Optimizing Flow Measurement in Demanding Process Conditions

Michael Franco, Director, Global Biopharma Sales at PSG Biotech, highlights the pain points that must be overcome in critical life science procedures and biopharmaceutical production operations. Specifically, the flow-measurement options currently offered can be a first-choice solution for use over a wide range of process-control conditions.

Key insights:

  • Achieving and maintaining consistent, reliable and accurate flow measurement is of vital importance in life science and biopharma applications, whilst operational variables must be controlled before the required level of flow-measurement accuracy can be achieved.
  • Cavitation is an issue in the transfer of cells in a liquid, the operator must stop and restart the pump to make sure all vapor bubbles have been evacuated from the line.
  • A compatible digital signal can also read the flow-measurement values instantaneously, which enables a quicker response to any operational problems or anomalies that might occur while also lessening the risk of human error.

In each and every life-saving or life-sustaining medical application, it is imperative that the safety, quality and reliability of flow-measurement functions are not compromised. This makes the early detection and prompt resolution of any flow-measurement difficulties or abnormalities – such as inadequate blood flow, changes in flow rate or the presence of air in the transfer lines – that may occur during a critical medical procedure vitally important.

The same is true for the development and manufacture of biopharmaceutical medicines, drugs and therapeutics, especially in applications on the downstream side that require flow measurement. Specifically, this typically includes chromatography and tangential flow filtration (TFF) processes that are used to separate cells or proteins through the removal of unwanted components in a liquid stream. Downstream bioprocessing includes other steps, for example, inline buffer formulation, column packing and virus filtration.

Charged with supporting the precise operation of the flow-measurement functions in these highly specific and challenging applications are Flow Measurement Sensors, which have been designed to deliver high performance, reliability and accuracy when handling delicate, sensitive and demanding liquids. The sensors and corresponding devices for flow evaluation must also possess the capability to provide optimized data outputs for process control when used in applications that have strict hygienic-manufacturing requirements.

The challenge

As mentioned, achieving and maintaining consistent, reliable and accurate flow measurement is a front-of-mind concern in life science and biopharmaceutical applications. What makes that difficult is the fact that there are many different operational variables that must be identified and controlled before the required level of flow-measurement accuracy can be achieved. These variables can include liquid density, mass flow rate, volumetric flow rate, liquid temperature and pumping pressure. 

To help standardize these procedures, some OEMs are beginning to develop and offer skid systems that are outfitted with all of the necessary components, from pumps and flow-measurement sensors to compressors and dispensers. The difficulty here is identifying and utilizing components that are able to communicate, or “talk” to each other via analog or digital signals, with digital communication preferred today due to its superior speed and reliability over analog communication.

A particular circumstance to avoid during flow-measurement activities is the creation of “cavitation” in the liquid stream. Cavitation is defined as “the formation of (vapor) bubbles within a liquid.” These bubbles can form when the pressure exerted on the liquid becomes low enough that it starts to evaporate. As the bubbles move through the measurement section of the flow sensor, they can implode back into liquid form. The rapid collapse creates a shockwave of energy in the liquid that can compromise the flow rate and the liquid’s overall integrity.

In biopharmaceutical applications that require the transfer of cells in a liquid, cavitation can create all sorts of problems. In this instance, the operator should run the pump for a few seconds, stop it and then restart it. At this point, after the restarted pump has been running for a bit, it is possible to check if all vapor bubbles have been evacuated from the line. If no bubbles exist, the transfer process can be restarted with no concern that cavitation will occur.

The solution

The manufacturers of flow-measurement sensors are familiar with the challenges that are inherent in achieving and maintaining proper flow-measurement values in life science and biopharmaceutical applications. Many have worked diligently to develop products – which can include flow-measurement sensors, liquid-handling pumps, mixers and feed systems, dispensing equipment and flow meters – that can be bundled together to create a customized solution that is capable of handling the unique process conditions of individual applications. 

In the flow-measurement realm, the industry’s latest technological advancement is a single-use model that has been designed to deliver optimized flow measurement in critical life science and biopharmaceutical applications. This next-generation flow-measurement tool features a disposable sensor that comes with an integrated straight flow path. Since it has been designed to fit the operational parameters of the majority of biopharmaceutical applications, there is no need for individual calibration as the process moves from application to application.

Other standard-setting features of this single-use sensor technology include:

  • A reusable and easy-to-mount holder with integrated electronics and Power over Ethernet (PoE) capabilities
  • An innovative locking mechanism that enables tool-less attachment of the disposable sensor
  • Standard ultrasonic technology that allows flow measurement and air-in-line detection with one sensor
  • A standard connection point for easy integration into manifolds
  • A straight-through flow path that imparts less shear stress on the liquid product
  • Cableless connection between the sensor and electronic cap for better IP protection
  • One holder that is compatible with all common sensor and tubing sizes: 1/4”, 3/8”, 1/2”, 3/4” and 1”

The creation of this new sensor joins two other established flow-measurement technologies to round out an offering of flow-measurement sensor options that cover a wide range of price points:

  • Clamp-on sensor: This type of sensor has been designed to support the reliable measurement and monitoring of flow rates in applications within laboratory and industrial applications. It features a click-fastening sensor that can be quickly and easily attached to flexible tubes with a non-invasive measurement method that prevents additional shear stress from being imparted on the pumped liquid. This is a notable advantage over invasive flow-measurement methods – like turbine flow meters – when it comes to handling shear-sensitive cells. The sensor’s ultrasonic transit-time method of operation, combined with customer-specific calibration in relation to the process’s liquid-handling parameters, results in highly accurate flow measurement that is flexible enough to satisfy most application requirements.
  • Single-use coriolis flow sensor: This sensor is constructed with USP Class VI-certified polyethylene ether ketone (PEEK) polymer and comprised of two assemblies: one that contains the single-use sensor and a second that contains the supporting electronics. This results in a sensor that is capable of measuring liquids in high-purity Life Science and biopharmaceutical applications that require all-plastic wetted surfaces and the ability to measure mass flow rate, total mass and temperature within an accuracy of +/-1% of the required reading. The sensor is also the industry’s only gamma-sterilizable Coriolis mass flow sensor that is disposable and drop-in capable for utilization in single-use applications.

These models possess the ability to communicate with other process-control components via analog or digital communication protocols. In this case, a compatible digital signal can also read the flow-measurement values instantaneously, which enables a quicker response to any operational problems or anomalies that might occur while also lessening the risk of human error.


Process conditions in life science and biopharmaceutical processing/manufacturing applications can vary greatly, but they have this in common: their performance must be optimized so that the application can be completed successfully. This means that the components, including flow-measurement sensors, must be able to help achieve and maintain the highest levels of safety, quality and reliability as they function.

Recognizing this, PSG Biotech has developed an end-to-end portfolio of flow-measurement sensors, with different levels of accuracy, that cover a very broad range of applications. This enables them to reliably and safely meet the unique or specific operational and communication parameters of every critical liquid-handling application in life science and biopharmaceutical manufacturing.

This article originally appeared on European Pharmaceutical Manufacturer