The mechanical system is primarily composed of power and execution systems. The execution system is located at the end of the mechanical system, making direct contact with the target object to accomplish the main functions of the mechanical system. Mechanical system design involves selecting execution system equipment and designing for safety.
Revolutionizing Fireworks Production: Analyzing Physical Properties to Select Equipment and Develop Structural Designs for Ingredient System, Mixing, Granulation, Sieving, Crushing, and Powder Conveying Mechanisms.
1. Requirements for Selection of Mechanical System Equipment
The production efficiency of the automatic production line for Fireworks Bright Beads is determined by the subsystem with the minimum amount of medicine required for a single operation. According to the “Technical Regulations for Occupational Safety of Fireworks and Firecrackers” GB 11652-2012, the mixing system is the subsystem with the minimum amount of medicine required for a single operation in the automatic production line for Fireworks Bright Beads, and the minimum amount of mixed medicine required for a single operation is 10Kg. Mechanical equipment for the mixing system was selected based on the single operation amount of 10 kg, the control process for the mixing system was designed, and the program for the mixing system was written based on STEP7-MicroWin. The single operation time for the mixing system is 8 minutes (Chapter 4 provides a detailed description of the single operation time for the mixing system).
The safety design of the automatic production line for Fireworks Bright Beads requires no material storage between subsystems. Therefore, the single operation amount for the batching, screening, and crushing systems is also 10 kg, and the single operation time is set to 6 minutes. During the operation of the granulating system, the total amount of medicine in the subsystem does not exceed 20 kg, and the output is 1.25 kg/min. The selection of equipment for the batching system, granulating system, screening, and crushing system, and safety interlocking explosion-proof device must meet the requirements for the single operation amount and single operation time.
2. Mixing System
Mixing medicine is a critical process in producing Fireworks Bright Beads and the most dangerous process in production. The quality of the mixed medicine is a key factor affecting the ignition effect. The mixing machine must automatically mix multiple components in proportion and uniformly, realize human-machine isolation, and achieve unmanned production on-site for mixing medicine.
1. Selecting Equipment for Ingredient System: Multi-bin Three-Scale Non-Continuous Cumulative Automatic Balance and Twin Screw Feeder
2. Developing Structural Design of Ingredient System for Red Light Formula
3. Analyzing Mechanisms for Mixing, Granulation, Sieving, and Crushing
4. Selecting Equipment Based on Physical Properties: Twin-Screw Cone Mixer, Disc Granulator, Electromagnetic Vibration Sieve, Inertia Linear Vibration Sieve, and Single-Roller Crusher
5. Analyzing the Working Principle of Twin-Screw Cone Mixer, Disc Granulator, and Electromagnetic Vibration Sieve
6. Selecting Equipment Based on Single Operation Drug Dosage and Time: Twin-Screw Cone Mixer, Disc Granulator, and Electromagnetic Vibration Sieve
7. Developing Safety Designs for Equipment: Twin-Screw Cone Mixer and Disc Granulator
8. Analyzing Mechanism for Powder Conveying
9. Selecting Safety Interlock Explosion-Proof Device for Powder Conveying Equipment
10. Developing Structural Design of Safety Interlock Explosion-Proof Device.
2.1 Double Helix Conical Mixer
2.1.1 Powder Mixing
Mixing, also known as the homogenization process, refers to the operation process in which the material undergoes changes in motion speed and direction under external forces (such as gravity and mechanical force), allowing the particles of each component to be evenly distributed [31].
2.1.2 Mechanisms of Powder Mixing
The mechanisms of powder mixing include three types: convection mixing, diffusion mixing, and shear mixing. Convection mixing refers to the movement of agglomerates from one part of the material to another, similar to fluid convection; diffusion mixing refers to the separation of particles dispersed on a continuously presented inclined surface, mixing and permeating with each other; shear mixing refers to the relative movement of particles within the material, forming several slip surfaces [32-35]. During the mixing process of particles with different particle sizes, segregation also occurs, mainly caused by the percolation mechanism. Larger particles float up to the upper surface of the particle flow while smaller particles sink. The actual mixing process is a competition between mixing and segregation. Under the joint action of various mechanisms, particles will eventually reach a relatively stable mixing and segregation state.
2.1.3 Selection of Mixing Equipment
There are two types of mixing equipment: rotary container type (gravity type) and fixed container type (forced type). Gravity-type mixing equipment mainly relies on the complex motion generated by gravity to mix, which tends to cause the material with large particle size or density difference to segregate. Forced-type mixing equipment mainly relies on the strong pushing force of the rotating paddles to generate complex motion and forced mixing. Due to the large density difference of the raw materials in the Bright Bead formula, a fixed container type mixing equipment is chosen. There are two types of fixed container mixing equipment: conical mixers and horizontal mixers. Since conical mixers can achieve “zero” materials residue in the cylinder, a double helix conical mixer is chosen [35-36].
2.1.4 Working Principle of Double Helix Conical Mixer
The working principle of the double helix conical mixer is shown in Figure 3.1. Inside the conical mixer cylinder, two non-symmetric screws rotate and lift the materials upwards. The slow revolution of the mixing arm causes the materials outside the screws to enter the screw column to varying degrees, achieving continuous updating and diffusion of the materials in full circle. The two material streams lifted to the top converge at the center cavity, forming a downward material flow that fills the void at the bottom and creates a triple mixing effect of convection circulation.
Figure 3.1: Double Helix Conical Mixer
2.1.5 Factors Affecting the Mixing Process
1. Mixing Time
The mixing process is shown in Figure 3.2. The mixing speed is fast during the early mixing stage, and the particles mix rapidly. After reaching the optimal mixing state, the mixing process can no longer reach the optimal mixing state due to the mixing and anti-mixing effects, especially for finer powders. The mixing time ranges from 2 to 8 minutes, depending on the mixing equipment.
The estimated optimal mixing time formula for the double helix conical mixer is [31]:
Where:
t – optimal mixing time in minutes
np – revolution speed of the screw axis in r/min
ns – rotation speed of the screw axis in r/min
Figure 3.2: Mixing Process
1. Loading Ratio
The optimal value for rotary container-type mixing equipment is 30% to 50%. The mixing area is the largest when it is 50% [31].
2.1.6 Technical Parameters of Double Screw Cone Mixer
The physical diagram of the double screw cone mixer is shown in Figure 3.3, and the main technical parameters are shown in Table 3.1.
Table 3.1: Technical Parameters of Double Screw Cone Mixer
2.1.7 Selection of Feeding and Discharging Equipment
A pneumatic slide gate valve is a special valve for opening and closing pipelines in solid material conveying systems. The completely sealed structure is suitable for outdoor environments and is mainly installed at the bottom of related equipment such as silos and hoppers. It has the advantages of a simple structure, small size, flexible process layout, strong sealing, and no leakage of materials. Suppose electromagnetic valves carry out the feeding and discharging of the double screw cone mixer. In that case, sparks may be generated when the electromagnetic valves are turned on and off, which may directly cause combustion and explosion accidents when in contact with gunpowder. Therefore, the feeding and discharging ports of the double screw cone mixer use pneumatic slide gate valves with a diameter of ϕ125mm for feeding and discharging.
2.2 Electromagnetic Vibrating Screen
The raw materials were crushed and sieved once with a single material and single element before weighing so that the particle size of the raw materials was relatively small. Due to the smaller particle size and larger specific surface area of the powder, the powder’s internal molecular gravitational and electrostatic forces are enhanced, resulting in a more compact particle stack, increased compression ratio, poorer flowability of the powder, and poorer mixing uniformity. Additionally, gunpowder is a viscous powder. The material between the screw blades and the container wall is not easily lifted and mixed during the asymmetric self-rotation and arm revolution of the screw, so the gunpowder mixed by the double screw cone mixer needs further mixing and refining.
2.2.1 Sieving
Sieving refers to placing solid particles on a sieve surface with a certain aperture size, allowing those that pass through the sieve holes to become the undersized material and those trapped on the sieve surface to become the oversize material.
2.2.2 Selection of Sieving Equipment
Sieving equipment can be divided into four categories according to the motion characteristics of the sieve surface: vibrating sieve, rocking sieve, rotating sieve, and fixed sieve. Among them, the material movement direction of the rocking sieve is basically parallel to the sieve surface, making it difficult to discharge material; the rotating sieve has a larger size compared to other sieving machines with the same processing capacity, and its sieve holes are prone to clogging; the fixed sieve is mainly used for coarse and medium screening of ores; the vibrating sieve is widely used in the production and processing of medium and small-sized powders. Therefore, a vibrating sieve is chosen as the sieving equipment.
Estimation formula for vibration amplitude and sieving particle size [31]:
A = 2+o.3d — (3.2)
Formula: A-amplitude mm
d-particle size of the material mm
Table 3.2 The range of amplitude and frequency for different vibration modes [31]
According to the estimation formula 3.2, it can be calculated that the amplitude of the 100 mesh mixed material is 2.045mm. According to the calculation results in Table 3.2, the mixed material sieved through the 100 mesh should use an electromagnetic vibrating screen.
2.2.3 Working Principle of Electromagnetic Vibrating Screen
The electromagnetic vibrating screen, as shown in Figure 3.4, has a heavy hammer (unbalanced hammer) installed up and down on the motor shaft, which transforms the motor’s rotational motion into a three-dimensional motion that is horizontal, vertical, and tilted. This motion is transmitted to the screen, causing the material to move outward in a spiral motion on the screen and be automatically discharged through the discharge port.
2.2.4 Technical Parameters of Electromagnetic Vibrating Screen
The physical diagram of the electromagnetic vibrating screen is shown in Figure 3.5, and the main technical parameters are shown in Table 3.3.
2.3 Safety Design of Mixing System
Based on the safety design of the automated production line for fireworks and firecrackers, the mechanical and electrical equipment of the product mixing system is designed for safety. The product specific contents are as follows:
1. The inner surface of the double spiral cone mixer and the electromagnetic vibrating screen is coated with an anti-static material, specifically Teflon.
2. The inlet and outlet valves of the double spiral cone mixer are pneumatic plug valves.
3. The screen of electromagnetic vibrating screen is made of brass.
4. Explosion-proof three-phase asynchronous motors are used for the double spiral cone mixer and the electromagnetic vibrating screen.
5. A cooling water jacket is added to the outer surface of the double spiral cone mixer. Cool circulating water is injected into the jacket during mixing to reduce the temperature.
3 Batching System
Batching is a critical process in producing fireworks and firecrackers, and the accuracy of batching is a key factor that affects the display effect. Inaccurate raw material proportioning during batching can lead to defects such as blind fire, broken fire, and poor color effects of the fireworks. The batching system precisely weighs multiple components according to the proportioning, improving the performance and uniformity of the products. The design of the batching system includes the selection of the balance, feeder, weighing method, and storage hopper design.
3.1 Balance
GB/T 14250 defines a balance as a measuring instrument that determines the mass of an object by the force of gravity acting on it. It can also determine other quantities, sizes, parameters, or characteristics related to the measured mass.
3.2 Selection of Weighing Apparatus
The powder industry’s most widely used weighing apparatus includes four types: non-automatic weighing apparatus, non-continuous cumulative automatic weighing apparatus, gravity-type automatic material weighing apparatus, and continuous cumulative automatic weighing apparatus. Among them, non-automatic weighing apparatus requires operator participation in the weighing process, which increases labor intensity. Continuous cumulative automatic weighing apparatus is installed on belt conveyors for continuous cumulative weighing of materials, but its weighing accuracy is not high and requires frequent automatic calibration. Non-continuous cumulative automatic weighing apparatus and gravity-type automatic material weighing apparatus has high accuracy and fast batching speed. Since the batching of fireworks and feed powders is similar, the batching process of multi-bin three-scale is selected for feed powder batching.
3.3 Selection of Feeder
The feeder is a mechanism that ensures the accurate completion of the weighing process in the batching system. The electromagnetic vibration feeder for conveying powdered materials includes three types: screw feeder, impeller feeder, and electromagnetic vibration feeder [38-39]. The electromagnetic vibration feeder is unsuitable for conveying extremely fine powdered materials, and the impeller feeder is suitable for feeding in pneumatic conveying systems. Therefore, the screw feeder is selected for material feeding and conveying. The screw feeder includes two types: single screw feeder and double screw feeder, as shown in Figure 3.6. The feeding accuracy of the single screw feeder is not high, and viscous materials are easy to cling to the rod, reducing the batching system’s production efficiency. The double screw feeder has high feeding accuracy, is not prone to rod clinging, and is suitable for conveying viscous materials. Since fireworks belong to viscous powdered materials and the batching system requires precise batching, a double screw feeder is selected for material feeding and conveying.
3.4 Design of Material Hopper
1. Design of cone angle
When the cone angle of the hopper is 30˚, the entire hopper is in the flow zone. The flow zone intermittently forms as the cone angle increases [40]. Sticky powders are easier to discharge from hoppers with a cone angle of 30˚ than from hoppers with a cone angle of 60˚. Therefore, the cone angle of the material hopper is designed to be 30˚.
1. Agitator
Due to the adhesion and friction of the powder inside the hopper, the powder is prone to forming a static arch in the hopper, which prevents the powder from being discharged normally. Therefore, a rubber agitator is added to the material hopper to ensure the discharge of the powder.
3.5 Selection of Weighing Method
Two common weighing methods are used in industry: additive and subtractive. Additive weighing consists of a material hopper and a weighing hopper, with a weight sensor installed on each side of the weighing hopper. The material hopper opens its discharge valve to add materials to the weighing hopper. The valve is closed when the weight added reaches the target value, achieving high weighing accuracy. On the other hand, subtractive weighing consists of a material hopper and a weighing hopper, with weight sensors installed on both sides of the material hopper. The discharge valve of the material hopper opens to add materials to the weighing hopper, and the weight controller measures the weight of the material hopper. The valve is closed when the weight of the material hopper decreases to the target value, resulting in lower weighing accuracy.
The automatic production line for fireworks and firecrackers requires precise ingredient ratios, so the additive weighing method with high accuracy is selected. With additive weighing, the raw materials are weighed in the weighing hopper, avoiding the need to weigh the raw materials in the material hopper as in subtractive weighing. The use of additive weighing allows for the continuous and automated addition of raw materials to the material hopper without stopping the machine, achieving continuous production.
3.6 Working Principle of the Three-Weighing System with Multiple Warehouses
Various raw materials in the fireworks and firecracker formulas are manually added to the corresponding material hoppers for storage. The feeding device sends the raw materials to the click on the button weighing hopper in order. Large-portion (≧20%) raw materials are weighed in the large weighing hopper, while small-portion (5%~20%) raw materials are weighed in the small weighing hopper. The quantity of each raw material is controlled by a programmable controller that controls the feeding device. When all the raw materials are weighed according to the set formula requirements and the cumulative weight reaches the target, the discharge outlet of the click on the button weighing hopper opens in sequence, and the raw materials in the weighing hopper are added to the mixing barrel. The mixing barrel is then transported to the next process by a mechanical hand. The schematic diagram of the batching device is shown in Figure 3.7, and the physical diagram is shown in Figure 3.8.
Figure 3.8: Physical Diagram of the Batching Device
3.7 Structure of the Multi-Scale Three-Bin Ingredients System
Fireworks and firecrackers come in over 6,000 different varieties, with different components and proportions in each recipe. Taking a red light recipe as an example, the specific ingredients are shown in Table 3.4. The structure of the ingredients system is shown in Figure 3.9. The fireworks and firecracker ingredients are weighed using large and small weighing bins according to their proportions. The principle of separate weighing of oxidants and combustibles is applied, with polyvinyl chloride, lacquer chips, and resin weighed in small weighing bin A, and magnesium-aluminum alloy weighed in large weighing bin B. Potassium chlorate and strontium carbonate are weighed in a large weighing bin C. [41-44].
Table 3.4: Red Light Recipe
4 Granulation System
Granulation in the production process of fireworks refers to the spherical particles that are rolled out using the ball-rolling method [45].
4.1 Disk Granulator
4.1.1 Granulation
Granulation or pelletization refers to adding a binding agent to a very fine powder to produce solid particles with good fluidity. Usually, the processed spherical particles are referred to as pellets.
4.1.2 Granulation Mechanism
The formation process of granulation includes three stages: the generation of granulation nuclei, the growth of aggregates, and the spheroidization and granulation of aggregates (as shown in Figure 3.10 (a), (b), and (c)). After spraying a liquid binding agent in the granulator, the powder surface absorbs enough water and forms a liquid arch bridge between adjacent particles. This aggregated structure is called a granulation nucleus. The powder and granulation nucleus repeatedly rise and fall in the granulator and continuously roll. Under the collision effect, these granulation nuclei coalesce into larger aggregates. When the granulator stops spraying the liquid binding agent, the aggregates continue to rise and fall and roll in the granulator. The capillary action of the liquid between the particles is strengthened, and the negative pressure generated gradually compacts the aggregates. Finally, the liquid on the surface of the aggregates is absorbed by the outer layer of dry powder, and the aggregates will no longer button to continue to grow, thus making the fine powder into pellets with a certain size and strength [46].
4.1.3 Equipment Selection for Granulation
Based on the basic principle of achieving small particle agglomeration in powder forming processing, existing powder processing technologies can be classified into four types: mixing, pressure forming, spray and dispersion atomization, and hot melt molding. When rotated, mixing is achieved through the flipping, rolling, and curtain-style falling motion of a disk, cone, or drum. Pressure forming confines the material in a specific space and compacts it into a dense state by applying an external force, but some materials are difficult to de-mold. Spray and dispersion atomization directly transform highly dispersed liquid or semi-liquid materials into solid particles in specific equipment, resulting in smaller particle sizes. Hot melt molding uses a special condensation method to solidify molten materials (with a melting point generally below 300℃) into the required shapes, such as sheets, blocks, and hemispheres.
As fireworks are mixed explosive and pyrotechnic, combustion and explosion accidents can occur due to any impact, friction, or high temperature. Therefore, mixing is the preferred method. Commonly used mixing equipment includes cylinder granulators and disc granulators. Cylinder granulators directly granulate the material at temperatures between 100-600℃, while disc granulators roll the material into particles in a rotating inclined disc. Therefore, a disc granulator is selected for granulation [47-52].
4.1.4 Working Principle of Disc Granulator
The working principle of the disc granulator is shown in Figure 3.11. Under the combined action of friction, gravity, and centrifugal force in the inclined rotating disc, the material moves upward with the rotation of the disc due to the friction force, rolls downward due to the gravity force, and is thrown to the edge of the disc due to the centrifugal force. After spraying the binder in the inclined disc, the material moves under the combined action of the three forces, allowing the material to grow gradually from a small agglomerate to a spherical particle inside the disc, and the finished product overflows from the edge of the disc.
Figure 3.11: Disc Granulator
The operating method of the disc granulator is shown in Figure 3.12. When the disc is rotating counterclockwise, material is fed in at point A, a binding agent is sprayed at point B, and the particles overflowing from the disc are collected at point F [31].
4.1.5 Factors Influencing the Granulation Process
1. Disc rotation speed
The materials collide and come together on the inclined rotating disc, bonding together due to the surface tension of the liquid phase.
If the disc’s rotation speed is too slow, the materials will accumulate at the bottom of the disc, affecting the particles’ sphericity. If the rotation speed is too fast, the particles will not take shape and will be thrown out of the disc, which will also affect the sphericity of the particles [53].
2. The tilt angle of the disc
The tilt angle of the disc pelletizer is generally between 40° and 60°. If the tilt angle of the disc is smaller than the natural rest angle of the mixed material before granulation, the material will adhere to the disc and rotate with it, affecting the sphericity. If the tilt angle of the disc is too large, the material will accumulate at the bottom of the disc and not rotate with it, which will also affect the sphericity [54].
3. Atomizing pressure
If the atomizing pressure is too low, the binder will form droplets, causing the material to agglomerate and affecting the sphericity. If the atomizing pressure is too high, the speed of the atomized droplets will be too fast, which can cause splashing at the edge of the pelletizing disc, resulting in insufficient contact between the binder and the material, also affecting the sphericity [20]. Therefore, it is necessary to analyze the influence of various factors on sphericity through experiments and determine the optimal process conditions by click on the button [55-57].
4. Load ratio
The pelletizer can feed 10-20kg at a time, and the average density of the red light formula is 2.2kg/L. According to the literature, the ratio of the volume of the pelletizing disc to the volume of the granulated powder should be greater than 7:1.
4.1.6 Technical Parameters of Disc Pelletizer
The physical diagram of the disc pelletizer is shown in Figure 3.13, and the main technical parameters are shown in Table 3.5.
4.2 Safety Design of Granulation System
Based on the safety design of the automated production line for fireworks and firecrackers, the mechanical and electrical equipment of the granulation system has been designed for safety. The specific details are as follows:
1. The interior surface of the granulator is coated with copper.
2. The granulator uses rubber scrapers to reduce the extrusion force on the fireworks and firecrackers.
3. The electric motor of the granulator uses an explosion-proof three-phase asynchronous motor.
5 Screening and Crushing System
Screening and crushing in the production process of fireworks and firecrackers refer to sieving the bright pearls into three sizes – target size, large particles, and small particles – through a sieve screen. The bright pearls of the target size are sent to the next process for further processing, while the large particles are crushed into small particles and mixed with the small particles sieved out by the sieve screen by click on the button. The mixture is then put back into the disc granulator for granulation.
5.1 Inertial Linear Vibrating Screen
5.1.1 Selection of Screening Equipment
According to the estimation formula 3.2 for amplitude and screening particle size, the amplitude of 5-20mm light ball particles is 3.5-8mm. As calculated from Table 3.2, the 5-20mm light ball particles should be screened using an inertial vibrating screen.
5.1.2 Working Principle of Inertial Linear Vibrating Screen
The working principle of the inertial linear vibrating screen is shown in Figure 3.14. Two vibrating motors produce relative motion, causing the eccentric blocks at both ends of the vibrating motors to generate rated exciting force, which is transmitted to the screen box. This force causes the material on the screen surface to throw in the direction of the discharge port continuously. After passing through the screen, materials of various particle sizes are obtained, completing the classification of the material.
5.1.3 Technical Parameters of Inertial Linear Vibrating Screen
The physical diagram of the inertial linear vibrating screen is shown in Figure 3.15, and its main technical parameters are shown in Table 3.6.
5.2 Single-roll crusher
5.2.1 Crushing
Crushing is the process in which solid materials, under external forces, overcome cohesive forces and reduce in size or increase in specific surface area.
5.2.2 Working principle of the single-roll crusher
The single-roll crusher has a high crushing ratio, produces uniformly sized products, and performs well in crushing sticky and wet materials (click on the next button to continue on). As shown in Figure 3.16, materials are fed into the crusher from the feeding hopper and then are squeezed and impacted by the teeth and jaws between the roll and the jaw plate to achieve crushing[58]. The physical diagram of the single-roll crusher is shown in Figure 3.17.
5.3 Safety Design for Screening and Crushing System
Based on the safety design of the fireworks and firecrackers automated production line, the mechanical and electrical equipment of the screening, loadings, loading and crushing system are designed for safety. The specific content is as follows:
1. The inner surface of the screening machine and crusher is sprayed with anti-static material, such as Teflon.
2. The screen of the screening machine is made of brass.
3. The crushing blades of the crusher are made of rubber to reduce the impact force of the blades on the fireworks and firecrackers. Just click on the button to continue
4. Explosion-proof three-phase asynchronous motors are used for the screening machine and crusher motors.
5. During the crushing process, cooling circulating water is injected into the bearing of the main shaft of the crusher to reduce the temperature.
6 Safety Interlocking Explosion-proof Device
In the fireworks and firecrackers automated production line in China, explosion-proof walls are used to isolate the batching system, mixing system, granulation system, and screening and crushing system from each other to prevent the spread and propagation of combustion and explosion accidents and limit the damage of combustion and explosion within a certain range. Selecting suitable conveying equipment to realize the transportation of materials for each system is a key factor in the composition of the fireworks and firecrackers automated production line.
6.1 Conveyor Machinery
Conveyor machinery refers to various mechanical equipment used in the industrial production process to complete the transportation of materials between different production stages and connect various production stages to form an assembly line.
6.2 Selection of Conveyor Equipment
The conveyor equipment is generally divided into mechanical conveyor equipment and pneumatic conveyor equipment. Mechanical conveyor equipment includes belt conveyors, screw conveyors, bucket elevators, and chain plate conveyors [59-63]. The pneumatic conveyor equipment is used for transporting dry powdered materials. Belt and chain plate conveyors unavoidably generate dust during transportation, causing environmental pollution, occupational hazards to employees, and the risk of combustion and explosion in the presence of a fire source. Screw conveyors generate significant frictional force between the trough and the screw blade, the screw surface and the material, and the trough and the material, which are unsuitable for transporting fireworks and gunpowder. Bucket elevators increase the frequency of maintenance due to the wear and tear of the chain links caused by dust, raw materials, fireworks, and gunpowder during operation. As a result, common conveyor equipment cannot meet the requirements for material transportation between different production stages. A safe interlocking explosion-proof device is designed to achieve automatic material transportation between various processes in the fireworks production line.
6.3 Working Principle of Safe Interlocking Explosion-Proof Device
As shown in Figure 3.12, the safe interlocking explosion-proof device includes two doors, A and B, which are interlocked using a programmable controller, an electromagnetic lock, an indicator light, and other components. When door A opens, the indicator light for door B turns off, indicating that door B cannot be opened. The electromagnetic lock for door B is activated to achieve interlocking. When door A is closed, the electromagnetic lock for door B begins to unlock, and the indicator light for door B turns on, indicating that door B can be opened.
6.4 Design of the Safety Interlock Explosion-Proof Device
The safety interlock explosion-proof device is made of 304 stainless steel, and the thickness of the steel plate is determined according to the explosive strength of the fireworks.
The safety interlock explosion-proof device uses explosion-proof doors to transport raw materials, fireworks, and bright bead particles. Explosion-proof doors are installed on the left and right sides of the device. The pneumatic transmission system and programmable controller control the opening and closing of the explosion-proof doors, ensuring that one side is closed when the other is open. When a combustion and explosion accident occurs in a neighboring process of the safety interlock explosion-proof device, the explosion-proof doors can effectively prevent the spread and propagation of the accident, avoiding damage to the safety interlock explosion-proof device and the adjacent process.
The safety interlock explosion-proof device adopts an upward venting method and installs a plastic cover on the top. When an explosion occurs inside the safety interlock explosion-proof device, the direction of the shock wave caused by the explosion is upward, avoiding greater damage to the safety interlock explosion-proof device.
7 Summary of this Chapter
Based on the physical properties of fireworks and the requirement for ingredient accuracy, equipment for the ingredient system has been selected, including a multi-bin three-scale non-continuous cumulative automatic balance and a twin screw feeder. The working principle of the multi-bin three-scale ingredient system has been analyzed, and the structural design of the ingredient system for the Red Light formula has been developed.
Mechanisms for mixing, granulation, Sieving, and crushing have been analyzed, and equipment for the mixing, granulation, Sieving, and the crushing system has been selected based on the physical properties of fireworks. Specifically, this includes a twin-screw cone mixer, a disc granulator, an electromagnetic vibration sieve, an inertia linear vibration sieve, and a single-roller crusher. The working principle of the twin-screw cone mixer, disc granulator, and electromagnetic vibration sieve has been analyzed, along with the factors that impact the mixing, granulation, Sieving, and crushing process. Specific equipment models, such as the twin-screw cone mixer, disc granulator, and electromagnetic vibration sieve, have been selected based on the requirements for single-operation drug dosage and single-operation time. Safety designs for equipment, such as the twin-screw cone mixer and disc granulator, have been developed in accordance with the safety design of the fireworks and bright beads automatic production line.
The mechanism for powder conveying has been analyzed, and the safety interlock explosion-proof device has been selected as the powder conveying equipment based on the physical properties of fireworks. The working principle of the safety interlock explosion-proof device has been analyzed, and the structural design of the safety interlock explosion-proof device has been developed.
At PyroEquip, we’re committed to creating the most stunning fireworks possible. That’s why we use top-of-the-line equipment and careful analysis to ensure the perfect formula every time.
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