ASTM B812-1996(2002)e1 Standard Test Method for Resistance to Environmental Degradation of Electrical Pressure Connections Involving Aluminum and Intended for Residential Applicati.pdf

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1、Designation: B 812 96 (Reapproved 2002)e1Standard 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 desig

2、nation 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.e1NOTEParagraph 1.4 was corrected editoria

3、lly in June 2002.INTRODUCTIONElectrical pressure connection systems 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,

4、 aluminum terminations,or any other aluminum current-carrying 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 syst

5、ems arecomprised of the wire or other structure being connected 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 i

6、n actual residentialapplications. Periodic observation of the 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 applicatio

7、n to specific typesof connection systems, set-screw neutral bus 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 cyc

8、lic temperature change (withinrating) and high humidity.1.3 The 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

9、rated at or below 600 V d-c or a-cRMS.1.3.3 This test method 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

10、 of theelectrical connection system to additional environmental 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 activit

11、ies such as photography, painting, sculpture,or similar activities.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 pressureconnectio

12、n systems.1.4 This standard does not purport to address all of 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 for this product/materia

13、l as pro-vided by the manufacturer, to establish appropriate safety and1This 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 May 10, 1996. Pub

14、lished July 1996. Originallypublished as B 812 90. Last previous edition B 812 90.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.health practices, and determine the applicability of regulatorylimitations prior to use.1.5 This standa

15、rd 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 not be used to describe or appraise the firehazard or fire risk of materials, products, or assemblies underactual ins

16、tallation conditions or under 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:B 54

17、2 Terminology Relating to Electrical Contacts andTheir Use22.2 Underwriter Laboratory StandardsUL486B, Standard for Wire Connectors For Use WithAluminum Conductors, ANSI/UL 486B3UL486C, Standard for Splicing Wire Connectors32.3 National Electrical Code:ANSI/NFPA 7043. Terminology3.1 residential appl

18、icationsresidential 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. E

19、xcluded are railroad cars, boats, air-planes, nonresidential, commercial (office buildings, stores)and industrial applications (factories, warehouses).3.2 pressure connection systeman electrical connectionintended to carry current between components or conductors incontact under mechanical pressure.

20、3.2.1 DiscussionThe 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-carr

21、ying and other 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 aluminumas the term “aluminum,” the material ofwhich condu

22、ctors (wire, cable, busbars, etc.), connectioncomponents, and test board components may be made, includesaluminum metal and its alloys.3.4 reference conductora continuous length of the sameconductor material (wire, cable, busbar, etc.) incorporated inthe connection system being tested by being mount

23、ed on thesame test board assembly and connected in the same seriescircuit.3.5 reference connection systemthe reference connectionsystem is the same connection system as that which is underevaluation, but which is exposed only to a dry environment atnormal 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 measurement

26、s 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 tempera

27、turecycling 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-meta

28、lcontact 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. St

29、ability 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 and

30、 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 suc

31、huse, 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 of2Annual Book of ASTM Standards, Vol 02.04.3Available from Underwriters Laboratories, 333 Pfingsten Rd., Northbrook, IL600622096.4National Fire Protection Association, 1 Batterymarch

34、 Park, Quincy, MA022699101.B 812 96 (2002)e12weeks, shall be mV relative to the reference connections.”Connection systems that are most resistant to thermal-cycle/humidity deterioration, within the limitations of determinationby this test method, show no increase in potential drop, relativeto the re

35、ference connections, when tested for indefinite time.Connections 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 ofmos

36、t stringent (No. 1) to least stringent (No. 3).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 permi

37、t correction forroom temperature changes for potential 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 in

38、dividualconnections are noted to be heating abnormally 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 meas

39、urementleads to erratic results. Calibration of 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 inst

40、rument ratings by checks both before and aftereach 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

41、moving theleads and observing the resultant voltage 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 o

42、r removal ofmagnetic field sources is required.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 too

43、utgassing at the maximum temperature of use in 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 pr

44、event condensate dripping onto test samples. The 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 duringth

45、e period of the test.NOTE 1This apparatus is intended 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 contro

46、l accuracy shall be within 62C. The lowertemperature 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 co

47、ld chamber, depending on theprescribed low temperature 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 supp

48、ly outputmust be isolated from the 120/240 volt 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 temper

49、ature 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 samples such that individualsamples are independent of adjacent samples in regards toeffects of mounting or the process of obtaining electricalmeasurements. As required by dimensions of the thermal orhumidity chambers used, the test sample population may bedivided am