The biopharmaceutical industry relies more and more on portable systems to perform a range of manufacturing processes. For example, liquid chromatography systems used for purification are often mounted onto portable skids with rollers allowing it to be moved around the production site. Likewise, single-use bioreactors and portable mixing systems may be similarly configured. Portability saves manufacturers tens of thousands of dollars in permitting, construction and piping costs. At the same time, portability presents its own set of special challenges including power sources, wiring, connectivity to the transmitters and communication with the distributed control systems. Another interesting challenge is proper electrical grounding for the transmitters. The pH transmitters must be electrically grounded correctly or erroneous readings will occur (also known as ground loops). Many of these problems, however, can be overcome with the simple addition of new technology – wireless.



Although not all measurement devices utilized on portable skids are available via wireless today, some are – notably the liquid measurements such as those for pH, conductivity and temperature. What users are finding is that installing even a few wireless devices on a portable skid can significantly reduce wiring costs and the need for power sources, as well as improve reliability and performance.


Today’s Wireless


Before making a “wireless” decision, a manufacturer will responsibly ask if the technology has progressed to the point that it is reliable in critical applications such as biopharmaceutical manufacturing. The answer is an emphatic yes. Over the last couple years, the industry’s first wireless transmitters for pH and conductivity measurement have entered the market. These transmitters utilize the WirelessHART 7 communication protocol – an open platform that is rapidly becoming the defacto standard for wireless communications. The analyzers, therefore, seamlessly integrate into any network of WirelessHART devices. Perhaps most important, the WirelessHART protocol allows wireless transmitters to operate in a “self-organizing” network. In this configuration, every wireless device on the network acts as a router for nearby devices. This means that all devices work together to identify and use the most efficient communication path for each message, and in the event of a problem with any single device, other devices are equally capable of carrying the message. The network dynamically reconfigures itself without manual intervention and without disrupting the flow of data. This makes for very high data reliability and availability, characteristics essential in biopharmaceutical production.


Security is, of course, a huge concern and the new pH and conductivity analyzers take full advantage of multilayered security features available in the WirelessHART standard. These include encryption with automatic key rotation, device authentication, and data verification. External interference is mitigated by spread-spectrum broadcast and automatic channel selection that avoids the noisy spectrum. Consequently, wireless networks can now offer security and reliability comparable to hard-wiring.


An additional benefit of the WirelessHART protocol is availability of diagnostics through the wireless signal. These diagnostic signals are relayed along with process variables to the plant’s asset management system, providing operators with a quantitative means of evaluating the validity of the measurements. This data sophistication aids in scheduling of maintenance and creation of the required calibration audit trail.


The Measurements


Analytical measurements play a critical role in several steps of pharmaceutical manufacturing. Key among these is in chromatography and purification systems designed for separating and purifying proteins and bio-engineered products. Conductivity is one of the key determinants of when to start and end this collection process. Tighter conductivity controls increase purity yields and may improve secondary collection processing steps. pH also plays an important role in the purification procedure, providing feedback control of buffer and effluent feed through the column. Three analytical control points (two conductivity, one pH) are included in most chromatography systems.


Bioreactors depend upon pH measurements and temperature transmitters to control acid addition within the process. Often, reactions must occur within an optimal pH range in order to maximize yields and minimize unwanted byproducts that would have to be removed by downstream purification. Portable mixing and buffer preparation skids are used in a number of biopharmaceutical processes such as cultivation, fermentation, purification and chromatography. These systems rely on pH and conductivity to maintain optimal pH salt content and other parameters of biologics within a desired range.


Portable Wireless Systems – An Example


It’s easy to see that wireless technology and portable single-use systems are a match made in heaven. A study done by BioProcess International asked users for the deciding factors in their decision to implement single-use systems. Among the leading answers were cost savings and increased flexibility. The addition of wireless technology to the portable skids forwards both goals.


Wireless analytical systems utilize field-replaceable lithium thionyl chloride power modules, requiring no external power sources or additional wiring. The life expectancy for the power module is six years based on a once-per-minute update rate at 25ºC.  The most obvious result is a substantial reduction in costs, power requirements, and an increase in true portability. Wireless also makes possible the collection of process data that might be too expensive to collect in a wired system.


The less obvious result of wireless technology, however, is a boost in measurement accuracy due to the improvement in grounding. Portable skids are on rubber wheels which don’t make good contact with the ground and can result in what’s called a “floating ground.” Without a well-grounded instrument, the cabling on a wired system can pick up interference from the motors, causing noise or readings offsets, resulting in less accuracy and reliability. Wireless transmitters substitute RF signals for twisted pair wires and, therefore, are significantly less susceptible to noise interference. In addition, they have no external power sources to create more potential noise.


As a way to reduce the number of wired connections and thus save money, some pharmaceutical processing plants have tested wireless to wired pH and temperature analyzers in applications such as cell culture manufacturing in small scale bio-reactors. The only notable difference in the operation of the wired and wireless instruments has been the fact that while the wired transmitters provide updates once per second, the wireless transmitters can be configured to update the primary variable less frequently. However, if the primary variable exceeds the pre-determined set points – in this case pH – the primary variable is updated more frequently on an exception reporting basis. This method, known as “Trigger Burst Mode,” communicates the process variables only when a measurement value changes significantly since the last communication, or if a required reporting period has been reached. This approach, sanctioned by the WirelessHART standard, optimizes the power module’s life.


The purpose of these tests in each case was to determine if there was any difference in the wired versus wireless systems. The result showed no difference in performance. Rosemount customers have uncovered an interesting bonus in the wireless operation, however. Because the wireless transmitters are self-powered, they are isolated from spurious ground-loop potentials that get introduced into any reaction vessel from a number of different sources. These potentials dramatically affect the accuracy of pH sensors. In tests, when a ground noise induced spike appears on the pH signal, it is not present in the wireless transmitter output.


Noise reduction can lead to significant qualitative improvements in the control of bioprocess applications since improvement in signal equates to better process control. Temperature, pH and dissolved oxygen are the basic measurements needed for high-value pharmaceutical reactors and wireless technology can become a key differentiator for a company providing portable systems.


For manufacturers of single-use portable systems, the integration of wireless analytical instruments is as close to a “no-brainer” as can be imagined since it meets the goals of cost reduction, increased flexibility and improved performance. It’s even possible to retrofit some existing systems with wireless capability. For pharmaceutical manufacturers, wireless technology only increases the advantages of portable systems.


About the Author


Dave Anderson is the industry marketing manager at Emerson Process Management, Rosemount Analytical. He has more than 20 years experience in various process industries. For more information, please visit