in the conduit itself or in any supporting structures. Expansion Fittings Required Section 355.44 of the National Electrical Code (NEC) requires that expansion fittings be installed for RTRC to compensate for therm
15、al expansion and contraction where the length change is anticipated to be inch or 6 mm or greater in a straight run between securely mounted items. Securely mounted items include boxes, cabinets, elbows, and other conduit terminations. Table 355.44 of the NEC shows the expansion characteristics of R
16、TRC Rigid Nonmetallic Conduit for different temperatures. When are expansion fittings used? Knowing when to use an O-ring expansion fitting is as important as knowing how to use it. Expansion fittings are predominantly used in aboveground installations where the length change is anticipated to be in
17、ch or 6 mm or greater. When are expansion fittings used? (continued) Expansion Epoxy Based Fittings for RTRC Rigid Nonmetallic Conduit All construction materials expand and contract with fluctuations in temperature. These temperature changes affect Reinforced Thermosetting Resin Conduit (RTRC) diffe
18、rently than other common materials such as steel or PVC. For example, the coefficient of thermal expansion for RTRC (1.5 10-5in./in./F or 2.710-5cm/cm /C) is slightly more than twice that of steel and is 50% that of PVC. RTRC has a coefficient of expansion of 1.5105in./in./F or 2.710-5cm /cm / C. A
19、19.68 foot or 6 meter section will change in length about 3/16” or 4.8 mm with a change in temperature of 120F or 66.7C. This equates to slightly more than 1” or 44 mm over a 100 foot or 30.5 m run. NEMA PRP 3-2009 (R2016) Page 2 2016 National Electrical Manufacturers Association Changes in conduit
20、temperature outdoors can exceed 140F or 77.8C considering the heat of summer and cold of winter. This means a 100-foot or 30.5-meter run of fiberglass conduit could change approximately 2 inches or 64 mm in length between summer and winter. If not compensated for with expansion fittings, this change
21、 in length can cause unsightly conduit bowing, distorted boxes, or broken couplings or fittings. The anticipated expansion and contraction per 100 feet or per meter for various lengths of runs and temperature changes is given in Table 355.44 of the NEC The table below expresses this expansion and co
22、ntraction per 100 feet or 30.5 meters of conduit for various temperature changes. Since the C changes in the table below are conversions of the F changes, the expansion values provided are for different C changes than Table 355.44. Expansion Characteristics of RTRC Coefficient of Thermal Expansion =
23、 1.5 10-5in./in./F or 2.7 10-5cm/cm/C Temperature Change Degrees F C Length Change per 100 ft/30.5 m in mm Temperature Change Degrees F C Length Change per 100 ft/30.5 m in mm Temperature Change Degrees F C Length Change per 100 ft/30.5 m in mm Temperature Change Degrees F C Length Change per 100 ft
24、/30.5 m in mm 5 2.8 0.09 2.3 55 30.6 0.99 25.1 105 58.3 1.89 48.0 155 86.1 2.79 70.9 10 5.6 0.18 4.6 60 33.3 1.08 27.4 110 61.1 1.98 50.3 160 88.9 2.88 73.2 15 8.3 0.27 6.9 65 36.1 1.17 29.7 115 63.9 2.07 52.6 165 91.7 2.97 75.4 20 11.1 0.36 9.1 70 38.9 1.26 32.0 120 66.7 2.16 54.9 170 94.4 3.06 77.
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