Vessels in pharma applications

Vessels in the pharma industry, are mainly used as a storage medium for liquid materials such as treated water and liquid chemicals. The vessels are used in almost all dosage formats because water, the primary raw material, is used in all departments of the pharma industry. Additionally, nearly all dosage forms have some liquid chemical composition in their formulation. 

There are different capacities of vessels in the pharma industry, which depend on the product type and processes involved.  

What are Vessels?

Vessels are large containers for storing liquid in the pharma industry, used during various manufacturing processes. During storage, they provide specialized features necessary for a specific liquid type. 

Commonly, vessels are made up of metals that are safe for the product being used and prevent contamination or product degradation. Commonly, product contact parts are made up of SS316L, and non-product contact parts are made up of SS304.

They are equipped with various accessories to monitor the liquid inside them. These accessories help monitor critical liquid parameters, which are necessary during routine operation. If these accessories are not provided, it will become difficult to monitor the current state of a liquid, prevent damage to the product, or become hazardous for humans, the area, the environment, or other instruments or machines. These accessories also help safety in processes, in cases the liquid is explosive and subsequently saving it.

Types of vessels

There are different types of vessels used in the pharma industry, the selection of which depends on the manufacturing process and product types. An important point is to know your requirements and select the required one.

Some vessel types used in the pharma industry include the following.

Storage Vessels

Storage vessels are used for storing liquid in them. Commonly, they are used at 

· Initial phase of manufacturing to store liquid raw material or treated water for manufacturing a product

· Intermediate stage, where a manufactured product ready for filling is stored until filing starts or completes

Since they store pharma-grade liquid or finished products, their material must meet ASME–BPE standards. If this standard is not implemented, the metallic body of a vessel will contaminate the product due to corrosion and material degradation. Also, chances are that non-standard metals will react with the product, changing its properties and making it dangerous for human consumption. 

They are designed to be used at normal atmospheric pressure and must not be used for high-pressure applications. Otherwise, the vessel will leak, wasting the product and can become hazardous for the surroundings.

Pressure Vessels

Pressure vessels are also ordinary storage vessels, but their design makes them ideal for high-pressure applications. In it, the wall of the vessel is strong enough to bear high pressure and is enforced by solid materials so that it does not explode or rupture during operations. 

Every pressure vessel has a design limit for specific rated pressure. The actual process pressure must not exceed the rated pressure. Otherwise, it will explode and become hazardous for the area, personnel, environment, and other instruments & machines.

Among other accessories, pressure vessels are supplied with safety valves. Its primary function is to release fluid if its pressure exceeds the set value on the safety valve, which is adjusted according to the maximum limit of the vessel. It prevents damage to the ship if pressure accidentally becomes more significant than the rated value of the pressure vessel.

Manufacturing Vessels

Manufacturing vessels are the types used in manufacturing a pharma product. They contain all the necessary accessories required during the manufacturing process. Some of them include the following.

Mixers: Mixers are mechanical parts that mix different chemicals with any liquid or water. It rotates in a speed set during the manufacturing process. The specific rate depends on the product type and manufacturing operation.

Motor: The motor is the driver of the mixer and rotates it at a fixed speed, which is set through the control panel

Temperature Control: This feature is used to control the temperature of the liquid inside the vessel because some materials require high temperatures to mix or react. It also consists of a temperature indicator that displays the actual temperature inside the vessel.

Jacket: It is an additional layer or covering of the external body to protect the losing temperature of the vessel so that the effect of temperature is not felt on the outer wall of the vessel. It consists of insulated material that cannot transfer the heat.

Pneumatic Fittings: These fittings supply air or other gas (such as Nitrogen) for various purposes. 

Requirements of vessels for pharma processes

As mentioned above, pharma vessels store the liquid in them, and liquid, being a critical constituent, can be affected if requirements are not adjusted, mainly the material of the vessel. 

For a vessel to be qualified for pharma applications, the body of the vessel must not contaminate or degrade the liquid inside it, which can be achieved by having the following characteristics.

Product Contact Parts

The Product contact parts, i.e., inside of the vessel, must be made up of Stainless Steel 316L, a low-carbon variant of stainless Steel. It is a special alloy of SS consisting of Iron, Chromium, and Molybdenum. Due to the addition of Molybdenum in SS316L, It resists corrosion, reacting with acidic elements and degradation due to high temperatures.

Outer Body Materials

The material of the outer body part, i.e., non-product contact parts, must be made up of Stainless Steel – SS304. It is also an alloy consisting of 18%chromium and 8% Nickel. It also contains low carbon and manganese, which helps prevent the oxidizing of the metallic body.

The benefit of using SS304 is that it makes the outer body easy to clean without using any specialized cleaning agent. It is less corrosion-resistant than SS316L, but with proper care, the material can be saved, and its life can be extended.

Welding

Like other pharma equipment, welding is used to join various components with a vessel's body, primarily for joining tubing and fittings with the vessel. 

In pharma vessels, the welding must be orbital, a specialized type in which welding is done from inside and outside. It makes welds smooth without any dead points. 

Surface Finish

The surface finish of a pharma vessel must be smooth enough to allow easy cleaning and prevent any reaction with the pharma product.

Surface finish is a characteristic of the following parameters.

Scratches: There must be no or minimum scratches for a smooth surface. A scratch is a damage to the upper surface without going deep into the surface. It decreases the material's resistance to chemically react and makes cleaning difficult. 

Pits: These are the small holes that go deep into the surface. It makes cleaning difficult and increases the probability of liquid trapping in it.

Surface Roughness: Surface roughness represents irregularities in the surface. Its typical value must be lower, than 0.8, as higher values make the cleaning difficult.

Dead points: Dead pints are isolated parts in a vessel that trap the liquid in it despite rigorous cleaning. The trapped liquid can cause contamination to the pharma product and even cause microorganisms to grow in it. 

Instrumentation and accessories for pharma vessels

Vessels in the pharmaceutical industry are supplied with different instrumentation and accessories to monitor the liquid inside them because the design and construction of vessels make it difficult to inspect the liquid properties visually.

Some common instruments and accessories are described below.

Level sensor

The level sensor monitors the level of a liquid inside the vessel constantly. It is helpful in cases such as

· to check and verify the level of a liquid when it is left filled at the end of the day

· Check and verify the level of liquid during the filling operation

The level sensor output is sensed by a main controller or Programmable Logic Controller – PLC to control the level during filing operation in the container filling machine.

In some designs, the level is displayed locally on the vessel for operator reference.

Sight glass

Sight Glass is a specialized glass to see inside the vessel. It is fixed at one side in a way that the operator can conveniently approach it. Also called viewports, they are sealed from the inside and outside to provide better sealing characteristics.

The sight glass can beat high pressure, corrosion, and high temperature. They are mainly used during manufacturing, cleaning, and maintenance.

Temperature sensor

The temperature sensor measures the temperature of the liquid inside the vessel. Commonly, there are two types of sensors used – thermocouples and RTD.

Like the level sensor, the temperature sensor output is used by a main controller or Programmable Logic Controller – PLC to control the temperature of the liquid inside it.

The temperature sensor is installed at a specific point on a vessel called a temperature port, specially designed for this purpose. The sensor comprises SS316L since it comes in direct contact with the product.

Motor with mixer

Mixers are mechanical structures that mix constituents of the vessel, mainly during the manufacturing stage. Mixers are driven by motors, the speed of which can be adjusted according to the process requirement. The operator controls the speed of the motor through the main control panel.

About the Author

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.