Real Story: Overcoming False Readings in a New Guided Wave Radar (GWR) Installation
In industrial projects, installing new equipment often comes with challenges that require innovative solutions. This is the story of a Guided Wave Radar (GWR) installation for level measurement, where a vendor’s design oversight led to false readings. Through troubleshooting and a temporary workaround, the commissioning team resolved the issue and restored the system’s functionality.
1. The Background
1.1 Project Overview
- Industry: Chemical processing.
- Application: Level measurement in a sealed process vessel.
- Device: A Guided Wave Radar (GWR) level transmitter designed to provide accurate and continuous readings.
- Vendor’s Design: A stilling well (a tube guiding the radar signal inside the vessel) was installed to improve signal stability and minimize interference from internal structures.
1.2 Problem Statement
During commissioning, the GWR provided inconsistent and false readings. These errors threatened to delay the project timeline and disrupt plant operations.
2. The Root Cause
2.1 Investigation
- Initial Observations:
- The radar intermittently lost signal or reported fluctuating levels unrelated to actual conditions.
- Manual level checks showed that the GWR readings were significantly off.
- Analyzing the Stilling Well Design:
- The vendor-designed stilling well was installed without perforations or holes along its length inside the vessel.
- This caused the pressure inside the stilling well to differ from the main vessel, creating a pressure imbalance that interfered with the radar signal.
2.2 The Core Issue
- The absence of holes in the stilling well prevented the liquid level inside it from equalizing with the vessel’s actual level.
- This mismatch caused false radar reflections and misinterpretations of the level.
3. Temporary Solution: Using a Flange with Breather Tubing
To address the issue quickly and proceed with commissioning, the team implemented a temporary workaround:
3.1 Installing a Breather System
- Modification:
- The team installed a modified flange with a breather tubing system, controlled by a ball valve.
- The tubing allowed controlled venting of air or gas inside the stilling well, ensuring the pressure equalized with the main vessel.
3.2 Operating the System
- During commissioning:
- The ball valve was used to regulate the pressure in the stilling well periodically.
- This setup allowed the liquid level to stabilize inside the stilling well, enabling accurate radar signal interpretation.
4. Results of the Temporary Solution
4.1 Immediate Improvements
- The GWR readings stabilized and aligned with manual level checks.
- The temporary solution allowed the project to proceed without significant delays.
4.2 Limitations
- The ball valve required manual intervention to maintain equalization.
- The solution was not viable for long-term operation due to safety and maintenance concerns.
5. Final Solution: Retrofitting the Stilling Well
After commissioning, the team collaborated with the vendor to implement a permanent fix:
5.1 Retrofitting the Stilling Well
- The stilling well was removed, modified, and reinstalled with multiple perforations along its length.
- These perforations allowed liquid and gas to freely flow between the stilling well and the vessel, ensuring pressure and level equalization.
5.2 Validation
- The modified stilling well resolved the issue permanently.
- The GWR provided consistent and accurate level readings under all operating conditions.
6. Key Lessons Learned
This experience highlights the importance of thorough design reviews and flexibility in problem-solving during commissioning. Here are some key takeaways:
6.1 Vendor Collaboration
- Engage the vendor early to verify designs against real-world conditions, especially for unique applications like stilling wells in sealed vessels.
6.2 Design Best Practices
- Stilling wells should include perforations or vents to ensure equalization of pressure and liquid levels.
- Simulate process conditions during the design phase to identify potential issues.
6.3 Troubleshooting Readiness
- A systematic troubleshooting approach can identify root causes and enable temporary solutions to keep the project on track.
6.4 Importance of Temporary Workarounds
- Temporary solutions, like the breather tubing and ball valve setup, can mitigate immediate challenges without compromising safety or delaying the project.
7. Conclusion
The successful resolution of this GWR installation issue demonstrates the value of adaptability, engineering expertise, and teamwork. By identifying the root cause and implementing a temporary solution, the team avoided delays and ensured the system met performance expectations. Retrofitting the stilling well with perforations provided a permanent fix, enhancing the reliability of the level measurement system.
For similar installations, thorough design reviews, collaboration with vendors, and readiness for onsite troubleshooting can prevent and resolve challenges effectively, ensuring smooth project execution and long-term success.