Numerous industrial processes require an exact monitoring of the values for the flow of liquids and gases. The selection of the optimal flow measurement technology depends on the specific application and the process media. Crucial criteria here include process pressure and temperature ranges, viscosity and chemical aggressivity.
The most commonly used method in industrial measurement technology is based on the principle of differential pressure measurement. A narrowing of the cross-section in the pipeline causes a decrease in pressure and a proportional increase in the flow rate.
Thus, the exact determination of the differential pressure before and after the restriction is sufficient to calculate the mass flow or the volume flow. The derivation of the quantities is based on the determination of the flow coefficients with the help of the Bernoulli equation. This method is also known as the differential pressure method.
In refineries, flow nozzles are used, for example, to measure the volume flow of steam flows that, under high pressure, escape into the atmosphere. Calorimetric flow switches with an integrated LED display are suitable for monitoring coolant circuits.
Volume flows in ventilation pipes in air conditioning technology are measured using compact air flow meters with electrical output signals. The exact control of the room air supply is used for energy-efficient air conditioning in accordance with applicable EU standards.In the chemical and petrochemical industries it is mainly robust primary flow elements which are used.
For high accuracies of ≤ ±1.0 % of the actual flow rate, orifice plates with longer measuring paths are used.
Electronic flow switches offer the operator a local display of the flow values and at the same time an output of an electrical signal (PNP, NPN or 4-20 mA) for transmission to a remote control room. The FSD-4 flow switch is based on the calorimetric measuring principle. The temperature difference that occurs due to the cooling effect of flowing media is measured here. The flow rate can thus be calculated on the basis of the temperature difference. Furthermore, the design of these flow meters allows exact monitoring of the temperature without the need to set up an additional measuring location. Calorimetric flow switches are also known as thermal flow monitors and are ideal for monitoring coolant circuits or for controlling filter units.
Flow monitors do not need any power supply and work on the float measurement principle. A float activates a reed contact as soon as the flow rate exceeds a preset value. Corrosion-resistant materials enable applications in areas such as the chemical industry, machine building, the pharmaceutical industry and in medical engineering.
For the monitoring of air flows in ventilation and air-conditioning systems, flow sensors are suitable for volume flow calculation based on the measured differential pressure and the fan constant (K factor) of the connected radial fans. The exact measurement of the smallest differential pressures is crucial for the cost-effective and technical monitoring of room air systems. PID controllers and pitot tubes are also used for this.