Intrinsic Safety Testing by

1
Intrinsic Safety Testingby

• Gail Nicola, Electrical Engineering Technician
• Ed Vensko, Electrical Engineering Technician

2
Battery Flash Current Testing

• Purpose To determine the maximum short circuit
  current of a battery.
• Pass/Fail Criteria None. The data is used to
  determine the intrinsic safety of a particular
  circuit.
• Samples 3 fresh or fully charged batteries for
  each battery manufacturer specified.
• Recommendations
• Submit samples with the application package, if
  possible.
• Individual cells should be submitted instead of a
  complete battery pack that may contain
  polyswitches or fuses.
• Verify that manufacturer part number of samples
  agree with documentation.

3
(No Transcript)
4
(No Transcript)
5
(No Transcript)
6
(No Transcript)
7
Cap Lamp Bulb Life

• Purpose To determine compliance with 30 CFR
  19.9(b) and 19.9( c)2.
• Pass/Fail Criteria
• 19.9(b) Average life of the bulb shall not be
  less than 200 hours and 92 shall have a life of
  150 hours.
• 19.9(c)(2) Current consumption of at least 94 of
  the bulbs shall not exceed the average current by
  more than 6. The candlepower of at least 90
  shall not fall short of the average candlepower
  by more than 30.

8
Cap Lamp Bulb Life

• Samples 50 marked bulbs, discharge rack capable
  of testing 10 bulbs max.
• Recommendations
• Submit samples with application package

9
(No Transcript)
10
(No Transcript)
11
Accuracy of Methane Detectors

• Purpose To determine compliance with 30 CFR
  Part 22 within the limits
  of error specified in 22.7(d)(2).
• Pass/Fail Criteria When more than 2 readings
  for each percentage or the average of all 10
  readings of any of the four samples exceeds the
  limits of error.
• Samples 4 representative samples, calibration
  kit and calibration procedures, probes, maximum
  length specified sampling lines, batteries and/or
  battery chargers.

12
(No Transcript)
13
Accuracy of Methane Detectors

• Problems
• Sensors have not been burned in.
• Calibration gas is not accurate.
• All specified battery packs have not been
  submitted.
• How detectors react with low battery voltage
• No low flow pump alarms
• Flow rate, gas concentration, and pump
  calibration procedures not adequately specified.
• Recommendations
• Check performance of detectors before submitting
• Verify concentration of calibration gas.

14
- 4 instruments (2 with pumps, 2 without
pumps) - calibration gas and instruction
manual - regulators - probes -
sampling tubing , specify length - battery
chargers
15
(No Transcript)
16
Surface Temperature Test

• Purpose To determine the maximum surface
  temperature of a component.
• Pass/Fail Criteria The temperature of the
  external surfaces of components shall not exceed
  150 C if exposed to coal dust or 530 C if
  exposed to a methane-in-air atmosphere.
• Samples
• 10 samples of the component under test.
• 10 samples of the current-interrupting device (if
  applicable).

17
Surface Temperature Test

• Recommendations
• Position the surface mount components on a PCB
  with 2 leads.
• Use adequately rated components.
• Use dust tight enclosures.
• Submit 10 samples of components likely to
  overheat (e.g. low value/rated resistor
  and zener diodes, etc.) with your application
  package.
• Submit fuse manufacturers time versus current
  characteristic curves.

18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
Coal Dust Blanketing Test

• Purpose If a small component exceeds 150 C
  during surface temperature testing then the
  component is subjected to the Dust Blanketing
  Test.
• Pass/Fail Criteria The component fails the test
  if there is evidence of smoldering or ignition of
  the coal dust.
• Samples 10 samples of each component
• Recommendations
• Design circuitry with fuses to prevent
  overheating of components.

22
Hot Wire Calibration and Small Component Ignition

• Purpose To determine if the heated element will
  ignite a methane-in-air mixture.
• Pass/Fail The component must not ignite the
  test gas.
• Samples 10 samples of each component specified
• Problems Sensors are submitted without the
  elements exposed (sintered metal screen removed)
• Recommendations
• Submit samples with the application package.
• Submit samples with elements exposed.

23
(No Transcript)
24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27
Current-Limiting Resistor Tests

• Purpose To determine if the resistor decreases
  in resistance by more than 10 .
• Pass/Fail Criteria The resistor shall not
  decrease in resistance by more than 10 of its
  pre-test value, flame, or deform such that it
  would be short-circuited by an adjacent
  conductor.
• Samples 10 samples of each CLR specified on
  the documentation and 10 samples of the
  current-interrupting device (if applicable).
• Recommendations
• Submit samples with the application package.
• Design circuitry with fuses to prevent
  overheating of components.
• Submit fuse time versus current curve (if
  applicable).

28
Spark Ignition Test

• Purpose To determine whether the circuit is
  capable of releasing enough electrical energy to
  cause an ignition of a flammable mixture of
  methane and air at the most easily ignitable
  composition.
• Pass/Fail Criteria An ignition occurs.
• Samples 3 samples each of motors, inductors,
  speakers, etc.
• Problems
• Unable to obtain a pretest calibration due to
  environmental conditions.
• Inductive calibration with copper electrodes
• Recommendations
• Design circuits with adequate current limiting
  resistance so spark testing may be waived.
  (Reference ignition curves.)

29
(No Transcript)
30
(No Transcript)
31
(No Transcript)
32
Optical Isolator Test

• Purpose Each optically-coupled isolator shall
  withstand a minimum dielectric voltage of either
  2500 volts (rms) or four times the maximum
  safe-area voltage (whichever is greater) between
  its input and output.
• Pass/Fail Criteria No breakdown shall occur.
• Samples 9 of each type of optical isolator
  specified on the submitted documentation.

33
Optical Isolator Test

• Problems
• Verifying internal spacing between input and
  output circuitry.
• Specification ratings of the optical isolator are
  not submitted.
• Recommendations
• Submit adequate specifications for the optical
  isolator so the device is accepted based on
  evaluation only and testing of the component is
  waived.
• Submit nine samples of each optical isolator of
  all manufacturers specified on the submitted
  documentation.

34
Protective Transformer Test

• Purpose Transformers for direct connection to a
  supply voltage shall be evaluated for dielectric
  strength.
• Pass/Fail Criteria There shall be no breakdown
  of the insulation between the test points during
  testing.
• Samples 3 samples of each transformer specified
  in your application.
• Recommendations
• Submit samples that are adequately marked with
  manufacturer and manufacturer part number.
• Submit samples with application package.

35
Drop Test

• Purpose To determine whether portable apparatus
  continue to be intrinsically safe after being
  subjected to 6 drops from a height of 3 feet onto
  an oak plank.
• Pass/Fail Criteria There shall be no separation
  or ejection of the battery or batteries from the
  apparatus, nor other fault that could affect
  intrinsic safety. For equipment requiring a
  dust-tight enclosure to exclude coal dust entry,
  the enclosure of the sample shall continue to be
  dust-tight after the drop test.
• Samples 1 representative sample of the
  manufactured portable instrument.

36
Drop Test

• Recommendations
• Drop an instrument at your facility before
  submitting for approval.

37
(No Transcript)
38
Piezoelectric Component Impact Test

• Purpose To determine the maximum output energy
  generated by the piezoelectric component when it
  is impacted with an energy of 20 joules (2 kg at
  1 m).
• Pass/Fail Criteria The maximum output energy
  generated by the piezoelectric component shall
  not exceed 1500 micro joules.
• Samples 3 each of the apparatus containing the
  piezoelectric component of a quality, design, and
  construction consistent with that of the final
  manufactured product.

39
Piezoelectric Component Impact Tests

• Problems
• Capacitance of the crystal is not specified
  and/or doesnt match submitted drawing.
• Connection directly to the crystal is not
  possible crystal is located in a potted assembly
  with other oscillating circuitry.
• 3 samples of the component were not submitted in
  a test mockup with the samples mounted in
  their normal position..
• Unable to obtain a second impact on the sample of
  the component since the first impact completely
  destroys the sample.
• Recommendations
• Submit three samples mounted in test mockups.
• Attach output leads directly to the crystal or to
  amplification circuitry.
• Submit specification data with regard to the
  maximum capacitance of the crystal.

40
(No Transcript)
41
(No Transcript)
42
(No Transcript)
43
(No Transcript)
44
(No Transcript)
45
Standard Test Procedures

• ASTP2002
• ASTP2004
• ASTP2008
• ASTP2009
• ASTP2010
• ASTP2012
• ASTP2022
• ASTP2026
• ASTP2030
• ASTP2036
• ASTP2040

• Battery Flash Current Test
• Accuracy of Methane-Indicating Detectors
• Cap Lamp Bulb Life Test
• Current Limiting Resistor/Surface Temperature
  Test
• Dust Blanketing Temperature Test
• Hot Wire Calibration and Small Component Ignition
  Test
• Spark Ignition Test
• Optical Isolator Test
• Protective Transformer Test
• Drop Test for Portable Instruments
• Piezoelectric Component Impact Test