Greetings! Today we will analyze the sequence of actions of an electrician when finding the source of low 440V insulation on the vessel. In the previous article we looked at the first actions of the ETO when searching for low insulation 220V, I recommend reading that article first, because it is more detailed. And the search methods are not much different, but there are nuances.
Finding low 440V insulation on a vessel involves tripping the circuit breakers one at a time, starting with the non-critical consumers.
It may happen that the reason for low insulation is immediately known, because a 440V high pressure machine was started on the deck and perhaps it was flooded with water. But it happens that you cannot find the source on the first try.
When disconnecting breakers, you need to pay attention to the pointer megohmmeter, which is located on the 440V feeder panel of the main switchboard.
This device instantly shows the change in insulation resistance when disconnecting consumers with low insulation relative to the ship's hull (the arrow goes to infinity).
The grounding monitor is a key device for measuring the insulation resistance of the entire power circuit and issues a corresponding signal (alarm) if the resistance values reach the set point (For example, 0.2 MOhm).
Low insulation on a 440V electrical system on a vessel is a serious issue that can lead to various operational problems and safety hazards. Electrical insulation is critical for preventing electrical leakage, short circuits, and potential electric shocks. Here's a comprehensive look at the implications, causes, detection, and mitigation of low insulation in a 440V system on a vessel.
Implications of Low Insulation
1. Electrical Safety Hazards:
- Electric Shocks: Risk of crew members receiving electric shocks.
- Fire Risk: Potential for electrical fires due to arcing and short circuits.
2. Equipment Damage:
- Short Circuits: Can lead to damage or failure of electrical equipment.
- Operational Downtime: Equipment failure can cause critical systems to shut down, affecting vessel operations.
3. Regulatory Non-Compliance:
- Safety Standards: Non-compliance with maritime safety regulations and standards.
Common Causes of Low Insulation
1. Environmental Factors:
- Moisture and Humidity: Water ingress and high humidity can degrade insulation.
- Saltwater Exposure: Saltwater can corrode and deteriorate insulation materials.
2. Aging and Wear:
- Material Degradation: Over time, insulation materials can break down.
- Mechanical Damage: Physical damage to cables and insulation from vibrations or impact.
3. Improper Installation or Maintenance:
- Faulty Installation: Poor installation practices can compromise insulation.
- Lack of Maintenance: Neglecting regular maintenance can lead to unnoticed deterioration.
Detection of Low Insulation
1. Insulation Resistance Testing:
- Megger Testing: Using an insulation resistance tester (megger) to measure the resistance of the insulation. Low readings indicate potential problems.
2. Thermographic Surveys:
- Infrared Cameras: Detecting hotspots that indicate potential insulation failure points.
3. Visual Inspections:
- Regular Checks: Routine visual inspections of cables and electrical components for signs of wear, damage, or corrosion.
4. Monitoring Systems:
- Continuous Monitoring: Using systems that continuously monitor insulation resistance and alert to potential issues.
Mitigation and Maintenance
1. Regular Maintenance:
- Scheduled Inspections: Regularly scheduled inspections and testing to detect and address insulation issues early.
- Cleaning and Drying: Keeping electrical components clean and dry to prevent moisture-related insulation degradation.
2. Immediate Repairs:
- Prompt Action: Repairing or replacing damaged insulation and cables as soon as issues are detected.
3. Environmental Control:
- Humidity Control: Using dehumidifiers and ensuring proper ventilation to control humidity levels in electrical compartments.
- Waterproofing: Ensuring all electrical enclosures are properly sealed against water ingress.
4. Training and Awareness:
- Crew Training: Ensuring that crew members are trained to recognize signs of insulation failure and understand the importance of regular maintenance.
Low insulation in a 440V electrical system on a vessel poses significant safety and operational risks. It is essential to detect and address these issues promptly through regular maintenance, proper environmental controls, and immediate repairs. By implementing robust inspection and monitoring practices, vessels can maintain the integrity of their electrical systems, ensuring both safety and operational efficiency.
List of circuit breakers when searching
Below I propose to familiarize yourself with the list of circuit breakers that I turn off sequentially when the 440V insulation is occured. This sequence or list may vary depending on the type of vessel, but is suitable for most.
- The first breaker I usually turn off is the galley and laundry.
- The second breaker is deck machinery and 440V sockets on deck (high pressure machines, cranes, ladder winches, mooring winches, windlasses, capstans, etc.). Of course, cranes should not be turned off during cargo operations, and deck winches should not be turned off during mooring operations.
- The third breaker is air conditioning and ventilation systems (superstructure and engine room).
- The fourth breaker is auxiliary mechanisms, the shutdown of which will not entail a blackout of the vessel or a stop of the main engine (on the move). For example, cathodic protection, ballast pump, etc.
- The fifth breaker is responsible devices, but first it is advisable to switch to a backup (standby) system, if possible. For example, start the second main engine Lube oil pump and stop the first one, which needs to be checked.
Search for low insulation
Suppose a low insulation 440V came out, we found that this is a group 5 circuit breaker, which includes galley equipment.
Turning off the power one by one and checking each breaker in this group, we find that this is cooking range in the galley.
Checking each hot plate, we conclude that the lower left hot plate with low insulation, also requires replacement of the cable and contact group (as you can see on the photo).
It is important to understand that if the switch on the hot plate is turned off while the plates are being tested, the device may not show low insulation. Because it will “check” only the circuit up to the switch and the switch itself; it will not check the hot plate if the switch not opens its contact.
We install a new plate and thus eliminate the low 440V insulation.
Which equipment most often gives low 440V insulation?
- heating elements (heating elements) (heaters, heaters in boiler and auxiliary engine systems, electric heaters of the main engine);
- hot plates and ovens in the galley;
- dryers and washing machines (440V);
- high-pressure deck machines, submersible motors/pumps;
- electric motors of mechanisms that are located on the open deck.
In this way, low 440V insulation on the ship is found and eliminated.
I also recommend reading articles about low insulation 440V:
No comments:
Post a Comment