How to select vessel for your pharma applications

What are vessels, and what are they used for 

Vessels are round metallic structures containing liquid without affecting their state, properties, and chemical composition. The liquid inside a vessel can be included for storage or processing using specified tools and accessories.

Depending upon the application and process requirements, they can be installed with additional components such as a mixer and heating system.   

In the pharmaceutical industry, vessels are used for various applications, such as 

• Holding liquid products during intermediate manufacturing stages

• Transferring liquid to a filling machine, such as an ampoule filling machine

• Mixing and blending liquid during the liquid dosage manufacturing process

• Filtration of the liquid product or raw material (during or before the manufacturing process

Vessels for pharma applications require specialized metal characteristics, because the pharma drug product comes in direct contact with the vessel, and these metal features are necessary for product safety.  It includes

• Stainless Steel 316L for product contact parts

• Dead points

• Welding requirements.

Additionally, some features are necessary for the successful execution of the manufacturing process, such as 

• Temperature sensors to monitor inside temperature for some applications. Because some products require heat to execute manufacturing successfully

• Pressure sensors monitor the vessel's pressure; some applications require elevated pressure inside the tank.

• A mixer or agitator is used to mix solvent with raw material during the manufacturing process. The material of construction of mixer or agitator must also be compatible with pharma drug requirements, as mentioned above

• Load cells are used to monitor the weighting data of the materials inside. It can be also programmed or modified to monitor the level inside a vessel by using its input through a central controller.

• Level sensors monitor the vessel's level and prevent overflow and accuracy in the attached process. 

Types of Vessels 

The vessel type is defined by the application for which it is being used and developed, including the following. 

Manufacturing vessels 

These vessels are specifically used to manufacture a liquid pharma product. It contains additional accessories, such as 

• Mixer to mix different raw materials and solvents.

• Heating element to achieve high temperatures required by different materials and chemicals

Storage Vessels

These vessels are only used to store liquid between intermediate stages, such as 

• Before filling process

• The results are processed by the quality department and awaiting approval

Pressure Vessels

Some applications require liquid inside the vessel to be stored at high pressure. For these applications, vessels are manufactured to sustain high pressure by re-enforce material strength. Additional accessories are also required to facilitate pressure-related applications, such as 

• Pressure indicator to monitor the pressure inside and to ensure it does not deviate form its working pressure

• Pressure safety device to prevent damage in case pressure abnormally increases without control

• Safety valve to release gas if the pressure increases above the maximum permissible limit 

What can go wrong if not selected appropriately?

The wrong vessel selection disturbs the attached process, which can include the following:

Vessel damage

 Vessels are constructed to perform a specific function, and if processes other than the design are used, it can damage the vessel's entire structure.

The main reason is that the vessel is a large mechanical structure whose strength and tolerance are added according to the product and process. If other than the approved methods & processes are used, they will exceed the tolerance level of the vessel, subsequently damaging the internal structure.

For example, if supply pressure is not applied w.r.to the design pressure, it will damage the vessel. 

Product Damage

An inappropriate vessel selection will affect the relevant pharma process, affecting the product inside. The vessel will lose the ability to perform the specified task related to this process, depriving the product of its required attributes and quality. 

For example, in pressure-related applications, if high pressure-specific vessel is selected for a low pressure product, the high pressure will tear off all the chemical composition of the product inside, depriving the product of its therapeutic effects.

Low productivity

If wrongly selected, it will decrease the vessel's total capacity of the production in a given time, thereby decreasing the total productivity. For this reason, a single batch will consume more time in the vessel. Additionally, in case of problems, the vessel will spend more time in the workshop for maintenance than on the production floor. 

Low productivity also affects the pharmaceutical manufacturer's market, causing the manufacturer financial loss.

Some guidance related to vessel selection

Some factors for selecting a vessel for pharmaceutical applications can include the following.

Vessel Capacity

The vessel's capacity is the accrual volume of a liter that can be contained or held in it, and it is the function of physical dimensions, i.e., Length, Width, and height.  Generally, it is expressed in liters, for example, 500 and 1000 liters. Pharmaceutical manufacturers look for vessels that suit their batch sizes. If a lower volume vessel has been selected, it will ruin the pharma product manufacturer's efforts to keep pace with the market demands. Similarly, if oversized vessel is selected, it will increase the pharma manufacturers' cost during the production process, maintenance and energy utilization

When planning to procure a vessel for your application, it is necessary to determine the operational capacity of your production needs, which must be communicated to the manufacturer.

Surface Finish 

The surface finish requirement for every pharma equipment must be within acceptable limits, and the same goes for the vessels in the pharmaceutical industry. So, it is necessary to verify the relevant surface finish requirements, which include the following:

• Product Contact parts or vessels inside the structure should be constructed of SS316 to prevent corrosion and product contamination.

• Non-contract parts, such as the vessel's outside body, must comprise SS304. It also includes the vessel frame, if required.

• There should be no dead points that accumulate liquid or chemicals, making cleaning difficult.

• Surface roughness must be less than 0.8

Vessel Types

As mentioned earlier, depending on the application, different types of vessels are used in the pharma industry. A vessel designed for a particular application cannot be used for other applications, including Storage, Manufacturing, and Pressure vessels.

When purchasing a vessel, 

• If you plan to use the vessel in manufacturing, the vessel contains features such as heating, a mixer, and relevant pneumatic components.

• If you plan to purchase a vessel for storing fluids, it would not require dedicated features, such as a mixer, instrumentation, and heating.

• If you plan to purchase a vessel for pressure applications, it should contain features such as pressure monitoring, safety devices, and pneumatic ports for applying pressure inside.

• A glass-lined vessel is specialized in which glass lining is applied inside the vessel's wall. These vessels are used to manufacture sensitive products such as parenteral.

Top Ports 

Ports are connection points for different piping and fittings to the vessels. The port selection depends on the physical variable required during the process.

Some factors to consider when selecting a port include the following: 

• Connection type - quick connect, NT type, vent ot tri-clamp

• Connection size - connection size in diameter

• Number of ports

• Application of ports, such as pneumatic

Bottom

It is the specification of the bottom of the vessel and typically includes a valve to discharge the liquid from the vessel. and can be 

• Butterfly

• Ball valve

• Any other as per the product requirement

Physical Variables

As mentioned earlier, some vessels require physical variables such as temperature and pressure for their process execution. For this, it is necessary to design the vessel for a specific variable range. Failure to comply with physical variables,

Temperature 

Some products require heat for process execution, commonly supplied by steam. For a vessel, its internal material must bear high temperatures. Otherwise, the material can degrade and damage the vessel's main structure. The outer surface of the vessel must be jacketed to nullify the effects of high temperature inside the vessel

Pressure

Pressure is applied as a part of different process requirements. The pressure-related vessels are specially designed and manufactured to sustain internal pressure and are made of leak-proof material to prevent leakage.

The process's operating pressure must match the vessel's design requirement, and if a vessel is not designed for high-pressure activities, it must not be used for high-pressure activities. the vessel must also contain safety devices to prevent damage related to abnormal pressure

When purchasing a vessel, carefully review your requirements; if your application requires pressure or temperatures, it must be specified at the time of purchasing to avoid confusion later.

Instrumentation

Instrumentation monitors different physical values inside the vessel, which mainly consist of the following:

Temperature

The temperature sensor is used to monitor the temperature inside the vessel. They are used if the vessel is designed to operate at high temperatures.

Pressure

The pressure indicator indicates the pressure inside the vessel and is used in vessel designed to operate at higher pressures.

Level

The level sensor measures the level inside a vessel for monitoring and preventing tank overfill. Commonly, there are two techniques for measuring level -proximity sensor and load cell.

When selecting a vessel for your application, it is necessary to assess which process variable requires monitoring, and is selected based on the variable involved in the process.

About the Author:

Muhammad Asim Niazi

Muhammad Asim Niazi has a vast experience of about 11 years in a Pharmaceutical company. During his tenure he worked in their different departments and had been part of many initiatives within the company. He now uses his experience and skill to write interested content for audiences at PharmaSources.com.