Function of the return valve at the outlet of the reciprocating compressor and the unloader
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Gentlemen, the load of a reciprocating compressor is generally controlled by a unloader, and a return control valve is also installed on the compressor’s outlet valve. What I would like to ask is: what is the relationship between this return control valve and the unloader? In other words, when the inlet pressure of the compressor decreases, does this outlet pressure control valve open or close? Is it that this return pressure control valve is used only to control pressure and not the flow rate of the compressor? However, if I close the return pressure control valve at the compressor outlet, the pressure at the compressor outlet will definitely increase. Since the gas pressure is related to the gas flow rate, doesn’t this also mean that the feed rate to the device increases?
The inlet pressure decreases; open the return valve wider
When the inlet pressure of the compressor decreases, this outlet pressure control valve opens wider, or it is possible to reduce the compressor load. The outlet pressure of a reciprocating compressor depends on the substance being compressed. This return is mainly used to control traffic flow.
In my understanding, the return line is mainly used as a means of adjustment when the inlet flow rate is too low, while the unloading valve serves as a means of controlling the load on the unit. I’m not sure if this understanding is correct!
Under normal circumstances, when starting to apply load and the compressor is operating without any issues, the unloader should be set to 100%. If it is not at full load, only one side of the cylinder is in operation, which can lead to fatigue on one side of the piston rod and affect its service life. (I also heard it from an expert). The return line controls the flow rate, while on the other hand it controls the compression ratio; the control valve for the return line here is a pressure-controlled valve.
When the compression ratio of the reciprocating machine increases, the power rises sharply, the motor gets overloaded, and it shuts down automatically. The check valve is opened to raise the inlet pressure and reduce the pressure ratio. . . @jiaguoyun
This post was last edited by jiaguoyun on 2015-7-30 15:39. What if mine is a reciprocating machine driven by a turbine? Is the pressure ratio high too? Power surge? ***? ***? If it is a reciprocating machine driven by a steam turbine, what are the differences in load adjustment compared to motor-driven ones? @HEJIYUER
The unloader is installed to adjust the load on the compressor according to process requirements; it helps to reduce the starting load and prevent overcurrent during startup. When the flow rate at the compressor inlet is insufficient, the return line can be opened to increase the inlet flow. If the compression in a particular compression cylinder of the compressor is too high or the load is excessive, resulting in excessively high cylinder temperatures, the load can be reduced by appropriately increasing the flow through the return line, thereby preventing shutdown due to overheating
This post was last edited by jiaguoyun on 2015-7-31 08:26. If it is driven by a turbine, then isn’t the speed used to adjust the load?