The Flygt MiniCAS II is a supervision relay designed to monitor various sensors in ITT Flygt pumps, ensuring their optimal operation and preventing damage. It is a panel-mounted device that plugs into an eleven-pin relay base, offering a compact and integrated solution for pump condition monitoring.
Function Description
The MiniCAS II monitors several types of sensors:
- Thermal switches: These detect stator overtemperature, indicating potential motor overheating.
- CLS (Capacitive Leakage Sensor): This sensor detects water in oil, typically in the oil inspection chamber, which can indicate a compromised seal.
- FLS (Float Leakage Sensor): This sensor detects liquid in the stator housing, a critical condition that requires immediate attention.
- FLS10 (Float Leakage Sensor 10): This sensor detects liquid in the inspection chamber, similar to CLS but using a float mechanism. It is specifically used in newer midrange pump series like 3153, 3171, and 3202.
The MiniCAS II processes signals from these sensors and provides indications for different conditions:
- Normal operation: Indicated by the amber supply LED being on.
- Overtemperature: Detected by thermal switches. The relay energizes when healthy, and a red overtemperature LED turns off when healthy.
- Leakage: Detected by CLS, FLS, or FLS10. The leakage relay de-energizes when healthy, and a red leakage LED turns off when healthy.
The device offers five alternative sensor combinations, each with specific current readings for different states (Overtemperature, OK, Leakage). For example, with FLS + thermal switches, 0 mA indicates overtemperature, 7.8 mA indicates OK, and 36 mA indicates leakage.
In installations with variable frequency inverters (VFDs), the MiniCAS II can experience nuisance tripping due to interference. To mitigate this, a suitable filter can be connected between the monitoring conductors (T1, T2) and ground (PE), ideally situated in the pump/mixer junction box. Power and control cables should be kept separate and at least 300 mm apart.
The MiniCAS II features automatic reset for leakage faults, but overtemperature faults require manual resetting.
Important Technical Specifications
MiniCAS II Supervision Relay:
- Operational principle: Current Sensing.
- Approvals: CE, C-UR (covering USA and Canada).
- Environment: -25 to 60°C (maximum 90% relative humidity).
- Supply voltage: 20-30 VAC (50-60Hz) or 23.5-30VDC.
- Relay contact rating: 250 VAC / 5A.
- Voltage to sensor: 12 VDC +/-5%.
- Values of operation (current measured by MiniCAS II):
- 3mA < I < 22mA: OK condition.
- I < 3mA: High temperature (or interruption).
- I > 22mA: Leakage (or short circuit), with a 10 s delay for alarm.
- Power supply required: 5 VA.
- Dimensions: Width 33 mm, Height 79 mm, Depth 75 mm.
- Part number: 83 58 57.
FLS Stator Leakage Sensor:
- Signal: 8 mA non-alarm current, 36 mA alarm current.
- Supply voltage: 12 VDC.
- Max. temperature: 90°C, 1h.
- Test temperature: 115°C, 1h.
- Max. duty temperature: 70°C.
- Material: Aluminium.
- Physical size: Length 27 mm, Width 16 mm, Height 16 mm.
- Part number: 518 89 02.
FLS10 Inspection Chamber Sensor:
- Signal: 10 mA non-alarm current, 28 mA alarm current.
- Supply voltage: 12VDC.
- Max. duty temperature: 90°C.
- Material: Stainless steel and nitril rubber.
- Physical size: Length 44 mm, Diameter 22 mm, Thread M12 x 1, length 9 mm.
- Part number: 608 26 00.
CLS Water in Oil Sensor:
- Trip emulsion: 35% of water in oil.
- Signal: 5.5 mA non-alarm current, 29mA alarm current (5 s delay of alarm).
- Poles: 2 wires protected with a diode (wrong polarity connection = 0 mA).
- Supply voltage: 12 VDC (± 10%) (brown = +, black = -).
- Metal parts: Acid-proof stainless steel.
- Sensor surface: Glass.
- Max. pressure: 10 MPa 1h.
- Test pressure: 40 MPa.
- Duty pressure: 2 MPa.
- Max. temperature: 90°C, 1h.
- Test temperature: 115°C, 1h.
- Max. duty temperature: 70°C.
- Physical size: Length 75 mm, Diameter 12 mm, Thread M16 x 1.5, length 15 mm.
- Part number: 505 12 00.
Usage Features
Sensor Connections:
- Thermal switches with FLS/FLS10: Pilot cores can be connected in either polarity.
- Thermal switches with CLS: Requires correct polarity (brown = +, black = -) due to diode protection. Incorrect connection results in an open circuit (0 mA), indicated by both amber supply and red overtemperature LEDs being on.
- Thermal switches with CLS + FLS: Requires correct polarity for CLS. However, FLS will cause the MiniCAS II to indicate healthy (amber LED ON) even if CLS is incorrectly connected. A current reading is necessary to confirm correct polarity (15.0 mA for correct, 7.8 mA for incorrect with healthy conditions).
- Thermal switches only: A 1000-1500 ohm resistor must be connected in series with the thermal switches. A 1000 ohm resistor is included in the package.
Leakage Alarm Configurations:
- Leakage alarm will stop the pump: Recommended when FLS is used, as liquid in the stator housing is critical. The MiniCAS II provides changeover contacts (11-8 normally closed for interlock, 11-9 closes for alarm).
- Leakage alarm will not stop the pump (only warning): Recommended for FLS10 (inspection chamber) or CLS (water in oil), as these conditions are less critical than stator housing leakage. The MiniCAS II provides a warning without stopping the pump.
Temperature Alarm:
- Operation: Changeover contacts (1-3 closes for interlock when energized, 1-4 normally closed for alarm).
- Reset: Manual reset is required for overtemperature alarms. This can be done by connecting terminals 6-2 with an external push button or by interrupting the 24V supply.
Maintenance Features
Checking the Sensor Circuit and Fault Finding:
- Current Measurement: A multimeter or the ITT Flygt sensortester "ST-1" (FD part no. 10-581700) can be used to measure the current in the sensor circuit. This helps determine the status of the sensors and identify faults.
- Polarity Check: For CLS, incorrect polarity results in 0 mA. For CLS + FLS, incorrect polarity reduces the current reading. Switching polarity and observing current changes helps identify correct connections.
- Alarm Delay: CLS has a built-in alarm delay of 5 seconds. The MiniCAS II has a 10-second delay for leakage alarms (for updated versions).
- Distinguishing Leakage Sources: When using circuit (4) (Therm sw. + FLS + CLS), a leakage alarm cannot be attributed to a specific sensor just by looking at the MiniCAS II. Measuring the sensor current is necessary to identify the tripping sensor.
- Zero Current: A zero current reading can indicate a broken sensor lead, an open thermal switch, or an incorrectly connected CLS.
- Leakage Alarm Causes: Can be caused by a short circuit due to pinched sensor leads or a correct leakage signal from FLS, FLS10, or CLS.
Checking Earth Faults:
- Procedure: Earth faults on monitoring cores must be checked using a multimeter in ohms scale. Insulation testers utilizing 500 V or above should not be used.
- Measurement: Measure between each sensor lead and earth. Ideally, the value should be infinite, but Mega ohm values are acceptable. Earth faults can cause spurious seal leakage indications.
Checking the MiniCAS II:
- Simulating Normal Condition: Connect a 1 kohm to 1.5 kohm resistor between sensor outputs 5 and 7. Reset the MiniCAS II by briefly connecting and disconnecting a lead between outputs 2 and 6. The SUPPLY lamp should be lit. A 1 kohm resistor should yield a 12 mA reading.
- Simulating Temperature Alarm: If nothing is connected to sensor outputs 5 and 7 (open circuit), the SUPPLY and TEMPERATURE lamps will be lit, and the current will be 0 mA.
- Simulating Leakage Alarm: Connect a 500 ohm (or less) resistor to sensor outputs 5 and 7. Short-circuiting the output with a multimeter or jumper is also possible. The LEAKAGE lamp will light after a 10 s delay (or 5 s for original versions). The MiniCAS II limits the current to 30 mA during a short circuit.
Warning: Always switch off the power supply before working with the MiniCAS II socket, as high voltage may be present at the socket connections. The CLS sensor body is made of glass and should be handled with care.
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