DGMS Approval Standards for Flameproof, Intrinsically Safe & Electrical Equipment | EX-d / EX-ia / IS Standards Explained

⚡ Flameproof, Intrinsically Safe & Electrical Equipment – DGMS Approval Standards Mining electrical equipment operates in methane-rich, explosive atmospheres, especially in underground coal mines.
To prevent ignition, DGMS mandates strict testing & approval under:

Flameproof (FLP / Ex-d)

Intrinsically Safe (IS / Ex-ia, Ex-ib)

Non-sparking / safe-area equipment

This blog explains DGMS standards, testing, certification workflow & statutory requirements in simple OnlineMiningExam style.

🔹 1. Why DGMS Approval is Mandatory for Electrical Equipment?

Because underground coal mines contain:

Methane gas (CH₄)

Coal dust

Fire/explosion hazards

DGMS ensures:

✔ No spark → No explosion
✔ Safe electrical circuits
✔ Internationally compliant EX standards
✔ Operators protected from electrical hazards

🔹 2. Indian & International Standards Used by DGMS

Protection Type Standard Used

Flameproof (FLP) IS/IEC 60079-1 (Ex-d)

Intrinsic Safety (IS) IS/IEC 60079-11 (Ex-ia / Ex-ib)

Dust-protected IS/IEC 60079-31

Non-sparking (Ex-n) IS/IEC 60079-15

Cable glands IS/IEC 60079-0 / 1 / 7

General electrical safety IS 5572 / IS 13408 / IS 2148

DGMS requires compliance with BIS + IECEx/ATEX for imported equipment.

🔹 3. Flameproof Equipment (FLP) – Ex-d

🔥 What is Flameproof?

A housing/enclosure that:

Contains internal explosion

Prevents flame propagation

Resists pressure surges

Typical examples:

FLP Motors

FLP Switchgear / Starters

FLP Junction Boxes

FLP Lighting Fittings

FLP Cable Glands

FLP Gas Detectors

⭐ Key DGMS Requirements for FLP Equipment

Flamepath dimensions must match approved drawing

Smoothness (Ra < 6.3 µm)

No scratches or damage

Gas test clearance maintained

Enclosure withstands 1.5 × maximum pressure

Joint length & gap within IS standards

BIS / IECEx certification mandatory

Proper earthing

Cable glands must be FLP type

🔹 4. Intrinsically Safe Equipment (IS) – Ex-ia / Ex-ib

🧯 What is Intrinsic Safety?

Limiting energy, voltage, current, and temperature so that the device cannot ignite gas even under fault conditions. Common IS devices:

Gas detectors

Communication systems

Cap lamps

Sensors & automation

Telemetry

Proximity Warning Systems (PWS)

⭐ IS Equipment DGMS Requirements

Safety parameters must be permanently marked

Energy storage (L, C) must be limited

Ex-test report (ExTR) mandatory

QAN/QAR mandatory

Fault tests must pass 2-fault conditions (for Ex-ia)

🔹 5. Non-Sparking Equipment (Ex-n)

Used in:

Surface mines

Non-gassy underground areas

Not allowed in: ❌ Degree II & III mines
❌ Hazardous zones 0 & 1

🔹 6. Hazardous Area Classification – DGMS Standards

Zone Condition Example

Zone 0 Gas present continuously Sealed off areas

Zone 1 Gas likely during operation Development headings

Zone 2 Gas unlikely, but possible Return airways

Usage Restrictions

Equipment Zone

Ex-ia Zone 0 / 1 / 2

Ex-ib Zone 1 / 2

Ex-d Zone 1 / 2

Ex-n Zone 2

🔹 7. DGMS Approval Process for Electrical Equipment

Manufacturer/IAR → Submit Form B/C ↓ Document Scrutiny by DGMS ↓ CIMFR/ERTL/CPRI Testing ↓ Factory QAR Audit ↓ Field Trial (If Required) ↓ DGMS Approval (Form K)

🔹 8. DGMS Testing Requirements

⭐ For Flameproof Equipment

Spark test

Temperature test

Pressure test

Impact test

Flame transmission test

Flamepath measurement

⭐ For IS Equipment

Spark ignition test

Component thermal testing

Fault simulation

Energy limitation verification

🔹 9. Typical Electrical Equipment Requiring DGMS Approval

Motors & switchgear

Lighting fittings

Transformers

Cables & glands

Cap lamps

Battery electric vehicles (BEVs)

Gas detectors

Communication systems

Proximity warning systems

🔥 25 MCQs (DGMS Pattern) with Answers

1) Flameproof equipment is denoted by —

a) Ex-n
b) Ex-e
c) Ex-d
d) Ex-m
e) None
Ans: c

2) Intrinsically safe circuits follow —

a) IS 2148
b) IS 5572
c) IS/IEC 60079-11
d) IS 3815
e) None
Ans: c

3) Flamepath should be —

a) Rough
b) Painted
c) Smooth and within tolerance
d) Plastic-coated
e) None
Ans: c

4) Ex-ia equipment is suitable for —

a) Zone 2 only
b) Zone 1 only
c) Zone 0/1/2
d) Surface only
e) None
Ans: c

5) FLP motors prevent —

a) Water
b) Smoke
c) Internal flame propagation
d) Heat
e) None
Ans: c

6) IS equipment limits —

a) Energy
b) Voltage
c) Current
d) All of the above
e) None
Ans: d

7) IECEx relates to —

a) Vehicles
b) Explosion protection
c) Timber
d) Temperature
e) None
Ans: b

8) Ex-d testing includes —

a) Colour test
b) Pressure & flame transmission test
c) Sticker test
d) Water test
e) None
Ans: b

9) Cap lamps are normally —

a) Ex-d
b) Ex-ia
c) Ex-n
d) Ex-e
e) None
Ans: b

10) Ex-n equipment allowed in —

a) Zone 0
b) Zone 1
c) Zone 2
d) All zones
e) None
Ans: c

11) Flamepath must not be —

a) Smooth
b) Steel
c) Damaged or scratched
d) Clean
e) None
Ans: c

12) IS circuits tested for —

a) One fault only
b) Two faults (Ex-ia)
c) Zero fault
d) Not tested
e) None
Ans: b

13) DGMS form for approval is —

a) Form J
b) Form L
c) Form K
d) Form A
e) None
Ans: c

14) Gas detectors require —

a) UV test
b) Ex certification
c) Water test
d) No test
e) None
Ans: b

15) Testing labs include —

a) Film studio
b) ETDC/ERTL
c) CPRI
d) CIMFR
e) All of these
Ans: e

16) Flameproof equipment prevents ignition in —

a) Kitchens
b) Methane atmospheres
c) Car parks
d) Offices
e) None
Ans: b

17) Ex-e means —

a) Extra dangerous
b) Increased safety
c) External engine
d) Energy excess
e) None
Ans: b

18) IS equipment required in —

a) Degree III mines
b) Degree II mines
c) Zone 0 areas
d) Gassy mines
e) All of these
Ans: e

19) Ex markings must be —

a) Hidden
b) Permanently engraved
c) removable
d) Sticker based
e) None
Ans: b

20) Equipment safety depends on —

a) Colour
b) Material
c) Approved design
d) Workmanship
e) All except (a)
Ans: e

21) Flameproof enclosure thickness —

a) Variable
b) Optional
c) Fixed as per drawing
d) Random
e) None
Ans: c

22) For imported equipment DGMS requires —

a) ATEX
b) IECEx
c) BIS compliance
d) Indian testing
e) All of these
Ans: e

23) Flamepaths must be checked during — a) Shipping
b) Maintenance
c) Driving
d) Painting
e) None
Ans: b

24) Non-sparking equipment is —

a) Ex-d
b) Ex-ia
c) Ex-n
d) Ex-e
e) None
Ans: c

25) Goal of DGMS electrical approval —

a) Increase sales
b) Reduce weight
c) Prevent explosions & protect miners
d) Improve colour
e) None
Ans: c

🔚 Conclusion

Flameproof, Intrinsically Safe and Electrical equipment are the backbone of underground mining safety.
DGMS ensures that:

No electrical spark causes methane ignition

Only IEC/IS-certified equipment is used

Mines maintain highest electrical safety standards

Imported equipment meets Indian laws

A deep understanding of EX standards is essential for DGMS exam aspirants and mine engineers.

🚀 Download DGMS EX Equipment Notes at OnlineMiningExam.com
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DGMS Approval Standards for Flameproof, Intrinsically Safe & Electrical Equipment | EX-d / EX-ia / IS Standards Explained

Because underground coal mines contain:

Methane gas (CH₄)

Coal dust

Fire/explosion hazards

DGMS ensures:

🔥 What is Flameproof?

🧯 What is Intrinsic Safety?

Manufacturer/IAR → Submit Form B/C ↓ Document Scrutiny by DGMS ↓ CIMFR/ERTL/CPRI Testing ↓ Factory QAR Audit ↓ Field Trial (If Required) ↓ DGMS Approval (Form K)

🔹 8. DGMS Testing Requirements

a) Ex-n
b) Ex-e
c) Ex-d
d) Ex-m
e) None
Ans: c

2) Intrinsically safe circuits follow —

a) IS 2148
b) IS 5572
c) IS/IEC 60079-11
d) IS 3815
e) None
Ans: c

3) Flamepath should be —

a) Rough
b) Painted
c) Smooth and within tolerance
d) Plastic-coated
e) None
Ans: c

4) Ex-ia equipment is suitable for —

a) Zone 2 only
b) Zone 1 only
c) Zone 0/1/2
d) Surface only
e) None
Ans: c

5) FLP motors prevent —

a) Water
b) Smoke
c) Internal flame propagation
d) Heat
e) None
Ans: c

6) IS equipment limits —

a) Energy
b) Voltage
c) Current
d) All of the above
e) None
Ans: d

7) IECEx relates to —

a) Vehicles
b) Explosion protection
c) Timber
d) Temperature
e) None
Ans: b

8) Ex-d testing includes —

a) Colour test
b) Pressure & flame transmission test
c) Sticker test
d) Water test
e) None
Ans: b

9) Cap lamps are normally —

a) Ex-d
b) Ex-ia
c) Ex-n
d) Ex-e
e) None
Ans: b

10) Ex-n equipment allowed in —

a) Zone 0
b) Zone 1
c) Zone 2
d) All zones
e) None
Ans: c

11) Flamepath must not be —

a) Smooth
b) Steel
c) Damaged or scratched
d) Clean
e) None
Ans: c

12) IS circuits tested for —

a) One fault only
b) Two faults (Ex-ia)
c) Zero fault
d) Not tested
e) None
Ans: b

13) DGMS form for approval is —

a) Form J
b) Form L
c) Form K
d) Form A
e) None
Ans: c

14) Gas detectors require —

a) UV test
b) Ex certification
c) Water test
d) No test
e) None
Ans: b

15) Testing labs include —

a) Film studio
b) ETDC/ERTL
c) CPRI
d) CIMFR
e) All of these
Ans: e

16) Flameproof equipment prevents ignition in —

a) Kitchens
b) Methane atmospheres
c) Car parks
d) Offices
e) None
Ans: b

17) Ex-e means —

a) Extra dangerous
b) Increased safety
c) External engine
d) Energy excess
e) None
Ans: b

18) IS equipment required in —

a) Degree III mines
b) Degree II mines
c) Zone 0 areas
d) Gassy mines
e) All of these
Ans: e

19) Ex markings must be —

a) Hidden
b) Permanently engraved
c) removable
d) Sticker based
e) None
Ans: b

20) Equipment safety depends on —

a) Colour
b) Material
c) Approved design
d) Workmanship
e) All except (a)
Ans: e

21) Flameproof enclosure thickness —

a) Variable
b) Optional
c) Fixed as per drawing
d) Random
e) None
Ans: c

22) For imported equipment DGMS requires —

a) ATEX
b) IECEx
c) BIS compliance
d) Indian testing
e) All of these
Ans: e

23) Flamepaths must be checked during — a) Shipping
b) Maintenance
c) Driving
d) Painting
e) None
Ans: b

24) Non-sparking equipment is —

a) Ex-d
b) Ex-ia
c) Ex-n
d) Ex-e
e) None
Ans: c

25) Goal of DGMS electrical approval —

a) Increase sales
b) Reduce weight
c) Prevent explosions & protect miners
d) Improve colour
e) None
Ans: c

🔚 Conclusion

OUR COURSES View More

DGMS Approval Standards for Flameproof, Intrinsically Safe & Electrical Equipment | EX-d / EX-ia / IS Standards Explained

Because underground coal mines contain: Methane gas (CH₄) Coal dust Fire/explosion hazards DGMS ensures:

🔥 What is Flameproof?

🧯 What is Intrinsic Safety?

Manufacturer/IAR → Submit Form B/C ↓ Document Scrutiny by DGMS ↓ CIMFR/ERTL/CPRI Testing ↓ Factory QAR Audit ↓ Field Trial (If Required) ↓ DGMS Approval (Form K) 🔹 8. DGMS Testing Requirements

a) Ex-n b) Ex-e c) Ex-d d) Ex-m e) None Ans: c 2) Intrinsically safe circuits follow —

a) IS 2148 b) IS 5572 c) IS/IEC 60079-11 d) IS 3815 e) None Ans: c 3) Flamepath should be —

a) Rough b) Painted c) Smooth and within tolerance d) Plastic-coated e) None Ans: c 4) Ex-ia equipment is suitable for —

a) Zone 2 only b) Zone 1 only c) Zone 0/1/2 d) Surface only e) None Ans: c 5) FLP motors prevent —

a) Water b) Smoke c) Internal flame propagation d) Heat e) None Ans: c 6) IS equipment limits —

a) Energy b) Voltage c) Current d) All of the above e) None Ans: d 7) IECEx relates to —

a) Vehicles b) Explosion protection c) Timber d) Temperature e) None Ans: b 8) Ex-d testing includes —

a) Colour test b) Pressure & flame transmission test c) Sticker test d) Water test e) None Ans: b 9) Cap lamps are normally —

a) Ex-d b) Ex-ia c) Ex-n d) Ex-e e) None Ans: b 10) Ex-n equipment allowed in —

a) Zone 0 b) Zone 1 c) Zone 2 d) All zones e) None Ans: c 11) Flamepath must not be —

a) Smooth b) Steel c) Damaged or scratched d) Clean e) None Ans: c 12) IS circuits tested for —

a) One fault only b) Two faults (Ex-ia) c) Zero fault d) Not tested e) None Ans: b 13) DGMS form for approval is —

a) Form J b) Form L c) Form K d) Form A e) None Ans: c 14) Gas detectors require —

a) UV test b) Ex certification c) Water test d) No test e) None Ans: b 15) Testing labs include —

a) Film studio b) ETDC/ERTL c) CPRI d) CIMFR e) All of these Ans: e 16) Flameproof equipment prevents ignition in —

a) Kitchens b) Methane atmospheres c) Car parks d) Offices e) None Ans: b 17) Ex-e means —

a) Extra dangerous b) Increased safety c) External engine d) Energy excess e) None Ans: b 18) IS equipment required in —

a) Degree III mines b) Degree II mines c) Zone 0 areas d) Gassy mines e) All of these Ans: e 19) Ex markings must be —

a) Hidden b) Permanently engraved c) removable d) Sticker based e) None Ans: b 20) Equipment safety depends on —

a) Colour b) Material c) Approved design d) Workmanship e) All except (a) Ans: e 21) Flameproof enclosure thickness —

a) Variable b) Optional c) Fixed as per drawing d) Random e) None Ans: c 22) For imported equipment DGMS requires —

a) ATEX b) IECEx c) BIS compliance d) Indian testing e) All of these Ans: e 23) Flamepaths must be checked during — a) Shipping b) Maintenance c) Driving d) Painting e) None Ans: b 24) Non-sparking equipment is —

a) Ex-d b) Ex-ia c) Ex-n d) Ex-e e) None Ans: c 25) Goal of DGMS electrical approval —

a) Increase sales b) Reduce weight c) Prevent explosions & protect miners d) Improve colour e) None Ans: c 🔚 Conclusion

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Because underground coal mines contain:

Methane gas (CH₄)

Coal dust

Fire/explosion hazards

DGMS ensures:

Manufacturer/IAR → Submit Form B/C ↓ Document Scrutiny by DGMS ↓ CIMFR/ERTL/CPRI Testing ↓ Factory QAR Audit ↓ Field Trial (If Required) ↓ DGMS Approval (Form K)

🔹 8. DGMS Testing Requirements

a) Ex-n
b) Ex-e
c) Ex-d
d) Ex-m
e) None
Ans: c

2) Intrinsically safe circuits follow —

a) IS 2148
b) IS 5572
c) IS/IEC 60079-11
d) IS 3815
e) None
Ans: c

3) Flamepath should be —

a) Rough
b) Painted
c) Smooth and within tolerance
d) Plastic-coated
e) None
Ans: c

4) Ex-ia equipment is suitable for —

a) Zone 2 only
b) Zone 1 only
c) Zone 0/1/2
d) Surface only
e) None
Ans: c

5) FLP motors prevent —

a) Water
b) Smoke
c) Internal flame propagation
d) Heat
e) None
Ans: c

6) IS equipment limits —

a) Energy
b) Voltage
c) Current
d) All of the above
e) None
Ans: d

7) IECEx relates to —

a) Vehicles
b) Explosion protection
c) Timber
d) Temperature
e) None
Ans: b

8) Ex-d testing includes —

a) Colour test
b) Pressure & flame transmission test
c) Sticker test
d) Water test
e) None
Ans: b

9) Cap lamps are normally —

a) Ex-d
b) Ex-ia
c) Ex-n
d) Ex-e
e) None
Ans: b

10) Ex-n equipment allowed in —

a) Zone 0
b) Zone 1
c) Zone 2
d) All zones
e) None
Ans: c

11) Flamepath must not be —

a) Smooth
b) Steel
c) Damaged or scratched
d) Clean
e) None
Ans: c

12) IS circuits tested for —

a) One fault only
b) Two faults (Ex-ia)
c) Zero fault
d) Not tested
e) None
Ans: b

13) DGMS form for approval is —

a) Form J
b) Form L
c) Form K
d) Form A
e) None
Ans: c

14) Gas detectors require —

a) UV test
b) Ex certification
c) Water test
d) No test
e) None
Ans: b

15) Testing labs include —

a) Film studio
b) ETDC/ERTL
c) CPRI
d) CIMFR
e) All of these
Ans: e

16) Flameproof equipment prevents ignition in —

a) Kitchens
b) Methane atmospheres
c) Car parks
d) Offices
e) None
Ans: b

17) Ex-e means —

a) Extra dangerous
b) Increased safety
c) External engine
d) Energy excess
e) None
Ans: b

18) IS equipment required in —

a) Degree III mines
b) Degree II mines
c) Zone 0 areas
d) Gassy mines
e) All of these
Ans: e

19) Ex markings must be —

a) Hidden
b) Permanently engraved
c) removable
d) Sticker based
e) None
Ans: b

20) Equipment safety depends on —

a) Colour
b) Material
c) Approved design
d) Workmanship
e) All except (a)
Ans: e

21) Flameproof enclosure thickness —

a) Variable
b) Optional
c) Fixed as per drawing
d) Random
e) None
Ans: c

22) For imported equipment DGMS requires —

a) ATEX
b) IECEx
c) BIS compliance
d) Indian testing
e) All of these
Ans: e

23) Flamepaths must be checked during — a) Shipping
b) Maintenance
c) Driving
d) Painting
e) None
Ans: b

24) Non-sparking equipment is —

a) Ex-d
b) Ex-ia
c) Ex-n
d) Ex-e
e) None
Ans: c

25) Goal of DGMS electrical approval —

a) Increase sales
b) Reduce weight
c) Prevent explosions & protect miners
d) Improve colour
e) None
Ans: c

🔚 Conclusion