Ingersoll-Rand CENTAC, Technical Reference Manual

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CMC TECHNICAL REFERENCE MANUAL
1X36003 Version 2.52

1996-1999 Ingersoll-Rand Company
Date of Issue: 18-Oct-1999
5
starters, inhibit loading, de-energize the prelube pump, and
disable the alternate alarm and trip setpoints.
Status Bar — The Status Bar provides four distinct types of
information (Compressor Operating State, Compressor Status,
Compressor Control Location and Page Number). This region
is always visible from any folder and page combination.
Stonewall — See Choke.
Surge Absorber — The reaction of the control system to a
surge that pops the bypass valve open by a small percentage
to get the compressor out of the surge condition. This feature
is initiated by surge detection.
Surge Anticipation — The ability of a control system to
prevent surge by predicting that a surge is about to happen.
Surge Detection — The ability of a control system to
indicate that a surge has happened. This feature is important
because a persistent surge condition can damage the
compressor. Once detected, the control system can respond
to the event by taking a corrective action; i.e., by opening the
bypass valve.
Surge Indexing — A method of automatically increasing the
setting of TL upon a surge.
Surge Indexing TL — The setpoint at which the inlet valve
controls to MinLoad.
Surge Line — A series of points that represent natural
surge for various inlet pressure conditions.
Surge PTX — Surge Pressure Transducer. Surge PTX is
mounted between the last compression stage and the check
valve.
Surge Sensitivity — A setpoint that is used to indicate the
magnitude of pressure and current changes that occur during
a surge condition. This setpoint determines when the control
system detects a surge.
Surge Unload — The reaction of the control system to a
surge that unloads the compressor to exit the surge condition.
This feature is initiated by surge detection.
System Pressure — The pressure at the location of the
system pressure transducer.
Terminal Block — A device that is used to connect to
wires. Typically, these blocks are provided for customer field
wiring to the panel and when one wire is to be connected to
multiple devices.
Terminating Resistor — A resistor placed at the end of a
communication network for absorbing or sufficiently
attenuating signals incident on it so that they are not reflected
back into the transmission line at amplitudes where they
would cause distortion of the data signal. Typically, a resistor
is placed at each end of the network to help eliminate noise.
Thermocouple — A device used to measure temperatures
accurately and consists of two dissimilar metals joined so that
a voltage is generated between to the contacts of the two
metals as the temperature changes.
Throttle Limit — See TL.
Throttled Surge — The condition created by closing the
inlet valve past the surge point to maintain constant
pressure.
Tight Closure — A term used to describe the inlet valve
position when the compressor is not running and starting.
The inlet valve ideally is closed tightly when stopped to
prevent reverse rotation of the compressor if the check
valve fails. Also, to reduce the load on the compressor
during starting, the inlet valve can be held closed for a
short period of time (less than thirty seconds) after the
start button is pushed. This is most typically done on
compressors at high altitude, most notably snow making
applications. Bearing analysis must be done prior to using
this option.
TL — Throttle Limit. Establishes the minimum flow through
the machine when loaded, it is the maximum point of inlet
valve throttling. If system demand is below this throttle
point, the compressor must bypass air to maintain pressure
setpoint or unload.
TL increment value — When Surge Indexing is enabled,
the TL increment value is the amount added to the Surge
Indexing TL upon a surge. The Surge Indexing TL will stop
being incremented when and if the value reaches
MaxLoad.
Transducer — An electrical device that provides a usable
output (4-20 mA, 0-5 vDC, etc.) in response to a measured
property (pressure, temperature, etc.).
Transformer — An electrical device that transfers
energy from one circuit to another by electromagnetic
induction.
Transient Voltage Surge Suppressor — An electrical
device that prevents temporary over-voltages of short
duration (typically associated with lightning strikes and
ground faults on an ungrounded system) from damaging
other electrical equipment.
Transmitter — An electrical device that sends the digital
representation of a real measured value (e.g., pressure,
temperature), to the BCM in the control panel for analysis
and display.
Turndown — The amount of capacity that can be
decreased from full load (maximum load) at a constant
pressure before the bypass valve begins to open to avoid
surge. This amount is usually expressed as a percent of
full load capacity.
TVSS — See Transient Voltage Surge Suppressor.
Twisted Pair Wire — Paired cables allow balanced signal
transmission, which results in signals with low noise. Due
to the improved noise immunity of twisted pairs, data
speeds are usually higher than those of multi-conductor
cables.
UCM — Universal Communications Module. The device that
allows outside systems to communicate with the CMC.
UL — Underwriter’s Laboratory.