Problems starting a centrifugal compressor

This post was last edited by shijiazhuang on 2017-3-29 21:19. 1. When starting up a turbine, should the pipes be warmed up first or should the turbine be rotated first? Warm the pipes first, then warm the machine ； No shaft turning is required for warming up the pipes in cold conditions, either for warm-up or normal operation (for condensing turbines). 2. What is the purpose of the shaft seal steam in turbines? When should shaft seal steam be used? Condensing steam turbines require shaft seal steam to establish a negative pressure, while back-pressure turbines do not. 3. What is the relationship between the sequence of starting up the heating system and the supply of shaft seal steam? Axial seal steam may not be required before warm-up; however, warm-up is necessary in order to establish a negative pressure as quickly as possible. 4. What is the minimum adjustable speed? The speed adjustment range is 10–20, with the minimum adjustable speed being 10 (as per my understanding). 5. What are the most common problems that occur when starting the compressor? What should be paid the most attention to? High vibration, surge. 6. Is the shaft seal steam and the turbine steam entering the turbine part of the same flow process? Shaft seal steam is used for sealing purposes, while turbine steam drives the turbine; they are not part of the same process

1. When starting a turbine, should the pipes be warmed up first or should the rotor be spun first? First, start the machine to prevent uneven heating of the shafts; after all, no one can guarantee that there will be no steam leaks. Heat transfer through the pipes also needs to be taken into consideration. 2. What’s the deal with the shaft seal steam in the turbine? When should shaft seal steam be used? Shaft seal steam is used to prevent air from entering and steam from the high-pressure side of the turbine from leaking out. It must be turned on before warming up a backpressure turbine, and it must also be turned on before creating a vacuum in a condensing turbine. 3. What is the relationship between the sequence of starting up the turbine warming system and the shaft seal steam? If it is for warming up, then 4 must be activated first. What is the minimum adjustable speed? This is likely the minimum operating speed of the turbine or compressor; it represents a range of speeds. This speed is higher than the speed at which sealing functions properly, and it is far from the critical speed, falling between 1X and 2X. The compressor also has a large anti-surge margin, providing ample operating range. Generally, once the speed reaches this level, the operation is considered complete, and control of the speed is handed over to other personnel for load adjustment. In simple terms, it is the speed at which process engineers can make adjustments to the load. 5. What are the most common problems that occur when starting a compressor? What should be paid the most attention to? Insufficient pipe warming and machine warming; failure to reach the critical threshold or water hammer occurring ； The warm-up time is too long, and the exhaust temperature is too high ； The compressor cylinder has not been drained of liquid. Generally speaking, as long as there are no problems with the instruments, mechanics, or oil system, there should be no issues when starting the compressor; just follow the operating procedures step by step, and problems are unlikely to occur. 6. Is the shaft seal steam and the turbine steam entering the turbine part of the same process? The shaft seal steam hardly enters the turbine; instead, it flows to a negative-pressure device, such as an air cooler or a shaft seal extraction pump.

What is the minimum adjustable speed? The minimum adjustable speed is the lowest adjustable speed at which the compressor switches from programmed control to manual control. It is the minimum value at which the set speed can be changed. This speed must be higher than the critical speed and the high-speed warm-up speed.

This post was last edited by gjn1970 on 2017-4-5 at 16:23. 1. When starting up a turbine, should the pipes be warmed up first or should the rotor be rotated first? Whether in a cold or hot state, the turbine must be rotated for at least 4 hours before startup. The pipes must be warmed up prior to starting the turbine; it is only after the steam temperature meets the requirements for turbine startup – that is, when the steam temperature is at least 50°C higher than the hottest part of the turbine, with a superheat of no less than 50°C – that startup can proceed. 2. What is the shaft seal steam in a turbine? When should shaft seal steam be used? Shaft seal steam is the steam used to supply power to the mechanical seal at the rotor shaft end. The characteristic of shaft seal steam supply is that, with the rotor in the cranking mode: during cold start, vacuum is drawn first before shaft seal steam is supplied; during hot start, shaft seal steam is supplied first before vacuum is drawn. 3. What is the relationship between the sequence of starting up the warm-up steam and the shaft seal steam? Whether in the cold or hot state, steam is first supplied to the shaft seal before the machine is warmed up; of course, backpressure turbines do not require steam for the shaft seal, as they only have shaft seal leakage. 4. What is the minimum adjustable speed? The minimum adjustable speed is the speed at which the control system begins to operate; below this value, the speed is controlled by the main steam valve. 5. What are the most common problems that occur when starting a compressor? What should be paid the most attention to? The main issues are shaft turning, pipe warming, trial operation, machine warming up, speed increase, and operation under load; the key challenge is the control of thermal stress in the turbine, so as to achieve smooth operation under load. 6. Is the shaft seal steam and the turbine steam entering the turbine part of the same process? Before startup, the steam for shaft sealing is usually taken from auxiliary steam; during operation, it is supplied by the turbine itself. This is the shaft sealing system. The steam that enters the turbine is main steam. If there is no auxiliary steam system (whose steam generally comes from a standby unit), then during startup, the steam for shaft sealing is provided by reducing the temperature and pressure of the main steam.

The principle for applying shaft seal steam in condensing units is as follows: in cold condition, evacuate first and then apply the shaft seal; in hot condition, apply the shaft seal first and then evacuate.

8# said it most professionally; I agree.

8# said it most professionally; I agree.