# A Case Study of Floating Offshore Super-Long Steel Pipeline Combing with Field Monitoring
## 3 Monitoring Instruments and Monitoring Programs  
### Monitoring Instruments  
In the Marine environment, waterproofing and data transmission of monitoring equipment are the first problems to be solved. The measures adopted in this monitoring are as follows: after the strain gauge was pasted on the pipeline, it was further fixed with AB epoxy resin glue, and then sealed and coated with 703 waterproof glue, the wireless anti-interference communication system was also used to solve the problem of the interference and long-distance signal attenuation.  
Figure 5 shows the specific monitoring equipment and data transmission process. The advanced isolation system of DH3819 has a strong anti-interference ability. Furthermore, it can automatically complete some functions such as the setting of parameters and the collection of data. This system has eight measurement points for each acquisition module. The maximum acquisition rate of each measurement point is 5 Hz, the obtainable strain range is \(\pm\)19,999 \(\mu\)\(\epsilon\), and the measurement error is less than 0.5% \(\pm\) 3 \(\mu\)\(\epsilon\). The adopted communication mode is the wireless network communication; ZigBee is lightweight and portable, which can be used for wireless communication extension to reduce the field workload and improve the field test safety; DH5902N can be synchronized with GPS and can be tested and monitored in extreme environments such as strong vibration, high/low temperature and high humidity. The strain gauge was connected with the DH3819 static strain acquisition instrument through a waterproof cable-tied and fixed on the pipeline. 4 to 32 channels are provided for the system of DH3819, and all the channels can synchronously collect data, and the maximum frequency of each channel is 256 kHz. ZigBee was used to extend the wireless transmission of data. Finally, the data was transmitted to the computer through USB. The acceleration sensor was connected with the DH5902N mode acquisition instrument via a waterproof cable, and the computer received data through WiFi. The floating transportation dynamic construction could be completed through real-time monitoring and data analysis and the real-time feedback of aerial photography technology.  
A lifting test was carried out before floating to ensure the reliability of testing equipment and the accuracy of steel pipe monitoring data. The test method is shown in Figure 6. The mid-point of the steel pipeline was carried out by a hoist on-site with the spacing of the buoyancy tank was 325 m. The strain at the mid-point was monitored with the results shown in Table 1. The pipeline was regarded as a statically determined structure with two hinged ends. The theoretical strain value was calculated according to the lifting height, and compared with the measured strain value.  
Figure 4: Deformation curve of steel-3 PE.  
Figure 5: Flow chart of field monitoring data transmission.  
Figure 6: Lifting test on site.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Case** & **Lift Height / (cm)** & **Theoretical Strain \(\epsilon\)=12\(df\)/12 (\(\mu\epsilon\))** & **Measured Strain \(\epsilon\) (\(\mu\epsilon\))** & **Deviation** \\ \hline
1 & 7.8 & 14.18 & 14.76 & 4.09\% \\
2 & 9.5 & 17.27 & 17.8 & 3.07\% \\
3 & 11.2 & 20.35 & 18.91 & 7.08\% \\
4 & 12.9 & 23.45 & 21.55 & 8.10\% \\
5 & 14.6 & 26.54 & 24.66 & 7.08\% \\ \hline \hline \end{tabular}
\end{table}
Table 1: Lifting test results.