1. Alarm Overview

The "DP201/251, AFU Filter Differential Pressure Too High" alarm typically occurs when the AFU filter element is completely clogged. Additionally, during ballasting operations, the “FM, Main Line Flow Low (Too Low)” alarm may also occur, or there may be insufficient main flow. In rare cases, the alarm may be triggered by a malfunction of the Pressure Transmitter (PT).

2. Troubleshooting Steps

Step 1: Check AFU Pressure Transmitters (PT2x1, PT2x2)

1. Close the Needle Valve:
   • Turn the handle of the PT sensor’s needle valve clockwise to fully close it.
2. Vent the System:
   • Remove the test plug to create an atmospheric pressure condition.
3. Verify Pressure Readings:
   • On the SYSTEM STATUS screen, check if the pressure readings for PT2x1 and PT2x2 are within 0 ± 0.05 bar.
   • If the readings fall outside this range, the PT sensor requires calibration or replacement.

Step 2: Address Filter Blockage

• If the PT sensors are functioning normally but the alarm persists, this indicates a completely clogged filter.
• Remove the filter element and clean it with high-pressure water of approximately 100 bar.
  • Caution: Ensure nearby equipment is protected from potential damage during the cleaning process.
  • For detailed cleaning procedures, refer to the product manual.

Step 3: Confirm Backwash System Functionality During Ballasting

• Even if automatic backwashing is performed, the filter may become clogged if the associated valves are closed, preventing the discharge of backwash water.
• Ensure the overboard valve in the backwash discharge line is open.
• Verify the proper operation of pneumatic valves in the backwash line, such as FV1x5 (e.g., FV105, FV155).

Step 4: ⚠️ Caution – Avoid Changing Geared Motor (GM) Wiring During Filter Element Cleaning

• During the disassembly and reassembly of the AFU filter element, incorrect wiring of the Geared Motor (GM) may result in the reverse rotation of the motor.
• Reversed motor rotation causes ineffective backwashing, leading to filter clogging.
• On ships where multiple filter elements are installed in the AFU housing, this may also result in damage to the chain and chain tensioner.
• Key Precaution:
  • Ensure the GM wiring remains unchanged during the cleaning process.
  • After reassembly, verify the rotation direction of the motor to prevent operational issues.

Step 5: Inspect Suction Unit Teflon Nozzles

• Worn Teflon nozzles in the AFU suction unit can reduce backwashing efficiency, leading to filter blockages.
• Since Teflon nozzles are consumables, replace them when wear is identified to maintain optimal performance.
• For purchasing inquiries, please contact the sales team at hanla@hanlaims.com.