Every mine that blasts needs a place to keep its explosives, and that place is one of the most regulated buildings on the lease. It is built to keep the explosive dry, cool and untouched, and to keep everyone else a safe distance away. That building is called a magazine.
In this post, we cover the three kinds of magazine, how explosives are issued to a shotfirer, what precautions are followed inside, and what a properly built main magazine looks like. If you are preparing for a DGMS exam, many of these points are regular questions.
What Is a Magazine, and What Types Are There?
A magazine is a place on the surface where explosives, detonators, safety fuse and detonating fuse are kept. There are three types.
Why is a service magazine needed?
The main magazine is deliberately far away from everything else. That is good for safety but not practical for issuing explosive to a shotfirer several times a day. So a service magazine is built near the shaft or incline. All the mine's explosive stays in the main magazine, and the quantity needed each day is brought to the service magazine.
How Explosives Are Issued to a Shotfirer
How much is issued?
The quantity is estimated from the coal balance left from the previous shift, that is, how much blasting will be needed. The indent is made for that amount, and only that amount is issued.
What if it is not all used?
At the end of the shift, the shotfirer returns whatever is left to the magazine in-charge, who writes it in the register.
What should the shotfirer check while taking delivery?
- The explosive and detonators match what is written in the register.
- There is no visible defect in them.
- The boxes are locked, and the key stays with the shotfirer.
How Many Detonators Can Be Issued?
The maximum number of detonators issued to a shotfirer depends on the gas degree of the mine and the capacity of the exploder. A multi-shot exploder allows twice the number of a single-shot exploder.
| Mine type | Single-shot exploder | Multi-shot exploder |
|---|---|---|
| Opencast | 60 | 120 |
| Degree I gassy mine | 50 | 100 |
| Degree II / III gassy mine | 40 | 80 |
Precautions Inside a Magazine
1. Prevent fire
- No open light or oil safety lamp inside. Only a cap lamp or safety torch may be used.
- No smoking, no naked flame, no mobile phones or walkie-talkies in the magazine or within 15 m of it.
- No packing paper, empty boxes, dry bushes, grass or other inflammable material around.
- Search everyone before entry to make sure they have no matches or lighters.
2. Keep out soil, sand and iron particles
- Wash shoes in water before entering. Nailed shoes are not allowed inside; wear overshoes.
- Brush the floor clean each time the magazine is opened, and again before it is closed.
3. Opening boxes and handling
- Open boxes only with wooden, copper or brass tools, never iron ones.
- Do not drag boxes along the floor.
- Keep no other goods inside. Tools stay in the lobby.
4. Keep the explosive from spoiling
- Place boxes on cement or wooden racks so that air can circulate and the type and date of manufacture can be read.
- Use the earlier-made explosive first.
- Issue the explosive returned from a shift before anything else.
- Do not stack higher than 2.5 m from the floor.
- Keep detonators in a separate chamber, in the manufacturer's own packing.
5. Other requirements
- The magazine is kept locked, with adequate guard for 24 hours a day.
- No more than 4 people inside at any one time.
- The lightning arrester is tested every year and the result recorded.
- Accurate records of stock and issue are kept and checked, with a quarterly return.
- When lightning strikes nearby, everyone is moved out and the magazine is locked.
- A copy of the licence is kept in the magazine, and stock must not exceed the licensed quantity.
- Senior officers, such as the General Manager or Director, can make surprise inspections.
Features of a Main Magazine
A main magazine is built to a fixed pattern. The list below follows the usual textbook features.
- Safe distance from houses, roads and power lines, as required by law.
- Strong construction: thick concrete, brick or stone walls and a concrete roof. Inside, waterproof plaster, a cement floor, and cement or wooden racks, with walking space between racks.
- Enough volume: 0.4 m³ of space for every 100 kg of explosive.
- Walking space for one person in front of the racks.
- Z-shaped ventilators, one high and one low on opposite walls (two on each wall for magazines larger than 500 kg). Iron rods on the outside mouth and a brass mesh of 3 meshes per cm on the inside.
- Windows: enough iron windows opening outward for light, with wooden lining on the inner surface.
- Doors: iron, opening outward, with dead-lock type locks.
- Red band: a 12 mm wide red line on the walls at 2.5 m above the floor, to show the maximum stack height.
- Vertical plaster strips: 25 mm thick and 50 mm wide, 300 mm apart, from 130 mm above the floor up to the red band. They let air circulate and keep boxes from pressing against the wall.
- Water pit: 15 cm deep, filled with clean water, outside the door, for washing feet and shoes.
- Separate detonator chamber and a lobby for tools. Detonating fuse is not kept in the detonator chamber. It can be kept in the explosive store, but on a separate rack.
- Lightning arrester on top, with a resistance of at most 10 ohm.
- No electric line in the magazine. Lights are arranged outside.
- Watch tower or cabin for the guard.
- Safety distance all around from public roads, buildings and similar.
Portable Magazines
Where are they used?
- Very small mines.
- Mechanised opencast mines, to hold detonators, detonating fuse and blasting relays, since bulk explosive is used there.
- When a new mine is starting, before the main magazine is built.
What does a portable magazine look like?
| Feature | Detail |
|---|---|
| Body | 5 mm thick iron sheet |
| Maximum capacity | 500 kg of explosive, or 44,000 detonators, or 10,000 m of detonating fuse |
| Availability and weight | Readymade units are available, weighing about 425 kg. Can be set up in 8 hours |
| Inside lining | Wood: 25 mm on the floor, 10 mm on walls and roof |
| Door | Iron, with 25 mm wooden lining and a dead-lock |
| Ventilation | Holes in walls covered with iron mesh |
| Interior volume | 2 m³ (0.4 m³ for every 100 kg of explosive) |
| Minimum safe distance | 50 m from houses and buildings; 95 m from roads, rail lines and similar |
The textbook diagram of a portable magazine also shows a lightning arrester about 5.3 m high, a light roof, and a channel-iron base.
Boxes for Carrying Explosives
The next topic in the book covers carrying and keeping explosives in the mine. In brief, the box for explosive and detonators must be strong enough to protect them from knocks, and detonators need their own separate box. The explosive box is made of wood or galvanised iron sheet. The detonator box is made of wood or leather, with a separate polythene compartment for each detonator. Hinges and lock are made of brass, or it is a self-lock or one that opens with the exploder key.
Quick Revision and FAQ
- Three types: main, service and portable.
- Maximum stack height is 2.5 m, marked by a 12 mm red band.
- Space needed: 0.4 m³ per 100 kg of explosive.
- Lightning arrester resistance: not more than 10 ohm. Tested every year.
- Not more than 4 persons inside at a time. No mobile phones within 15 m.
- Max detonators issued: opencast 60/120, degree I 50/100, degree II/III 40/80 (single/multi-shot).
- Portable magazine: up to 500 kg, 5 mm iron sheet, 50 m and 95 m safety distances.
Why are detonators kept in a separate chamber?
Detonators are more sensitive than explosive cartridges. Keeping them separate, in their own packing, reduces the chance of an accident.
Why can't iron tools be used to open boxes?
Iron can cause sparks and bring in iron particles. Wood, copper or brass tools are used instead.
Why is there a water pit outside the door?
So that people wash their shoes and feet before entering and do not carry in soil, sand or grit.
Can a portable magazine replace a main magazine?
It is meant for very small mines, mechanised opencast needs and the start-up period of a new mine. It holds a maximum of 500 kg of explosive.
Conclusion
A magazine is more than a locked shed. Its walls, ventilation, racks, lightning protection, registers and guard all exist to do one job: keep explosives stable and in the right hands. If you remember the logic behind each rule, such as keeping grit out, keeping air moving and keeping records exact, the numbers become much easier to recall.
Found this useful? Share it with a friend preparing for DGMS exams, and leave your questions in the comments.
Disclaimer: This post is for educational purposes and is based on standard mining textbook content. Requirements such as safe distances, licensed quantities and construction details are set by the law in force. Always follow the Explosives Rules, the latest DGMS circulars, the Coal Mines Regulations and your mine's own approved procedures.
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