Should an interlock or alarm be installed at the temperature measurement point of the thrust bearing shell of the centrifugal circulating hydrogen compressor?
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Our company currently has one Shengli BCL409/A centrifugal hydrogen circulation compressor, which is equipped with two temperature measurement points at the main thrust bearing and the auxiliary thrust bearing respectively. The original design called for a single-point interlock that would shut down the machine at 115°C. Recently, there have been multiple faults related to the temperature measurement of the thrust bearing bushings (manifested as fluctuating temperature readings at the measurement points). To prevent high-level interlocks, the instrument has been programmed to adjust the temperature values downward when the system detects high resistance levels, at the isolation barrier within the 3500 system cabinet. However, there are still abnormal fluctuations in the temperature of the thrust bearing pads at certain measurement points. To resolve this issue completely, and after weighing the needs to protect the unit and ensure production, several proposals are put forward for discussion among experts: 1. Change the existing single-point interlock for temperature monitoring to a two-out-of-two interlock; the purpose is to reduce the risk of shutdown caused by single-point failures. 2. Without changing the existing interlocks, introduce a delay in the interlock responses; the goal is to reduce the likelihood of shutdown due to single-point failures through a certain delay period. 3. Change the interlock related to thrust bearing pad temperatures to an alarm system; the aim is to ensure the safety of the unit by using existing shaft displacement interlocks and other mechanisms, thereby eliminating the possibility of false interlock activations. We would appreciate it if experts could share the logic behind the setup of such temperature measurement points for thrust bearing pads in their respective units, as well as the advantages and disadvantages of the above proposals. Thank you. Chemical Equipment and Machinery
Regarding the issue of the temperature measurement point setup for the thrust bearing of the centrifugal circulating hydrogen compressor that you mentioned, here are several possible solutions along with their advantages and disadvantages: 1. Change from a single-point interlock to a two-out-of-two interlock for the existing temperature measurement points: Advantage: By increasing the number of temperature measurement points, the risk of shutdown due to a single-point failure can be reduced. Interlock is triggered only when the temperatures at multiple temperature measurement points are abnormal. Disadvantages: It increases the number of temperature measurement points and the corresponding interlock logic, thereby increasing the complexity and cost of the system. 2. With the existing interlock settings unchanged, a delay is applied to the interlock output: Advantage: Delaying the interlock output provides a certain amount of buffer time in the event of sudden temperature abnormalities, preventing the engine from being activated due to such transient fluctuations. Disadvantage: Careful selection of the delay time is required; an excessively long delay may prevent timely response to actual failures, while an excessively short delay may fail to effectively avoid false alarms. 3. Change the thrust bearing temperature interlock to an alarm: Advantage: Changing the interlock to an alarm prevents the engine from starting accidentally, and safety in the operation of the engine is ensured through other means (such as shaft displacement interlocks). Disadvantage: Relying solely on alarms may not allow for timely action; human intervention is required to identify and address temperature abnormalities. When choosing among these options, it is necessary to take into account both the safety of the units and the continuity of production. You can evaluate the feasibility and suitability of each option based on the specific circumstances, and choose the one that is best suited for your company. Furthermore, it is also possible to exchange experiences with other peer organizations to understand their logic for setting temperature measurement points on similar equipment and the solutions they employ. I hope this information is helpful to you. If you have any other questions, feel free to ask. Thank you! .
Do you have similar crew setup alarms? If so, we can discuss it in more detail
We organized an internal meeting to switch from single-point interlocking to two-out-of-two interlocking; the necessary change procedures were just completed recently. It is essential to weigh the pros and cons in terms of equipment safety and production stability, and to make decisions based on risk identification and assessment.
You can only change it to a 2-out-of-2 interlock; otherwise no one will sign off on any other changes. All Shenmu compressors have now been upgraded to a dual-point interlock, so this approach is feasible. Changing the alarm is not feasible; the crew has already set a wattage alarm, so there is no need to set one again
Here, the units generally use temperature alarms and displacement interlocks
It’s just the temperature of a thrust bearing; just change the alarm setting