Time-delayed fuses

In 1935 the Italians invaded Abyssinia (Ethiopia) and over 700 tons of mustard gas was shipped for use by the Italian Air Force. Torpedo-shaped 500-lb bombs, with time-delay fuses, were also utilised. These bombs burst about 200 ft above the ground scattering spray over a considerable area. Later, aerial spraying was the preferred method. Groups of 9 to 15 aircraft followed one another so that the liquid issuing from them formed a continuous fog... soldiers, women, children, cattle, rivers, lakes and pastures were drenched continually with this deadly rain. 6... 

A typical aerial shell used in fireworks displays. Time-delayed fuses cause a shell to explode in stages. In this case a red star-burst occurs first followed by a blue starbursb and finally a flash and loud report. Reprinted with permission from Chemical Engineering News, Vol. 59, Issue 26, June 29,1981, p. 25. Copyright 1981 American Chemical Society. 

A typical aerial shell is shown in the diagram. The shell is launched from a mortar (a steel cylinder) using black powder as the propellant. Time-delayed fuses are used to fire the shell in stages. A list of chemicals commonly used in fireworks is given in the table. 

These shells can be arranged as multi-break shells, which explode in phases, similar to a two-stage rocket, and possibly contain stars of different types or colors. They may also contain noisemakers such as whistles. Each of these shells has a different time-delayed fuse that fights it so each shell can... 

Replace with time-delay fuses matched to nameplate amperes. If motor has service factor greater than 1.0, use fuse size up to 12.5% of motor amperes. Check for grounded winding. 

Time-delay fuses activate the reactions in the other chambers... 

The cylinder of a multiple-burst rocket contains separate reaction chambers connected by fuses. A common fuse ignites the propellant and the time-delay fuse in the first reaction chamber. 

Explosives may be detonated electrically or nonelectrically. A nonelectric firing system will consist of a blasting cap, a length of time (safety) fuse or a firing device attached to the cap, and a means of activating the system match, fuse lighter, delay mechanism, or trip wire. The electric system requires an electric cap which has two wires attached, perhaps additional wire, and a battery or batteries to provide the current which activates the cap. 

The only sure way to determine the burning time of any kind, or even roll, of safety fuse is to cut a measured length of it, light it, and time it. The operator can then select a length which will provide the time delay he desires. 

Gunpowder is best ignited by safety fuse. It burns very quickly and with a great deal of heat, so allow sufficient time delay for safe withdrawal from the vicinity. 

Author s Comments This is probably a 2A fuse with T —that is, Time Delay. The time delay ensures that the fuse will not blow due to the high inrush current of most switchers. However, also note that the max load being applied is 3A. But this is a 24V to 5V conversion, so the input supply current will be almost 24/5 5 times less, that is, only 0.6A for a 3A load, not even close to 2A. That cannot be the issue. In any case, there is almost no way the input fuse can blow if the switch of the IC has not failed. A blown fuse in power supplies is almost 99.9999% the result of a switch failure, caused by some other malfunction that we need to investigate. Further, no problems can start once the fuse blows, as the customer seems to state That seems like an obvious typo, but it should have been clarified delicately. 

The shell case can be made from paper or plastic. For a given calibre, the cylindrical shell holds more stars and is the more straightforward to produce, especially when multiple breaks are required. The much revered ten-break shell (yes, it does burst ten times in the sky ) comprises separate compartments, each connected with a delay fuse to give sequential exploding effects during the flight of the shell. Of course. 

Pressed gunpowder delay fuses are initially prepared, the top fuse being charged with 25 mm of powder (for a longer burn time) while the remaining two fuses contain about 18 mm of powder each. 

The gunpowder explodes in a further fraction of a second, the explosion blowing the shell out of the mortar tube in the manner of a shot from a cannon. At the same time a return section of piped match is lit by the explosion, transferring flame back to the top compartment where it reaches the quickmatch placed across the head of the 25 mm pressed delay fuse. 

Delay Composition A general term for a mixture that burns at a seleeted, reproducible rate, providing a time delay between activation and production of the main effect. A fuse containing a core of black powder is an example of a delay. Highly-reproducible delay mixtures are needed for military applications, and much research effort has been put into developing reliable compositions. 

Fuse A train of slow-burning powder (usually black powder), often covered with twine or twisted paper. Fuses are lit by a safety match or other hot object, and provide a time delay to permit the person igniting the device to retreat to a safe distance. 

Our home circuit breakers, or fuses, are, of course, trips to prevent overheating electric circuits or electric motors. The only difference is that at work, our electric circuit breakers have a built-in time delay. This is needed to allow the motor driver to overcome the starting torque inherent in most large pieces of rotating process equipment. 

P.Becker 6- H.Mencke, GerP 1061245 (1959) CA 55, 25256(1961) (A short-time delay compn for use in elec fuses consists of Pb O 60... 

This simplified picture of self-phase modulation neglects dispersion, time-delayed nonlinearities and shock formation which is all known to occur in optical fibers. While no in fused silica is at least as fast as a few fs, the GVD broadens the pulses as they travel along the fiber so that the available peak power Pa is decreased. Effective self-phase modulation however takes place when the so called dispersion length is much smaller then the nonlinear length whose ratio is given by [27]... 

In the military, delay fuses are complete shell fuses which set off the explosive charge a definite time after impact. 

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