Under what circumstances can a turbine have its crisis shutdown device removed?
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I would like to ask under what circumstances a turbine requires a turning gear and a crisis shutdown device. I recently participated in a turbine commissioning process, and both of these devices were not available; I still haven’t figured out why. I hope experts can provide some guidance, and any relevant information would be appreciated. Thank you.
An electrical overspeed protection device should be used; previous turbines likely only had a crisis shutdown device but no electrical overspeed protection device.
A stupid question: isn’t the overspeed protection device standard equipment?
A crank device is necessary; otherwise, what will you do when you stop the machine? Dry and stopped? Then it’ll be fun next time you start the machine again. Crisis interruption is also necessary; it will not be absent (mechanical overspeed). Turning the rotor is generally done during shutdowns (normal or emergency) to ensure even cooling of the rotor and prevent it from bending. Emergency shutdown is triggered in cases of mechanical overspeed; it represents the final level of protection against such situations. Before that, there are also electrical over-speed protections and such.
I just saw your question. The emergency shutdown is the ultimate mechanical protection mechanism, meaning it operates at the highest speed and cannot be disabled. During testing to check for mechanical overspeed, the electrical overspeed controls are turned off in order to conduct such tests; at this time, extra care must be taken, and the air supply may need to be shut off if necessary.
A crisis cut-off device (mechanical overspeed) is essential; it represents the last line of defense for the turbine. Electronic overspeed is generally set on the control system, and the electronic overspeed setting is lower than the mechanical overspeed setting. Crankshaft rotation can be done automatically or manually; manual crankshaft rotation is exhausting for the operator! Turning the rotor is mainly to prevent it from bending.
Mechanical overspeed protection can be omitted if electronic overspeed protection is available, as mechanical overspeed protection is difficult to adjust and results in low accuracy in speed control. As for the barring device, it depends on the specific equipment; generally, small steam turbines do not have one (I don’t have information regarding the exact size). I have several small steam turbines here that lack a barring device, and these turbines are used to drive both multi-stage centrifugal compressors and multi-stage centrifugal pumps. Some are equipped with automatic turning devices, while others use manual turning; generally, large steam turbines and compressors have automatic turning systems.
I humbly ask for your advice, sorry if this is embarrassing. I am referring to mechanical emergency shutdown systems. Turbines with a power output of over 8,000 kilowatts use electronic overspeed protection devices, but turbines produced in China still rely on mechanical emergency shutdown systems. Although such systems are relatively inexpensive, they have their inherent drawbacks; they tend to malfunction after long-term operation. There is also a turning gear. First, it’s necessary to understand the purpose of this device; if the issue of uneven heating can be resolved from the design stage, then the turning gear can be omitted. The steam turbine I’ve worked on does not have such a turning gear.
Won’t your equipment need to stop operating once it’s in use? It’s a very difficult question to understand