Particle monitoring goes wireless

Wireless technology has brought many innovative changes, enabling us to communicate in new ways. This article will explain how wireless technology can improve the way that particles are monitored within pharmaceutical cleanrooms, while meeting validation and calibration requirements.

Traditional particle monitoring systems (Facility Monitoring Systems) are comprised of the following components:

• Particle sensors
• Environmental sensors (temperature, humidity, and differential pressure sensors)
• Vacuum pumps
• Computer
• Data collection software
• Communication cabinet with network switches, plc type of device for collection of 4-20 mA signals from environmental sensors and triggering of alarm lamps, power supply to particle and environmental sensors, etc.

Another problem with the existing "wired" method is when a communication failure between the particle sensors and the data collecting software occurs; the common particle sensors do not have a built-in memory to save collected data. This can result in expensive production batches being forfeited.

There is also a high demand for vacuum pumps to deliver correct and continuous airflow through the sensors for the collection of particle data. This normally requires an installation of up to three pumps with a control panel programmed to switch between pumps at pre-set intervals.

Lately, the pharmaceutical industry has looked to new technologies to simplify installation while also improving the quality of the particle monitoring system.

In Scandinavia, a pharmaceutical company recently installed a wireless particle monitoring system. The core of the wireless system is built up around a particle sensor with a built-in pump and electronics that monitor and adjust the airflow to the desired one cubic foot per minute. It also has a built-in memory that saves data in case communication is lost. The stored data is then automatically transferred to the data collection software when communication is restored. This provides a very robust system.

Validation

When considering a wireless system, concerns about validating the data arise and the following should be taken into account:

1. How do I verify that the facility is suitable for wireless communication?

2. What security do I need to set up within the wireless network?

3. How do I verify that the collected data set is the correct one?

Before choosing to go wireless, a simulation of the system should be performed to verify that it is possible to get a good signal in the facility. This can be achieved by taking the particle sensor and putting it on a cart in the production cleanroom. Set up a laptop with the software that will be used to collect the particle data. Configure the sensor in the software so that you can receive real-time data. Move the cart to the areas that will be monitored. At the other end of the room, a laptop can test that the data is being properly received and that no communication failures are detected.

Although it is easier to test in non-production areas, it is essential to do the testing in a true-to-life setting. A production environment should be simulated as much as possible to verify whether the signal is experiencing interference from other production equipment or personal.

Within most wireless networks the signal strength can also be verified; a recommended level is 85-100%. If the signal is too weak, a second access point can be installed or high power antennas with extension cords mounted to pinpoint the sensors with a weaker signal.

Data security

As always with wireless data communication, the security of the network is imperative. If a system is installed without adequate security, signals can be transferred through the walls to unsecured recipients.

There is a vast selection of security systems to choose from. The most basic method requires a user ID and password to prevent any free surfers from using the wireless network. A more secure system involves setting the wireless network to only allow registered computers or sensors to communicate with the network; this is called "MAC address filter". Each of the particle sensors has its own unique address that can be entered into the access point security authorization list.

Verifying the data

Any system is only as valuable as the data it provides, and so it is important to ensure that the correct data is being sent through the system. The best method to test this is to take a portable particle counter with a built-in printer and connect it to the wireless network via the built-in Ethernet communication connection. Data can be printed from the particle counter and compared with the data from the wireless collection method.

The most critical item to verify is what occurs if there is a communication failure between the sensor and the software. Since the sensor has a built-in memory it will store all data if communication is lost and then transfer it when communication is restored.

A communications failure can be simulated by disconnecting the Ethernet cable between the access point and the data collection software. The communication failure will register as a change in the colour on the display and no data will be logged.

By writing down the time for the last registered sample for each sensor, on reconnecting the cable, it can be verified that all sensors received the historical data that was missing. This historical tabular data can then be printed and attached as test result raw data.

The signal can also be tested by blocking off the inlet of the sensor, forcing it to send a flow error signal to the software.

Conclusion

Wireless technology has two main advantages. It ensures that critical data is not lost, and it is simpler to install. New security provisions ensure that the data is secure and can be validated.