How to Fill Liquid in Magnetic Compass on Vessel

The magnetic compass on a vessel is a vital navigation tool that must be well-maintained to ensure accuracy. One key aspect of compass maintenance is ensuring the bowl is properly filled with liquid, usually a special compass fluid like ethyl alcohol or mineral oil. Here’s a step-by-step guide to safely refill a ship’s magnetic compass.

Tools and Materials Needed

• Compass liquid (ethyl alcohol/mineral oil as specified)
• Funnel or syringe with flexible tube
• Clean lint-free cloth
• Sealant (if needed)
• Protective gloves and eyewear

Step-by-Step Procedure

1. Inspect the Compass: Check for cracks, leaks, or cloudiness. If any damage is visible, consider replacing the bowl or unit before proceeding.
2. Locate the Filling Plug: The filling plug is usually on the side or top of the compass bowl. Carefully unscrew it.
3. Drain Residual Liquid (if necessary): If the fluid is contaminated, drain it completely before refilling.
4. Prepare the New Fluid: Use only the type recommended by the manufacturer to prevent discoloration or damage.
5. Fill Slowly: Using a funnel or syringe, slowly fill the bowl until it is completely full with no air bubbles visible.
6. Tap to Release Air: Gently tap the side of the compass to help trapped air bubbles escape.
7. Top Off: Once the bubbles are out, top off the liquid until it’s flush with the fill port.
8. Secure the Plug: Replace and tighten the filling plug. Use a small amount of sealant if necessary.
9. Clean Up: Wipe any spillage and ensure there are no leaks.
10. Test the Compass: Verify the compass card moves freely and accurately after refilling.

Maintenance Tip

Inspect the compass periodically for liquid levels and clarity. Refill immediately if levels drop due to evaporation or small leaks.

Frequently Asked Questions (FAQ)

1. Q1: What liquid is used in a magnetic compass?
   A: Typically, a specialized compass fluid such as mineral oil, alcohol-based fluid, or silicone oil is used.
2. Q2: Can I use water to fill the compass?
   A: No. Water can cause corrosion, freezing, or distortion of readings.
3. Q3: Why is my compass cloudy?
   A: Cloudiness usually indicates contamination, aging fluid, or water ingress. It should be drained and refilled.
4. Q4: How often should compass liquid be checked?
   A: At least monthly, or before each voyage during pre-departure inspections.
5. Q5: What happens if the compass is low on fluid?
   A: Low fluid can allow air bubbles, which distort readings and reduce accuracy.
6. Q6: Can I refill the compass myself?
   A: Yes, with proper tools and caution. Follow manufacturer instructions.
7. Q7: What causes compass fluid to leak?
   A: Leaks can be due to cracks, aging seals, or overfilling under temperature changes.
8. Q8: Is compass fluid toxic?
   A: Some types can be mildly toxic. Always wear gloves and follow safety guidelines.
9. Q9: Can I use silicone oil as a compass fluid?
   A: Yes, if recommended by the manufacturer. It’s stable and has a low freezing point.
10. Q10: How do I remove bubbles from the compass?
    A: Tap the bowl gently during filling, and fill slowly to prevent trapping air.
11. Q11: Does temperature affect the fluid?
    A: Yes, extreme temperatures can cause expansion or contraction. Leave space for expansion if advised.
12. Q12: Do I need to calibrate the compass after filling?
    A: Not usually, but it’s good practice to check it against a known heading or gyrocompass.

Conclusion

Proper maintenance of the magnetic compass, including timely fluid refills, ensures safe and accurate navigation. Always use manufacturer-approved fluids and follow safety procedures during refilling.