In an air-loaded valve, the mechanical pressure of the spring is replaced by a pneumatic pressure acting on a diaphragm or piston.

Bernoulli's equation is the cornerstone of classical fluid mechanics. It describes the conservation of energy for a flowing fluid and tells us something very fundamental: as the velocity of a fluid increases, its pressure decreases (and vice versa).
The equation can be viewed as an accounting of the energy within a pipeline. As long as we do not add energy (via a pump) or remove it (via friction), the sum of the energy must always be constant.

A butterfly valve regulates or stops flow using a circular disc mounted on a rotating shaft in the centre of the valve body. With just a 90-degree turn, it switches between fully open and closed positions. This valve type is compact, lightweight, and suitable for large pipe diameters. In hygienic versions, the butterfly valve is widely used in food, dairy, and beverage plants, where it meets the requirements for cleanability and CIP compatibility.

A ball valve uses a bored-through ball to open or close the flow with a quarter turn. It is robust, quick to operate, and can handle a wide spectrum of media, pressures, and temperatures. The ball valve is one of the most widely used valve types in industry and is seen in everything from food and beverage production to pharmaceutical process plants, where its simple construction and low pressure drop make it attractive.

A Coriolis flow meter directly measures mass flow by utilising the Coriolis force that arises when a medium flows through a vibrating tube. Unlike volume-based meters, the measurement is independent of the medium's viscosity, density and temperature, providing high accuracy even under changing process conditions. The Coriolis flow meter is widely used in pharmaceutical production for precision dosing and batch control, as well as in the food and beverage industry, where accurate mass flow measurement is crucial for product quality and resource optimisation.

Compressible flow is the branch of fluid mechanics that deals with liquids and gases whose density changes significantly in response to pressure changes. In contrast to incompressible flow (like water at low speeds), where density is assumed to be constant, compressibility is crucial when speeds approach or exceed the speed of sound.

Continuous flow chemistry is a method where chemical reactions are carried out in a continuously flowing stream rather than in stationary batches. If batch chemistry is like cooking in a large pot, flow chemistry is chemistry's answer to a high-tech assembly line.
Instead of mixing all the reactants in a flask and waiting, they are pumped through tubes, microchips or reactors, where they meet, react and leave the system as a finished product at the other end.

A closed-loop control system automatically monitors its output and adjusts its input using feedback. It continually compares the actual output with the desired setpoint and makes corrections to reduce any difference or error. This self-correcting process helps maintain accuracy, stability, and consistent performance, even when external conditions change.

A bypass valve directs flow around a component or part of a plant – typically a pump, a filter or a measuring instrument – via a parallel pipe section. During normal operation, the bypass is closed, but the valve opens in case of excess pressure, for service purposes or during CIP cycles, where the cleaning medium must be directed straight through the system to ensure complete cleaning. In hygienic pharma and food plants, correct design of the bypass is crucial: a bypass line that is not sufficiently flushed can itself constitute a dead leg and thus promote microbial growth. The bypass valve is available in pneumatically and manually operated versions, often with a CIP override function to ensure cleanability of the entire circuit.

The D-term (the derivative part, also called Derivative control mode) is the PID controller's “fortune teller”. Where the P-term looks at the present, and the I-term looks at the past, the D-term tries to predict the future by measuring how quickly the error is changing.
The D-term can be regarded as the system's brake. Its purpose is to dampen oscillations and prevent you from overshooting the target.

A dome-loaded regulator (often called a dome regulator) is a high-performance pressure regulator that differs from standard regulators by using gas pressure as a reference signal instead of a mechanical spring.

An electronic pressure regulator precisely controls the output pressure using an electrical control signal – typically 4–20 mA or 0–10 V. Unlike mechanical regulators, it can be adjusted and monitored continuously without manual intervention, making it ideal for automated process plants. In pharmaceutical production, it is used for accurate pressure regulation in single-use systems and bioreactors, while in the food and beverage industry, it ensures consistent process pressure in filling and packaging lines.

A heat exchanger is a process equipment that transfers heat between two media without mixing them. The heat is transferred via a separating surface, typically metal, where a hot medium gives off heat to a colder medium.

Heat exchangers are used for heating, cooling or temperature control in process plants and are widely used in the food, pharma and chemical industries. The choice of heat exchanger depends on factors such as temperature, pressure, flow, media properties and hygiene requirements.

The ideal gas law is one of the most important equations in thermodynamics and chemistry. It describes the physical relationship between the pressure, volume, temperature, and amount of a gas.
The equation combines several older gas laws (Boyle's, Charles’ and Avogadro's laws) into one simple formula, which gives a very accurate description of how gases behave under most normal circumstances.

Incompressible flow is a flow condition where the fluid's density is regarded as constant. This means that the volume of a given quantity of fluid does not change, even if it is subjected to pressure changes during the flow. Within fluid mechanics, the assumption of incompressibility is one of the most important simplifications, as it makes the mathematical calculations considerably easier.

The I- (integral) term (also called integral control) is the PID controller's “memory”. While the P-term exclusively looks at the current error, the I-term looks at the past by summing the error over time.
Its primary – and absolutely most important – task is to eliminate the permanent residual error (offset) that the P-term leaves behind.

A magnetic flow meter – also called a magmeter or electromagnetic flow meter – measures volumetric flow using Faraday's law of electromagnetic induction. A magnetic field is generated across the meter tube, and when an electrically conductive medium passes through the field, a voltage is induced that is proportional to the flow velocity. The measurement principle is independent of the medium's viscosity, temperature, and pressure, and requires no moving parts, which ensures high reliability and minimal maintenance. In hygienic versions, the magnetic flow meter is widely used in dairies, breweries, and beverage production, as well as in pharmaceutical process plants for measuring conductive process media such as water for injection (WFI) systems, solutions, and cleaning agents. An important limitation is that the measurement principle only works on electrically conductive media – typically with a conductivity above 5 μS/cm.

Mass flow meters (MFMs) measure the amount of a medium expressed in mass units per unit of time – typically kg/hr or g/min – rather than volume. Mass flow measurement is independent of changes in pressure and temperature, which otherwise affect volume-based measurements, thereby providing reproducible results across varying process conditions. In pharmaceutical bioprocessing, the mass flow meter is central to controlling gas feeds in bioreactors, where precise and traceable dosing of oxygen, carbon dioxide, and nitrogen is critical for cell growth and product quality.

A diaphragm regulator/valve uses a flexible diaphragm as the sealing and regulating element, separated from the moving parts. This construction completely isolates the process fluid from the actuator and all moving mechanical parts, eliminating the risk of contamination and making the valve particularly suitable for sterile and hygiene-critical applications. The diaphragm regulator is a standard component in single-use systems and pharmaceutical process equipment, just as it is widely used in food and beverage production, where strict hygiene requirements apply.

Multifase flow is a branch of fluid mechanics that deals with the simultaneous flow of several different phases of matter.
Multiphase flow covers all combinations of the three states of matter: solid, liquid and gas.

A non-Newtonian fluid is a liquid whose viscosity (resistance to flow) changes depending on how much force or stress it is subjected to.
Unlike “normal” liquids such as water or alcohol, where viscosity remains constant whether you stir them slowly or quickly, non-Newtonian fluids sometimes behave more like solids and other times like thin liquids.

A needle valve regulates flow with high precision using a narrow, cone-shaped spindle that moves in and out of a corresponding seat. The fine mechanical adjustment makes it suitable for applications where even very small flow rates need to be controlled accurately. In pharmaceutical laboratories and single-use systems, the needle valve is used for precision dosing and calibration of gas feeds, while in the food and beverage industry, it is used for fine-tuning flavourings, CO₂ addition, and other flow-critical processes.

An open-loop control system is a type of control process where the output does not affect the control action. It operates based on pre-set instructions or input settings and does not use feedback to make adjustments. Once the system is activated, it follows its commands and continues to function even if the actual output deviates from the desired outcome.
Because there is no feedback, it cannot automatically detect or correct errors caused by changes in the environment or process conditions. Open-loop systems are simple, fast, and cost-effective, but less precise and adaptable than closed-loop systems.

A PID controller is a control system that continuously corrects a process parameter – typically pressure, flow, or temperature – by calculating the deviation from a desired setpoint. The control is achieved through three terms: Proportional (P), Integral (I), and Derivative (D), which together ensure a rapid response, elimination of steady-state errors, and damping of rapid process changes.

A proportional valve continuously and variably regulates flow or pressure based on an electrical control signal – typically 0-10 V or 4-20 mA. Unlike a conventional on/off valve, the valve's opening degree can be adjusted steplessly throughout its entire operating range, enabling precise and reproducible process control. The proportional valve is central to automated dosing, mixing, and pressure regulation and is widely used in pharmaceutical production systems, as well as in the food and beverage industry, where accurate control of ingredient quantities, temperatures, and flow rates is crucial for product quality.

The P-term (the proportional part, also called proportional control) is the foundation of a PID controller. Its task is to react to the current error in the system.

Pipe friction is the resistance that a fluid (liquid or gas) encounters when it flows through a pipe. This resistance results in a pressure loss along the length of the pipe, as some of the fluid's energy is converted into heat due to friction between the fluid and the pipe wall, as well as internally between the fluid's molecules (viscosity).
Within engineering, the calculation of pipe friction is crucial for sizing pumps, selecting pipe sizes, and ensuring sufficient pressure at the endpoint.

A back pressure regulator is used to maintain a constant upstream pressure by continuously modulating the outflow from the system. It gradually opens as the pressure approaches or exceeds the setpoint, and closes again as the pressure drops. The back pressure regulator is a critical component in flow chemistry and continuous pharmaceutical manufacturing, where stable system pressure is necessary for reproducible reaction conditions. It is also used in laboratory and pilot plants for precise pressure control of reactors and separation equipment.

A rotameter – also known as a Variable Area flow meter – measures the flow rate of liquids and gases using a float that moves freely up and down in a conical measuring tube that widens upwards. The float's position in the tube reflects the flow rate: as the flow increases, the float is lifted until the buoyant force and gravity are in equilibrium. The reading is taken visually directly from a scale on the tube, or via magnetic coupling to an external indicator on metal tube versions. Rotameters are robust, typically do not require an external power supply, and are particularly well-suited for low flow rates. They are used in pharmaceutical laboratories and process plants for monitoring solvents and process gases, as well as in food and beverage production for controlling ingredient and cleaning medium flow. A limitation is that rotameters typically need to be mounted vertically with flow from bottom to top to ensure stable measurement.

Mixed-phase flow is a branch of fluid mechanics that deals with the simultaneous flow of several different phases of matter.
Mixed-phase flow encompasses all combinations of the three states of aggregation: solid, liquid, and gas.

A gate valve shuts off the flow by lifting a flat or wedge-shaped disc out of the flow path using a threaded spindle. The valve is primarily designed for full opening or full closing and is not suitable for regulation or throttling, as partial opening causes vibrations and increases wear on the seat. In versions with a rising stem, the valve position is visually apparent, as the stem rises when the valve is opened. The gate valve is used as an isolation valve in supply lines, steam systems and water treatment systems. It is not preferred in hygiene-critical pharmaceutical and food processing plants, as the design makes complete CIP cleaning difficult, and the choice of materials and surface treatment do not typically meet hygiene standards such as EHEDG or 3A.

Tangential flow filtration (TFF) is a filtration technique where the medium is pumped parallel to the filter surface instead of directly through it. This minimises clogging and allows large volumes to be processed repeatedly without replacing the filter. TFF is a core technology in biopharma and downstream processing, where it is used for, among other things, concentrating, clarifying and buffer exchange of biological products such as proteins, antibodies and viruses. In single-use versions, TFF systems support full traceability and eliminate the risk of cross-contamination between product runs.

Thixotropy (Thixotropic shear thinning) is a time-dependent non-Newtonian property where a fluid's viscosity decreases when subjected to a constant mechanical stress (shear stress) over time, and gradually returns to its original thickness when the stress is removed.
Where shear-thinning (pseudoplasticity) reacts instantaneously to force, thixotropy is about the duration of the force. It is popularly described as a fluid with “memory”.

Two-phase flow refers to the simultaneous movement of two different phases (typically gas-liquid, liquid-solid, or gas-solid) through a pipe or system. The complexity of two-phase flow arises from the deformable interface between the phases and the different “flow regimes” that occur depending on the velocities and properties of the fluids.

A vacuum regulator (vacuum regulator/valve) maintains a stable, defined negative pressure in a system by means of a spring-loaded/dome-loaded diaphragm that regulates the inflow of ambient air. When the vacuum level falls below the set point, the diaphragm opens the valve and allows air to enter in order to increase the pressure again. In pharmaceutical production, vacuum regulators are used to control pressure during lyophilisation (freeze-drying) and sterile packaging, where precise and stable negative pressure is crucial to product quality. In the food and beverage industry, they are used in vacuum filling systems and concentration processes, and in cleaning equipment for cleanrooms and produced water systems, they are available in versions made from 316L stainless steel with FDA and USP VI-approved seals.

A vacuum breaker (Vacuum breaker) is a safety valve whose sole purpose is to prevent the formation of a vacuum in a pipe or vessel. It functions as a “reverse” safety valve: where a normal safety valve releases excess pressure, a vacuum breaker lets air in.

Valve authority is a measure of a control valve’s ability to regulate flow in a system circuit (heating/cooling), expressed as the ratio of the pressure drop across the valve at full load to that at full closure. A typical rule of thumb is an authority of at least 30–50% to ensure stable regulation and avoid poor control.
A high valve authority ensures that the valve actually controls flow, rather than the pipeline's resistance doing so. For low authority (e.g. < 0.25) often results in the valve acting as an on/off control rather than a regulating valve. If a valve is too large, the authority decreases and control becomes unstable. If it is too small, this can lead to noise and a risk of cavitation. Ideal value: An authority of 0.5 (50%) is often considered ideal for good control.

Volumetric flow rate is a measure of the volume of a fluid that passes a given point in a system per unit of time. It is typically denoted by the symbol Q and expressed in units such as m³/s, l/min or l/h depending on the application. Volumetric flow rate is particularly useful when the density of the medium is constant, as in water systems and liquid-based process plants. In contrast to mass flow rate, volumetric flow rate is sensitive to changes in pressure and temperature, which must be taken into account for gases or media with varying densities. Volumetric flow rate is a fundamental control and design parameter in all process plants and is measured with instruments such as rotameters, magnetic flowmeters and turbine flowmeters.

Inches water column is a unit of measurement for pressure that describes the pressure exerted by a column of water exactly 1 inch (25.4mm) high at a standard temperature.