Flexible diaphragm NATM Stress Cells have been designed to optimize measurements of radial and tangential stresses in shotcrete and concrete tunnel lining.

The stress cell consists of a pressure pad connected to the trancducer by a hydraulic line. The internal cavity between the two steel plates of the pressure pad and the hydraulic line is filled at factory with oil. The oil is deaired as well as the pressure pad under high vacuum in order to obtain the minimum oil compressibility.

The rigidity of the cells are assured by the transducer, which has a ceramic diaphragm with negligible volume displacement in comparison with the cell cavity.

Technical specifications

RADIAL STRESS CELL (PRODUCT CODE 0L112R05000)
Measuring range    0-5 MPa (50 Bar)
Resolution    0.04 MPa with C6002
Accuracy    ˂0.3% FS
Pressure pad size    Square 150x150mm
Pad thickness    5mm
Transducer size    0D 25mm, 130mm long

TANGENTIAL STRESS CELL (PRODUCT CODE 0L112T20000)
Measuring range    0-20 MPa (200 Bar)
Resolution    0.01 MPa with C6002
Battery    ˂0.3% FS
Operating time    Rectangular 100x200mm
Environmental    5mm
size    0D 25mm, 130mm long

C6002 DIGITAL INDICATOR (PRODUCT CODE 0C6002MV000)
Digital display    3.5LCD
Resolution    10 kPa (0.01 MPa)
Battery    9V DC alkaline disposal
 2 hours continuously
 -5C +50C, dust-proof case
 130x75x40mmg

REPRESSURIZING DEVICE (PRODUCT CODE 0L111PUMP00)
This device allows the operator to increase the hydraulic oil pressure inside the cavity of the cell for maintaining close contact between the pressure pad and the surrounding material or for expanding the cells after the concrete has cured..