aci eRCM Express Manual

aci eRCM Express Manual Manual pdf 1 page image

eRCM Express™ACI’s eRCM Express is an add-on device that calculates extensive compressorperformance (load, flow, unit safety, etc.), provides useful information needed to controlthe compressor (Next Step Up, Next Step Down, allowable pressure and speed ranges,etc.), and provides for certain condition monitoring tasks (such as estimating cylinderleakages from valves and rings, based on actual discharge pressures and temperatures).To complete the millions of calculations required to generate a full set of compressor data,for all cylinder ends, for all throws, for all stages, and for all load steps, the unit requiressome time. Most unit models can be completed within 150 ms, while others may takeupwards of 350 ms to complete.• Data synchronization is critical. Most data input items, such as pressures,temperatures, and speed will vary very little from call to call, and as a result thecalculated performances will generally vary slightly. Thus, while being out of synchfor a half second to a second is rarely an issue, a change in load step can result insignificant changes to the calculated performance data.• Allen-Bradley: The mCore unit will set the ACI_PLC_ACK[1] tag to a 1 to let youknow when calculations are complete, and thus the resulting data can be used.• Modbus: Make sure that the PLC (or gateway) waits long enough after writing datato the unit before reading data back to use.o When waiting is not practical, make sure that the PLC waits at least a fewwrite/read cycles before acting onresults – especially with a load stepchange.o ACI’s eRCM Express DiagnosticSoftware is a great free program tohave installed on a PC. It providesvaluable feedback which cansignificantly minimize efforts whenchecking Modbus communicationsand data validity.o Download software from the ACIwebsite: www.ACIServices.com.• The mCore unit allows previewing dynamic data to/from device directly via the web UI.