• April 20, 2024

The pharma spray gun is used to spray liquid in various pharmaceutical equipment during pharma processes.  Spraying is critical for manufacturing certain pharma products, such as in the granulation section. It is also used in cleaning applications such as Clean in Place – CIP, to clean equipment and accessories used in manufacturing pharma products.

What is a pharma spray Gun?

Pharma Spray Gun is a small mechanical component with a precisely designed hole in its center. It is used to pass the pharma liquid or water with varying flow characteristics to match the process requirements. The spray gun can control parameters such as speed, pattern, and atomization of the sprayed liquid.

The spray gun increases the pressure of the liquid being sprayed for a given volume and helps control the amount being sprayed.

The spray pattern, amount, and pressure of the sprayed liquid can be controlled and changed by varying physical factors such as flow rate and air pressure. This is useful and critical because every product has different spray requirements, which can be easily controlled, as discussed above.

The spray gun is fixed at the metallic manifold inside the equipment and faces the target location of the equipment. Depending upon the product and process requirement, more than one spray gun can be mounted on a single manifold.

What are the processes that require a pharma spray gun?

Some processes and equipment where pharma spray guns are commonly used, include the following

Tablet Coating

Pharma spray guns are used in tablet coating equipment to coat pharma tablets with the desired material. Spray guns are attached to the manifold inside the coating pan. The pan is filled with tablets according to capacity and rotates after filing. The spray gun sprays the liquid on the tablet bed as the pan rotates. Hot air passes through the tablet bed, which dries the sprayed liquid.

Vessel Cleaning

Pharma spray guns clean vessels in various processes, such as storage and manufacturing. The pharma spray gun is included as a part of the vessel design. When cleaning is required, the agent is sprayed through a spray gun to wash the entire vessel.

Spray Drying

Spray drying is a method of drying a liquid to form solid particles. The liquid to be dried is sprayed in a drying chamber through spray guns. Hot air passes through the chamber, ultimately evaporating the sprayed liquid’s moisture.

High Shear Granulation

Spray guns are used in high-shear granulations to spray binder liquid during the granulation process to form granules.

Fluid Bed Dryer

Spray guns are also used in Fluid Bed Dryer for spraying pharma liquid to form large size particles, called granules, during the drying process

What are the factors that affect the performance of pharma spray gun?

For efficient spraying, quality process, and product, the spray gun must be optimized for some factors before the spraying process. Let’s discuss some of these factors and see how these impact the performance of a spraying process.

  • Spray gun angle
  • Atomization
  • Pressure
  • Viscosity
  • Nozzle physical condition

Spray Gun Angle

The pharma spray gun angle is the total coverage area of the gun and depends on the distance of the gun from the product bed. The spray angle is also affected by the liquid’s viscosity – the higher the viscosity, the lower the angle is, and vice versa. Additional factors include nozzle capacity and spraying pressure.

Pharma spray gun angle is the total coverage are of a spray gun
The pharma spray gun angle is the total coverage area of a spray gun

 

Choose the spray angle that best matches the liquid’s viscosity and pressure for an effective spaying process. The spray angle should cover the entire product bed without accumulating at a specific point and crossing the product bed onto the side walls.

Atomization

Atomization is the process of generating individual drops in the spray stream. For tablet coating and drying, it affects the physical characteristics of the tablet. Very big or small drop sizes result in incomplete drying and coating.

Pharma spray gun atomization
Atomization is the formation of individual drops from the pharma spray gun

 

Also, improper drop size could result in liquid accumulation on the nozzle head, causing the hole to block. It results in machine breakdown and increases the frequency of maintenance and associated costs.

Some factors that control the Atomization are gun type, pressure, and spray pattern. Atomization rate is selected when ordering the spray gun, i.e., some spray guns are designed for smaller drops, while others are designed for larger drops. The liquid pressure for a given spray gun also affects the Atomization, which can be changed by altering the compressed air supply to the gun.

Pressure

Pressure is the force by which the liquid forms a spray stream. Spray guns are designed for a specific flow rate at a given pressure.

During spraying, enough pressure must be provided to the gun to spray a liquid with the desired pattern over the tablet bed. Spray gun manufacturer specifies these pressure values in their data, sheer or manual.

The pressure of the spray gun can be varied through Atomization air, typically supplied by compressed air. Increasing the atomization of air increases the pressure of the spray gun and vice versa.

Viscosity

Viscosity is the resistance to the liquid flow and is critical in defining the spray parameters. It affects the drop formation and distance an individual drop travels when sprayed.

When viscous liquids are sprayed, the pattern can be improved by altering the spray pressure. Increased pressure improves the spray characteristics, liquid impact, and drop formation for an effective and quality product.

The physical condition of the pharma spray gun

The physical condition of the spray gun also affects the spray patterns. A common problem in spray guns is the defect in the hole of the gun that changes the drop formation for a given atomization pressure and liquid.

The accumulation of liquid on the gun head also affects the spray pattern. Some other problems related to spray guns include the following.

  • Corrosion,  due to chemical reaction between liquid and gun material. It results in degradation in material with time and cracks the gun.
  • Contamination of the spray gun nozzle with dirt or other foreign bodies, blocking the spray gun
  • The build-up of coating material on the inside and outside edges of the orifice is a common phenomenon called bearding of the spray gun.
  • High-temperature liquid deteriorates the gun’s material with time.
  • Human errors, such as incorrect gun installation

 

These errors can be avoided by proper gun maintenance and include the following

  • Preventive maintenance with a proper schedule
  • Proper cleaning after the completion of each batch
  • Daily inspection
  • Look for an anti-bearding feature when purchasing a new spray gun or equipment.
  • Replacing the gun, if necessary

 

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