aci eRCM Express, Manual

Page: 1 / 97

e
RCM Express
™
ACI’s eRCM Express is an add-on device that calculates extensive compressor
performance (load, flow, unit safety, etc.), provides useful information needed to control
the compressor (Next Step Up, Next Step Down, allowable pressure and speed ranges,
etc.), and provides for certain condition monitoring tasks (such as estimating cylinder
leakages 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 requires
some time. Most unit models can be completed within 150 ms, while others may take
upwards 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 the
calculated performances will generally vary slightly. Thus, while being out of synch
for a half second to a second is rarely an issue, a change in load step can result in
significant changes to the calculated performance data.
•
Allen-Bradley : The mCore unit will set the ACI_PLC_ACK[1] tag to a 1 to let you
know 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 data
to the unit before reading data back to use.
o
When waiting is not practical, make sure that the PLC waits at least a few
write/read cycles before acting on
results – especially with a load step
change.
o
ACI’s eRCM Express Diagnostic
Software is a great free program to
have installed on a PC. It provides
valuable
feedback which can
significantly minimize efforts when
checking Modbus communications
and data validity.
o
Download software from the ACI
website:
www.ACIServices.com
.
•
The mCore unit allows previewing dynamic data to/from device directly via the web UI.