Safety

Safety First! Precautions/procedures and equipment.

Moderators: richardh08, Boophoenix, Lloyd

Post Reply
User avatar
Pyro-Gear
Site Admin
Posts: 3034
Joined: Wed Jul 10, 2013 8:24 am

Safety

Post by Pyro-Gear »

A general review of basic safety considerations for fireworks makers is perhaps overdue. The new-comer amateur or pro can especially benefit from the safety facts of this pyro-chemical art and science. Years of hard earned experience, mistakes, and tragedy should not be relearned in bits and pieces. This only invites history to repeat its tragedies. Nor does space in AFN allow an in-depth and fair study of this vast subject. However, a look at some basics may inspire readers, with a thirst for more knowledge, and a desire for future existence to do research and ask questions.

It must be borne in mind that any mixture of oxygen and fuel, under the right conditions, may explode if it ignites. It must be also remembered that fireworks mixtures are mixtures of chemically bound oxygen and fuels in solid form. It is therefore the responsibility and duty of all fireworks makers, from the hobby mixer to the industrialist pro, to take all steps to prevent accidental ignition. The second most important duty is to limit exposure by preventative means, should accidental ignition occur. This means limitation of quantities being worked on, and isolation of all other quantities of explosives. It also means to limit the number of workers on an operation to the bare minimum required, and to isolate the operation from accidental propagation to all other operations on the premises.

Almost all the ingredients used in fireworks compositions are used as finely divided powders, which greatly increases their surface area in a given volume and/or density. For example, a charcoal dust cloud in air explodes violently when ignited. Therefore, all finely divided mixtures of materials should be handled with care. This is especially important with finely divided metals, which are hard enough to cause friction ignition. Finely divided metals present a hazard to violent explosion when ignited, and are susceptible to ignition by static electricity more easily than other mixtures due to their conductivity. Steel tools must be avoided in grinding, mixing, charging, pressing, tamping, ramming, or other similar loading operations. Steel tools create sparks when struck. The almost as hard bronze, may be used for certain purposes, but the much softer brass and lead are safer. Wood and aluminum tools, and mallets made of rawhide are also non-sparking safe.

Potassium chlorate, in many ways one of the best fireworks ingredients, may under certain conditions of temperature and acidity, slowly break down giving chloric acid, or chlorine dioxide, both of which are more active oxidizing agents than potassium chlorate itself. When this happens, potassium chlorate mixtures are extremely hazardous, with disastrous results often occurring. Sensitivity to heat, shock, friction and impact are greatly enhanced with ignition occurring, in some cases, as little as a flick of the fingernail. Sulfates, sulfides, and sulfur itself may be slowly oxidized to form sulfuric acid, which can then break down the potassium chlorate into dangerously active chloric acid.

Places where plain mixing is done containing sulfur, (but no potassium chlorate;), must be kept separate from the places where chlorates are mixed. This separation also applies to personnel, clothing, tools, and utensils, which should be thoroughly washed between operations. No chlorate should ever be used with ammonium salts because of the probability of forming ammonium chlorate, which violently explodes at the temperature of boiling water (212 degrees F). All the oxidizing agents, when mixed with finely divided metals, should be handled with extra care and respect.

Carbon, (in the form of charcoal, lampblack, or carbon black), potassium nitrate, and sulfur mixtures, seem to be fairly safe to handle. Barium nitrate also seems fairly safe when mixed with sulfur, carbons, or finely divided metals. Finely powdered metals, in mixtures with barium and strontium nitrates and potassium perchlorate, even when sulfur is present, appear to be fairly stable mixtures. It is reported, the sensitivity of such mixtures is increased by the addition of powdered charcoal. There is no doubt charcoal does indeed speed-up the burning rate of some mixtures, and also lowers the surface ignition temperature of certain mixtures. There is some evidence that mixtures containing both potassium perchlorate and asphalt gums, cause the perchlorate to be changed into the chlorate, with disastrous results during storage. Asphalt gums should be avoided with perchlorates or chlorates because the asphalt gums contain sulfur and sulfur acids, which break down the chlorates to chloric acid.

The smallest amounts as possible should be used when experimenting with new compositions, as the slightest incident can turn a mixture into an explosion.

Magnesium metal powder should be avoided by the inexperienced pyrotechnician. This metal must be treated with special coatings to avoid spontaneous combustion before it can be safely mixed with oxidizers. Magnesium cannot form a protective metal oxide layer on its surface as aluminum can.

Mixes of any type of aluminum powder, potassium nitrate and sodium oxalate, with water, will often heat;-up, and can result in spontaneous combustion. Atomized aluminum, because of its strong aluminum oxide outer layer, appears to be far less reactive than other aluminum powders in mixtures known to react with aluminum.

Titanium seems to be relatively safe in regard to spontaneous ignition, and has not been reported to cause such problems. Finely divided titanium powder or dust, is a fire and explosion hazard by itself, when dry. For this reason titanium dust is packed wet (with water) in sealed drums for shipment. Titanium dust has no useful purpose in fireworks due to its hazardous nature. However, in granular form (sponge), it is used to make many beautiful sparking effects. Titanium is an extremely hard metal, and as such, poses a friction;-ignition hazard. It especially increases the sensitivity of mixtures containing chlorates or perchlorates. Extra care must be exercised when ramming devices such as whistles, gerbs, fountains, etc., that contain perchlorates and titanium. Ramming of devices containing potassium or barium chlorate should never be attempted, especially if titanium is an ingredient.

During commercial manufacturing, the amount of chemical composition in a building at any one time should be kept as low as possible. The workers should wear non-sparking or conductive shoes. Floors should be conductive as outlined in the National Fire Protection Agency (NFPA) standard #99. Cotton clothing should be worn, and all metal machinery and moving parts should be well grounded electrically, to bleed off static electricity before it can build up a dangerous charge. No matches should be allowed in the manufacturing area. Change houses or areas where smoking is permitted will help keep the dangers of smoking under control. Safety training and periodic scheduled safety review meetings with employees are required by OSHA. Close supervision during work is essential to safety.
- WO



ON CHEMICAL SENSITIVITY

Sensitivity of chemical mixes not only relates to how easy (or difficult) one can "strike fire" by friction or impact, but also involve other considerations. The level of heat energy required for combustion (ignition temperature), and whether the chemicals are susceptible to spontaneous combustion should also be considered. The choice of fuel and oxidizer may very well be compatible and free of the danger of spontaneous combustion when water dampened or wet mixed. However, in some instances, the choice of fuel and the ratio of fuel to oxidizer, can render the same mix sensitive to heat by having a low ignition temperature characteristic. The lower the ignition temperature, the easier a spark, (electrical or mechanical), can set it off.

I have often heard pyros say, "Oh, that stuff is safe, its not sensitive, don't worry!" Compared to what? Everything we measure in life is relative compared to some standard. So how do we base our judgment on the "relative" sensitivity of fireworks chemical mixes? Unless you have access to a good explosives engineering library, a lot of money for special apparatus, a lot of time to set-up and conduct experiments, and a good education to interpret the data of your findings you can't make an accurate judgment on relative sensitivity.

Attempts at establishing practical measurement standards are being made and that's good! (See AFN #15, Oct. '82, pp5 "Impact Sensitivity;" by L. S. Oglesby). However, the fireworks industry generally does not have any practical standards of sensitivity measurement other than government specs for military signals. For the most part, the work of professionals and amateurs alike has relied on the knowledge (or hearsay) of those who are experienced and willing to share their knowledge. Unfortunately, there are, and always will be, those who work in the "dark", without regard or ability to conduct controlled experiments for determining relative sensitivity.

Be it a question of chemical compatibility or heat, friction, shock, and impact sensitivity;; we must presume an inherent and intrinsic danger exists by treating all chemical mixes with equal care. It can be dangerously misleading to use the words "never" and "always". However, when handling fireworks chemicals, we must never trust in the unknown and must always respect what is known.

The following is a list of chemical combinations known to cause sensitivity problems. Next to each listing are letters to indicate the types of sensitivity. The code key is given as follows:


F = Friction

HY = Hygroscopic

I = Impact or Shock

SP = Spontaneous Combustion

U = Unstable (poor shelf life, slow decomposition or unpredictable)


AVOID THESE COMBINATIONS OF CHEMICALS

1. Potassium Chlorate & Sulfur, Sulfides, or Sulfates - F, I, SP, U

2. Barium Chlorate & Sulfur, Sulfides, or Sulfates - F, I, SP, U

3. Potassium or Barium Chlorate & Ammonium Compounds - F, I, SP, U

4. Potassium or Barium Chlorate & Calcium Carbonate - F, I, U

5. Potassium or Barium Chlorate & Aluminum - F, I, U

6. Barium or Potassium Nitrate & Aluminum (when wet) - U, SP

7. Ammonium Perchlorate & most Nitrates - HY, U

8. Untreated (coated) Magnesium & any Oxidizer - SP, U

9. Barium Nitrate & Sodium Oxalate - HY, U

10. Barium or Potassium Chlorate & Sodium Oxalate - HY, U, F, I


Bill Ofca
User avatar
richardh08
Site Admin
Posts: 2226
Joined: Wed Aug 07, 2013 1:54 pm
Location: Bedfordshire

Re: Safety

Post by richardh08 »

An excellent - and timely - summary.
Even when I'm wrong, I'm convincing.
User avatar
Pyro-Gear
Site Admin
Posts: 3034
Joined: Wed Jul 10, 2013 8:24 am

Re: Safety

Post by Pyro-Gear »

The worrying thing is that ammonium perchlorate is currently available and does not need an EPP to purchase so I will put up a little bit of information regarding this oxidiser, for now approach with extreme caution AP is not a substitute for potassium perchlorate.
Post Reply