Q3 (16 Marks) Auxiliary Systems
MEP • Written Exam

Your ship is due for Drydocking. Prepare repair specifications for the following:

(a) Main Engine cooling sea water Overboard valve

(b) Aft winch hydraulic oil pressure line, holed at deck penetration in Steering Compartment

(c) Deck seal of a IG system used in an oil tanker

Appeared In: Jan 2023

✓ Verified Model Answer (Text Solution)

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REPAIR SPECIFICATIONS FOR DRYDOCKING

Part (a)

Main Engine cooling sea water overboard valve

  • The overboard (sea water) valve is to be overhauled/ repaired. The specification should state:
  • The valve is to be dismantled, the valve and seat inspected for corrosion, pitting, wastage and damage.
  • The valve seat and disc are to be re-faced/ re-ground or renewed as required to give a tight shut-off.
  • The valve spindle/ gland packing is to be renewed; the gland is to be repacked.
  • The valve body is to be inspected for corrosion/ wastage (ultrasonic thickness check) and repaired/ renewed if below the safe thickness.
  • The valve is to be pressure-tested (to the working pressure) after repair to confirm a tight shut-off.
  • The valve is to be re-fitted with new gaskets/ bolts and the flange joint made good.
  • The valve is to be surveyed/ approved by the Class surveyor as required.
Part (b)

Aft winch hydraulic oil pressure line, holed at deck penetration in Steering Compartment

  • The hydraulic oil pressure line is to be repaired. The specification should state:
  • The holed section of the hydraulic line at the deck penetration is to be cut out and renewed with new pipe of the same material/ size/ rating.
  • The new pipe is to be welded/ flanged to the existing line with proper joints.
  • The deck penetration/ gland is to be inspected and made good (renew the gland/ seal) to prevent water ingress and to support the pipe.
  • The hydraulic line is to be pressure-tested (to the system working pressure) after repair to confirm no leaks.
  • The hydraulic system is to be bled/ purged and the winch tested for correct operation.
  • The repair is to be carried out to the maker's/ Class requirements.
Part (c)

Deck seal of an IG (Inert Gas) system used in an oil tanker

  • The deck seal (the water seal/ P.V. breaker of the inert gas system) is to be repaired. The specification should state:
  • The deck seal is to be inspected for corrosion, wastage, cracking and damage.
  • The seal is to be cleaned and the water seal/ P.V. breaker internals inspected.
  • Worn/ damaged parts (the seal plates, the water level control, the non-return/ flame screen) are to be renewed.
  • The seal is to be pressure-tested/ leak-tested to confirm it maintains the inert gas seal.
  • The deck seal is to be re-commissioned and the inert gas system tested for correct operation (maintaining the inert gas pressure/ seal).
  • The repair is to be carried out to the maker's/ Class requirements and surveyed as required.
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