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 Horizontal Press and Cutting House. (Greer, n.d.)

The Solvent Recovery House Building 214 was where the solvents, ether, and alcohol were extracted from the black powder.

Warm air was used to evaporate most of the remaining alcohol and ether and the powder was again screened for defective pieces and foreign material in the Debagging House Building 218. Powder containing 3% to 5% of the solvent was sent to the Water Dry House Building 219 where it was aged to free it of any remaining solvent. The powder was soaked in water.

The Control Circulation Dry House Building 220 dried the remaining solvent out of the powder before it went to the blending tower.

It was then sent to Power Pack House Building 221 for blending to achieve a set burn rate. Because of slight differences in each batch of powder that was produced, several batches were mixed in the blending towers to make one uniform lot of about 150,000 pounds.

Each lot was then packaged, with the containers checked to ensure they were airtight. They were then sent to an igloo for storage or to a shipping house for distribution.

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IOW No. 2 was to be a rocket propellant plant with three lines to produce double-base rocket powder. Nitroglycerine was to be produced and then mixed with nitrocellulose to form a paste and shaped for use as a propellant for use in the Army’s newly designed experimental robot bomb, similar to the V-1 bomb the Germans had developed. Although construction of the facility began in December 1944, work was never completed because of the conclusion of World War II.

At HOP, several different types of charges were produced but the processes involved were similar. The LAP process at HOP involved two distinct operations, starting with bag manufacturing which consisted of a Dye House where the fabric would be dyed, washed, and tumble dried first. The igniter end of a charge was always red so it could be identified in the field while short-range charges, also used for training, were bagged in green cloth.

Flow of material through the Bag Manufacturing Building (Building 1001) for the manufacture of 105 mm howitzer charges.. (Greer, n.d.)

The fabric was then sent to the Bag Manufacturing Building where it was sent into two directions. Future end pieces and tying straps went to long lay-up and cut tables, where the end pieces were cut by punch presses from stacked cloth 20 layers thick. Those to be printed were then sent to the press, inspected, and moved to the first two sewing assemblies where the pad for the igniter was added. These then joined the pieces of the body at an inspection and collection point. The body pieces had been cut into long strips by a sliter, folded, and sewn into long tubes, then cut to the length required for the charge being made. They were then inspected and sent to join the end pieces and straps. Lastly, the ends were sewn on, straps added to some bags, and inspected.

The second operation involved the load, assembly, and pack process where the components that went into most charges were loaded onto two different lines: one for black powder igniter and the other for other increments such as smokeless powder. There were eight propellant loading lines, each with “A” and “B” side LAP buildings, as well as four igniter loading lines, and black powder screening and drying facilities. The charges produced ranged in weight from two-thousandths of a pound to 896 pounds.

Smokeless powder was brought from storage igloos and delivered to one of the line’s two service magazines where it was transferred to the loading buildings (Buildings 3001-3017), and taken by elevator to the second floor where it was placed in non-sparking copper hoppers that would deliver it to a powder tub, where the increment was then weighed, placed into a bag, and sewn shut. The increment was then passed to the center aisle through a transfer chute, inspected, and passed to the assembly and passing section of the building via another transfer chute, which helped reduce airborne powder circulating through the structure. The increments would then be stacked in order, placed in the outer charge bag, and inspected again to make sure the diameter and length were within tolerance. After passing through another chute, they were packed into containers and taken to the service magazine, and sent to storage or to boxcars for shipping.

This is just a brief explainer of how nitrocellulose and black powder was produced at IOW No.1 and how it was loaded, assembled, and packed at HOP at the now-demolished Indiana Army Ammunition Plant in Indiana. For several decades, the facility was a vital component of the Ordnance Department’s munitions production program during World War II, the Korean War, the Vietnam War, and the Cold War.

Source: Gaither, Steve and Kimberly L. Kane. “The World War II Ordnance Department’s Government-Owned Contractor-Operated (GOCO) Industrial Facilities: Indiana Army Ammunition Plant Historic Investigation.” US Army Corps of Engineers, Dec. 1995.

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