What is the most reliable Mechanical Seal for Fuel Gas Compressors? Hello everyone, at my power plant we utilize a fuel gas compressor (specifically a one-stage centrifugal type) to increase the fuel gas pressure from 24 bar(a) to 33 bar(a) for our gas turbine engine. With a fuel gas flow rate of approximately 65,000 kg/hr and a compressor rotation speed of 31,800 rpm, we have experienced the compressor tripping more than 6 times in the last 6 months, resulting in plant shutdowns. The manufacturer has attributed these trips to failures in the mechanical seal dry gas seal and plans to replace it with a new design and material next year. This new seal will feature a change from SiC to SiN material and a reduction in rotation speed to 27,500 rpm (decreasing circumferential speed from 176 m/s to 152 m/s). However, doubts remain about whether this modification will ensure the compressor's reliable operation. Have you encountered similar failures? What was the root cause and how was it resolved? Can this modified compressor and mechanical seal combination guarantee reliable performance? If not, what is the most dependable mechanical seal for a fuel gas compressor in this scenario? Your insights are greatly appreciated. Thank you for your assistance.
The issue at hand is quite complex, with limited data provided to the forum, especially regarding the failure mode of the Dry Gas Seal in a high-speed integrally geared centrifugal compressor. To gain a deeper understanding, more detailed information is needed through further questioning. Have you been experiencing issues with the Dry Gas Seal? What specific failure modes have you noticed before any trips occurred? For example, have you observed a low seal gas flow alarm or a consistent increase in leaks? What were the findings after dismantling the equipment? Did you observe any signs of chemical corrosion or damage to components? Please offer more details for a thorough analysis. From a recommendation perspective, it appears that the decision was made to switch from Silicon Carbide to Silicon Nitride for the seal design. It's important to note that Silicon Carbide is considered superior to Silicon Nitride in terms of various properties such as Modulus of Elasticity, Thermal Conductivity, Hardness, and Coefficient of Thermal Expansion. What led to the choice of Silicon Nitride over Silicon Carbide? It's crucial to ask the right questions in order to arrive at appropriate solutions.
John Crane is widely recognized as the industry leader in dry gas seal technology. Their innovative solutions have set the standard in the field. - Irshad.
Identifying the root cause of failure often involves gathering various inputs, with the OEM being a reliable source of information. Discovering the reason behind a failure can be complex, but consulting the original equipment manufacturer (OEM) can provide valuable insights.
Before making any hasty decisions to switch the type or supplier of your Dry Gas Seal, it is advisable to conduct a comprehensive Root Cause Analysis (RCA) with the Seal manufacturer, compressor expert, and your Operations and Maintenance teams. Only after the RCA recommends an upgrade to the Dry Gas Seal should any changes be made. Simply switching the type or supplier without addressing the root cause of failure will not prevent future issues. It is important to identify and eliminate the actual cause of failure to avoid future struggles. Regards, Mohammad.
Is this compressor equipped with an integrally geared design (IGC)? The operational speed seems to indicate that it is. The unique overhung impeller layout of IGCs can result in significant vibration levels at the seals, even though the vibrations at the bearings remain minimal. I once had a conversation with a senior engineer from a leading dry gas seal manufacturer who mentioned that their seals could handle up to 50 mils of vibration at 40,000 rpm continuously. Fiftly mils! IGCs are particularly prone to imbalance issues caused by fouling. For instance, one of our refineries has an IGC in hydrogen recycle service that requires frequent shutdowns for cleaning. Consider conducting a lateral rotordynamic analysis to gain insights into shaft displacements near the seals due to impeller imbalance.
Hey there! I understand your concerns. We too had issues with the mechanical seal of our fuel gas compressor, although on a slightly different model. After a few unfortunate shutdowns, we ended up switching to a Diamond-Coated Silicon Carbide (D-SiC) Mechanical Seal and it has been holding up extremely well so far. The hardness and excellent wear resistance of diamond, combined with the tough mechanical properties of silicon carbide (SiC) seem to provide a good match for such demanding applications. But remember, it is equally important to maintain optimal compressor operating conditions and monitor real-time performance to prevent unexpected shutdowns. Hope this helps and that you soon find a reliable solution for your compressor issues. Good luck!
Hello there. From my experience working with gas compressors, it indeed sounds like your troubles stem from the mechanical seal. I’ve encountered similar issues in the past. However, while the manufacturer's redesigned seal may improve performance, there are other factors to take into consideration, such as potential alignment issues, vibrations, or issues arising from maintenance procedure or operations which may affect the seal life. While choosing a reliable seal is important, its reliability truly depends on how well it is managed in its operational environment. That being said, I have seen an improved performance with Tungsten Carbide and Silicon Carbide seals, which are tough and highly resistant to thermal shocks. Also, they can handle high rotation speeds quite well. I’d recommend a thorough investigation into the root cause of these frequent failures before you make a decision; it’s crucial to fix existing issues before going ahead with any upgrades.
Hi there, your situation seems quite challenging. It appears that mechanical seal failures have caused headaches for many of us in this forum! In my experience, changes in materials and design can indeed improve reliability, but they aren't a guaranteed fix. The switch from SiC to SiN, for instance, might reduce wear and heat production due to SiN's greater hardness and thermal conductivity. However, a precise alignment is crucial for optimal performance, so if the issue lies in the installation process or in ongoing vibrations due to the high rpm, even a switch in material and design might not solve the problem completely. I'd suggest carrying a thorough root-cause analysis before proceeding with the proposed change. It might even be worth considering other types of seals like cartridge seals that might be more tolerant towards misalignment and vibrations. But, a conclusive decision can only be made after considering all factors specific to your plant's operation.
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Answer: - The manufacturer attributes the trips to failures in the mechanical seal dry gas seal.
Answer: - The new design will feature a change from SiC to SiN material and a reduction in rotation speed from 31,800 rpm to 27,500 rpm.
Answer: - Doubts remain about the reliability of the modified design, and the thread seeks insights on whether this modification will ensure reliable operation.
Answer: - The thread aims to gather recommendations and insights on the best mechanical seal for ensuring reliable performance in a fuel gas compressor operating at the specified conditions.
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