DGMS Guidelines for Audio Visual Alarms in Surface Transport & HEMM – Safety Provisions & 25 MCQs

🧾 DETAILED NOTES

1️⃣ Introduction

Surface transport machinery and HEMMs such as dumpers, dozers, shovels, graders, loaders, and cranes operate in noisy and dusty environments where human visibility is often limited. DGMS mandates the installation of audio-visual alarms (AVA) to alert nearby workers of equipment movement, especially during reversing, starting, or approaching blind spots. These alarms significantly reduce run-over, collision, and entrapment accidents in opencast mines.

2️⃣ DGMS Concern

A number of accidents in opencast mines have occurred because nearby workers or drivers were unaware of machine movement or reversing operations. DGMS issued circulars ensuring all HEMMs are equipped with dual warning systems (audio + visual) to provide clear alerts even in noisy environments.

3️⃣ Legal Framework

Reference	Description
The Mines Act, 1952 – Sec. 23	Obligation to ensure worker safety.
CMR 2017 – Reg. 106, 107, 108	Rules for transport and use of HEMMs.
DGMS (Tech.) Circular No. 08/2017	Safety standards for HEMM operation.
DGMS Circular 05/2015	Guidelines for reversing and signaling systems.
IS 10323	Specification for audible reversing alarms.

4️⃣ Purpose of Audio Visual Alarm

To warn nearby personnel of equipment start or reverse movement.
To ensure safe communication between operator and ground staff.
To minimize collision risks in low-visibility areas.
To support multi-layered safety—visual, sound, and physical barriers.

5️⃣ DGMS Guidelines

All surface transport and HEMMs must have functioning audio and visual alarms (beacon + buzzer).
The audio alarm should be clearly audible over background noise.
The visual beacon must be visible at least 50 meters in daylight.
Alarms should automatically activate during reversing or startup.
Equipment should not operate if the alarm is defective or muted.
Periodic inspection and functional testing of alarms every shift.
Alarms to be flameproof (FLP/IS approved) if used in gassy areas.

6️⃣ Typical Alarm Systems

Alarm Type	Function	DGMS Requirement
Audio (Buzzer)	Reversing alert	≥ 90 dB sound level
Visual (Beacon Light)	Flash during reversing	Visible ≥ 50 m
Combination System	Both alerts together	Mandatory for dumpers, dozers
Cabin Indicator	Alerts operator of failure	Required

7️⃣ Inspection and Testing

Conduct pre-shift checks for alarm functioning.
Record inspections in HEMM logbook.
Replace or repair faulty alarms immediately.
Maintenance supervised by competent engineer (mechanical/electrical).
DGMS inspectors verify alarm functioning during mine audits.

8️⃣ Accident Case Study

In a 2022 incident at an opencast coal mine, a helper was crushed while standing behind a dumper reversing without an operational alarm. DGMS investigation revealed: audio alarm had been disconnected during maintenance. Action taken: Management penalized under Sec. 72 of Mines Act, and strict instructions were issued for daily alarm checks.

⚙️ QUICK ONE-LINERS (Revision Points)

DGMS Circular 08/2017 – HEMM safety including alarms.
Alarms required for all surface transport machinery.
Audible alarm level – 90–110 dB.
Visual beacon visibility – ≥ 50 meters.
Must auto-activate during reversing.
Checked every shift before operation.
Alarm failure = machine out of service.
CMR Reg. 107/108 – Transport safety provisions.
DGMS mandates FLP/IS type alarms in gassy mines.
Audio + visual = mandatory dual system.

🧩 DESCRIPTIVE MODEL QUESTION & ANSWER

Q. Explain DGMS requirements for audio-visual alarms in surface transport machinery and HEMMs.

Answer:
As per DGMS Circular 08/2017 and Regulation 107/108 of CMR 2017, all surface transport and heavy earth moving machines must have audio-visual alarms (AVA) that automatically activate during startup and reversing. The audio alarm should produce a distinct sound audible up to 90–110 dB, and the visual beacon must be visible at least 50 meters away. The alarm’s functioning must be checked every shift, and machines with defective alarms must not be used. This system prevents collisions, protects workers, and ensures compliance with DGMS safety standards.

🧮 25 DGMS-Based MCQs

Q1. DGMS circular for HEMM alarm system:

Solution: DGMS (Tech.) Circular No. 08/2017 provides comprehensive safety standards for HEMM operation, including alarms.

Q2. Audio-visual alarm must operate:

Solution: Alarms are critical during startup (to warn people nearby) and reversing (to warn people in the blind spot).

Q3. Minimum visibility for beacon light:

Solution: The visual alarm (beacon) must be bright enough to be seen from at least 50 meters away, even in daylight.

Q4. Minimum sound level for audible alarm:

Solution: The alarm must be loud enough to be heard over the ambient noise of the mine, typically requiring 90 dB or more.

Q5. DGMS circular for reversing alarm:

Solution: DGMS Circular 05/2015 specifically addresses guidelines for reversing and signaling systems on HEMM.

Q6. Alarm failure means:

Solution: A defective safety-critical device (like an alarm) renders the machine unsafe, and it must be taken out of service until repaired.

Q7. CMR 2017 Reg. 107 & 108 relates to:

Solution: Reg 107 (Dumps) and Reg 108 (Transport) both include provisions for the safe operation of transport machinery.

Q8. Alarm type required in HEMM:

Solution: DGMS mandates a dual-warning system (both audio and visual) to be effective in all conditions.

Q9. Alarms in gassy mines must be:

Solution: Any electrical equipment used in potentially gassy atmospheres (like some coal mine surface areas or oilfields) must be Flameproof (FLP) or Intrinsically Safe (IS).

Q10. Frequency of alarm testing:

Solution: The operator must perform a pre-start check, which includes testing the alarms, at the beginning of every shift.

Q11. Typical beacon color:

Solution: Amber is used for general movement/warning, and Red is often used specifically for reversing.

Q12. Alarm activation method:

Solution: To be reliable, the reverse alarm must be automatic, linked directly to the reverse gear.

Q13. Sound level measured in:

Solution: Decibel (dB) is the standard unit for measuring sound intensity or level.

Q14. Purpose of audio alarm:

Solution: The alarm's function is to alert pedestrians and other drivers who may be in the vehicle's path.

Q15. Alarm malfunction action:

Solution: A defective safety device must be reported and repaired before the machine can be safely used.

Q16. Alarm visible range ensures:

Solution: A long visible range (50m+) gives other people enough time to notice the vehicle and move to safety.

Q17. Operator must check alarm:

Solution: The pre-start check is the most critical time to identify defects before the machine begins operation.

Q18. Audio alarm intensity should:

Solution: To be effective, the alarm's sound level must be significantly higher than the background noise of the mine.

Q19. Who ensures alarm maintenance?

A. Competent engineer B. Miner D. Clerk E. None

Solution: The appointed Mechanical or Electrical Engineer is responsible for the statutory maintenance of all safety equipment.

Q20. DGMS requires alarms on:

Solution: Alarms are mandated on all HEMM and surface transport machinery.

Q21. Visual alarm used for:

Solution: The flashing beacon provides a visual warning, which is especially effective at night or for workers using hearing protection.

Q22. DGMS inspection checks:

Solution: The functionality of safety-critical devices like alarms is a key item on a DGMS inspector's checklist.

Q23. Common accident prevented by alarms:

Solution: Reversing alarms are specifically designed to prevent "run-over" accidents, where a vehicle hits a person in its blind spot.

Q24. Audio alarm must not exceed (to prevent hearing damage):

Solution: While it must be loud (min 90 dB), it also shouldn't be excessively loud (e.g., > 110-115 dB) to avoid causing hearing damage to those nearby.

Q25. Alarm testing record kept in:

Solution: The results of pre-start and weekly inspections of HEMM safety devices are recorded in the machine's statutory logbook.

🔗 INTERNAL LINKS

Related Topic	Read More On...
Opencast Transport	Accidents Due to Dumpers and Tippers
HEMM Safety	Safety Features in Crawler/Tyre Mounted Machinery
Opencast Dumps	Design & Monitoring of Pit/Dump Slopes
Risk Assessment	DGMS Campaign on "Risk Calculator"

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