Page 287 - Industrial Power Engineering and Applications Handbook

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Tests for the second number as in Table 1.11: Since such installations may be highly prone to explosion
protection against ingress of water and fire hazards, third-party agencies are generally
appointed by the government of a country to certify the
These tests may be carried out as shown in Table 11.8. use of particular equipment or device at such locations.
These agencies, ensure that the equipment is designed
and manufactured in conformity with the requirements
11.6 Tolerances in test results of the relevant standards. It is mandatory on the part of
a manufacturer, supplying equipment for such locations,
The test results so obtained will be subject to a tolerance to first obtain certification for a product from such agencies
as noted in Table 11.9, compared to data provided by the before it can be used for such installations. For instance,
manufacturer based on their design data. the Central Mining Research Institute (CMRI), Dhanbad,
is the authorized agency in India which undertakes
11.7 Certification of motors used in Scrutiny of design and constructional details
hazardous locations Thorough testing of the machine.
Based on the test certificates of CMRI, approval certificates
Motors intended for such locations need special attention. are issued by the relevant statutory authority.

Table 11.8 Protection against ingress of water

Second characteristic Test requirements
number
0 No test i< required
1 The test is carried out by the apparatus illustrated in Figure 11.9. Water is used and adjusted so that the discharge
is 3 to 5 mm of water per minute.
The enclosure under test is placed for IO minutes in its normal operating position below the dripping apparatus,
the base of which should be larger than the enclosure under test.
After the test the amount of water which might have entered the interior of the enclosure should not interfere with
satisfactory operation of the equipment. No water should accumulate near the cable gland plate or enter the
cables.
The test equipment is the same as described for degree of protection I. But the enclosure under test is tilted up
to an angle of +15" in respect of its normal operating position successively, in two planes at right angles (to cover
all four sides). The total duration of the test will be IO minutes (2.5 minutes each side). The test results should
be the same as for degree of protection 1,
The test is carried out by the apparatus illustrated in Figure lI.lO(a). It consists of an oscillating tube, formed into
a semi-circle, the radius of which is kept as small as possible, depending upon the dimensions of the enclosure
under test, but not more than I m. For larger surfaces, a hand sprayer, as illustrated in Figure Il.lO(b), may be
used. During the test the moving shield is not removed from the spray nozzle. The water pressure is adjusted for
a delivery of IO litreshin. The test duration should be 1 minute/m? of the surface area under test, but for not less
than 5 minutes. The tube is oscillated to describe an angle of 60" from the vertical in either direction. The duration
of one oscillation will be about 2 seconds. The water supply should be at least IO litres/min, at a pressure equal
to a head of nearly 8 m of water (80 kN/m*).
The enclosure under test is mounted in its normal position on a turntable, the axis of which will be vertical and
height variable, located near the centre of the semi-circle formed by the oscillating tube. The table is rotated to
spray all parts of the enclosure equally. The enclosure should be kept under a spray of water for IO minutes.
The test results should be the same as for degree of protection 1.
4 The test is similar to that described for degree of protection 3 except that the oscillating tube will now oscillate
through an angle of almost 180" with respect to the vertical in both directions and at a speed of 90" per second.
The support for the equipment under test may be grid-shaped, so that no water is accumulated at the base. The
duration of the test will be 10 minutes.
For larger surfaces the second method as noted in Figure I 1. IO@) may be adopted but the moving shield must
now.be removed from the spray nozzle. The rest of the details remain the same as noted for number 3, when using
a hand sprayer.
The test results should be the same as for degree of protection I.
5 The test is carried out by washing down the test enclosures in every direction by means of a standard hose nozzle
of 6.3 mm inside diameter, as illustrated in Figure 1 1.1 I, held at 3 m from the enclosure with a water pressure
equal to a head of nearly 3 m of water (= 30 kN/m2), enough to give a delivery rate of 12.5 litreshin. The
duration of the test will be determined at 1 min/m' of the surface area under test, subject to a minimum of 3
minutes.
The test results should be the same as for degree of protection 1,