Issue of fluctuations in downstream products during primary/secondary switch of reciprocating machines
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Currently, a compressor with two stages is in use, and the unloader has three adjustment levels. In addition, the machine is equipped with bypass lines for starting and stopping the flow of fluid at the inlet and outlet. Problems always arise during shutdown due to excessive fluctuations in flow rate, as the processes downstream of the reciprocating compressor cannot tolerate such large fluctuations. The compressor operates at around 40,000 standard liters per minute, while the processes require that the flow rate fluctuation be kept within 1,500 standard liters per minute, which is equivalent to less than 5%. Originally, only import/export cross-line cutting machines were used, but during the cutting process, the diameter of the cross-line pipes might be too small, making it difficult to adjust and control them. I would like to ask whether using only the unloader in its 0–50–100 settings can meet the error range required for such flow fluctuations. How should it be operated? Are there any other good methods available? As long as the flow rate at the time of machine shutdown remains stable, that’s sufficient
This description is too technical; it’s better to send a simple diagram, as visual aids make discussions easier.
It is recommended to consult the equipment manufacturer； Simply using a unloader for adjustment will definitely cause significant fluctuations in flow rate ； Including the difference in the speed at which the unloading devices operate during load adjustment for the two units ； The speed of manual operation also has an impact. 100 load 40,000 liters ； The fifty-load should be around twenty thousand ； It’s a huge difference from 5 percent
It is still necessary to develop a set of operating procedures through practical experience
In my opinion, if it is desired to achieve stable flow with minimal fluctuations, it is quite difficult to rely solely on three-stage unloading regulation. If possible, it would be better to replace the unloader with a system that allows for variable air volume control; such a system provides more stable operation and also helps save energy. If there are any nearby, one can go to learn from them* and take a look.
You can refer to reducing the load and then increasing it again; we have applied this approach when performing machine switching
You can refer to reducing the load and then increasing it again; we have applied this approach when performing machine switching
Cutting on both sides at the same time isn’t a big problem
It seems that regarding the timing issue when switching loads, the principle of first increasing and then decreasing should be followed. After the backup unit starts to handle more load, the operating unit should not reduce its load immediately, as there are a few seconds between the moment the backup unit begins to handle more load and the actual start of gas supply. In my opinion, it is more stable to reduce the load of the operating unit as soon as the first increase in the total outlet flow is detected. The load can be switched from 50 to 100 simultaneously; what’s important is the initial switch from 0 to 50. If the company is willing to invest, it would be better to have two sets of infinitely adjustable mechanisms
It is better to reduce the load on the main compressor once the outlet pressure of the standby unit reaches that of the operating unit; simultaneously, after the load on the main compressor is reduced, the control valves for the gas return lines at various stages of the standby unit should be adjusted promptly to stabilize the inlet pressure of the compressor
If only the three settings of the unloader (0-50-100%) are used for switching, the fluctuations will be relatively large and not meet the requirements; the unit should be equipped with a return line, and this line can be used for control in order to achieve smaller fluctuations.