Rockwell Automation T6050 SurgeGard Incipient Surge-Conditioning Module - Manual (Page 40)

ICS Triplex Turbo Machinery Control
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Chapter 4 - Operations
T6050 SurgeGard™ Field Gain Adjustment Procedure
For the T6050 SurgeGard™ field gain adjustment procedure, it is assumed that a current (motor I or
KW) or a flow transmitter is used in the process. The transmitter is assumed to have a 4-to-20mA
output (that oscillates during incipient surge) which feeds into the T6050 SurgeGard™ module input
Terminals 1 and 2. ICS Triplex recommends adjusting the gain (X5 – X30 potentiometer) of the
T6050 to show full incipient surge (20 mA at the T6050 output Terminals 5 and 6) when the
oscillations at the input Terminals 1 and 2 are 10% of the full range of the transmitter. Thus, for the
example case, the output of the T6050 at Terminals 5 and 6 should be 20mA when the input signal
indicates oscillation amplitudes of 5.6 mA. This translates to a voltage swing of 0.40 V peak-to-peak
(10Hz) at the input Terminals 1 and 2 of the T6050 (across the internal 250-ohm resistor)
corresponding to a 20mA output from the T6050 Terminals 5 and 6.
Note that if it is desired to indicate a full scale incipient surge from 25% of the full range of the
transmitter (instead of the 10% as used in the example above), the gain (X5 – X30 potentiometer)
should be adjusted so that the output of the T6050 at Terminals 5 and 6 should be 20mA when the
input signal at Terminals 1 and 2 indicate oscillation amplitudes of 8.0 mA. This translates to a
voltage swing of 1.00 V peak-to-peak (10Hz) at the input Terminals 1 and 2 of the T6050 (across the
internal 250-ohm resistor) corresponding to a 20mA output from the T6050 Terminals 5 and 6.
Actual Surge Limits
A request to test the compressor’s surge limits in order to determine the true surge control line is
understandably unpopular because of the perceived risk of damage to the machine. However, the
anti-surge control system minimizes this danger by allowing to quickly open the recycle/blow-off
valve upon detection of incipient surge (flow reversal at the inlet of the compressor impeller, the re-
circulation zone).
Field testing of surge points is important since the actual compressor surge limits usually differ
significantly from the limits indicated by the compressor map. The surge line shown on a
manufacturer’s compressor map results from an analysis of the compressor design and is not
normally verified by testing with the actual gas. The map data is usually conservative. Also, piping
arrangements on the compressor suction side can account for significant surge point discrepancies.
Accommodating these inaccuracies often requires unnecessarily wide surge margins, which can
result in excessive recycling or blow-off. Therefore, a strong economic incentive exists to establish