Motors and panels for underground mining: what DGMS, CMRI and CCE approval actually cover

DGMS approval is what makes electrical equipment legal to use below ground in an Indian mine. CMRI, now CSIR-CIMFR, is the Dhanbad laboratory that tests explosion-protected equipment; its test report feeds an approval but is not one. CCE approval, from the Chief Controller of Explosives at PESO, covers hazardous areas under the Petroleum Rules, not coal mines. A motor or panel for an underground coal seam of second or third degree gassiness must be flameproof, certified for Group I, and carry a current DGMS approval for that exact type. New India Electricals Ltd (NIEL) supplies flameproof motors listed with approvals from CMRI Dhanbad, DGMS Dhanbad and CCE Nagpur.

TL;DR

• The Coal Mines Regulations, 2017 require “only flame proof electrical apparatus and equipment” below ground in every gassy seam of the second or third degree.

• A second degree seam has more than 0.1 percent inflammable gas in the general body of air, or emits 1 to 10 cubic metres per tonne of coal. A third degree seam emits more than 10.

• DGMS approves equipment type by type. Its 2013 approval policy lists flameproof and intrinsically safe equipment against IS/IEC 60079 standards, with BIS licensing required and a three-month field trial.

• CSIR-CIMFR, Dhanbad tests and certifies Ex d, Ex i, Ex e, Ex p and other protection types. A test certificate proves the design meets the standard; DGMS approval permits its use in mines.

• CCE (PESO) approval applies under the Petroleum Rules, 2002 and the gas cylinder and pressure vessel rules. It does not make equipment legal underground in a coal mine.

• Mining equipment is Group I under IEC 60079-0. The ABB guide to IEC motors for explosive atmospheres notes that “the zone classification is not used in mines.”

• The CEA Safety Regulations, 2023 cap earth fault current at 750 mA for 250 to 1100 V below ground. New 1.1 to 11 kV mine installations are limited to 10 A.

Who approves what: DGMS, CIMFR (CMRI) and CCE?

Three bodies appear on Indian flameproof equipment paperwork, and each does a different job. DGMS approves equipment for use in mines. CSIR-CIMFR tests and certifies explosion-protected designs. The Chief Controller of Explosives, who heads PESO, approves Ex equipment for petroleum and gas premises. Buyers confuse them because one motor can carry all three documents.

The practical rule follows from the table. Match the approval to the site’s governing regulations, not to the equipment. A flameproof motor with a valid PESO approval for an LPG bottling plant is not thereby approved for a longwall face. A DGMS-approved gate end box is not thereby approved for a petrol depot.

When does underground equipment have to be flameproof?

Underground electrical equipment has to be flameproof wherever the Coal Mines Regulations or the CEA Safety Regulations require it. That depends on the seam’s degree of gassiness and the equipment’s position. Regulation 208(2) of the Coal Mines Regulations, 2017 states that “in every gassy seam of the second or third degree, only flame proof electrical apparatus and equipment shall be used belowground.”

The regulations define the three degrees:

Regulation 112 of the CEA (Measures relating to Safety and Electric Supply) Regulations, 2023, “Precautions where gas exists,” adds location rules.

• First degree seams: all apparatus, including portable and transportable apparatus and lighting, used in-bye of the last ventilation connection must be flameproof. Signalling, telecommunication, remote control and insulation tester circuits must be intrinsically safe.

• Second and third degree seams: apparatus within 90 metres of any working face or goaf in a second degree mine must be flameproof. In a third degree mine the distance is 270 metres. Apparatus in-bye of the last ventilation connection or in any return airway must also be flameproof, and all electric lamps must be in flameproof enclosures.

Regulation 112 also sets a hard trip threshold. Where inflammable gas in the general body of air exceeds “one and one quarter per cent,” supply must be disconnected from all cables and apparatus in the area. The CEA regulations further require that in second and third degree seams, the main mechanical ventilator is interlocked with the switchgear so that stopping the fan disconnects the mine’s supply.

A mine can change category. CMR 2017 lets the authorities permit non-flameproof equipment already in use to continue for no more than one year after a first degree mine is reclassified as second or third degree. Equipment bought for a first degree mine that may be reclassified should be specified flameproof from the start.

What does a DGMS approval actually cover?

A DGMS approval covers a specific type of equipment from a specific manufacturer. It is based on test reports against the relevant standard, a factory inspection for first-time Indian manufacturers, and a successful field trial in a mine. Regulation 208(3) of CMR 2017 allows the Chief Inspector to specify equipment that must be of a type “approved by the Chief Inspector.” Once specified, “any such appliance, equipment, machinery, or material, other than that approved… shall not be used in any mine.”

The DGMS Approval Policy 2013 sets out the process. DGMS issued a second revision in 2016. The policy states that approvals assess “the actual performance in mines and pit worthiness of the products… in addition to examining conformity to relevant standards.” For flameproof and intrinsically safe equipment, its Appendix I lists:

The process runs in stages. Test reports and documents are scrutinised, and “approval for field trial is granted.” After the trial, performance reports signed by the manufacturer and the mine’s management go to DGMS. For items requiring a BIS licence, the policy allows a field trial without one, but “approval shall be granted only after submission of valid BIS license.” Prototypes are tested “in a Government Laboratory/ Government approved Laboratory/DGMS approved Laboratory.”

Three conditions determine whether an approval still applies to what arrives on site:

• It is type and manufacturer specific. The approval covers the design tested and field tried. A different frame, rating or terminal arrangement is not automatically covered.

• It is subject to revalidation. The policy requires revalidation when standards are revised, and allows withdrawal if approval conditions are violated or a quality complaint is substantiated.

• The mine carries the duty to check. CMR 2017 regulation 208(5) makes the owner, agent or manager responsible for ensuring that approved equipment conforms “to approved specifications in all respects.” Regulation 208(6) requires a copy of every approval to be kept at the mine office.

What does a CIMFR (CMRI) test certificate prove?

A CIMFR test certificate proves that a design was tested against the relevant explosion-protection standard and complied. It is the technical evidence behind an approval, not the approval itself. CSIR-CIMFR’s Flame Proof and Equipment Safety laboratory in Dhanbad states that it has tested explosion-protected equipment “since CSIR-CIMFR’s inception in 1956.”

The laboratory lists testing and certification for these protection types:

• Flameproof (Ex d)

• Intrinsically safe (Ex i)

• Increased safety (Ex e)

• Non-sparking

• Restricted breathing

• Pressurisation (Ex p)

• Encapsulation, oil filled and sand filled

It describes itself as an NABL accredited laboratory. It also tests non-electrical items such as conveyor belts, brattice cloth, ventilation ducting and flame arresters.

Many buyers and older nameplates still say “CMRI Dhanbad.” That is the name under which much existing mining equipment was certified. For procurement, the name matters less than three facts on the certificate:

• The standard and edition tested to

• The equipment group, Group I for mines

• The exact model and rating covered

Why must a mining motor be Group I, and why do zones not apply?

Underground mining equipment belongs to Group I under IEC 60079-0, because the hazard is firedamp (methane) and coal dust, not the process gases of surface industry. ABB’s guide to IEC motors and drives for explosive atmospheres explains the split. Group I “covers underground mines or mines susceptible to firedamp,” Group II covers surface gas atmospheres and Group III surface dust.

The same guide records a point that catches surface engineers out: for Group I, “the zone classification is not used in mines.” Mines use equipment protection levels Ma and Mb instead of Zone 0, 1 and 2. In India, the operative classification is the degree of gassiness and the position rules in CMR 2017 and CEA regulation 112, not a zone drawing.

That has a direct consequence for procurement. A motor certified Ex d for Group IIB, suitable for a Zone 1 area in a chemical plant, is not by that fact suitable for an underground coal mine. The certificate and marking must cover Group I. NIEL’s guide to hazardous area classification and flameproof motor selection covers Group II zones, gas groups and temperature classes. Underground mines add Group I and DGMS approval on top of that.

NIEL’s flameproof motor range covers 0.09 to 200 kW, frames 63 to 355, 4 to 10 poles, 220 to 690 V, at 50 or 60 Hz. It is built to IS 325 and IS 2148, with Class F or H insulation and IP55 enclosure. Enclosures are hydraulically tested to 10 kg/cm2, and the cast iron terminal box forms a separate flameproof enclosure. The page lists coal mine pumps among applications. For a mine enquiry, confirm the Group I marking and the DGMS approval reference for the exact frame and rating being quoted.

What changes for panels, starters and switchgear?

Panels follow the same rule as motors, with an added complication: a panel is an assembly. Switchgear, starters and control gear installed where CMR 2017 or CEA regulation 112 requires flameproof apparatus must be flameproof, of an approved type, with intrinsically safe control and signalling circuits where the regulations call for them.

For petroleum and gas premises, PESO has made the assembly point explicit. PESO’s guidelines for licences under the Petroleum Rules, 2002 cite Rule 102: no electric apparatus shall be used where petroleum is refined, stored or handled “unless it is approved by the Chief Controller of Explosives.” From 1 May 2024, PESO stopped approving pre-assembled combinations of Ex apparatus as assemblies. Instead, the assembler, manufacturer, Indian distributor and end user must ensure “all the Ex Electrical Apparatus used in assembly are approved by the Chief Controller of Explosives and the approval is valid as on date.”

Surface panels feeding a mine are a different category. The main substation switchgear, NGR and motor control boards that sit on the surface in a safe area do not need to be flameproof. They do carry mine-specific duties under regulation 103 of the CEA Safety Regulations, 2023:

The regulation requires these limits to be achieved by “suitably designed, restricted neutral system of power supply including neutral-ground monitoring protection system.” At 11 kV that typically means a neutral grounding resistor sized for the 10 A limit, with a monitoring relay. NIEL supplies Power+ N neutral grounding resistor panels up to 66 kV, with options including earth leakage relays and current transformers. Surface HV switching and motor control fit NIEL’s Power+ V VCB panels and Power+ M motor contactor panels.

What documents should a mine ask for before equipment goes below ground?

Ask for four documents for every item of flameproof or intrinsically safe equipment: the test certificate, the DGMS approval, the BIS licence where the policy requires it, and the equipment marking that ties them together. Each must name the same manufacturer, model and rating as the equipment delivered. CMR 2017 requires the approval copy to be kept at the mine office.

• Test certificate from CSIR-CIMFR or another government-approved laboratory, stating the standard, edition, group and model

• DGMS approval letter for the type, showing whether it is a field trial approval or a regular approval, and its validity

• BIS licence, where DGMS lists licensing as required, current on the date of supply

• Nameplate marking showing Group I, the protection type and the certificate reference

• Cable gland and entry details, since the entry forms part of the certified enclosure

• Maintenance instructions from the manufacturer covering flame path inspection and permitted repairs

Keep the approval with the asset, not with the purchase order. The mine manager is responsible under CMR 2017 for ensuring approved equipment conforms “in all respects.” If a revalidation or a change in standards alters the approval, that is the record the inspector will ask to see.

What should a mining motor or panel enquiry state?

• Mine type: coal, metalliferous or oil; underground or open cast

• Degree of gassiness of the seam, and the equipment’s location relative to working face, goaf, last ventilation connection and return airways

• Equipment group: Group I for underground coal

• Protection type required: flameproof, intrinsically safe or increased safety where permitted

• DGMS approval required, and whether a field trial approval is acceptable for the order

• kW, voltage, frequency, duty, mounting and cooling

• Supply system: restricted neutral, earth fault current limit and monitoring arrangement under CEA regulation 103

• Cable entry type and gland arrangement

• Any additional regime from the owner, the insurer or an export market

• Documentation required with delivery

Specifying a motor or panel for an underground mine?

NIEL supplies flameproof motors from 0.09 to 200 kW, listed with approvals from CMRI Dhanbad, DGMS Dhanbad and CCE Nagpur, along with the NGR and switchgear panels that go with them. Send us the mine type, degree of gassiness, equipment location and ratings, and our engineers will confirm the group, approval references and documentation available for the specific model before quotation.

Find the right equipment for your mine:

• Flameproof motors: 0.09 to 200 kW, frames 63 to 355, built to IS 325 and IS 2148.

• Power+ N neutral grounding resistor panels: restricted neutral systems up to 66 kV.

• Power+ V VCB panels: surface HV switching from 3.3 kV to 11 kV.

• Power+ M motor contactor panels: surface motor control.

Call +91 80 42434343, email support@newindiaelectricals.com, or contact our team with your mine details.

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