Fiber Optical Sensing -- new scene in rotating equipment

Fiber optical sensing (FOS) is an emerging alternative technology for monitoring pumps, compressors and other rotary machinery, and their processes. This can be done with optical sensors that are externally attached to the equipment, integrated into the equipment or inserted into parts of the equipment (for example the bearings). The sensing is done in either precise single or multiple points in the optical fiber or by using the complete fiber as a continuous sensor. These methods are insensitive to electric and magnetic fields, and can transmit signals over very long distances, several of them are intrinsically safe. The methods applied are highly sensitive to strain, temperature, angular or distance changes. FOS is therefore an ideal technology to apply in oil & gas installations, as for example in many static applications today e.g. for down-hole, pipeline and structural monitoring.

This article contains excerpts from the paper, “Fiber optical sensing of bearing performance and pump conditions”, presented by Lars Kahlman of AB SKF and Eric van Genuchten of B. V. Nieuwegein at the 2017 Turbomachinery Symposium.

In addition, FOS is becoming available as a technology for monitoring rotating equipment such as pumps, gear trains and screw compressors. Fiber optical load and temperature monitoring of rolling and hydrodynamic bearings is expected to be generally available in the near future in combination with temperature and pressure monitoring of the processes. This combination of optical sensing will enable monitoring of pumps and compressors and utilizing the data for process equipment optimization (PEO) by interacting with variable speed drives (VSD) and process settings. In this way a third new online proactive method of monitoring compared to the traditional reactive and predictive methods is added:

Reactive: Instant protection of single equipment at occurring failure;

·  Predictive: Broad avoidance of instant failures by monitoring of early signs of coming failures; and

·  Proactive: Process Equipment Optimization that may give significant reduction in operating expenses (OPEX) by tuning the equipment to work under optimized conditions and by so avoiding the failure causing conditions.

For example a significant reduction in OPEX due to 20-50% lower energy consumption and much improved mean time between repair (MTBR) are anticipated. The MTBR reduction is expected to come from tuning the equipment, e.g. pump, compressor or motor, to work under known and favorable mechanical conditions. This should ensure higher reliability and availability of an installation. In addition, fiber optical sensing is potentially very favorable from capital expenditure cost (CAPEX) due to anticipated lower installation costs (especially in cabling) and equipment costs for use in: explosive atmospheres (EX), magnetic and electric fields, submerged or enclosed areas.