Q1 (16 Marks) Engine Construction & Components 🔥 Repeated 6x in exams
MEP • Written Exam

With reference to reciprocating air compressors explain the cause of the following faults:

(a) Collapse of discharge valve springs.

(b) Breakage of plate valves.

(c) Overheating the discharge air with an unrestricted air intake.

(d) Inoperative piston rings.

Appeared In: Oct 2025Jul 2025Jun 2022Oct 2019Aug 2019Feb 2019

✓ Verified Model Answer (Text Solution)

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Part (a)

Collapse of Discharge Valve Springs

  • Overheating or Insufficient Cooling due to Cooling water supply failure.
  • Fouling or choking of the intercooler.
  • Choked suction filters restricting airflow.
  • Excessive Deposits on the valve due to carryover of oil from the compressor.
  • Use of improper oil grades.
  • Worn-out scraper rings leading to oil ingress.
  • Oxidation of oil causing carbonaceous deposits.
  • Fatigue Failure caused by repeated stress cycles over time causing material fatigue.
  • Improper assembly of the valve after maintenance.

Part (b)

Breakage of Plate Valves

  • Incorrect assembly leads to uneven stress distribution.
  • Fatigue failure due to repeated high-pressure cycles.
  • Overheating of the valve leads to structural weakness.
  • Prolonged use causes the plate to become thin and lose strength.
  • Exposure to moisture or aggressive contaminants in the air system.
  • Accumulation of oil or carbon deposits hinders valve movement and causes mechanical failure.

Part (c)

Overheating of Discharge Air with Unrestricted Air Intake

  • Failure of the cooling water supply.
  • Fouled or choked aftercoolers reducing heat transfer efficiency.
  • Faulty cooling water pump.
  • Scale formation in cooling passages, hindering heat dissipation.
  • Aging piston rings lead to inefficient compression and heat buildup.
  • Worn-out liners increase friction and generating additional heat.
  • Incorrect or degraded oil.
  • Insufficient lubrication causes increased friction and heat generation.

Part (d)

Inoperative Piston Rings

  • Insufficient lubrication leading to metal-to-metal contact.
  • Excessive heat due to inadequate cooling.
  • Carbon deposits building up around the piston and ring grooves.
  • Use of incorrect or substandard oil.
  • Aged or worn-out liners and rings reducing efficiency.
  • Use of incorrect spare parts leading to improper fitment.
  • Excessive temperature causing the piston rings to expand and stick.
  • Carbon accumulation due to overheating or oil oxidation.
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