On the inlet pressure control of 3K turbines

Control it at 0-35 KPA; negative pressure is preferable to avoid, but there is some negative pressure during operation. It should not exceed -6.0 KPA, otherwise the surge detection system will activate

I remember that the pressure adjustment limit for its import version was ±10 Kpa, but it is usually kept at around +1 Kpa of positive pressure. A possible reason is that if the pressure is too high, the backflow volume is correspondingly large, resulting in more wasted work. If the negative pressure is high, air may enter, and the moisture content cannot be guaranteed. Of course, the pressure level controlled by the hydrogen system is also related to this. It’s been some time now, so I can’t remember clearly; please point out any mistakes if there are any!

As for the inlet pressure control of the KKK turbine, it is primarily determined by the settings of the actuator provided by the manufacturer. Let the operator pull up the data to check. If the data represents a certain value, your operations will not go below this value; once that value is reached, the reflux valve will act automatically, unless the reflux valve is fully open in which case the regulating function is lost. The setting of this value is one of the parameters used by the manufacturer to prevent surge. We have the ability to change these values (instrument settings), and by doing so we alter the operating condition curve of the anti-stall valve. Generally, this is not a problem, but theoretically it poses potential risks. The inlet pressure, outlet pressure, and flow rate are the three parameters that determine the operation of the anti-stall valve.

The inlet pressure control of the KKK turbine depends on the appropriate opening degree of the inlet guide vanes; the manufacturer provides a characteristic curve table that you can take a look at； Regarding surge protection, it is determined by the built-in PLC, which includes surge control, outlet pressure control, and inlet pressure control. Among these, surge control and outlet pressure control are very important, while inlet pressure control is usually turned off. Once set, it’s best not to change it easily.

In my opinion, this is mainly due to the pressure difference between nitrogen and chlorine in the turbine. The mechanical seals of German KKK turbines are sealed with nitrogen, and in order to prevent chlorine from leaking in, it is necessary for the pressure of nitrogen to be slightly higher than that of chlorine (in our case, it’s 14 KPa). This pressure is maintained through a pneumatic valve on the nitrogen pipeline. However, the nitrogen supply cannot be cut off (also to avoid a situation where there is pressure but no flow). Therefore, Germany has implemented a protection mechanism that shuts down the turbine when the flow rate falls to a very low level (in our case, it shuts down when the flow rate is below 4 Nm3/h). In such a situation, if negative pressure appears at the turbine’s inlet, it will inevitably cause the nitrogen flow rate to drop to such a low level that the turbine shuts down. If the inlet pressure of the turbine is controlled at -14 KPa, then in order to maintain that pressure difference, all the nitrogen valves will definitely close, resulting in a very low flow rate and thus shutdown of the machine.

That friend could please explain in detail the control principle of the anti-surge valves in turbines? Every time the machine is started, there are problems related to this aspect. Sometimes all the inlet guide vanes are fully opened, but the backflow valve (the anti-surge valve built into the unit, i.e., the backflow valve) fails to operate. At this point, the only option is to gradually increase the chlorine volume while reducing the outlet pressure! That friend is also from Germany’s KKK Turbines; I would be extremely grateful if you could provide a detailed introduction!

This post was last edited by ibqyun on 2010-5-24 22:41. The anti-surge valve of the KKK turbine is, in essence, a control valve for backflow. In the PLC settings for surge control, there are options for anti-surge control, outlet pressure control, as well as DCS output selection. When the surge threshold is reached, the DCS output ceases to function, and control automatically switches to surge control, which means the backflow valve is opened. The supplier conducted surge tests prior to delivery. Additionally, poor surge control may also be due to a malfunctioning return valve or an internal blockage. The normal opening angle of the inlet guide vanes should be between 20 and 60; full opening is not reasonable. The manufacturer provides a characteristic curve table for the inlet guide vanes, which you can study carefully.

Could that technician please provide a detailed description of the operating procedures when starting up the 3K chlorine compressor in conjunction with the ion membrane electrolyzer? This is relevant to aspects such as anti-surge control, outlet pressure control, and inlet pressure control.

The last edit to this post was made by wlntjs on 2010-5-24 at 19:45. 1. The control of the anti-surge valve is carried out by a separate controller; the valve position output for the 3K unit depends on three factors: the unit’s corrected flow rate, the inlet pressure, and the DCS setpoint. OUTPUT=MAX(OUTPUT1,OUTPUT2,OUTPUT3)； (1) The so-called corrected flow rate of the unit refers to the value obtained by correcting the flow rate measured by the orifice plate for temperature, as well as for design pressure and temperature. The formula is V=K*V(measure)*1/2; this parameter serves as the main basis for the controller to determine whether surge is occurring. Each unit has a designated surge limit, and the controller calculates a valve position output, OUTPUT1, based on parameters such as flow rate and inlet pressure. (2) The anti-surge valve also serves another purpose, namely controlling the inlet pressure. The value set on our unit’s controller is -6 kPa; the values for other units are likely determined according to design requirements. The principle of this control circuit is that when the inlet pressure of the unit reaches or exceeds -6 kPa, the controller calculates a valve position output, OUTPUT2, based on the difference between the inlet pressure and the set value ； (3) The setpoints of the DCS are easy to understand; the MV value set manually is OUTPUT3 ； (4) The controller will, based on the output values of these three valve positions and through a maximum value selector, send feedback to the on-site anti-surge valve to trigger the corresponding switching action ； 2. If, while driving, the DCS setpoint is set to 0% and the IGV is kept at its manual opening position, then the anti-surge valve is adjusted automatically entirely by the controller; conversely, if the DCS setpoint is set to 100%, it is adjusted manually ； 3. The issue mentioned above regarding the failure of the anti-surge valve to function during driving should be caused by problems with flow rate or inlet pressure; for example, the flow rate may not be outside the surge zone, or the inlet pressure may be too low, among other reasons ； 4. The key data points on the unit are monitored by controllers, and there are numerous interlock points; issues such as open circuits or broken connections can cause the main motor to stop. As a result, some conventional methods used in the DCS system may not be suitable in such situations. Therefore, when dealing with these control points, it is necessary to be extremely careful and thorough in considering all aspects ；

“If, while driving, the DCS setpoint is set to 0% and the IGV is kept open manually, then the anti-surge valve is adjusted automatically entirely by the controller; conversely, if the DCS setpoint is set to 100%, it is adjusted manually； ”What does IGV refer to? Is it an guide vane?