Archive for April 2007

Control of Pyrotechnic Burn Rate

B. J. and K. L. Kosanke

ABSTRACT: There may be many times when a firework manufacturer will want to adjust the burn rate of pyrotechnic compositions. Sometimes this may be for matters of esthetics and other times for safety. For example, all of the following are unacceptable:

• Strobe stars that flash with so low a frequency that they fall to the ground still burning.

• Color stars that burn so rapidly that they occasionally explode when a shell flowerpots.

• Rockets that fail to lift-off because their thrust is too low.

• Rockets that explode upon firing because internal pressures exceed the casing strength.

• Salutes that burn like fountains instead of  exploding with violence.

• Flash powder that explodes when unconfined,  even in small quantity.

In each case, taking action to adjust burn rate should solve the problem. Depending somewhat on how they are counted, there are at least 15 factors that control pyrotechnic burn rate. A  anufacturer that understands how these factors act to affect burn rate may better anticipate when product performance difficulties will occur. Also, such a manufacturer will be better prepared to modify product formulations to correct any problems that do occur. Each of the burn rate control factors act by affecting one or more of the following: activation energy, heat of reaction, and efficiency of energy feedback. In this paper, the 15 factors are presented, explained and examples given.


Ref: Selected Pyrotechnic Publication of K.L. and B.J Kosanke, Part 3, (1993-1994), pp 62-75
(K3_62)
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The Effect on Mortars of Explosions within Them

K. L. Kosanke and L. Weinman

An earlier article[1] that appeared a little over a year ago discussed one type of mortar bursting explosion. The article described a process whereby a sufficiently powerful explosion occurring internally near the muzzle of a high density polyethylene (HDPE) mortar would not only burst the top of the mortar, but could also burst the plugged end of the mortar, frequently leaving the middle section of the mortar fully intact. Since publishing that article, readers posed two questions: 1) do the conclusions of the earlier article apply equally to explosions occurring near the plugged end of mortars; and 2) do the conclusions of the earlier article apply equally to mortars made of other materials. The simple answers to the two questions are no and yes, respectively. However, before addressing these two questions, the current article will very briefly summarize the observations made in the earlier article.


Ref: Selected Pyrotechnic Publication of K.L. and B.J Kosanke, Part 7, (2003-2004), pp 142-144
(K7_142)
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Fireworks Displays: When Is Safe, Safe Enough?

K. L. and B. J. Kosanke

At a recent meeting of the National Fire Protection Association's Technical Committee on Pyrotechnics, there was a proposal to increase the site size requirement for public fireworks displays from the current 70 feet (21 m) to 100 feet (30.5 m) radius per the largest shell size in inches. It was the consensus of the committee that this was not needed because fireworks displays using the current distances were “safe enough”. However, no one was able to substantiate their opinion with data. As part of that discussion the authors offered their own unsubstantiated opinion that it was likely that people were at a significantly greater risk while on the round trip drive to witness a fireworks display, than from the fireworks in the display. After offering some background information, this article presents a calculation of the comparative risks of driving to and attending a fireworks display, estimating that people are at least 7 times more likely to be killed or injured as a result of driving to attend a public display than they are from the fireworks in the public display.


Ref: Selected Pyrotechnic Publication of K.L. and B.J Kosanke, Part 7, (2003-2004), pp 140-141
(K7_140)
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The Effect of Intentionally Caused Fire Leaks into 3-Inch Display Firework Aerial Shells

K. L. and B. J. Kosanke

This article is the second report on a series of tests to more definitively establish the difference between the causes of so-called flowerpots and muzzle breaks. A previous article[1] reported on a similar study using 2-1/4 inch (57-mm) plastic aerial shells (formerly classed as consumer fireworks). The current article extends the earlier work by considering relatively high quality, although small, display firework shells. To conserve space and avoid needless repetition, some of the background and supporting information presented in the earlier article will not be repeated in the present article.


Ref: Selected Pyrotechnic Publication of K.L. and B.J Kosanke, Part 7, (2003-2004), pp 136-139
(K7_136)
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Warning Extremely Dangerous Directions for Firing

K. L. and B. J. Kosanke

The title of this very short article is, in effect, a direct quote from a label found on some display firework aerial shells, see Figure 1. As it turns out, the label is more literally correct than might have been intended. Note that one of the instructions is to “LIGHT FUSE BEFORE PUT IN TO MORTAR…”


Ref: Selected Pyrotechnic Publication of K.L. and B.J Kosanke, Part 7, (2003-2004), pp 135-135
(K7_135)
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When Is Wind Speed Excessive for the Safe Display of Fireworks

K. L. and B. J. Kosanke

While working on the 2006 edition of NFPA- 1123 Code for Fireworks Display, the Technical Committee on Pyrotechnics of the National Fire Protection Association (NFPA) received a request for a “Formal Interpretation” regarding the 2000 edition of the code. In effect, a request for a Formal Interpretation is a request for the committee to provide clarification or a ruling regarding one or more paragraphs in the code. According to NFPA practice, a request for a Formal Interpretation must always be phrased in such a way that it can be answered either “yes” or “no”. This article addresses that request for a Formal Interpretation and was written because: 1) the question being posed was reasonable and important; 2) a simple yes or no will not meet the needs of the requestor; and 3) to stimulate a discussion of the issue, such that the display fireworks industry might then provide guidance to the committee before they address the issue at their next committee meeting.


Ref: Selected Pyrotechnic Publication of K.L. and B.J Kosanke, Part 7, (2003-2004), pp 130-134
(K7_130)
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Muzzle Breaks That Appear To Be Flowerpotsd

K. L. and B. J. Kosanke

As is sometimes the case when doing research: A) one occasionally discovers something which was not being sought; B) the thing discovered then seems intuitively obvious and one is amazed (and a little embarrassed) not to have figured it out long ago; C) the thing discovered helps to answer some other previously seemingly inexplicable observations; and D) one finds there are some new questions for which no certain answer is immediately available. All four of these happened recently while the authors were investigating the size of hole in the casing of aerial shells (of various sizes) that is needed to produce a fire-leak sufficiently great to cause the shell to explode while it is still inside the mortar.[1,2] During the course of those studies, it was found that a number of events, which visually appeared to definitely be flowerpots, were actually muzzle breaks.


Ref: Selected Pyrotechnic Publication of K.L. and B.J Kosanke, Part 7, (2003-2004), pp 125-129
(K7_125)
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From a Technical Standpoint, What is Flash Powder?

K. L. Kosanke and L. Weinman

Introduction: In a recently published article on the regulatory definitions of firework flash powder[1] it was concluded that none of those definitions provided sufficient information to objectively establish whether or not a pyrotechnic composition is a flash powder. That is to say, those definitions are all subjective to the extent that they depend on the intended use of the composition and none provide a quantifiable measure that can be used to determine whether a particular pyrotechnic composition is a flash powder. The purpose of the present article is to suggest a general approach that might be used as the basis for producing a quantitative definition of flash powder.

The reason such an objectively quantifiable definition is needed is that – from both a regulatory and safety standpoint – flash powders are treated differently than other pyrotechnic compositions. The rationale for this is that the hazards posed by firework flash powders are generally significantly greater than most other commonly encountered pyrotechnic compositions. Accordingly, both pyrotechnic manufacturers and regulatory enforcement personnel need to be able to unambiguously identify whether a composition is or is not a flash powder.


Ref: Selected Pyrotechnic Publication of K.L. and B.J Kosanke, Part 7, (2003-2004), pp 120-124
(K7_120)
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Product Warning !!!

K. L. and B. J. Kosanke

Display operators need to be aware of the potential for some tiger tail comets to produce extremely dangerous fallout. The problem was discovered only recently and was then investigated by the authors on a visit to the display company’s facility. The shells in question are 4- and 5-inch (100- and 125-mm) White and Red Tiger Tail comets as shown overall in Figure 1. While all of the shells have the same basic labels, there were slight differences as noted in Table 1. However, in trying to determine whether any particular tiger tail comets have the problems found in the ones being discussed in this article, it is probably wise to consider that Chinese manufacturers frequently subcontract work and otherwise share production. Thus, it is possible that not all of the items labeled and appearing as shown in this article may have a problem, and it is also possible that items labeled and appearing differently may have the same problem described in this article.


Ref: Selected Pyrotechnic Publication of K.L. and B.J Kosanke, Part 7, (2003-2004), pp 117-119
(K7_117)
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An Interesting New Design???

K. L. and B. J. Kosanke

It is difficult to argue that the quality of Chinese fireworks has not improved greatly over the past 25 years. However, that is not to say that on occasion, one still does not encounter quality related problems, sometimes so extreme that it is hard to believe. The photo in Figure 1 is of a 3- inch (75-mm) aerial shell and is such an example.


Ref: Selected Pyrotechnic Publication of K.L. and B.J Kosanke, Part 7, (2003-2004), pp 116-116
(K7_116)
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