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Vol. 2.6 © 2020 Hanbell Precise Machinery Co., Ltd. All rights reserved
pressure in condenser, and as a result, high pressure gas flows reversely back into the compressor
and the airflow inside the compressor becomes unsteady and turbulence which leads to heavy
vibrations and noise. During surging, high speed shaft can be damaged due to heat accumulation
inside the compressor. In addition, the rotating parts will experience an alternating stress induced
by periodically varying pressure due to reversal of flow which increases the loads on bearings and
may destroys the bearings. Therefore, the operation of compressor must be limited within the
allowable operating range under the safety margin line.
Figure 3.5 illustrates the operating range of a fixed-frequency water-cooled compressor.
Surge occurred due to dramatic change of working condition can be detected by measuring the
current value of motor as the compressor will be in a state of unsteady loading due to the reversal
of flow during surging. With an approximately 5 seconds/cycle of surge frequency, the compressor
can be considered as surging when three consecutive peak current differential is 10% higher than
the average current within 15 seconds (except during loading control of the compressor). Please
refer to section 3.3.1 for surge protection strategy (mechanism).
Note
：
RT series compressors use rigid bearings and are capable of withstanding short-term surge
up to 15 seconds. However, the compressor cannot withstand long-term surge, thus using
only current detection for surge protection is not allowed. Safety margin line formula should
always be used as primary surging protection.
Warning
：
：
：
：
Once surging occurred, labyrinth seal gaps will become larger, which increases the
leakage of labyrinth seals. In addition, the vibration of compressor will also become larger
due to greater imbalance. Such effects are detrimental and should be avoided.
Warning
：
Normal operations of compressor should always be within the allowable operating range.
Current detection is mainly used when surging occurred due to dramatic change of
working condition.
P
