Rockwell Automation T6050 SurgeGard Incipient Surge-Conditioning Module - Manual (Page 38)

ICS Triplex Turbo Machinery Control
10
Same criteria as for motor driven compressors. The incipient surge conditions (flow oscillations at the inlet of the
impeller) are transformed to torsional load oscillations (electric motors are very sensitive to changing torque).
The parameter for incipient surge detection is the motor power transducer (I or KW, without filtering). However,
where multiple electric motor driven blowers are powered from the same grid, it is necessary to apply a fall-back
level to mask mutual noise from adjacent blowers (or other motor-driven equipment) being started or stopped.
Turbine GG Applications
The most suitable parameter for incipient surge detection on turbine GG is normally the compressor discharge
pressure transmitter signal. Since the pressure signal sensitivity to the velocity pressure changes is critical for
detection of fluidic backflow oscillations, it is important that the pressure transmitter does not have a lag of
greater than 2 milliseconds (Viatran model 548 or equal transmitter,
www.viatran.com ). The transmitter should
be located at the compressor discharge manifold.
T6050 SurgeGard™ Stand-Alone Applications
Same signal selection criteria as for motor driven compressors The T6050 SurgeGard™ is normally powered by
any two-wire 4 - 20mA primary analog channel (24 Volt DC) as found in typical ICS Triplex or third-party DCS
or PLC control system. The incipient surge detection/override function complements the primary anti-surge
control algorithm. It will enhance the capabilities of most compressor control systems, especially those with
fairly slow loop scan rates. The T6050 SurgeGard™ can identify and correct for shifts in the compressor’s surge
point/line. It can also function as an independent backup to the primary anti-surge control system. However, it is
essential that if applied independently and without compressor startup interlock (SurgeGard™ function bypass)
that “conservative” SurgeGard™ Gain tuning is applied to compensate for fluidic oscillations during compressor
startup (build up of discharge head).
T6050 SurgeGard™ Factory Calibration Procedure
The T6050 SurgeGard™ output typically feeds into the Incipient Surge PID on the Anti-Surge controller. As
mentioned above, the output of Incipient Surge PID is used in parallel (via a high selector function) with the
Primary Anti-Surge PID control loop to control the recycle/blowoff valve. Based on the selected process signal,
current (motor driven machines= I or KW) – flow (h) – pressure, etc. – if such information is provided – the
T6050 SurgeGard™ is calibrated at the factory such that the output of the Incipient Surge PID signals an
incipient surge only under the correct conditions. This calibration can be accomplished using the following
procedure.
Each T6050 SurgeGard™ is tested at the factory for complete 4-20mA output range and the two potentiometers
on the T6050 are set to generate this complete range of output signal. The following paragraphs describe the steps
to be executed to perform this same calibration procedure.
Equipment Required for Factory Calibration Procedure
A T6050 SurgeGard™, a waveform generator, an oscilloscope, a digital voltmeter, a 250-ohm precision 1 watt
resistor, a 24 Volt DC power supply, test clips, and a separate 0 – 5 VDC power supply.