1、Designation: B 812 96 (Reapproved 2008)Standard Test Method forResistance to Environmental Degradation of ElectricalPressure Connections Involving Aluminum and Intended forResidential Applications1This standard is issued under the fixed designation B 812; the number immediately following the designa
2、tion indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONElectrical pressure connection s
3、ystems involving aluminum are those in which one or more of thecomponents of the system in the direct electrical path or carrying any electrical current is fabricatedof aluminum, including aluminum wires, aluminum bus bars, aluminum bolts, aluminum terminations,or any other aluminum current-carrying
4、 member. Included are systems which must carry current forsafety purposes such as ground shields or straps attached to aluminum framing or other structuralmembers. Pressure connection systems can be evaluated by this test method. Such systems arecomprised of the wire or other structure being connect
5、ed and the means of connection, any elementof which is made of aluminum.Connection systems tested are exposed sequentially to ambients of high relative humidity andtemperature cycles of 75C, such as may be encountered by some connections in actual residentialapplications. Periodic observation of the
6、 potential drop across the connection interfaces while carryingrated current provides a measurement of connection performance.1. Scope1.1 This test method covers all residential pressure connec-tion systems. Detailed examples of application to specific typesof connection systems, set-screw neutral b
7、us connectors andtwist-on wire-splicing connectors, are provided in AppendixX1 and Appendix X2.1.2 The purpose of this test method is to evaluate theperformance of residential electrical pressure connection sys-tems under conditions of cyclic temperature change (withinrating) and high humidity.1.3 T
8、he limitations of the test method are as follows:1.3.1 This test method shall not be considered to confirm aspecific lifetime in application environments.1.3.2 The applicability of this test method is limited topressure connection systems rated at or below 600 V d-c or a-cRMS.1.3.3 This test method
9、is limited to temperature and watervapor exposure in addition to electrical current as required tomeasure connection resistance.1.3.4 This test method does not evaluate degradation whichmay occur in residential applications due to exposure of theelectrical connection system to additional environment
10、al con-stituents such as (but not limited to) the following examples:1.3.4.1 Household chemicals (liquid or gaseous) such asammonia, bleach, or other cleaning agents.1.3.4.2 Chemicals as may occur due to normal hobby orprofessional activities such as photography, painting, sculpture,or similar activ
11、ities.1.3.4.3 Environments encountered during construction orremodeling such as direct exposure to rain, uncured wetconcrete, welding or soldering fluxes and other agents.1.3.5 This test method is limited to evaluation of pressureconnection systems.1.4 This standard does not purport to address all o
12、f thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to become familiarwith all hazards including those identified in the appropriateMaterial Safety Data Sheet (MSDS) for this product/materialas provided by the manufacturer, to establish appropr
13、iatesafety and health practices, and determine the applicability ofregulatory limitations prior to use.1.5 This standard should be used to measure and describethe properties of materials, products, or assemblies in responseto electrical current flow under controlled laboratory condi-tions and should
14、 not be used to describe or appraise the fire1This test method is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of SubcommitteeB02.11 on Electrical Contact Test Methods.Current edition approved March 1, 2008. Published March 2008. Origin
15、allyapproved in 1990. Last previous edition approved in 2002 as B 812 96 (2002)e1.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.hazard or fire risk of materials, products, or assemblies underactual installation conditions or under
16、actual fire conditions.However, results of this test may be used as elements of a firerisk assessment which takes into account all of the factorswhich are pertinent to an assessment of the fire hazard of aparticular end use.2. Referenced Documents2.1 ASTM Standards:2B 542 Terminology Relating to Ele
17、ctrical Contacts andTheir Use2.2 Underwriter Laboratory Standards:UL486B Standard for Wire Connectors For Use With Alu-minum Conductors, ANSI/UL 486B3UL486C Standard for Splicing Wire Connectors32.3 NEC Document:ANSI/NFPA 70 National Electric Code43. Terminology3.1 residential applications, nresiden
18、tial applications arethose involving a structure or vehicle used entirely for perma-nent or temporary human habitation. Included are homes(single or multiple-unit houses and mobile or modular struc-tures), motels, hotels, dormitories, hospitals, rest homes, andrecreational vehicles. Excluded are rai
19、lroad cars, boats, air-planes, nonresidential, commercial (office buildings, stores)and industrial applications (factories, warehouses).3.2 pressure connection system, nan electrical connectionintended to carry current between components or conductors incontact under mechanical pressure.3.2.1 Discus
20、sionThe mechanical pressure may be appliedby clamping, tightening of threaded components, spring force,crimping, swaging, or other means. For the purpose of the testprocedure, the connection system consists of all componentsnormally present in the application, including both current-carrying and oth
21、er metallic components, and non-metalliccomponents (insulators, insulation, protective boots or sleeve,etc.). Also see definition of “Connection, Pressure (Solder-less),” in Article 100 of reference noted in Section 2.3 (NEC).3.3 aluminum, nas the term “aluminum,” the material ofwhich conductors (wi
22、re, cable, busbars, etc.), connectioncomponents, and test board components may be made, includesaluminum metal and its alloys.3.4 reference conductor, na continuous length of the sameconductor material (wire, cable, busbar, etc.) incorporated inthe connection system being tested by being mounted on
23、thesame test board assembly and connected in the same seriescircuit.3.5 reference connection system, nthe reference connec-tion system is the same connection system as that which isunder evaluation, but which is exposed only to a dry environ-ment at normal room temperature.4. Summary of Test Method4
24、.1 The environmental exposure of the connections testedconsists of weekly sequences consisting of five thermal cyclesof 75C temperature change (taking a maximum of8htoaccomplish), followed by exposure for the balance of the weekto conditions at or near 100 % relative humidity at roomtemperature. The
25、 text exposure cycle is repeated for a mini-mum of four one-week cycles. Reference connections are keptin a dry environment at room temperature for the sameduration. Potential drop measurements, at rated current, aremade prior to each weekly environmental exposure cycle, anda final set of measuremen
26、ts is taken at the end of the test.5. Significance and Use5.1 The principal underlying the test is the sensitivity of theelectrical contact interface to temperature and humidity cyclingthat electrical pressure connection systems experience as aresult of usage and installation environment. The temper
27、aturecycling may cause micromotion at the mating electrical contactsurfaces which can expose fresh metal to the local ambientatmosphere. The humidity exposure is known to facilitatecorrosion on freshly exposed metal surfaces. Thus, for thoseconnection systems that do not maintain stable metal-to-met
28、alcontact surfaces under the condition of thermal cycling andhumidity exposure, repeated sequences of these exposures leadto degradation of the contacting surface indicated by potentialdrop increase.5.2 The test is of short duration relative to the expected lifeof connections in residential usage. S
29、tability of connectionresistance implies resistance to deterioration due to environ-mental conditions encountered in residential service. Increas-ing connection resistance as a result of the test exposureindicates deterioration of electrical contact interfaces. Assur-ance of long term reliability an
30、d safety of connection types thatdeteriorate requires further evaluation for specific specifiedenvironments and applications.5.3 UseIt is recommended that this test method be used inone of two ways. First, it may be used to evaluate and reportthe performance of a particular connection system. For su
31、chuse, it is appropriate to report the results in a summary (ortabular) format such as shown in Section 17, together with thestatement “The results shown in the summary (or table) wereobtained for (insert description of connection) when tested inaccordance with Test Method B 812. Second, it may be u
32、sed asthe basis for specification of acceptability of product. For thisuse, the minimum test time and the maximum allowableincrease in potential drop must be established by the specifier.Specification of connection systems in accordance with this useof the standard test method would be of the form:
33、“Themaximum potential drop increase for any connection, whentested in accordance with Test Method B 812 for a period ofweeks, shall be mV relative to the reference connections.”Connection systems that are most resistant to thermal-cycle/humidity deterioration, within the limitations of determination
34、by this test method, show no increase in potential drop, relativeto the reference connections, when tested for indefinite time.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information
35、, refer to the standards Document Summary page onthe ASTM website.3Available from Underwriters Laboratories (UL), 333 Pfingsten Rd., North-brook, IL 60062-2096, http:/.4Available from National Fire Protection Association (NFPA), 1 BatterymarchPark, Quincy, MA 02169-7471, http:/www.nfpa.org.B 812 96
36、(2008)2Connections that are less resistant to thermal-cycle/humidityconditions applied by this test will demonstrate progressiveincreases in potential drop with increasing time on test. Thus,the following examples of specifications are in the order ofmost stringent (No. 1) to least stringent (No. 3)
37、.Duration, weeks Maximum Potential Drop Increase, mV1. 52 02. 16 0.23. 4 1.06. Interferences6.1 TemperatureBecause resistance of metallic conduc-tors is a function of temperature, provision of a standard lengthof conductor wire has been provided to permit correction forroom temperature changes for p
38、otential drop measurements.However, degraded electrical connections among the testsamples can be a source of abnormal heat during the measure-ments (when current is flowing), causing temperature varia-tions from point-to-point on the test assembly. If individualconnections are noted to be heating ab
39、normally when potentialdrop measurements are being made (as determined by rela-tively high potential drop), it is desirable to minimize tempera-ture nonuniformity by using temporary thermal isolation bar-riers.6.2 CurrentCurrent variation during the measurementleads to erratic results. Calibration o
40、f the required constantcurrent source shall be maintained.6.3 InstrumentsInstrument stability shall be maintainedby means of frequent calibration checks. Stability of referencevoltage drop across a standard resistor should be maintained towithin the instrument ratings by checks both before and after
41、each group of measurements.6.4 Magnetic FieldsVoltage signals resulting from straymagnetic fields intersecting the voltage probe leads or powersupply leads need to be assessed prior to beginning each seriesof measurements. Generally, this can be done by moving theleads and observing the resultant vo
42、ltage changes. Alterna-tively, a source of stray magnetic field such as an energizedautotransformer can be moved adjacent to the measurementcircuit for detection of voltage changes. If voltage instability isobserved, corrective action such as shielding or removal ofmagnetic field sources is required
43、.7. Apparatus7.1 MaterialsOther than materials normally considered tobe part of the connection system being evaluated, materialsselected for use in the test system (for construction of testframes, fixturing, humidity chamber, etc.) shall be resistant tooutgassing at the maximum temperature of use in
44、 the test.7.2 Humidity VesselThe humidity vessel shall be a cleansealed chamber, the bottom of which is covered with deionizedwater to a depth of approximately 30 mm, and a platform forsamples above the water level. The vessel shall include a shieldto prevent condensate dripping onto test samples. T
45、he materialof the humidity vessel shall be inert with regards to humiditysuch that no contamination of test samples or deionized wateroccurs. The vessel is to be operated in a normal laboratoryenvironment which has continuous temperature control duringthe period of the test.NOTE 1This apparatus is i
46、ntended to expose samples to relativehumidity at or near 100 %.7.3 Temperature ChamberThe temperature chamber shallbe capable of control at the defined upper temperature of thethermal cycle such that chamber temperature stability, unifor-mity, and control accuracy shall be within 62C. The lowertempe
47、rature of the cycle may be achieved in the same chamber,if it is capable of cooling to the lower defined temperature.Alternatively, the thermal cycle can be achieved by transferbetween the high-temperature chamber and a room-temperature environment or cold chamber, depending on theprescribed low tem
48、perature of the thermal cycle.7.4 PowerA 50/60 Hz ac constant current supply isrequired, capable of continuously maintaining the specified testcurrent within 61 %. For safety reasons, the maximum outputpotential at open circuit shall be 12 V and the supply outputmust be isolated from the 120/240 vol
49、t alternating current(VAC) primary circuit.7.5 Test BoardA mounting board or frame shall be pro-vided for the test samples such that the board or frame be inertwith regard to humidity and dimensionally stable with regardto the thermal cycle of 75C temperature change. To the extentpossible, the thermal expansion coefficient shall match that ofthe material being tested. (Example: frame shall be aluminumif aluminum wire or cable is a major part of the connectionsystem being tested.) The board or frame shall provide formechanical mounting of the test samp
