electric detonators

NORABEL IGNITION SYSTEMS AB Phone (+46) 581 871 81 P O Box 154 Telefax (+46) 581 149 44 SE-711 23 Lindesberg e-mail [email protected] SWEDEN www norabel.com

ELECTRIC DETONATORS A general product presentation describes electric detonators available from Norabel Ignition Systems. The presented electric detonators are standard types and all CE marked in accordance with Directive 93/15/EEC. The detonators presented are intended for initiation of explosives. The electric detonators must not be used in gassy environments such as in coal mines and other work sites where explosive gasses may occur.

NIS/2009-11-26/TB


DETONATOR DESCRIPTION The principle of operation of an electric detonator is that, when a high enogh electric current is passed through the legwires, a bridge wire is heated in the fusehead, which then deflagrates and initiates the delay element which in turn initiates the explosive in bottom of the detonator after a time determined by the length and content of the delay element.

There are in principal two types of detonator designs available;

• Non Primary Explosive Detonator (NPED) • Lead azide based detonator.

Both are of full strength type, rating No. 8 (according to Prior test approx 10). The detonator shell, which is made of aluminium, contains a base charge of RDX in case of NPED detonators, and of PETN in case of the lead azide detonators. The total amount of explosives in the detonator is approx. 1 g. In the delay element the detonation is delayed pyrotechnically for a predetermined time after the firing impulse has reached the detonator.


The delay times vary in steps between 25 ms and 5000 ms (0,025 – 5 seconds). Enclosing the fusehead is an electrostatic protective sleeve that decreases the risk of unintentional initiation due to static discharge. The detonator is fitted with a sealing plug to make it water resistant. Electric detonators are manufactured with three types of delay:

• Instantaneous – no delay element, thus the detonator initiates directly after receiving the firing impulse.

• Millisecond delay (MS) – the delay time increases in increments of 25 ms between each period number.

• Half second delay (HS) – the delay time increases in increments of 500 ms between each period number.

Electric HS-detonators are designed for use in underground operations as longer delay times are neede in tunnel rounds to give enough time for the rock to break and be thrown from the tunnel face. HS detonators are prohibited for use in surface operations as the delay times are too long and can cause flyrock. Electric MS-detonators are used in surface operations and mostly in smaller operations. For safe and successful blasting with electric detonators the following is needed:

1. A firing pattern designed for the round to be blasted. 2. A blasting machine capable of firing the size of the round with the type of detonators

being used. 3. Knowledge of electric hazards at the worksite and ensuring they are eliminated. 4. That each series in series/parallel blasts are of the same size. Careful connection of

lead wires and scrupulous testing of the different parts of the round. The design of the firing pattern depends on the number of detonators in the round and the type of blasting machine that is used. Generally rounds with less than 50 detonators can be connected in one series. Larger rounds can be divided into several series which are then connected together in parallel. The source of energy that is used for the initiation of an electric blast must be approved by the appropriate authority in the country where it is used. A capacitor blasting machine which is capable of firing the number of detonators in the round is the most reliable means of initiation. Knowledge of the hazards at the worksite that could cause unintentional initiation of one or several electric detonators is absolutely necessary in order to be able to eliminate them. See page 6 for the risks that may occur and recommendations for their elimination.


TYPES of DETONATORS Different types of detonators have different firing properties and must not be used in the same round. The same is true for detonators from different manufacturers. Electric detonators are classified in 4 classes depending on their electric properties. There are older and other national denominations for the classes, such as “group”, and subdivisions. According to the European Standard (EN 13763-1) the denomination is class with subdivisions 1, 2, 3 and 4. European denomination Nordic denomination Older denomination Class 1 Group 1 Type A/S/NT Class 2 Group 1A Type U Class 3 Group 2 Type VA Class 4 Group 3 Type HU/XS For electrical data of each class, see table below. Mechanical properties: Detonator type: NPED Lead Azide Recommended working temperature:

-25°C - +50°C

Recommended storage conditions:

Normal room temperature, occasionally max +50°C at max RH 50%

±0°C - +45°C

Maximum hydro static water pressure:

3 bar during 7 days 2 bars during 48 hours

Tensile strength, single wire:

4 kg during 2 minutes up to +50°C

Electrical data: Class 1 2 3 4 Fuse head resistance, [Ω] 0,9 – 1,4 0,4 – 0,9 0,15 – 0,25 0,04 – 0,09 Max. no firing current, [A] ≤0,25 ≤0,45 ≤1,2 ≤4,0 Recommended firing current (single det), [A]

≥0,6 ≥1,0 ≥2,2 ≥6,0

Recommended firing current (series), [A]

≥1,0 ≥1,5 ≥3,5 ≥25

Firing impulse, [mJ/ Ω] 3 - 5 8 - 16 80 - 140 1100 - 2500


Classification: Detonator type: NPED Lead Azide Technical name: Electric Detonators, for blasting UN no. 1.1B/UN no. 0030

1.4S/UN no. 0456 1.1B/UN no. 0030

Authorisation CE 0402 CE 1453 Guarantee period 1 year from date of purchase Colour coding of electric detonators Electric detonators are colour coded by different colours on the legwires. There is no international standard for the colour coding, thus each supplier and country may set local standards for their area/manufacture. The colour coding indicates what delay series the detonator belong to (Instantaneous, MS or HS) respectively its electrical properties (class belonging). In principal the legwire colours is set upon customer request. Note that for the suppliers non-standard colours, a minimal quantity is needed to be ordered. Standard colours are as per following: Red, Green, Grey, Yellow, Brown, White, Blue Legwire lengths and types The legwires are available in different lengths and based on different metal wires. There are standard lengths from 2 – 35 m, but that may vary depending on supplier and customer order. The type of leg wire metal is dependent on the detonators electrical properties and is therefore defined and set by the manufacturer. The wire materials are copper, steel or brass. Detonator shell The detonator is by standard in aluminium. The diameter is ø7,5 mm and the length depending on the delay time (usually 56 – 95 mm). For special applications (usually for underground coal mining) the detonator shell can be of copper.


Hazards in connection with electric initiation Thunderstorms are with no doubt the greatest risk in rock blasting due to its unpredictable nature and the high amount of energy released. A lightning strike may have a voltage of over 1.000.000 V and a current of over 100.000 A. A direct lightning strike in a worksite using electric detonators will initiate one or several detonators in the round, but even a distant lightning strike constitutes a risk due to the high current flow. When a thunderstorm is approaching, the worksite using explosives must be evacuated and guarded in the same way as when a blasting is to take place. Stray currents may occur close to electric welding operations and a safety distance of 30 m should be considered. Close to operating powerstations, stray currents occur and a non-electric firing system should be used (such as ST Systems). Powerlines may cause unintentional initiation by flashover, induced currents and through capacitive discharge. The risk may be reduced by:

• Placing the firing cable on dry ground. • Not extending the firing cable parallel to the power line or in loops. • Avoiding that firing cable, connecting wires or legwires coming into contact with

earth. • When extending the firing cable from the round to the firing point, the cable ends

should be short circuited. • When connecting to the blasting machine, the cable must be insulated from any

conductive object. Close to powerlines and electric cables, it is always hazardous to do blasting with electric detonators. The safety distances are different in different countries due to national restrictions. Electric detonators may be accidentally initiated by radio transmitters or radar during the charging operation. It is mainly stationary radio transmitters that constitute a problem and then mainly the large medium wave and long wave transmitters. When carrying out blasting operations close to radio transmitters, it is imperative to contact the authorities (owner) to establish the safety distance. Alternatively non-electric detonators may be used. Cellular telephones may initiate a class 1 detonator. Communication radios or other mobile radio transmitters should not be used in the close neighbourhood of the worksite when electric initiation is used. For class 2 and 3 detonators, transmitters with a power output over 5W are strong enough to initiate a detonator. With regards to radar installations, contact should be take with the owner for information about the danger zone.


Static electricity cab be built up during sand and snow storms causing unintentional initiation. Static electricity can also be built up during covering work with heavy mats under dry conditions. A person charged up with static electricity can constitute a risk to safety, especially when using class 1 detonators.


Delay time selection Period/Interval number MS-series HS-series 0 Instantaneous (<10 ms) 25 ms 1 25 ms 500 ms 2 50 ms 1000 ms 3 75 ms 1500 ms 4 100 ms 2000 ms 5 125 ms 2500 ms 6 150 ms 3000 ms 7 175 ms 3500 ms 8 200 ms 4000 ms 9 225 ms 4500 ms 10 250 ms 5000 ms 11 275 ms 12 300 ms 13 325 ms 14 350 ms 15 375 ms 16 400 ms 17 425 ms 18 450 ms 19 475 ms 20 500 ms


Product selection A guideline to choose the correct type of electric detonator:

1. Choose which kind of electrical class is required. (Class, 1, 2, 3 or 4) 2. Choose the delay time of the detonator. (Instantaneous – 5000 ms) 3. Choose colour of leg wires. (Standard: grey, green, red, white, yellow, blue, brown, or

optional other colours on demand) 4. Choose length of leg wires. (2 – 35 m)

Other optional requirements*:

• Type of base charge – (PETN or RDX) • Transportation classification – (1.1B or 1.4S) • Leg wire material – (steel or copper) • Type of detonator – (NPED or Lead azide) • Type of detonator shell – (Copper or aluminium)

*) Note that not all combinations are available. If no optional requests are given, we presume

and offer standard design.

Note that for types other than standard, a minimum quantity is required! Civil or military/police use Also be informed that the presented selection of electric detonators are classified as civil products. If the products are intended for military or police use, there might be national restrictions for import and sales which must be considered before purchase.

electric detonators

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