Dosing and mixing line for military powders

Install a dosing and mixing facility for the preparation of propellant powder. The project then considers three objectives in line with critical requirements: safety, precision and production continuity.

As the traditional activity is pyrotechnics, the powders to be processed are highly explosive and in powder form. This means that it is necessary to be aware of the risks of electrostatic discharge, dust emission and differential friction, which causes the powders to ignite. In addition, the dosing and mixing equipment should allow the powder to be transferred without excessive mechanical stress and, at the same time, ensure perfect homogeneity of the mixtures.

In addition, the project specifies that the margin of error is milligrams in order to respect the small amount of graphite and moderator to be dosed on each grain to ensure the stability and dynamic performance of a batch.

Finally, the installation should be operational and continue with a capacity of up to 300 kg/h. The project aims to meet these conditions while reducing human intervention, an action that would minimise the occupational risk for workers handling pyrotechnic powders. The project therefore aims to improve the ergonomics, inclusion of dust and closed-loop controls.

In order to meet customer needs, a dosing and mixing line has been developed to improve the accuracy of formulations while ensuring maximum safety when handling pyrotechnic powders.

The installation is based on an automated chain made up of various essential pieces of equipment:

Secure drainage points:

• A Sacktip Enclosed bag tipper for graphite, which reduces dust emissions thanks to an integrated particle removal system, a glove box and a safety sieve that prevents the entry of unwanted objects.
• For the moderator, this is a Sacktip SDEP-type manual unpacking equipment, equipped with a containment system by means of an isolated glove enclosure (isolator) and a bag compressor to improve worker ergonomics.

Controlled transfer systems:

• Pneumatic dense phase transport is used to ensure the movement of graphite and moderator without the risk of segregation or excessive friction. This system also helps to reduce the build-up of electrostatic charges.
• A speed-up device installed downstream of the loading isolators to ensure a constant and regular flow in the transfer pipes. The electrical continuity of the pipes is guaranteed by a double ground braid and a continuity controller (ohmmeter) is installed on the transfer, which regulates the authorisation to operate.

High-precision dosing:

• A D12 screw feeder, equipped with an integrated buffer hopper for graphite, ensures controlled distribution in the mixer with adjustable precision according to the powder indices.
• A D14 twin-screw feeder with a weighing frame for propellant powder and moderator, allowing precise adjustment of the doses distributed.

Mixer with conveying ploughshare:

• A mixer with a double heating jacket that allows the incorporation of various ingredients at different stages.
• A heating device based on glycolated water that guarantees the fusion and coating of the powder particles.
• An automated batch cycle with modified mixing times depending on the type of powder and the presence or absence of certain elements.

Storage and disposal:

• A buffer silo at the mixture outlet, equipped with a vibrating bottom and a de-bunging device to ensure an uninterrupted flow to the next production line.

This option ensures meticulous control of dosages and perfect uniformity of the mixture, while guaranteeing strict confinement of pyrotechnic powders. The integration of sensors for temperature, grounding and level detection offers real-time monitoring and instant response to any anomaly.

The installation is based on a set of advanced industrial equipment to ensure accurate dosing, safe operations and uniform mixing of pyrotechnic powders.

1. Powder unloading and supply positions

Sacktip confined empty bags. Included:

• Isolator that can be handled with gloves (full safety for operators).
• Ergonomic design including an integrated dust removal system.
• Contamination is avoided by means of a safety grid at the entrance.
• The operator is not exposed to fine particles.

Drainage position Sacktip SDEP for the organiser:

• System for depositing bags and compacting empty packaging.
• Optimisation of suction and containment to reduce emissions.

Benefits: Increased protection when handling sensitive powders and improved working conditions for operators.

2. Powder transfer

Dense-phase pneumatic conveying:

• Graphite and moderator are transported without degradation or separation of particles.
• Reduction of electrostatic accumulations by means of an integrated grounding system.
• Made of 304L stainless steel, this equipment is fully compliant with industrial standards.

Acceleration box:

• Control of powder flow to ensure uniform transfer.

Benefits: Maintains the properties of the powders and minimises the dangers associated with handling explosive substances.

3. High-precision dosing

D12 screw dispenser with built-in 20L storage tank:

• Precise management of the flow of graphite.
• Integrated scales for optimal dosing accuracy.

D14 twin-screw dispenser equipped with a weighing frame:

• Accurate measurement of propellant powders and regulator.
• Capable of operating in batch or continuous mode according to process requirements.

Benefits: Ensures uniform dosing and improved accuracy in accordance with propellant powder formulations.

4. Powder combination and coating

Ploughshare mixer with double heated jacket:

• Produces a smooth powder.
• Heating system based on glycol water.
• Uniform distribution of the elements.

Benefits: Impeccable uniformity of the mixtures and ideal control of thermal factors to guarantee the final quality of the powder.

With this installation, Palamatic Process offers a reliable, safe and efficient solution for the preparation of pyrotechnic powders. The use of appropriate equipment allows precise control of dosages, ensures handling without risk of deterioration and guarantees a perfectly uniform mixture, all while following the most rigorous safety rules.