In industrial cleanrooms across many industries, staff and management are realizing the advantages of automated continual monitoring and data collection. Many manufacturers and researchers have automated their environmental monitoring to pass inspections and document the process to show full regulatory compliance regardless of size or application. Temperature monitoring is ideal for reducing bacteria and mold which otherwise may thrive and contaminate products and processes. Whether your cleanroom is designed around an assembly line, product compounding area, sensitive machinery, or another application, there are a few factors to consider before automating your setup including your regulatory needs, temperature range, sensor type, and sample rate. We’ll show an example of how automating your data collection can improve safety measures, help ensure full regulatory compliance, and save time.
In addition to factors such as differential pressure (monitored just inside and outside the room), a temperature monitoring system easily complements other measures. In these setups, an automated system records the room’s ambient temperature; while pressure transducers monitor the differential pressure inside and outside the cleanroom, humidity sensors watch for rising humidity levels to reduce mold and other microbes.
To meet their regulatory needs and ensure product/process quality, facilities managers have to identify what their actual monitoring range needs to be. You should place temperature sensors according to your particular room layout.
Data loggers and sensors
In addition to using HEPA filters to improve air quality and control particulate levels, effective environmental monitoring often requires users to closely monitor air temperature to prevent growth of mold, bacterial agents, and other contaminants. Additionally, many applications require continual monitoring for temperature-sensitive products and equipment. As an example, say you know that your cleanroom’s process needs to be maintained at 70°F with a variance of +/- 2°F (and a relative humidity hovering close to 50%). Given that limit, how should you automate your data collection? Which sensor types should you use, and where are the optimal places for them?
Data loggers—or data recorders as they are sometimes called—record and store temperature and other values, encompassing a range of products including software and hardware. Data loggers track information electronically from internal or external sensors or other equipment that provides digital or serial outputs. Examples of temperature data loggers which can read the signals from temperature sensors include portable, power over Ethernet, and wireless models. Whether you need a simple single-channel unit to log temperature or a multi-channel system to log several temperature inputs and other parameters at the same time, you can find a data logger to meet your exact needs.
There are several common types of temperature sensors that are used with data loggers. You should go with the sensor type that’s best suited to your specific application. Thermocouples are the most common type of temperature sensor and are widely used where cost, simplicity, and wide operating range are paramount and extremely high accuracy is not required. Thermocouples are low-cost devices that are easy to use. Semiconductor devices are similarly low-cost and provide an output voltage or current proportional to temperature, with a limited operating range and accuracy comparable to thermocouples. RTDs and thermistors provide a change in resistance that is related to temperature, and while they offer higher accuracy than thermocouples, RTDs have a more limited operating range.
Meeting regulatory standards
U.S. cleanroom standards and regulations include the FDA’s CFR PART 210 and CFR PART 211 outlining cGMP relating to drugs and finished pharmaceuticals. ISO standard 14644-1 covers air cleanliness—effective temperature monitoring overlaps with this regulation as far as mold reduction etc.
Accsense Inc. Product Manager Dana Kennedy comments, “When it comes to ensuring your full compliance, we need to understand what your cleanliness standards are for our probes and the housings in which we mount them. For example, we have a stainless steel RTD probe with 10 feet of jacketed cable. Now the traditional way to record ambient temperature in a cleanroom is to place sensors in a closed vented box with adequate air flow, but that setup means you have to have a program to clean it out regularly, and many managers don’t want that in their room. With that in mind, we have ambient probes covered with plastic shrink tubing that sticks out of the data logger’s housing a bit and won’t collect a lot of debris. These details are important to consider in the initial phase of deciding on your automated setup.”
System installation: wired or wireless?
Whether you want to go with an Ethernet or wireless setup is often already decided by your facility layout. However, you can make this decision depending on how you want to automatically transmit the temperature data. Ethernet-capable devices are often more affordable than wireless systems and can be mounted wherever you need to measure the temperature. The pod has connections for both external RTD and thermocouple sensors and can be plugged into an Ethernet port to automatically send your data to a secure server.
In some instances, you may just find it’s too costly in time or budget to run wires. Wireless systems usually have a wireless gateway enabling connection between the room’s sensor data and the Internet. Once connected to the gateway, the pods continually monitor and sample the temperature data, giving you the ability to view and remotely access your data in real-time. Many wireless systems also offer cloud-based services such as data storage and reporting, and these devices can allow administrators to modify the system configuration from anywhere an internet connection is available.
Where and how often should you sample?
Even the most accurate system will only gather data where and when you tell it to. Again, your room layout will dictate some of these decisions depending on filter location, air flow, etc. Optimal placement areas include near HEPA filters, areas where personnel most commonly travel, and adjacent to any temperature-sensitive equipment or products.
While some users know beforehand that their particular application or policies require them to log temperature at a certain interval (commonly once an hour or once a day), others may consider it sufficient to take a recording just once a day or week for auditing purposes. However, it’s good practice to log more frequently if your system allows you to configure sampling rates, and in fact many data logger models allow users to select how often the device takes a sensor reading. Always configure a sample rate appropriate for your particular product or environment under monitoring. For example, your facility might have a recurring problem with mold, so setting a 30-minute sample rate would be an effective way to take early measures against the problem.
Automating alarms and staying secure
First and foremost, an effective environmental monitoring system enables managers to ensure cleanroom integrity by addressing out-of-specification temperature conditions as they happen. Many data loggers allow you to set the frequency of alarm checks by setting an alarm sample rate which can be different from the normal rate at which the logger takes a sensor reading. Following setup and configuration, a data logger automatically takes readings from connected temperature sensors so that users are also immediately alerted when temperature suddenly goes out of specification, further helping to eliminate delays in staff response. Some models can also continue to log during power or Internet outages. Systems with more advanced functionality can even give managers 24/7 access to a cloud-based service via smartphone to periodically check for alarms and irregularities for extra peace of mind. If you’re concerned about the possibility of users inadvertently modifying or deleting archived data, many kinds of system software can prevent this by giving you the ability to assign different access levels.
Putting it all together
A major university’s fabrication facility is currently using their wireless setup to ensure that temperature is held to specification in its 12,750 sq. ft. cleanroom. Strict environmental monitoring and control is necessary to their research work which includes semiconductor-based device fabrication and thin-film processing. Staff enter and exit through an airlocked antechamber. This particulate-free environment is kept at a positive pressure by blower systems and HEPA filters allowing air into the room. In the case of a leak, air is forced out of the chamber, preventing process contamination from incoming, unfiltrated air.
Their automated temperature monitoring system consists of 16 wireless Accsense data loggers; a Wireless Gateway for connecting the sensor network to the Internet; and an online account for real-time viewing, automated alarming, and data storage. In addition to monitoring the lab’s environment, the system also monitors the cleanroom’s other operation-critical systems which include PLCs, chilled water, and air pressure, and sends that data on the Web in real time. If any of these systems suddenly fail, the university’s on-call technicians receive a phone call.
Realizing the benefits
Using data loggers for continual temperature monitoring and alarming enables cleanroom staff to stay in compliance by responding at a moment’s notice to out-of-specification conditions. Sophisticated alarms monitor the incoming data and can even send email, pager, or phone warnings to multiple recipients whenever an alarm is triggered. With automated alarming, you’re able to instantly contact staff so that equipment can be serviced or replaced without delay.
Dana Kennedy sums up the benefits of automated monitoring: “Wired and wireless dataloggers are ideal temperature monitoring solutions for cleanroom environments. Many of today’s managers are now setup with turnkey systems that handle all their data collection, alarming and documentation needs. For pharmaceuticals, research, manufacturing, just about any setup you’re working in, this technology really showcases how automation is increasingly connecting managers to their critical process and product data.”
Stew Thompson is a Technical Writer with CAS DataLoggers Inc. www.dataloggerinc.com
This article appeared in the May 2014 issue of Controlled Environments.
