Fuse chain

A fuse chain is used for shooting in mining , as well as for blasting outside of mining, the interconnection of several electric fuses . The interconnection of the individual detonators in the detonator chain ensures that the detonators are ignited at the same time.

Basics

When shooting, several shots are usually fired at the same time. The number of these shots is limited by the power of the blasting machine. Care must be taken that the individual detonator wires are carefully laid and interconnected. In particular, when connecting the wires, care must be taken that insulation faults do not result in shunts or short circuits . In addition, it must be ensured that no stray currents occur in existing electrical systems . By shunting, it can happen that the required ignition current no longer flows through the igniter, which leads to failure of the shot. Short circuits also lead to failure of the shot. Stray currents can lead to premature ignition of the igniter.

Circuit variants

The individual detonators can be connected together to form a detonator chain by means of various circuit variants. In principle, the individual detonators can be connected to one another either in series or in parallel. There are also various combinations of these circuit variants. Which circuit variant is used depends on the voltage and current of the blasting machine and the respective resistances of the detonators. Ultimately, the possible circuit must be calculated by the shooting master .

Cascading

The series connection, also called series connection or series connection, is the circuit variant that is most frequently used in mining. It has a simple structure, is easy to understand for the shooter and leads to the least amount of wiring errors. The interconnection of the individual detonators takes place in such a way that a wire of one detonator is connected to a free wire of the next detonator. The interconnection can be made in any order. The still free wire of the igniter is now connected to a free wire of the next igniter. If necessary, the individual wires of the detonators can be shortened or lengthened. The interconnection continues until all detonators are interconnected and there is still one wire left from the first and the last detonator. These two wires are connected to the blasting machine via the poles of the explosive line. This circuit means that all connected detonators receive the same current. The total resistance of this detonator chain corresponds to the sum of the individual detonator resistances. The disadvantage of this circuit variant is that the current delivered by the ignition machine cannot be used optimally. Due to the high total resistance, this circuit variant can lead to ignition failures in operations where there is a risk of shunt, especially if there is a large number of detonators.

Parallel connection

With the parallel connection, all detonators are connected directly to the ignition cable. With this detonator chain, the total resistance decreases proportionally with the number of detonators. The current emerging from the ignition cable branches into several partial currents. This circuit cannot be carried out as easily as the series connection. This is because it isn't that clear. In order to be able to carry out this circuit variant, several dry wooden stakes must first be inserted into the drill holes provided. Two bare wires, the antennas, to which the ignition cable is then connected, are attached to these wooden pegs. Therefore this circuit is also called a two-antenna circuit. The detonators are each connected with one wire to one antenna and with the second wire to the other antenna. In this circuit variant, the resistance of the ignition cable is particularly important and acts as a series resistor in front of the igniter. For this reason, only detonators with detonating wires of the same length may be used. Lengthening or shortening is not permitted. Due to the low resistance of this fuse chain, ignition failures due to shunts cannot occur.

Group switching

Above a certain number of detonators, the ignition voltage of the blasting machine is often insufficient to ignite the detonators in a simple series connection. The parallel connection cannot always be carried out here either, since an ignition line with a large cross-section is required due to the large ignition current required. Especially at operating points such as As the sinking of shafts is so difficult to use an ignition. Here the detonators can be connected in a combination of the series connection and the series connection. For this purpose, the detonators are divided into a certain number of equal groups and interconnected with one another. The interconnection takes place in such a way that either two or three detonators connected in series form a group and the groups are interconnected in parallel. This circuit variant is called group parallel circuit. A special form of group parallel connection is the three-antenna circuit , also known as the three-ring blasting process. In order to carry out this circuit variant, which is usually used when sinking the shaft, dry wooden pegs are inserted into the drill holes provided for this purpose, as with the two-antenna circuit. Three bare wires, the antennas, are attached to these wooden pegs in parallel. The detonators are now alternately connected with a wire to the first antenna or to the second antenna. The second wire of all detonators is connected to the third antenna. The ignition cable is connected to the upper and lower antenna. The advantage of this circuit variant is that there are hardly any shunts, since the middle antenna has a current-balancing effect and therefore there is no failure. In addition, the ignition cable can be selected thinner than with the pure parallel connection. It is also possible to connect the detonators in series in groups. For this purpose two detonators are always connected in parallel, these pairs are then connected in series with other pairs.

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g Helmut Fritzsche: Textbook of mining studies with special consideration of hard coal mining. First volume, tenth completely revised edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1961, pp. 217–220.
↑ Wolf-Ingo Hummig: Textbook for the state-recognized special course in pyrotechnics. 3rd expanded and modified edition, Hummig Verlag, Peißenberg 2009, ISBN 978-3-931360-22-1 , pp. 65–85.
↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Heinrich Otto Buja: Engineering manual mining technology, deposits and extraction technology. 1st edition, Beuth Verlag GmbH Berlin-Vienna-Zurich, Berlin 2013, ISBN 978-3-410-22618-5 , pp. 155-161.
↑ ^a ^b ^c ^d ^e ^f ^g ^h G. Lathan: Drilling and shooting in mining. Volume II Shooting. Fachbuchverlag, Leipzig 1958, pp. 72–76.
↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Ernst-Ulrich Reuther: Textbook of mining science. First volume, 12th edition, VGE Verlag GmbH, Essen 2010, ISBN 978-3-86797-076-1 , pp. 118-121.
↑ ^a ^b Helmut Fritzsche: Textbook of mining science with special consideration of hard coal mining. First volume, ninth completely revised edition, Springer Verlag, Berlin / Heidelberg 1955, p. 181, 187–189.
↑ ^a ^b ^c ^d ^e Gustav Köhler: Textbook of mining science. Sixth improved edition, published by Wilhelm Engelmann, Leipzig 1903, pp. 222–225.
↑ Fritz Heise: Explosives and detonation of high explosive shots with special consideration of the fire weather and coal dust danger in coal mines. Published by Julius Springer, Berlin 1904, pp. 220–227.
↑ ^a ^b ^c ^d ^e ^f ^g Mining test route Blasting expert body of the Westphalian Mining Union's Office (ed.): Leaflets for carrying out blasting work. Spresa 1984, pp. 1.8.1-1.8.5.

↑ ^a ^b Horst Roschlau, Wolfram Heinze, SDAG Wismut (Hrsg.): Knowledge storage mining technology. 1st edition. German publishing house for basic industry, Leipzig 1974, pp. 47–49.

↑ Helmut Fritzsche: Textbook of mining science with special consideration of hard coal mining. First volume, eighth edition, Springer Verlag, Berlin 1942, pp. 274, 275.

Remarks

↑ Ignition currents are referred to as shunts that are lost during the ignition process due to defects in the ignition circuit and are therefore not available to the igniter for ignition. They arise when an inadequately or insufficiently insulated electrical line of the ignition circuit is routed through salty mine water or over a damp track impact . (Source: Helmut Fritzsche: Textbook of Mining Studies with a special focus on hard coal mining. First volume, tenth completely revised edition.)
↑ The wooden pegs are expediently distributed around the profile of the site cross-section or the shaft bottom. (Source: Ernst-Ulrich Reuther: Textbook of Mining Studies. First Volume )
↑ The three antennas are divided so that the first antenna is attached to the top of one half of the row of stakes and the second antenna is attached to the top of the other half of the row of stakes. The third antenna is attached to all pegs in the lower area. The distance between the antennas must be at least 30 centimeters on each post. (Source: Mining test route blasting expert center of the Westphalian Mining Union's Office (ed.): Leaflets for carrying out blasting work. )

[Quelle_1-1] ↑ ^a ^b ^c ^d ^e ^f ^g Helmut Fritzsche: Textbook of mining studies with special consideration of hard coal mining. First volume, tenth completely revised edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1961, pp. 217–220.

[Quelle_11-2] Wolf-Ingo Hummig: Textbook for the state-recognized special course in pyrotechnics. 3rd expanded and modified edition, Hummig Verlag, Peißenberg 2009, ISBN 978-3-931360-22-1 , pp. 65–85.

[Quelle_2-3] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Heinrich Otto Buja: Engineering manual mining technology, deposits and extraction technology. 1st edition, Beuth Verlag GmbH Berlin-Vienna-Zurich, Berlin 2013, ISBN 978-3-410-22618-5 , pp. 155-161.

[Quelle_3-4] ↑ ^a ^b ^c ^d ^e ^f ^g ^h G. Lathan: Drilling and shooting in mining. Volume II Shooting. Fachbuchverlag, Leipzig 1958, pp. 72–76.

[Quelle_4-5] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Ernst-Ulrich Reuther: Textbook of mining science. First volume, 12th edition, VGE Verlag GmbH, Essen 2010, ISBN 978-3-86797-076-1 , pp. 118-121.

[Quelle_5-7] Helmut Fritzsche: Textbook of mining science with special consideration of hard coal mining. First volume, ninth completely revised edition, Springer Verlag, Berlin / Heidelberg 1955, p. 181, 187–189.

[Quelle_6-8] Gustav Köhler: Textbook of mining science. Sixth improved edition, published by Wilhelm Engelmann, Leipzig 1903, pp. 222–225.

[Quelle_10-9] Fritz Heise: Explosives and detonation of high explosive shots with special consideration of the fire weather and coal dust danger in coal mines. Published by Julius Springer, Berlin 1904, pp. 220–227.

[Quelle_8-10] ↑ ^a ^b ^c ^d ^e ^f ^g Mining test route Blasting expert body of the Westphalian Mining Union's Office (ed.): Leaflets for carrying out blasting work. Spresa 1984, pp. 1.8.1-1.8.5.

[Quelle_7-11] Horst Roschlau, Wolfram Heinze, SDAG Wismut (Hrsg.): Knowledge storage mining technology. 1st edition. German publishing house for basic industry, Leipzig 1974, pp. 47–49.

[Quelle_9-12] Helmut Fritzsche: Textbook of mining science with special consideration of hard coal mining. First volume, eighth edition, Springer Verlag, Berlin 1942, pp. 274, 275.

[Anm._Fritsch.-6] Ignition currents are referred to as shunts that are lost during the ignition process due to defects in the ignition circuit and are therefore not available to the igniter for ignition. They arise when an inadequately or insufficiently insulated electrical line of the ignition circuit is routed through salty mine water or over a damp track impact . (Source: Helmut Fritzsche: Textbook of Mining Studies with a special focus on hard coal mining. First volume, tenth completely revised edition.)

[Anm._Reuth.-13] The wooden pegs are expediently distributed around the profile of the site cross-section or the shaft bottom. (Source: Ernst-Ulrich Reuther: Textbook of Mining Studies. First Volume )

[Anm._Merkbl.-14] The three antennas are divided so that the first antenna is attached to the top of one half of the row of stakes and the second antenna is attached to the top of the other half of the row of stakes. The third antenna is attached to all pegs in the lower area. The distance between the antennas must be at least 30 centimeters on each post. (Source: Mining test route blasting expert center of the Westphalian Mining Union's Office (ed.): Leaflets for carrying out blasting work. )