Air Conditioning

Question 1

What are the objectives ofair conditioningon ships ?

Answer 1

1.To extract excess heat
2.To raise air temperature when required
3.To add moisture as required
4.To reduce moisture content as required
5.To maintain sufficient oxygen and air flow
6.To remove dust

Question 2

How is the correct temperature on a ship achieved

Answer 2

Comfortable temperature range is about 22°C and relative humidity (RH) about 60% (usually 40 ~ 70%)

1.Controlled by compressor suction pressure, via solenoid valve as step controlling.

2.Thermostat, placed at some accommodation space actuates the Master Solenoid Valve of theplant, which will stop the Compressor, when pre-set temperature is reached

3.Capacity unloader of compressor units, does last step controlling, as required

4.Local cabin temperature can be adjusted by volume control at delivery point of air duct controller.

Question 3

What is ventilation ?

Answer 3

It is the circulation and refreshing of the air in the space without necessarily a change oftemperature.

Question 4

What isair conditioning?

Answer 4

It is the control of temperature and humidity in a space together with the circulation, filtering andrefreshing of the air.

Question 5

What is comfort zone ?

Answer 5

It is between the 40 to 70 % relative humidity at the temperature of 20 to 29 °Cdry bulb temperature andair motion is 100mm per sec.

Question 6

What is defrosting ?

Answer 6

A method of removal of frost, built-up on evaporator coils. Defrosting should be done beforesnow thickness exceeds ¼”.

Question 7

What are the reasons for defrosting ?

Answer 7

Affecting heat transfer properties
Affecting air flow and circulation
Liquid back to compressor

Question 8

what are some defrosting methods

Answer 8

By stopping the system
By washing with warm water
By means of electric heater coil fitted at the evaporator
By hot gas defrosting method

Question 9

How would u defrostbrine system?

Answer 9

Hot brine thawing
Best and fastest method, used powerful brine heater with separatethawing system. Watertight trays under the pipes, collect the dripping water.

Hot air from atmosphere
It is important that isolating doors in air trunks are perfectly tight, soas to prevent hot air going into cargo spaces.

By shutting off brine
Allow the snows to be melted by the heat of the air incirculation .Very slow operation and tends to throw back great deal of moisture into cargo space.

Question 10

What is the purpose of ventilation for cargo hold ?

Answer 10

1.To remove surplus heat and humidity
2.To prevent the condensing of moisture on cargo or hull
3.To remove gases produced in ripening process of some fruits and vegetables cargos.

Question 11

What is relative humidity ?

Answer 11

Ratio of amount of water vapour in given volume of air, to maximum amount of water vapourthat can be present before precipitation occurs.

It is the mass of water vapour per unit volume of air compared to the mass of water vapour perunit volume of saturated air at the same temperature.

Question 12

What is saturated air ?

Answer 12

The air contains maximum weight of water vapour at the particular temperature.

Question 13

What is super heating ?

Answer 13

Keeping refrigerant at a temperature above the saturated temperature.

Question 14

what is the Cause of expansion valve chocking ?

Answer 14

When a valve is functioning correctly frost forms on the outlet side of the valve, and if the inletside does show frosting then this is a sign of blockage.
It is caused by dirt or freeze up by water present in the system.
Starving of evaporator and rapid consider pressure rise cause compressorshort cycling.

Remedy
Clean the expansion valve filter
Renew the drying agent of dehydrator or drier. (activated alumina or silica gel )

Question 15

What are the indications of leaky suction and discharge valves in refrigeration system ?

Answer 15

Leaky Suction valve
1.Continuous running of compressor
2.Insufficient cooling effects
3.Noisy operation
4.High suction pressure

Leaky Discharge valve
1.Continuous running of compressor
2.Insufficient cooling effects
3.Noisy operation
4.High suction pressure during running
5.Low discharge pressure during running
6.Suction pressure increase faster after compressor is shut down
7.Warm cylinder head

Question 16

What is High pressure (HP) cut out and low pressure (LP) cut out in refrigeration system on ships ?

Answer 16

HP cut out
Occurs due to condenser coolant failure, low coolant pressure and malfunction of considercooler valve operation.
Also can cause dirty or chocked condenser tubes.
The refrigerant can not liquefy rapidly .The discharge pressure will abnormally raise and highpressure cut out will take in action.

LP cut out
Operate the solenoid valve is closed when the cool room temperature reach its desired temperature(setting temperature)
Can cause when expansion valve is chocked by dirt or freeze up by water present in thesystem.
Starving of evaporator and rapid condenser pressure rise.
Compressor may stop by low pressure cut out.

pressure and temperature variations in a refrigeration circuit canprovide information about the operating condition of the refrigeration plant.In particular, suction and condenser pressures as well as the temperatures of suctionand discharge gases may provide important information as to the operating conditions ofthe plant. It often takes only very slight modifications of variable pressures and temperatures toproduce considerable changes in operating conditions

Question 17

list 4 reason why a compressor is failing to start and how to remedy situation

Answer 17

Causes
1.Control current circuit open
2.High-pressure cut-out
3.Low-pressure cut-out
4.Oil-pressure cut-out

Remedy
1.Pinpoint open switch and remedycause of interruption.

2.Reset pressure cut-out andinvestigate cause of highcondenser pressure.

3.Compressor cannot start beforesuction pressure has risen aboveset point for pressure cut-outrestarting.

4.Compressor starts at reset.Check oil level.

Question 18

Compressor starts and stops too often what are possible reasons and how to remedy situation

Answer 18

Causes
1.High-pressure cut-out cutsat high pressure
2.Low-pressure cut-out cuts attoo low suction pressure
3.Low-pressure cut-outdifferential is too smallbetween stopping andstarting
4.Compressor capacity toohigh
5.Filter in suction line clogged
6.Solenoid valve in liquid linedoes not close tight
7.Discharge valves oncompressor are leaky

Remedy

1.Check condenser cooling andadjust pressure cut-out to correctbreaking pressure.Replace defective pressure cut-out.

2. If low-pressure cut-out is set toohigh, adjust pressure cut-out.

3.Increase differential pressure.

4.Check operating conditions and, ifnecessary, reduce capacity.

5.Check suction filters incompressor.

6.Check direction of flow.Replace any leaky valves.

7.At compressor stop,
pressureequalizes relatively quicklybetween suction and dischargeside.Clean or change discharge valves.

Question 19

Compressor starts, but stops again immediately. what are possible reasons and how to remedy situation

Answer 19

Causes
1.Motor protection cuts
2.Low-pressure cut-out hascut
3.Defective oil-pressure cutout
4.Oil charge insufficient
5.Oil pressure failing owing toformation of foam in oil.

Remedy
1.Look for cause of overloading.If star-delta start, set starting timeat minimum.
2.Open any suction stop valve whichis closed.
3.Replace cut-out.
4.Top up with oil and investigatecause of oil shortage.
5.Reduce capacity.

Question 20

Compressor operates continuously. what are possible reasons and how to remedy situation

Answer 20

Causes
1.Thermostat or low-pressurecut-out does not cut at toolow temperature/pressure
2.Restricted supply ofrefrigerant to evaporator.Compressor working at toolow suction pressure.
3.Refrigerant chargeinsufficient.

Remedy
1.Adjust operating points.
2.Remove dirt in filters and checkfunction of expansion device asper special instructions.
3.Top up with refrigerant of correcttype.

Question 21

there is Abnormal noise from compressor what are possible reasons and how to remedy situation

Answer 21

Causes
1.Compressor capacity toohigh during start-up
2.Oil pressure too low
3.Liquid refrigerant in suctionline
4.Incorrect alignment of motorand compressor.Loose bolts in coupling
5.Worn or defective bearings
6.Too much oil circulatingthrough the plant, resultingin toolow oil level incompressor
7.Capacity regulationoscillating owing to failing oilpressure

Remedy
1.Reduce capacity.
2.See section below
3.Slugging.Adjust expansion or float valves.
4.Check alignment as per specialinstructions.Tighten with torque wrench.
5.Overhaul or replace
6.Check oil level.Solenoid valve, filter or jets in oilreturn system may be clogged.Leaky suction valve ring plates,piston rings and worn-out cylindermay also produce such oilconsumption.
7.Low oil pressure

Question 22

there is Too little capacity for compressor what are possible reasons and how to remedy situation

Answer 22

Causes
1.Insufficient oil charge
2.Iced-up evaporator
3.Defective oil pump andhence failing oil pressure
4.Defective capacityregulating system

Remedy
1.Top up with fresh oil of same typeand make.
2.Defrost evaporator; adjustdefrosting time if required.
3.Repair or replace oil pump.
4.Cause is most often failure in oilpressure or refrigerant in oil.

Question 23

explain what is meant by slugging in a compressor

Answer 23

Slugging occurs when liquid refrigerant — or liquid refrigerant and oil — enters the compressor’s cylinder during an on-cycle or run-cycle. can cause rupture of the valve ring plates and damage thebuilt-in relief devices. Furthermore, it can result in damage to theconnecting rod bearings and cylinders if the coolant degreasesthe faces and impairs the lubricating capacity of the oil.

Slugging in compressor during start-up

Causes
1.Sudden reduction inpressure across the oilsump (suction pressure)produces foaming
2.Refrigerant has condensedin suction line or crankcase.Suction line has free falltowards compressor

Remedy

1.Reduce compressor capacity orstart throttling suction stop valve.
2.Heating element in crankcaseshould be connected for 6-8 hoursbefore starting, so that refrigerantdissolved in oil can be separatedbefore starting compressor up.Start throttling suction stop valve –stop when hammering is heard.Liquid separator should bemounted in suction pipe.

Slugging in compressor during operation

Causes
1.Refrigerant gas in liquid line
2.Superheating of expansionvalve is set too low

Remedy
1.Expansion valve is oscillating.
2.Adjust superheating, which shouldnormally be 5-8°C

Question 24

Too low condenser pressure, what are possible reasons and how to remedy situation

Answer 24

Causes
1.Excessive condenser cooling
2.Defective piston rings or worncylinders
3.Discharge valves are defectiveor leaky
4.By-pass between high pressureside and suction sideof compressor
5.Compressor lacks capacity

Remedy
1.Regulate condenser cooling
2.Replace worn parts.
3.Check valve ring plates andpiston rings
4.Check compressor for internalleakage by performingpressure-drop test.
5.Check whether compressorcapacity corresponds to load onplant. Reduce condensercooling.

Question 25

Excessive condenser pressure, what are possible reasons and how to remedy situation

Answer 25

In the event of abnormally high pressures in the refrigerationsystem, there is a risk of damage to the compressor. At very highpressures, the risk of the components inthe refrigeration plant exploding can constitute a threat to life.Abnormally high pressures may occur in the case of:
Extreme heating of plant parts (fire, solar radiation or otherabnormal heating)
Volumetric expansion of fluids in sealed-off premises.

Causes
1.Overfilling with refrigerant
2.Insufficient condensercooling, e.g. if cooling waterfails, fan/cooling water pumpclogs, soiling, scaling orfouling of heat-transmittingsurfaces
3.Presence of non condensablegases(especially air) in condenser

Remedy
1.Refrigerant fills condenser andreduces its effective area.Draw-off coolant.
2.Regulate water/air supply orreduce compressor capacity, ifcalled for. Check condenser as perinstructions for same.
3.Blow air out of condenser.Follow instructions for condenser.

Question 26

Excessive suction pressure for compressor what are possible reasons and how to remedy situation

Answer 26

Causes
1.Error in setting of liquidregulation valve
2.Leaky suction valves.
3.Open by-pass between suctionside and high-pressure side ofcompressor. Safety valvesleaky, or opens prematurely.
4.Compressor lacks capacity.

Remedy
1.Liquid refrigerant in suctionline.Adjust, repair or replaceexpansion valve.
2.Remove cylinder covers; checkvalve plates. Renew if needed.
3.Check system for any by-passdetectable as for instance awarm connection.Adjust or repair leaky valves.
4.Regulate compressor capacity.Check whether all cylinders areoperating.Check function of capacityregulator.

Question 27

Too low suction pressure for compressor what are possible reasons and how to remedy situation

Answer 27

Abnormal low pressure in the refrigeration plant will increase thecompression ratio of the compressor with a subsequent risk ofdamage to the compressor. The danger of air being sucked intothe refrigeration plant also increases at abnormal low pressure.

Causes

1.Oil in evaporator
2.Refrigerant charge of plantinsufficient.Bubbles in liquid line sightglass and possibly a warmliquid line.
3.Freezing-up of expansion valve(HFC/HCFC plant)
4.Thermostatic expansion valvehas lost charge
5.Excessive superheating ofsuction gas
6.Filter in liquid line clogged
7.Solenoid valve in liquid line failsto open
8.Compressor has excessivecapacity

Remedy

1.Draw-off oil
2.Check refrigerant charge.Charge plant with refrigerant.Find and seal any leak.
3.Thaw out expansion valve withhot, wet cloths.Replace desiccant in dryingfilter.
4.Valve fails to open. Changevalve.
5.Regulate expansion valves tohigher capacity
6.Check and clean filter in liquidline
7.Coil may have blown. Controlsignal lacking.
8.Reduce compressor capacity.Check capacity regulatingsystem.

Question 28

what is the Purpose of a Marine Compressed Air Dryer

Answer 28

The main purpose of a marine compressed air dryer is to eliminate moisture from the compressed air. In a marine environment, humidity is ever-present, and when compressed air is exposed to it, it tends to become saturated with water vapour. When moisture-laden air passes through pneumatic systems and equipment, it can lead to several detrimental consequences.

Some of these include the following;

Corrosion of air tools and equipment –moisture in the compressed air can cause rust and corrosion in pneumatic components, pipes, and machinery, leading to premature failure and potential safety hazards.

Damage to electrical components –moisture can damage sensitive instruments and controls, causing malfunctions and compromising the overall safety and reliability of the vessel.

Reduced efficiency of air tools and equipment –water in the compressed air can hamper the performance of pneumatic tools and systems, leading to decreased productivity and higher operational costs.

Question 28

explain the operation of a marine compressed air dryer

Answer 28

Operation of Marine Compressed Air Dryer

The humid air flows into the air inlet connection and is pre-cooled in the heat exchanger before it enters the evaporator. As the air passes through the evaporator, which is cooled by the liquid refrigerant, the air temperature drops to 10°C, which is the dew point at which the moisture in the air is condensed. The condensed water is now separated from the air and is purged out of the system through the automatic drain trap. The high pressure liquid refrigerant now passes through the expansion valve and is evaporated in the evaporator, before returning to the compressor to continue the refrigeration cycle.

To operate a marine compressed air dryer correctly, it is important to follow the manufacturer’s instructions. To ensure the marine compressed air dryer operates efficiently and effectively do the following

Proper Installation –install the dryer in a clean, well-ventilated area away from potential sources of contamination, such as chemicals or exhaust fumes. Adequate ventilation prevents overheating and prolongs the lifespan of the dryer.

Filtration –prioritize the installation of filtration systems upstream of the dryer to remove larger particles, oil, and other contaminants that could clog the dryer and reduce its performance.

Adjust Air Pressure –normally dryer is connected to the compressed air supply line. Set the air pressure within the recommended range as per the manufacturer’s guidelines. High pressures can stress the dryer unnecessarily, while low pressures may result in insufficient drying.

Drain Moisture Regularly –most marine compressed air dryers are equipped with automatic drains. Ensure these drains are functional and regularly inspect and clean them to prevent blockages and ensure proper moisture removal.

Monitor Performance –regularly check the dryer’s output dew point and pressure levels to verify its efficiency. An increase in the dew point may indicate potential issues that need to be addressed promptly.

Question 29

State some maintenance practices to follow for a Marine Compressed Air Dryer

Answer 29

Cleaning –clean the dryer’s exterior regularly and ensure that the surrounding area is free from dust and debris that could obstruct air intake vents.

Filter Replacement –Follow the manufacturer’s guidelines for filter replacement intervals. Clogged or dirty filters can restrict airflow, leading to decreased performance and increased energy consumption.

Heat Exchanger Inspection –Regularly inspect and clean the heat exchanger to prevent a build-up of scale or debris, which can reduce the dryer’s efficiency.

Check Drains –Routinely inspect and test automatic drains to ensure they are functioning correctly and effectively removing moisture from the system.

Lubrication –If the dryer has any moving parts, ensure they are well-lubricated according to the manufacturer’s recommendations.

Question 30

what are some common problems that occur with a Marine Compressed Air Dryer

Answer 30

Insufficient Drying –if the dew point remains high despite correct settings, check for clogged filters, heat exchanger fouling, or malfunctioning drains. Clean or replace components as needed.

Excessive Pressure Drop –a significant pressure drop across the dryer can indicate clogged filters or obstructions in the air passages. Inspect and clean the filters and air pathways to restore normal pressure.

Unusual Noises or Vibrations –noises or vibrations may indicate loose components or worn-out bearings. Inspect the dryer and address any issues promptly to prevent further damage.

Leakage –check for air leaks around fittings, valves, and connections. Repair or replace damaged components to maintain the dryer’s efficiency.

If the dryer is not operating at all –it may have a problem with its electrical connections.

Question 31

with the aid of a system drawing explain the zone control system

Answer 31

This is the most popular because of its simplicity. The accommodation is divided into zones, having different heating requirements. Separate air heaters for each zone are provided at the central unit as shown in the system below.

see EOOW ORAL/ IAMI Sketch pack for system drawing

1.Filter
2.Cooler
3.One, Two, or Three zone heaters as required
4.Pre-insulated pipes delivering air to zones
5.Sound attenuating air terminal, with volume control
6.Automatic steam valves, one per zone heater
7.Steam trap, one per zone heater
8.Multi step cooling thermostat
9.Compressor
10.Automatic Capacity Control valves
11.Condenser
12.Thermostatic expansion valve
13.Sea water pump
14.Fan starter
15.Compressor starter
16.Sea water pump starter

The regulation of air temperature by individual air quantity control in this system can give rise to difficulties unless special arrangements are made. For instance, a concerted move to reduce the air volume in a number of cabins would cause increased air pressure in the ducts, with a consequent increase in the air flow and possibly in noise level at the other outlets. This can be avoided but the economic factors usually put a limit on this. Some degree of control is possible through maintaining a constant pressure at the central unit, but since most of the variation in pressure drop takes place at the ducts, the effect is very limited. A pressure sensing device some way along each branch duct, controlling a valve at the entry to the branch, strikes a reasonable mean, and is fairly widely applied. The temperature of the air leaving the heater varies in accordance with the outside temperature prevailing. This can be effectively performed by a self actuating regulator controlled by two thermostat sensors, one in the air leaving the heater, the other outside. Air quantity control in each room served gives individual refinement. In summer, air temperature is controlled by a multi step thermostat in the re-circulating air stream, which governs the automatic capacity control of the refrigerating plant.

Question 32

what is the purpose of air conditioning systems onboard ships

Answer 32

Air-conditioning systems are used to create and maintain certain temperature, relative humidity and air purity conditions in indoor spaces. This process is typically applied to maintain a level of comfort for passengers and crew. Air conditioning systems may be divided into two main classes, the central unit type in which the air is distributed to a group of spaces through ducting, and the self contained type, installed in the space it is to serve. Air-conditioning and ventilation-related conditions on ships have a considerable impact on the comfort of passengers, the well-being of the crew, and the efficient operation of equipment, systems, and installations, regardless of the type of ship.
Both temperature and humidity must be controlled in order to provide a comfortable environment. Higher temperatures are more tolerable if the air is dryer. The cooling impact on the air as it travels over the evaporator coil removes moisture, but comfort requires a certain level of humidity, thus it is required to humidify the air again by sprinkling water into the circulating air flow.

The central unit type is most widely used, in one or other of a number of alternative systems, characterized by the means provided to meet the varying requirements of each of the spaces being conditioned.

The systems in general use are as follows:
1.Zone Control System
2.Double Duct System
3.Reheat System

Question 33

with the aid of a system drawing explain the double duct system

Answer 33

In Double Duct system, two separate ducts are run from the central unit to each of the air terminals, as shown in figure below. In winter two warm air streams, of different temperatures, are carried to the air terminals, for individual mixing. The temperatures of both air streams are automatically controlled. In summer the air temperature leaving the cooler is controlled by a multi-step thermostat in the re-circulating air stream, which governs the automatic capacity control of refrigerating plant, as with the zone control. Steam is supplied to one of the heaters, so that two air streams are available at the air terminals for individual mixing.

see EOOW ORAL/ IAMI Sketch pack for system drawing

1.Filter
2.Cooler
3.Low duty heater
4.High duty heater
5.Pre-insulated pipes delivering air
6.Sound attenuating air terminal, with volume and temperature control
7.Automatic steam valve for tempered air stream
8.Automatic steam valve for warm air stream
9.Steam traps
10.Multi-step cooling thermostat
11.Compressor
12.Automatic Capacity Control valves
13.Condenser
14.Thermostatic expansion valve
15.Sea water pump
16.Fan starter
17.Compressor starter
18.Sea water pump starter1.Filter
2.Cooler
3.Low duty heater
4.High duty heater
5.Pre-insulated pipes delivering air
6.Sound attenuating air terminal, with volume and temperature control
7.Automatic steam valve for tempered air stream
8.Automatic steam valve for warm air stream
9.Steam traps
10.Multi-step cooling thermostat
11.Compressor
12.Automatic Capacity Control valves
13.Condenser
14.Thermostatic expansion valve
15.Sea water pump
16.Fan starter
17.Compressor starter
18.Sea water pump starter

Question 34

with the aid of a system drawing explain the reheat system

Answer 34

In reheat system, the air is pre heated at he central unit; its temperature is being automatically controlled. The air terminals are equipped with electric or hot water heating elements. These raise the temperature of the air to meet the demands of the room thermostats which are individually set. In summer, the air temperature is controlled by a multi step thermostat in the re-circulating air stream, which governs the automatic capacity control of the refrigerating plant. In the case of electric reheat, fire protection is provided by overheat thermostats which shut down he heaters in the event of air starvation, while a fan failure automatically cuts off the power supply.

The diagram shows a reheat system for air conditioning

1.Filter
2.Cooler
3.Pre heater
4.Pre insulated air pipe
5.Sound attenuating air terminal containing electric re-heater and overheat thermostat
6.Automatic steam valve
7.Steam trap
8.Multi step cooling thermostat
9.Compressor
10.Automatic Capacity Control valves
11.Condenser
12.Thermostatic expansion valve
13.Sea water pump
14.Fan starter
15.Compressor starter
16.Sea water pump starter
17.Heater Contractor
18.Room type thermostat

Question 35

what are the functions of an air conditioning plant

Answer 35

The air conditioning plant is designed in principle to be self-contained within the fire zones or water tight compartments and to perform the following functions:

Supply cool air to the accommodation and wheelhouse.
Provide heating to the accommodation and wheelhouse air when necessary.
Remove excess moisture from the air or humidify it to a comfortable level if necessary.
Filter the air before it passes to the accommodation and wheelhouse.

The air is supplied to the accommodation by an air handling unit (AHU), which is usually located inside accommodation block, in the air conditioning unit room.
The unit consists of an electrically driven fan drawing air through the following sections starting from inlet to the outlet:
One air filter
One steam preheating unit
One enthalpy exchanger of the rotating composite type (Econovent)
One steam reheating unit
Two air cooler evaporator coils

The exhaust section of the air handling unit comprises, from inlet to the outlet:
One return air filter
One exhaust ventilator

Question 36

what is the working principle of the air handling unit?

Answer 36

Air handling unit working principle.

Automatic control for the humidification of the air is installed in the outlet portion of the AHU and the humidistat controller is positioned in the room housing the air handling unit. The humidifier nozzles are supplied with steam from the ship’s steam system. The air is driven through the distribution trunking that supplies the living quarters and wheelhouse. Air may be drawn into the system either from outside or from the accommodation via the recirculation trunking. With heating or cooling coils in use, the unit are generally designed to operate on 70% fresh air supply. The ratio of circulation air may be varied manually using the damper in the inlet trunking. The inlet filters are of the washable mat type and preheating of the air is provided by coils supplied with steam from the ship’s steam system.

Question 37

The starting procedure of air conditioning compressor

Answer 37

The starting procedure of air conditioning compressor

All stop valves, except the compressor suction, in the refrigerant line should be opened and fully back seated to prevent the pressure in the valve reaching the valve gland.
The crankcase heater on the compressor to be used should be switched on a least 3 hours prior to starting the compressor.
Check that the crankcase oil level is correct.
Check the quantity of refrigerant charge.
Start the cooling water supply for the condenser cooling. The cooling water comes from the engine room low temperature central cooling FW system and will probably already be running.
Start the compressor.
Slowly open the suction stop valve until it is fully open. If the compressor starts making a knocking noise, close the valve immediately as this indicates that liquid refrigerant has been drawn into the machine. When the noise has stopped open the suction valve again very slowly. Repeat this operation if necessary, until the compressor runs smoothly with the suction valve fully open.

Question 38

briefly describe how are air handling units are cleaned

Answer 38

AHUs are kept clean as follows:
AHUs should be regularly cleaned internally.

Air filter material should be replaced at suitable intervals depending on dust concentration in the air.

Damper control mechanism must be lubricated at regular intervals.

Steam heating coil steam traps are to be regularly checked for correct operation.

In the cooling section, ensure that drip pans are kept clean and that drains are clear.

It is also important to note that the moisture removed from the air is collected into a drain pan inside AHU and therefore it is essential that no water should be lying in the air conditioning system as this can become a breeding ground for legionella bacteria, which can have serious, or even fatal, consequences. Drains should be kept clear and areas where water can lie should be sterilized at frequent intervals.

Question 39

what is the procedure for starting the ventilation system on a ship

Answer 39

When starting the ventilation system, the following procedure generally applies

Check that the air filters are clean.
Set the air dampers to the outside position.
Start the AHU supply fan, exhaust fan and enthalpy exchanger.
Check that air is flowing to all parts of the accommodation.