Pressure sensors for machine integration and harsh environments (fiber

Energy-efficient and fail-safe machinery are fundamental to industrial competitiveness and sustainability. Advanced monitoring of equipment condition is crucial.

Optical fibre sensors are an emerging technology for condition monitoring since these sensors often are very small, discrete, cause minimal impact on the material and the environment and can be seamlessly integrated in natural and man-made structures such as bearings, pumps, and boreholes. 

In particular, Fibre Bragg Gratings (FBG) is a mature and established technology in industry. These sensors are ubiquitously used as thermometers and strain gauges in machine monitoring nowadays, but are, intrinsically, poorly sensitive to external pressure, making them inefficient for pressure monitoring.

In this project (PRINTS), we developed multiplexable, highly sensitive fibre-optic pressure sensors based on Fibre Bragg Grating technology, the same underlying technology commonly used by fibre-optic strain and temperature sensors.

The fact that this new pressure sensor can be installed on the same optical fibre and probed by the same read-out equipment as its strain and temperature counterparts is an important feature since it allows monitoring of an addition parameter without addition of further costs. The primary target application is health monitoring of pumps and similar machinery. 

The project consortium was made up of

• RISE, coordinator and expert in fiber optic sensor technologies,
• SKF, a provider of bearings and machinery with integrated sensors,
• Proximion, a manufacturer of Fibre Bragg Gratings and a provider of industrial sensor solutions, and
• Svensk Kärnbränslehantering (SKB), an end-user with the need for stable long-term monitoring in boreholes.

The primary target application was health monitoring of pumps and similar machinery, where we aimed at designing and advancing the maturity of a pressure sensor prototype to a state where it has been validated for machine integration by SKF. 

The project also evaluated the applicability for borehole monitoring. SKB sees potential benefits because of the use of fibre sensors for monitoring purposes due to its inherent advantages: compact sensors, long-range deployment possibility, the possibility to have many sensors on the same fibre, and the long life time in harsh environments. Here, the time horizon is longer, and the project aims more at evaluating the applicability of these sensors in the demanding and harsh environment of boreholes rather than developing an advanced prototype for pressure monitoring. 

These two applications illustrate the wide potential applicability of the proposed sensor technology in PRINTS.

The PRINTS project was carried out within the Strategic Innovation Program "Smarter Electronic Systems", a joint venture by Vinnova, Formas and the Swedish Energy Agency.