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1、FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION Subject 635 SUMMARY OF TOPICS The following changes in requirements are being proposed: Modify Construction and Performance Requirements for Bushings For your convenience in review, proposed additions to existing requirements are shown un
2、derlined and proposed deletions are shown lined-out. Modify Construction and Performance Requirements for Bushings RATIONALE UL proposes to revise various construction and performance requirements for insulating bushings in Standard UL 635. ULs proposed revisions include: Deleting the Humidity and E
3、levated Temperature Tests described in Sections 11 and 12 respectively; Deleting the requirements for temperature ratings described in Section 14; and Changing the numerical designation of the sections for the Sharp Bend Protection Test and Markings, Details, from 13 and 15 to 11 and 12 respectively
4、. The intent of the proposed revisions is to ensure that the requirements in Standard UL 635 are similar to requirements for insulating bushings provided in the majority of ULs end-product standards in which bushings are required to be used. PROPOSAL 1.2 This Standard does not cover bushings used in
5、 the following applications: a) Bushings for the protection of uninsulated conductors. b) Strain-relief insulating bushings used to hold more than one cable, wire, or cord. c) Bushings that are an integral part of a fl exible cord. d) Bushings used at the end of a raceway at the point of connection
6、to open wiring and bushings used in conjunction with rigid or fl exible conduit, conduit fi ttings, electrical metallic tubing, armored cable, or non-metallic sheathed cable. e) Bushings for power circuit breakers, transformers, or similar power apparatus rated more than 600 volts. f) Bushings inten
7、ded for outdoor use. -,-,- FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION g) Bushings used on armored cable between the conductors and the outer armor. h) Insulating bushings provided either separately or as part of a conduit fi tting. i) Rainproof or liquid tight bushings. j) Bushing
8、s for use on the ends of rigid or fl exible conduit. k) Closures of the type used to plug holes in outlet boxes or outlet box covers: 1)Covered by the Standard for Metallic Outlet Boxes, UL 514A and by the Standard for Nonmetallic Outlet Boxes, Flush-Device Boxes, and Covers, UL 514C or 2)Of the typ
9、e used to plug holes in enclosures. k l) The following items covered by the Standard for Conduit, Tubing, and Cable Fittings, UL 514B: 1) Cord grips; 2) Insulating bushings; 3) Liquid-tight fl exible cord fi ttings; 4) Mesh grips; 5) Strain relief grips; 6) Strain relief grips for bus drop cables; 7
10、) Strain relief grips for fl exible cords; and 8) Strain relief with wire mesh cord grips. 4.4 A strain-relief bushing shall be constructed so that it performs its intended function without damage to the fl exible cord or insulated wire. An anti-rotation feature shall be provided. See 15.5 12.3 (d).
11、 4.5 A bushing that is intended to be used with a cord that is in motion during normal use shall provide sharp bend protection as indicated in the Sharp Bend Protection Test, Section 13 11. 5.1.1 Ceramic materials and some molded compositions such as phenolic and urea formaldehyde are capable of bei
12、ng used as materials for a separate insulating bushing. Vulcanized fi ber is not prohibited from being used when the bushing is not less than 3/64 inch (1.2 mm) thick, and when it is formed and secured in place so that it is not adversely affected by conditions of typical moisture. Other materials,
13、such as nylon, are capable of being used after a suitable investigation. See Humidity Test, Section 11, and Elevated Temperature Test, Section 12. SUBJECT 635-2- -,-,- FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION 5.3.1 The temperature rating of the device, as indicated in 10.1, 12.3
14、, and 15.4, a bushing is to be based on the mechanical-without-impact relative thermal index (RTI Strength) of the material used in the device insulating bushing. The relative thermal index shall be determined in accordance with the Standard for Polymeric Materials Long Term Property Evaluations, UL
15、 746B. Note: The relative thermal index of a material is an indication of the materials ability to retain a particular property (such as physical or electrical) when exposed to an elevated temperature for an extended period of time. For each material, a number of relative thermal indices are establi
16、shed, each related to a specifi c property, and specifi c thickness of the material. 5.3.2 The temperature rating of a polymeric device insulating bushing shall not exceed the mechanical-without-impact relative thermal index of the material that is selected for the insulating bushing device, in the
17、devices bushings minimum critical thickness. When a bushing model number is evaluated with alternate or substitute materials (see Substitution of materials, Section 5.4) the temperature rating for that specifi c model number can not exceed the lowest mechanical-without-impact relative thermal index
18、of the materials authorized for that model. 5.4.1 Another polymeric material shall be allowed to be substituted in a device having met the requirements of this Standard only when all of the following conditions are met and compliance is determined through an appropriate investigation: a) There is Th
19、e substitute material has an identical generic description (for example: Type 66, 30 percent glass fi lled, FR type, polyamide). b) Tensile The tensile strength of materials the substitute and the originally evaluated material, determined in accordance with the Standard for Polymeric Materials Short
20、 Term Property Evaluations, UL 746A or ISO 527-1, Plastics Determination of Tensile Properties Part 1: General Principles, and ISO 527-2, Plastics Determination of Tensile Properties Part 2: Test Conditions for Moulding and Extrusion Plastics, shall be compared, and shall indicate that the substitut
21、e material has a strength of at least 95 percent of that of the original material. The tensile strengths used in this comparison shall be generated by either: 1) A previous investigation or 2) Side-by-side testing of both materials. c) The substitute materials mechanical-without-impact relative ther
22、mal indices index shall be used for the temperature rating of the device as specifi ed in 5.3.1 equal to or higher than the originally evaluated material. 6.3 The cord guard supplied with a bushing shall be fl exible enough to conform to the motion of the cord in normal use without producing a sharp
23、 bend at or near the point of attachment to the bushing. See Sharp Bend Protection Test, Section 13 11. Exception:A rigid guard is capable of being used when, upon investigation, it is determined to provide protection equivalent to that of a fl exible cord guard. See Sharp Bend Protection Test, Sect
24、ion 13 11. SUBJECT 635-3- -,-,- FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION 8.3 When any type of bushing uses a bell-mouth construction having a radius not less than 1.5 times the overall diameter of the largest cable or cord it is intended to accommodate, the construction is not p
25、rohibited from being used where the fl exible cable or cord is in motion during use, when it is determined to provide protection from sharp bends as indicated in the Sharp Bend Protection Test, Section 13 11. 9 Installation Feed-through Test 9.1 Three samples of each feed-through bushing shall be ca
26、pable of performing their intended functions when tested as indicated in 9.2 and 9.3 without any cutting of damaging the insulation of the conductors and without displacing the bushing. 10.1 Six Three samples of a strain-relief bushing are to be assembled and placed in an oven that has been preset a
27、t rated temperature of the bushing. After one hour the bushings are subjected to a strain-relief test while still at the rated temperature in a metal plate in accordance with 10.2. Three of When tested in accordance with 10.2, the samples are to have the force applied normal to the exit of the cord
28、or wire, and three samples are to be subjected to the strain-relief test applied at a 90 angle to the normal plane of exit perpendicular to the metal plate. See Figures 10.1 and 10.2. Figure 10.1 Strain-relief test (straight-through bushing) and Figure 10.2 Strain-relief test (right-angle bushing).
29、To view the proposed revisions of Figures 10.1 and 10.2, click onto the cell in the table titledSummary of Topicsin the CSDS Proposal Review Work Area for UL 635, then click onto the termDocumentationlocated under the Actions menu in the navigation bar on the left hand side of the page. 10.2 Each sa
30、mple is to be assembled to a metal plate in accordance with the recommendations of the manufacturer in regards to: a) The fl exible cable or cord size and type; b) Mounting means or hole size and shape; and c) Minimum panel thickness. The fl exible cord or single insulated wire is to be 30 inches (0
31、.7 m) in length, and is to extend 1-3/4 inches (44 mm) from the inside face of the bushing. The last 1/4 inch (6.4 mm) of the cord or wire is to be a bare conductor. The plate is to be fi rmly supported in a horizontal plane. A gradual pull of the force indicated in Table 10.1 of 35 pounds is to be
32、applied to the length of cord exiting the outside face of the bushing hanging beneath the plate. The force is to be applied for a period of one minute. SUBJECT 635-4- -,-,- FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION Table 10.1 Strain-relief test values Wire size (AWG)Force (pounds
33、) 10 and larger100 12 and 1450 16 and 1835 2020 27 (tinsel)12 11 Humidity Test 11.1 Three samples of each type of bushing are to be assembled as illustrated in Figure 11.1 or 11.2 in a hole of the intended size and shape in a metal plate along with a length of cable, cord, or wire. The cable, cord,
34、or wire shall be the size and type intended for use with the bushing. The complete assembly is to be placed in a humidity chamber in which the relative humidity has been adjusted to 85 5 percent at a temperature of 32C 2C (89.6F 3.6F) for a period of 7 hours. Immediately after removal from the chamb
35、er the samples are to be subjected to the tests indicated in 11.2 or 11.3. This is generated text for fi gtxt. This is generated text for fi gtxt. Figure 11.1 Humidity test (feed-through bushing) SUBJECT 635-5- -,-,- FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION 11.2 A feed-through b
36、ushing is to be supported and positioned so that the plane of its opening is vertical. The cord or wire is to be physically secured at the upper end, pass through the bushing, and make a downward right-angle bend against the edge of the bushing. A 10-pound (4.5-kg) weight is to be attached to the en
37、d of the wire or cord that emerges downward from the edge of the bushing. See Figure 11.1. 11.3 A strain-relief bushing is to be secured and positioned so that a 10 pound-force (44.5 N) can be gradually applied for one minute in a direction normal to the plane of the cord exit from the bushing. See
38、Figure 11.2. 11.4 There shall be no observable deterioration of, or other adverse effects on, the bushing due to the humidity-force combination. The bushing shall not be forced out of its mounting hole. 12 Elevated Temperature Test 12.1 Three samples of a feed through bushing, or six samples of a st
39、rain-relief bushing are to be assembled in the intended manner in metal plates having the largest intended opening and minimum thickness. The sample assemblies are to be placed in an air-circulating, draft-free oven for 7 hours at a temperature of 100C (212F), or 20C (68F) above the temperature rati
40、ng of the bushing, whichever is greater. Following the oven conditioning the sample assemblies were allowed to return to room temperature and subjected to a thorough visual inspection to verify the bushing has not warped, charred, blistered, or otherwise unduly alter its characteristics. Following t
41、he visual examination the bushings are to be tested in accordance with 12.2 or 12.3. Figure 11.2 Humidity test (strain-relief bushing) SUBJECT 635-6- -,-,- FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION 12.2 The three conditioned feed through bushings are to be tested at room temperat
42、ure in accordance with 9.2 and 9.3 with the results complying with the requirements in 9.1. 12.3 The six conditioned strain relief bushings are to be tested at room temperature in accordance with 10.1 and 10.2 with the results complying with the requirements in 10.3. 11 Sharp Bend Protection Test 11
43、.1 To determine that the cord guard complies with the requirement in 6.3, the guard is to be tested with a 3-pound (1.4 kg) weight attached to a length of fl exible cord or insulated wire extending at least 12 inches (305 mm) beyond the cord guard that is installed in the appropriate bushing and ass
44、embled to a fi xed metal plate. 11.2 The bushing is to be mounted as illustrated in Figure 11.1. Dimension X is to be measured while the axis of the cord and the cord guard coincide with the axis of the bushing. No weight is to be applied to the cord during this measurement. This is generated text f
45、or fi gtxt. SUBJECT 635-7- -,-,- FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION Figure 11.1 Test of cord guard SUBJECT 635-8- -,-,- FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION 11.3 With the 3-pound (1.4 kg) weight applied, Dimension Y shall not be less than 60 percen
46、t of Dimension X, and Dimension Z shall not be less than 5/8 inch (15.9 mm). 11.4 To determine whether or not a bushing having a bell-mouth construction complies with the requirements in 8.3, it is to be tested with a 3-pound weight attached to a short length of fl exible cable or insulated wire tha
47、t is installed in the bushing and assembled to a fi xed metal plate, extending at least 12 inches (305 mm) beyond the bushing. 11.5 The bushing is to be mounted as illustrated in Figure 11.2. With the 3-pound (1.4 kg) weight applied, the Radius of Curvature of the fl exible cable or cord shall not b
48、e less than 1.5 times the overall diameter (D) of the cord. This is generated text for fi gtxt. RATING 14 Details 14.1 The temperature rating of an insulating bushing shall not be higher than the temperature rating of any insulating material used in its construction. Figure 11.2 Test of bell-mouth bushing SUBJECT 635-9- -,-,- FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION 14.2 An insulating bushing shall be rated 60, 75, 90, or