Environmental Testing and Results
Large-scale environmental tests were carried out over 6-months whereby the Wrapsense technology was installed on a ten-metre section of representative steel pipe and subjected to 6-months of winter weather. The pipe, a 300mm OD steel pipe, was fitted with ten 1-metre long sensors and connected to an IoT controller unit to transmit data from the sensors hourly. Meanwhile, a wireless weather station was installed alongside the pipe to correlate conditions including temperature, wind direction, wind speed, rainfall and humidity as well as any environmental damage to the sensors’ readings, to ultimately assess the sensors’ performance.
The objectives of this testing were to:
- Validate sensor performance under environmental loading
- Correlate slight sensor disturbances to the relevant weather information
The data from the exposure testing was assessed over a 3-month period from January to March and again in July, after 6 months of installation. No false alarms were registered during the test period and the system remained stable while the weather testing was also completed successfully, demonstrating correlations with temperature and humidity despite May 2021 being the wettest May on record in the UK.
The data received from the ten sensors (Figure 2) during the 6-month testing period was processed in order to normalise the signals and take account of short offline periods when the system was restarted and a 5-day period when the system was disconnected from the cloud service.
The weather station data showed that the maximum temperature recorded was 29°C on 14 June at 13:45 and the minimum was -5°C on 11 February at 2:00. Humidity, rainfall and wind speed were also measured, revealing that wind speed showed no measurable trends across the six-month period.
The signal data from each sensor was divided by month and then auto-correlated across a 15-day lag before being cross correlated with the final humidity and temperature data to demonstrate periodic weather variables. Data was also correlated with the non-periodic variables of rainfall and wind speed. Although this showed some disturbance in the sensor oscillation as a result of heavy rainfall, this soon returned to normal. The WrapSense performance assessment showed that there was no noticeable disruption to functionality for wind speeds of 42 kilometres per hour.
Aviation Hydraulics Testing
TWI also tested the Wrapsense technology to see if it was capable of detecting hydrocarbons in aviation hydraulics. Testing was undertaken on commercially-available hydraulics, including mineral oil-based fluids, synthetic hydrocarbon-based fluids, and phosphate ester-based fluids. A syringe was used for the controlled application of the fluids along with a multimeter, a camera to record values and a spill kit in case of any spillages.
The hydraulics were tested in 2ml and 10ml quantities and the multimeter readings were recorded for 5 minutes, with the electrical resistance for each test obtained from the video recordings every five seconds.
The results showed that the hydraulics tested made the sensor steadily increase in electrical resistance until reaching a saturation level, demonstrating that a full set of alarms could be developed by establishing thresholds of 1% increase in resistance.