Rockwell Automation T6050 SurgeGard Incipient Surge-Conditioning Module - Manual (Page 37)

T6050 Operations & Maintenance Guide Chapter 3 – Applications
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Typical T6050 SurgeGard™ Applications
Motor Driven Compressor Applications
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). Depending on the compressor-motor gear
sensitivity, a good parameter for incipient surge detection is the motor power transducer (I or KW, without
filtering). However, where multiple electric driven machines are powered from the same grid, it is necessary to
apply a fall-back level (already pre-configured in T6100/6200/6300) to mask mutual noise from adjacent
machines being started or stopped. Therefore, only Incipient-Surge-PID signals within the limits of the fallback
levels are ramped forward to a safe signal selector, which is “or”ed with the primary Anti-Surge-PID output to
ease the compressor away from a region of instability. It is an optional configuration facility to increment the
surge control line by a small percentage for each incipient surge occurrence. The offset may be cancelled
automatically at the next shutdown of the compressor, or remain in the configuration until the next surge test.
Turbine Driven Compressor Applications
The most suitable parameter for incipient surge detection on turbine-driven machines is normally a differential
flow transmitter signal. Since the inlet flow or eye differential pressure signal sensitivity to the velocity pressure
changes is critical for detection of fluidic backflow oscillations, it is important that the flow transmitter does not
have a lag of greater than 100 milliseconds. For rapid process dynamics (small compressor, rapid upstream-
downstream dynamics, etc), it must be a simple analog device with no filtering - less than 7 milliseconds delay
(Statham PD3000 or equal transmitter,
www.gultonstatham.com ). It should ideally be located in the suction
manifold or compressor eye, downstream of any throttling device. A discharge flow or pressure transmitter is
suitable for certain high pressure ratio applications. The incipient surge signature should be verified before
enabling SurgeGard™ if a discharge pressure transmitter is used. For some applications, for example when the
suction flow signal quality is questionable (excessive noise during normal operation), a combination of suction
and discharge flow measurement may be applied. The primary anti-surge controller configuration must provide
for high signal selection (already pre-configured in the T6100, T6200 & T6300).
Pipeline Compressor Applications
The same incipient surge parameters apply as for motor or turbine driven applications described above. However,
on the detection of surge spikes the signal selection criteria is different. Due to the traditionally low pressure ratio
of pipeline compressors, together with high capacity, the most volatile surge spike parameter is the pressure
transmitter at each compressor’s discharge. The anti-surge-PID and incipient surge PID should be fast tuned to
the head/flow surge control line, while the surge spike detection and pressure PID should be fast tuned to the
compressor discharge transmitter. This provides protection from mutual interaction between stations, whereby
an unplanned trip of a downstream compressor causes a pressure spike to travel up the pipeline to cause a high-
pressure shockwave. Typically, this wave causes high vibration trips, as it momentarily causes a rapid surge line
transgression. The suction and discharge SurgeGard™’s, in conjunction with the incipient and surge spike loops,
alleviate this shock by identifying the pressure spike and easing open the recycle valves to a pre-set percentage
for a given time (determined by testing) until the line has stabilized once more. The timing of the surge spike
action depends on the distance between stations and is set per application.
Motor Driven Centrifugal Blower Applications