19 April 2016
The quality of air present onboard is of vital importance to both ship’s crew and its machinery systems. Most of the ship’s systems use air for operation in one or the other way. Quality of air intake by ship’s machinery systems play a major role in deciding the performance and maintenance criteria of the machine.
In this article we have provided a general overview about ten harmful effects of impure air on ship’s machinery systems:
1. Poor Ventilation Harms Machinery:
The engine room ventilation is the main consumer of intake air for all machinery systems located inside it. If the intake air is of poor quality, the performance of machinery systems can be severely affected. Special care must be taken especially in dry dock when blasting of hull is carried out. Precautions should also be taken while loading cargo with abrasive dust as ventilation fans will suck dust inside the engine room and these abrasive particles are very harmful for machinery such as turbochargers, compressors etc.
2. Reduced Compressor Performance:
Hot or contaminated intake air can impair compressor performance and result in excess labour and maintenance costs. If moisture, dust, or other contaminants are present in the intake air, such contaminants can build up on the internal components of the compressor such as valves, impellers, rotors, and vanes, leading to premature wear and reduced compressor capacity.
3. Marine Engine Air Explosion:
Excess oil in the starting air bottle will be transferred to the starting air manifold of the marine engine system, which may lead to explosion if the air start valve is leaking and which is an excellent heat source for completing the fire triangle. Read more on air line explosion here.
4. Marine Engine Improper Combustion:
If the temperature of intake air is very low or if the air contains moisture, it will lead to bad combustion and result in air pollution even when the fuel system and injection parts of the marine engine are working properly.
5. Erratic Engine Control System:
The main engine automation system comprises of engine control system with electro-pneumatic controls. The command is given from the engine control room via electronic system and later converted to pneumatic signals which locally operate the engine from support of various other parts. If the quality of control air is poor (oil, moisture, dust etc.), the response of the engine room signal will be erratic, leading to inefficient operation or even emergency situation during critical manoeuvring operation.
6. Damage the Turbocharger:
Turbocharger fitted in main and auxiliary engines take air suction from atmosphere. If basic filtration methods are not maintained or when the intake air quality is very bad, downfall in the turbocharger performance can be expected along with mechanical problems in compressor blades and choked nozzles. Moreover, if the air contains abrasive particles, it may even damage or break the turbine blades.
7. Sluggish Operation Of Control Valves:
Air is also used to operate “control valves” in various engine room systems such as boiler, jacket water, sea water system etc. If the air consists of any type of impurity, the diaphragm inside the valve will be affected, leading to stuck up and sluggish operation.
8. Failure Of Level Gauges:
Pneumatic level gauges are used in those tanks which are graded intrinsically safe. Normally a pressure transducer is used in the level measuring system which is supplied with air in the pressure range of 1 to 7 bar. Poor quality of air containing oil and dust may lead to erratic level response or complete failure in reading the actual level.
9. Failure Of Safety Systems:
Many safety systems on ships such as funnel flaps, fire dampers, quick closing valves etc. are air operated. If the quality of air operating these system/ equipment is poor, the use of such equipment in emergency may lead to deteriorated operational condition or stuck up of the equipment which can be extremely dangerous in the emergency situation.
10. Improper Firing Operation In Boiler:
Boiler in the ship’s engine room provides steam – an essential aspect of machinery operations on board. During boiler operation, control air is used to provide signals. If the air used for this operation is impure, the firing operation of the burner would be severely affected, causing black smoke and reduced in performance of the boiler.
Seafarers working on ships must take necessary precautions to ensure that the quality of air supplied to all machinery systems on board is clean and devoid of impurities.