Smokeless Powder Production at Indiana Army Ammunition Plant

This guide explains how nitrocellulose (smokeless powder) and black powder was produced at Indiana Army Ammunition Plant in Charlestown, Indiana.

The most important function of the Indiana Army Ammunition Plant (INAAP) in Indiana was to produce nitrocellulose (smokeless powder) and black powder at Indiana Ordnance Works (IOW) No. 1 for distribution to load, assemble and pack (LAP) facilities at Hoosier Ordnance Plant (HOP). Black powder was the more volatile of the two and was used to set off the smokeless powder in the igniter. The powder sent the projectile through space and provided the power when the projectile contacted the target.

At LAP facilities like the HOP, the smokeless powder was placed into bags called increments, then stacked and fixed together into charges, the unit which was actually placed in the gun. IOW No. 1 also produced diphenylamine, dimethylaniline, barium nitrate, weak nitric acid, concentrated nitric acid, sulfuric acid, ethyl ether, and aniline, all of which were used in the production of nitro and black powder.

Four of the six lines at IOW No. 1 that produced smokeless powder were devoted to the manufacture of multi-perforated cannon powder which could utilize both cotton linters and wood pulp as the nitrocellulose base. The other two lines were used to produce single perforated cannon powder and rifle powder, for which cotton linters were needed for the nitrocellulose base.

At IOW No. 1, the process began in Warehouse Building 101, where the cotton linters and wood pulp were stored.

The cotton linters and wood pulp was delivered to the Cotton Dry House Building 104 where they were shredded. They were then pretreated in large ovens to reduce the moisture to less than 1% before being blown in ducts to the Nitrating House. it was picked, dried, and weighed.

Wood pulp went to Building 122 where it was dried, shredded, and weighed. The products were put into cans, weighed again, and sent by conveyor to the Nitrating House Building 105, where 32 pounds of cellulose fiber were mixed in stainless steel nitrators that contained 1,500 pounds of nitric and sulfuric acids that were blended together. The treated nitrocellulose and spent acids were then discharged from the bottom into centrifugal wringers that removed most of the acid through the exterior of the wringer. The acid was used in the production of pyrocellulose or fortified for reuse.

Equipment layout at the Nitrating House. (Greer, n.d.)

The nitrocellulose was then immersed in water and pumped to the Boiling Tub House Building 108, where impurities in the nitrocellulose were removed by boiling for 40 to 70 hours.

It was then sent to the Pulping House Building 109, where the nitrocellulose was cut into smaller pieces to open the embedded fibers which exposed any remaining impurities in the capillary channels. During this process, a very large amount of water was used, which resulted in a slurry that was pumped into the Poacher House.

It was then sent to the Poacher House Building 112 to reduce the acidity of the nitrocellulose. It also reduced the fibers remaining to minute fragments in a mechanical operation. Hot water washes in sodium carbonate, an alkaline solution, further reduced acidity. The nitrocellulose was then bathed in cold water under mechanical agitators to purify the nitrocellulose and ensure for longer shelf life. Samples were sent to a nearby laboratory to determine the percentage of nitrogen, the solubility of the ether-alcohol mixture, and the fineness degree.

Pyro and high grade were combined in ratio to give the blend a 13.15% nitrogen content in the Blending and Wringer House Building 113, which was then put into wringers to dry the nitrocellulose as much as possible.

Still damp, it was dumped into small railroad cars and pushed by hand out of the 100 area into the NC Lag Storage Building 201 where tests determined the moisture content of each batch.

Once confirmed, the batches were sent to the Dehydration Press House Building 202 where a Loomis Press or a Baldwin-Southwark Press was used to simultaneously compact and add denatured ethyl alcohol to the nitrocellulose, dispelling the remaining moisture, and compacting the nitrocellulose into blocks.

The blocks, which came from the Loomis Press, weighed about 69.5 pounds each and were sent to the Mixer House Building 208, where dinitrotoluene (DNT), ether (from the Ether-Mix House Building 206), DPA, dibutylphthalate (DBP), and other ingredients were added.

This was macerated and formed into blocks of about 30 cm. and twice as long and transferred to the Horizontal Press House Building 211, where the blocks were pushed through a macaroni press to again screen out foreign materials, then formed into blocks and then extruded through dies. The extrusion process shaped the nitrocellulose into strands that were cut to lengths determined by the type of charge they were to fill.

Equipment layout at the Horozontal Press and Cutting House. (Greer, n.d.)

Solvents, ether, and alcohol were extracted from the black powder at the Solvent Recovery House Building 214.

Warm air was used to evaporate most of the remaining alcohol and ether in the Debagging House Building 218. 34