Fluctuations in nitrogen flow rate for dry gas sealing
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In recent days, the nitrogen seal flow rate of the company’s centrifugal compressors has been fluctuating significantly. It used to be 80 Nm3/h, but now it varies between 70 and 110 Nm3/h. The pressure difference across the nitrogen filter is normal. Does this situation indicate a problem with the dry gas seal? Could it be a problem with the pressure relief valve? I have a question.
Anyway, I’ve heard that the main flow rate keeps increasing, which definitely means the main seal has been damaged... I’m also studying * here
What type of dry gas seal is it – single-face or double-face, in series or in parallel? Is nitrogen used as the primary sealing gas, an auxiliary sealing gas, or a shielding gas? Are the large flow rate fluctuations caused by variations in the pressure of the external exhaust pipe?
It is single-sided and connected in parallel; the primary sealing gas is process gas, while nitrogen serves as the secondary sealing gas. The flow rate fluctuates significantly, but the average flow rate remains relatively constant. There are some fluctuations in the sealing gas pressure, while there are no fluctuations in the exhaust pressure.
Check whether the pressure is stable; if it is stable, then it’s not a problem with the pressure relief valve
Some time ago, one of the inlet flow rates of our circulation machine (process gas) fluctuated greatly, and so did the flow rate of its exhaust gas. However, the pressure difference of the primary seal remained unchanged. The reason is still unknown at the moment.
If the differential pressure control valve of your balance line is set to automatic mode, it’s likely that the dry gas seal is damaged. Fluctuations in the flow rate or pressure at the compressor’s inlet and outlet should not be sufficient to cause such significant fluctuations in the flow rate of the primary seal; observe carefully to see if there are also fluctuations in the exhaust flow rate or exhaust pressure. If those two parameters also fluctuate, it can be determined with certainty that the seal is damaged.
Reply to 6# yuwei6688: The flow rate of the primary seal gas has almost no impact on the flare flow rate; it is mainly the secondary seal gas that constitutes the majority of the flow going to the flare
Reply to 8# jinniuyulin521: The flow rate of the primary air is around 240 cubic feet per hour; most of this air returns to the compressor cylinder, while a small portion leaks out and is vented along with the secondary sealing air (N2). However, the flow rate of nitrogen is only 8 cubic feet per hour
Replace the primary and secondary nitrogen filters; it might be caused by dirty filters, as dirty filters can also contaminate the seals.
Gap pressure, back pressure, inlet pressure – apart from these, there are also instrument-related factors; by checking these, the cause can generally be identified