How to Select a Depyrogenation Tunnel for Your Applications

What is a depyrogenation tunnel?

A depyrogenation tunnel is sterilizing equipment in the pharma industry. They used to remove pyrogens from glassware and containers for injectable manufacturing. It is largely used as a replacement for the sterilization system, where each item is sterilized in a Dry Heat sterilizer, requiring some time or a day to cool before being filled with containers.

Depyrogenation tunnels are largely used for the sterilization of glass containers that can be directly filled with product, without storing or holding. It is the part of the injectable line that consists of washing, depyrogenation tunnel and filling machine.

The depyrogenation tunnel sterilizes items at high temperatures like the Dry Heat Sterilizer - DHS. The difference is the technique for accomplishing the task. In the tunnel, items are placed on a belt through the feeding station, at a fixed rate. The speed of belt determines the sterilization time and is immediately set to match the sterilization time for a particular container

The feeding station is commonly connected to the washing machine that provides the continuous supply of washed containers to the tunnel

The inside of the tunnel is divided into different temperature zones, known as preheating, heating, and cooling.

● In the preheating zone, the temperature remains below the sterilization temperature to warm up the container. Warming - up the containers helps to protect containers against sudden temperature rise in the heating zone

● In the heating zone, the actual sterilization temperature is maintained.

● In the cooling zone, the temperature is lowered.  

After the cooling zone, items are discharged from the tunnel through the outfeed station or side.

The outfeed of the depyrogenation tunnel is commonly connected to the filling machine to fill the product and further processing.

Some common parts of the depyrogenation tunnel include, but are not limited to, the following.

● HEPA filter

● Air Blower, to blow hot air to maintain high temperature

● Heaters - to heat the air inside the tunnel

● Conveyor belts - to move the items forward through different temperature zones

● Electronic components - different electronic components, such as PLC, HMI, sensors, VFDs, and airflow meters to control the operation of the depyrogenation tunnel

● Validation port- to perform the validation

Air blower generates a steady stream of airflow, which is heated by heaters to heat. A controller or a PLC is used to automate the entire process

HEPA filters are installed inside tunnels to filter out impurities from air. Because, the air comes in direct contact with the containers, and it is necessary to maintain the purity of the airflow.  

Since the depyrogenation tunnel is often used with the washing machine at the infeed and the filling machine at the outfeed, there is a mechanism to synchronize these two machines with the operation of the depyrogenation tunnel.

● A sensor installed at in-feed synchronizes the washing machine's operation. It commands the main controller of the tunnel to start/stop if the washing machine starts/stops. Similarly, this sensor is also used to signal the washing machine to synchronize its operation.  

● A sensor installed at the outfeed of the depyrogenation tunnel synchronizes the tunnel operations with the filling machine. Similarly, the filling machine synchronizes its operation with the tunnel through this sensor.

What can go wrong if an appropriate Depyrogenation tunnel is not selected?

Some problems that a machine buyer can face if they do not select an appropriate tunnel

● The process will not yield the required sterilization level

● The machine buyer will face capacity-related issues

● Frequent problems with the machine, keeping the machine in breakdown state

● Problems in tunnel operation

● Erratic behavior of sensors & instrumentation, making the process unreliable and dangerous

● Non-compliance with the regulatory regulations.  

Some factors to consider when selecting a depyrogenation tunnel

Let's discuss some factors when considering depyrogenation tunnels for your applications.

Capacity

The capacity of the depyrogenation tunnel is its ability to produce total output in a given time.  

Since pharma product manufacturers often procure new equipment to increase their productivity in response to market requirements or upgrades in existing production, the capacity must be strictly considered during the procurement. As with other required parameters, it must be conveyed to the machine supplier earlier.

What items will be sterilized?

Depyrogenation tunnels in the pharma industry are commonly used to sterilize glass items, such as vials and ampoules. However, there are also varying specifications within these glass items.

For example, in cases of vials & ampoules, fill volumes impact their physical dimension. To fit containers, the inside of tunnel is adjusted through mechanical means for effective sterilization.

When selecting a depyrogenation tunnel for your applications, determine the container's characteristics, such as physical dimensions and any other specialized requirements.

Area availability

Like other pharma equipment, area availability is the basic requirement for the tunnels.

Depyrogenation tunnels are bulkier in their load and require more area for its installation and operation. Because, it requires a specified amount of time for the containers to remain into the tunnel, which is made possible through increased length. This increases the overall area of the tunnel.

Additionally, utility piping is extensive for the tunnel and also adds to the machine's area. Furthermore, instrumentation installed at various locations must also be considered.

When purchasing tunnels for your pharma applications, determine the available area in your facility. Is the available area sufficient for the machine's main structure, piping, instrumentation, and other necessities? Or, are you planning to increase the area to make it suitable for the machine?

Working type

As discussed earlier in this article, the tunnel can be synchronized with the washing and filling machine, where it takes feedback from these machines and adjusts its operation for smooth flow and preventing jamming at any of these machines. This system requires interlocking sensors, relevant mechanical components (if needed), and programming in the main controller or PLC.

However, some pharma manufacturers use it without integrating it with the washing machine and/or filling machine. In this scenario, synchronization is not required.

When selecting a tunnel for your applications, determine whether you require a synchronization technique or not. If not, the tunnel can be used as standalone machine

HEPA Filters

The temperature inside a tunnel is maintained by blowing hot air, which comes in direct contact with the sterilized items. If the air becomes contaminated or contains foreign particles, it will ruin the sterilization process.

HEPA filters are installed over the conveyor belt to filter the air flowing into the tunnel. It prevents contamination and filters out foreign bodies from entering the air.

Always ensure that

●  the manufacturer provides HEPA filters when considering tunnels for your application.

● These HEPA filters must be high temperature and made up of specialized material that can withstand high temperatures.

● HEPA filters must not shed particles, due to the material degradation at high temperature.

Record keeping.

While Instrumentation collects process-related data, the tunnel must also include a system to record the entire process for documentation and regulatory requirements. The record system,

● Record each process value, such as temperature at each zone, time and airflow

● The tunnel system must have enough memory to retain it for days.

● Record can be maintained through main controller or PLC

● Data logger can also be used to record all process variables.

● It must follow 21 CFR part 11 FDA regulations.

● The record must be maintained for all zones, such as preheating, heating, and cooling.

When selecting a depyrogenation tunnel, ensure the recording system for all parameters & data points is satisfactorily developed and working. It must also follow FDA 21 CFR part 11 requirements.

If there is any discrepancy or some modification required, it must be communicated to the manufacturer promptly before the final procurement decision.

Instrumentation

Instrumentation is used to monitor the sterilization process & its different parameters. It enables you to adjust the process in case of deviation. Instrumentation involves monitoring of several physical variables at different locations.

Some common instrumentation in tunnel includes the following

● Temperature sensor to monitor temperature values at each zone

● Airflow sensor to monitor airflow inside the tunnel

● Pressure sensors to monitor pressure profiles at different locations

● Cooling water flow sensor to monitor for cooling purposes

● Process parameters recording for regulatory compliance requirements

● Belt speed indicator to monitor the sterilization time

It is necessary to look out for the required instrumentation in your tunnel. Some machine manufacturers include all instrumentation in their basic machine model, while others may require extra fees to include instrumentation.  

Utility requirements

Utilities for tunnels are required to perform basic and critical functions, such as lowering the temperature of the cooling zone and controlling different actuators & valves. Each utility is utilized to perform specified functions and must be provided according to its specification.

When considering tunnel for your pharma application, it is necessary to determine whether your facility can provide all of the specified utilities with their required specifications. If it is not possible to make arrangements, talk to the machine manufacturer and discuss what alternative can be used.