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MEO Class II: MEKG MEKM MEP MET SC&S SSEP 📊 Trends
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 of 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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Exam Ready
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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