FLEXSIL® Tubular Membranes For OTT Diffuser Bodies with Retaining Ridge

Material specification

FLEXSIL® is a polyorganosiloxane elastomer (silicone elastomer)

Colour white-grey
Shore hardness DIN 53505 A 60 +/- 5
Maximum service temperature 140 °C / 284°F
Tear propagation resistance ISO 34-1 B > 35 N/mm


Dimensions / FLEXSIL® tubular membranes
Article designation Article number A Aktive membrane length B Overall length D Inner diameter Active membrane surface Material Colour
MB FLEXSIL® 500 3110500000 500mm / 19.69" 560mm / 22.05" Ø 65,0mm - 66,0mm / 2.56" - 2.60" 0,08m² / 0.86ft² FLEXSIL® white-grey
MB FLEXSIL® 750 3110750000 750 mm / 29.53" 810 mm / 31.89 Ø 65,0mm - 66,0mm / 2.56" - 2.60" 0,12 m² / 1.3ft² FLEXSIL® white-grey
MB FLEXSIL® 960 3111000960 960 mm / 37.8" 1020 mm / 40.2" Ø 65,0mm - 66,0mm / 2.56" - 2.60" 0,18m² / 1.9ft² FLEXSIL® white-grey
MB FLEXSIL® 1000 3111000000 1000 mm / 39.37" 1060 mm / 41.73" Ø 65,0mm - 66,0mm / 2.56" - 2.60" 0,16m² / 1.7ft² FLEXSIL® white-grey

Slit pattern and slit size

The tubular membrane is perforated by a specially configured pattern of slits. It has no perforation at its 6 o’clock and 12 o’clock positions as well as on both ends. The slit size is dimensioned in accordance with the specific diffuser type and application at hand. Slit sizes are available in the following range: 

0,6mm / 0.024"

1,0mm 0.039"

1,2mm / 0.047"

1,4mm / 0.055"

2,0 mm / 0.079"

Pressure drop vs. throughput for OTT FLEXSIL® membranes in new condition with different perforation grades

The diagram above is a plot of maximum diffuser pressure drop (i.e. the pressure drop used for blower dimensioning) as a function of air throughput for different perforation grades. The pressure drop data applies for diffusers and membranes in new condition. The actual pressure drops across new diffusers/membranes will be lower and can vary in a given delivery lot within a window of 6 mbar (0.09 psi).

For example, a 1.0 mm thick FLEXSIL® membrane used at an air throughput of 10 m³/h will have:

a maximum pressure drop (i.e. the pressure drop used in blower dimensioning) of: 60 mbar (0.87 psi) and a pressure drop window within the lot of e.g.: 50 – 56 mbar (0.72 – 0.81 psi).

The pressure drop across a diffuser or membrane can change in subsequent operation. The amount of change depends on the purity of the inlet air, composition of the wastewater treated, process chemicals used and their concentrations as well as the aeration process technology and process conditions.

Due to these many variable factors, we cannot specify the increase in pressure drop to be expected in actual operation in your WWTP. We will however gladly advise you in accordance with our experience and develop, using your input parameters, operating conditions and maintenance plans which reduce pressure drop build-up.