Detect overflow at very small differential pressure
Schmidt Technology says its SS 20.400 flow sensors significantly improve energy efficiency in cleanrooms, while ensuring product and process safety.
To obtain excess pressure in cleanrooms, very high volume flows are usually required in the air-conditioning system. The EN ISO 14644 standard specifies excess pressure values from 5 to 20 Pascal.
For the installation of an additional flow sensor, it is sufficient to create a small opening of approximately 50mm, as shown here, above the access door
In pharmaceutical cleanrooms, they often lie between 15 and 30 Pascal and even higher. The air volume required to control room pressure accounts for a significant share of the energy consumption needed by an air conditioning system to supply cleanrooms. The consumption of the ventilators, for example, accounts for approximately 57% of the energy costs.
Schmidt says the best way to save energy is to adjust air volume to process requirements. The air overpressure must be decreased to a value as close to the minimum requirements of the standard as possible and then adjusted or maintained in a stable condition with the smallest possible amount of supply air.
To complement pressure measurement, a flow measurement unit would be installed in a suitable wall opening of approximately 50mm diameter to measure the overflow.
The SS 20.400 can measure the compensation flow at an overflow opening in the cleanroom wall
The measuring range of the SS 20.400 starts at a flow velocity (WN) of 0.05m/s. Schmidt says this is far below the differential pressure of 0.01 Pa and, thus, below the capacities of a differential pressure sensor. Thus, it detects overflow in an opening of a cleanroom wall even at very small differential pressure.
The use of differential pressure sensors allows the functional safety of cleanrooms and energy efficiency to improve significantly, the firm says. A simulation performed by AL-KO Therm, one of the largest manufacturers of components for ventilation and air-conditioning systems, has found that it is possible to reduce energy costs by 50%.