Ensuring optimum oil levels
GERMANY: Armaturenwerk Altenburg (AWA) has launched a new oil level regulation system, OLC, for use in compound systems with reciprocating or scroll compressors.
AWA’s OLC employs an electronic float sensor to provide variable level measurement. It can be used in systems of up to 120bar for a variety of refrigerants and oils and is said to ensure permanent and instantaneous level detection. In addition to the level, the speed of change of the level is also evaluated.
The electronic float is said to be insensitive to foaming and swashing oil.
Other features include a large sight glass, an LED display on the front for fast status recording and a modular adapter system for connection to all common compressor types. Installation dimensions are reduced by up to 25%, making it possible for plant constructors to design more compact composite plants.
The OLC includes two new functions to protect the refrigeration compressors: Power ON and Emergency Injection.
The Power ON logic is activated the first time the compressor and AWA OLC are switched on. If the compressor level falls within the alarm range in less than ten seconds, the OLC immediately sprays oil into the compressor until the normal range is reached again. If the oil level does not fall within the alarm range when switching on, the Power ON monitoring is deactivated again and the OLC operates in normal mode.
Emergency injection is operated when there is a sudden increase in oil demand, which can occur with frequency-modulated compressors. This rapid oil level change is detected by the OLC which deactivates the delay in normal operation and injects oil immediately.
For optimum lubrication of the compressor, the AWA OLC regulates its oil quantity to a level of 40%-60%. If the value falls below the normal range, a delay counter is activated. During normal operation, this prevents the system from swinging up and the compressor from overfilling. After ten seconds the injection of oil begins. If the oil level drops below the critical range (40%-25%) despite active filling, an alarm counter starts which switches an alarm relay after 80 seconds. This relay contact can be tapped and used, for example, to switch off the compressor or trigger an alarm routine.