CEl IEC 60068-2-18:2000 pdf download
CEl IEC 60068-2-18-2000 pdf download.Environmental testing -Part 2-18:Tests – Test R and guidance: Water.
5 Test Ra: Falling drops
5.1 Object
This test is applicable to products which, during transportation, storage or in service may be exposed to vertical falling drops, the origin of these being, for example, natural rain, seepage or condensation. It shall be clearly stated in the relevant specification whether a product hereinafter referred to as a specimen has to function during testing or merely to survive conditions of falling drops. In either case, the relevant specification shall always prescribe the acceptable tolerances in performance.
5.2 Method Ra 1: Artificial rain
5.2.1 General description of the test
The test specimen is mounted on an appropriate fixture or base support. It is then subjected to falling waterdrops, which simulate natural rain.
The basic requirements for the test apparatus are:
— Drop-generating nozzle or nozzles (see C.2.1 and figure C.1).
— Fixture for the specimen
The fixture shall simulate as far as possible the mounting of the specimen when in service; for example, for wall-mounted equipment the fixture shall simulate a wall.
— Support of the test specimen
The support shall have a base area which is smaller than the base area of the specimen. The support shall be either a turntable which has a rotation speed of 1 r/min and the eccentricity (distance between turntable axis and specimen axis) is approximately 100 mm, or a table which does not turn. The support shall be able to hold the specimen in any test position and, if necessary, be tilted to a maximum of 900 from the vertical plane.
— Water supply with controls
The water used for the test shall be fresh tap water of good quality. In order to avoid clogging of the nozzles, the water shall be filtered and may be demineralized. Details of the characteristics of the water are given in annex A. During the test, the water temperature shall not differ by more than 5 K from the temperature of the specimen under test. If the water temperature is more than 5 K below the temperature of the specimen, a pressure balance shall be provided for the specimen.
5.2.2 SeventIes
The seventies, as indicated by intensity (and associated drop-size distribution), duration and tilt angle of specimen shall be prescribed in the relevant specification. The values shall be selected from those given below. Wind-driven rain is not simulated by this test as the wind velocity is not a parameter of test.
— Intensity, mm/h and (associated drop-size distribution, mm):
10 ± 5 (D= 1,9 ± 0,2); 100 ± 20 (D50= 2,9 ± 0,3); 400 ± 50 (D50= 3,8 ± 0,4).
— Duration, minutes:
10, 30, 60, 120
— Tilt angle a, degrees:
0, 15, 30, 60, 90
NOTE The relevant specification may prescribe a longer duration.
5.2.3 Precondltioning
Preconditioning of the specimen and seals shall be carried out if prescribed in the relevant
specification.
5.2.4 Initial measurements
The specimen shall be submitted to the visual, dimensiona’ and functional checks prescribed by the relevant specification. All features of the specimen likely to affect the test result, for example surface treatment, enclosures, covers or seals, shall be inspected to ensure that the instructions of the relevant specification have been followed.
5.2.5 TestIng
The specimen shall be mounted on the support either
— in its normal operating position, as prescribed in the relevant specification; or
— tilted from the normal operating position and provision made for rotating the specimen in a plane perpendicular to the tilted axis. The rotation may be achieved by a rotating support table or by repositioning the specimen at regular intervals during the test. Alternatively, the specimen can be oscillated through an arc of 270° to avoid the need for slip-ring contacts.
The relevant specification shall specify the tilt angle or angles, the face or faces to be exposedto the drop field and the duration of exposure for each side, or whether the specimen shall becontinuously rotated or oscillated through 270°.See also figure 2.
