MARINE AUXILIARIES

• Put in slide show mode to play the gif

• The pressure relief valve is used in the auto air- conditioning compressor to prevent unusual pressure build-up within a system by opening it's valve when the internal fluid pressure starts to exceed the preset pressure level and close it's valve when the internal pressure decrease to the preset pressure level.



A thermal expansion valve or thermostatic expansion valve (often abbreviated as TEV, TXV, or TX valve) is a component in refrigeration and air conditioning systems that controls the amount of refrigerant released into the evaporator and is intended to regulate the superheat of the vapor leaving the evaporator. Although often described as a \"thermostatic\" valve, an expansion valve does not regulate temperature, the temperature of the evaporator will vary with the evaporation pressure. components of TEV

The flexible diaphragm actuates the poppet valve, an increasing pressure in the sensing bulb will press down on the poppet and open the valve further. There is also an adjustable spring providing a closing force on the valve which controls the superheat.

how TEV works in GIF animation

The sensing bulb is positioned near the end of the evaporator and ensures enough refrigerant flows to chill the whole evaporator, but not so much that liquid reaches the sensing position. The equalisation connection is needed when the pressure at the sensing position differs from the pressure at the valve output.



• Check oil level in the compressor’s sight glass • Check all gauges on compressor and condenser are working properly • Open air purge plug in front and rear covers of condenser water side to prevent water hammering • Ensure that the condenser cooling water valves-inlet and outlet, are fully open • Open the suction valve of the compressor till half way and fully open the discharge valve • The crankcase heater on the compressor to be started at least 6 hours before the operation

• Fully open the refrigeration inlet and outlet valves for condenser • Fully open the liquid outlet valve • Fully open the stop valve before and after the back pressure regulating valve provided in the vegetable room • Fully open the stop valve for the suction side of other rooms • Start the cooling water pump for condenser and purge the air from it • Check if the settings of HP and LP cut-outs are proper and then start the compressor • Gradually open the suction valve fully while checking the suction pressure, taking care that liquid doesn't flow into the compressor • Switch on the ozone generator in the rooms where fitted • If any knocking noise is heard from the crankcase or excessive foaming of oil is detected, immediately throttle the suction valve • Increase the capacity gradually before allowing the next level, so that the compressor is adjusted to new conditions • Check the oil return pipe from the oil separator is warm “Check the temperature of oil return piping between oil separator and compressor. If it is slightly hot than the ambient temperature, plant is in normal operation.”

• Stop the liquid outlet valve for the condenser • The refrigerant will get collected in the condenser and the compressor will trip on low pressure switch • Push the stop button of the compressor and shut the outlet and inlet valve to the compressor • Stop the cooling water pump to the condenser and shut the inlet and outlet valves for water • Fully close the inlet and outlet valves to the drier • Trip the breaker for the compressor

1. Soap Bubble Detection • This test is rather simple to carry out. All you need to do is mix up some soap with warm water. Then, you’ll need to mix this solution for several minutes. • After it has been stirred up enough, send it through your AC refrigerant system. If there are leaks in your system, air bubbles will be visible. You can then mark these areas so that an HVAC technician knows precisely where patches are required.

2. Nitrogen Detection • First, the remaining freon in your system will need to be removed. Then, nitrogen is pumped back into your home AC system. Since nitrogen is held at a higher pressure than refrigerant, it will make audible noises where leaks are present. • Then, all that’s required is listening for these audible sounds and then marking these areas off. You’ll also know if leaks are present if you monitor the nitrogen using pressure gauges. If these gauges show significant changes in pressure, you know a leak is present. 3. Oil Detection • wear protective gloves when performing this step, so you don’t get your hands dirty or cut them on a sharp part • Feel around different components and keep checking your gloves for visible signs of oil. If an area produces a lot, chances are there is a leak that needs to be repaired right away. If you don’t have protective gloves, you can also use cloth. Make sure it’s light colored, so if oil is present, it will be visible.

While in operation, the refrigerant used in the refer plant gets consumed or is reduced in quantity because of leakage in the system. Reduction in quantity of refrigerant may lead to troubles in the plant such as- • Short Cycling of Compressor • Too low suction pressure • Difficult to maintain temperature of rooms and holds • Reduction in the efficiency of the plant When the above mentioned problems occur, it indicates that the plant has to be charged with the refrigerant. There are two methods for charging reefer plants: Liquid charging and Gas charging. Now a day’s gas charging is preferred over liquid charging because it is more safe and simple.

Gas Charging of Refrigeration Plant: For gas charging, a special T piece valve block with mounted pressure gauge is provided to combine three connectors inter-connecting: -Vacuum pump -Charging Cylinder -Charging Point

Following steps are to be taken for charging gas into the reefer plant: 1. Connect gas bottle or charging cylinder, vacuum pump and charging point in the reefer system to the valve block. 2. The discharge of the vacuum pump is to be connected in the empty recovery bottle 3. First open the valve between vacuum pump and charging bottle located in the valve block without opening the main valve of the charging cylinder. This will remove all the air inside the pipe. Once vacuum is reached, close the valve of charge cylinder in the valve block 4. Now open the valve of the charging point pipe in the valve block and run the vacuum pump until the vacuum is reached. This will remove the trapped air from this pipe. Then shut the valve in the valve block 5. Now keep the system idle for 5 minutes to check there is no pressure drop. This will ensure there are no leakages in the system

6. Now open charging bottle pipe valve and the charging point pipe valve located in the valve block. This will set the line for charging. Ensure that the vacuum pump valve is shut 7. Now open the main valves in the charging cylinder and charging point of the reefer system 8. Do not overfill the system. Make sure the receiver has 5 % space for expansion Ensure that no refrigerant is leaked out in the environment as these effects the ozone layer in the atmosphere. Note* :Gas bottle is kept on weighing scale for measuring the amount of charged supplied to the system.

When air enters a refrigeration system, it collects in the top of the condenser and is trapped. Air is a noncondensable and thus, it cannot be condensed like refrigerant vapors. The liquid seal — subcooled liquid at the condenser bottom — will prevent air from leaving the condenser. Air will cause a reduction in condenser surface area, which will cause a high condensing pressure. Air can enter the refrigeration system through a leak in the low side of the refrigeration system. Refrigerant leaks will eventually lead to an undercharged system. Severely undercharged systems can run vacuums on the low side of the system. These vacuums will pull in air from the atmosphere because the low-side (suction) pressure is lower than the atmospheric pressure. There is no way for a noncondensable like air to get to the receiver if there is a liquid seal at the condenser’s bottom. The old way to rid air from the top of the condenser was to slowly purge it from the compressor’s discharge service valve, if one existed or on the purging valve at the condensor. This was done with the machine off and soaked to ambient temperatures.



Brine is a common fluid used in large refrigeration installations for the transport of heat from place to place. It is used because the addition of salt to water lowers the freezing temperature of the solution and the heat transport efficiency can be greatly enhanced for the comparatively low cost of the material. At a concentration of 23.3%, the freezing point of NaCl brine is lowered to -21°C (252.15 K, -6°F)[citation needed], and that of CaCl2 brine down to -40°C (233.15 K, -40°F):69

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Obviously, water has its limitations for lower temperature work due to its freezing, but this disadvantage can be overcome by adding a salt to form a brine. In general brines can be divided into four classes: 1. Brines with a salt base, commonly being water solutions of calcium or sodium chloride. 2. Brines with a glycol base, commonly water solutions of ethylene or propylene glycol. 3. Brines for low temperature heat transfer being pure substances, such as methylene chloride, trichloroethylene, Rll, acetone, methyl or ethyl alcohol. 4. Brines for special or unusual applications due to availability, extreme temperature range, experimental usage, etc. Typical examples are a petroleum product, synthetic oil, a silicone fluid, or sugar brine. The freezing point will obviously depend on the amount of salt in the water (i.e. proportion or concentration of the salt or material in the water. Each mixture has a concentration at which the freezing is a minimum. This concentration is the Eutectic Concentration. The minimum freezing point is the Eutectic Temperature and the point in the Temp/Conc. diagram is the Eutectic point. However, it is desirable to keep the brine slightly alkaline, with pH between 8·0 and 8·5. If found to be acid (e.g. litmus test papers), caustic soda should be added.



6D5ME - UniKL MIMET In this system, the refrigerant after the expansion valve passes into a brine circulator evaporator extracting heat from the brine. This brine is then circulated through the piping grid of the chamber. The heat from the chamber is extracted by the brine and returned to the evaporator. Circuits run in parallel, each with its own control valve for regulating the brine flow. Brine is calcium chloride in water.





• Refrigeration is needed on board a cargo ship for storing of food provisions. Food provisions are stored in cold rooms. The cold rooms are demarcated for various temperatures. • The rooms for storing meat, and fish are set at minus 25 degree C, while those used for vegetables are set at 10 degree C. When the proper temperatures are maintained, the food can last very long. • This is required if the ship were to travel for long voyages lasting several months. The lack of fresh food it can be demoralizing for the seamen at sea. It is the Chief Engineer's job to make sure that the refrigeration system works well all the time.

6D9ME - UniKL MIMET • The materials having extremely low thermal conductivities are called insulating materials. • Desired properties of an ideal insulating material – Thermal conductivity – Permanence – Strength – Water-repellent – Fire-proof – Light weight – Odorless – Low-cost

Classification of insulating materials: • Flake insulation DME - UniKL MIMET 70

7D1ME - UniKL MIMET Classification of insulating materials: • Fibrous insulation – Organic or inorganic and may or may not be bonded. – Glass or Rockwool are the most common materials

7D2ME - UniKL MIMET Classification of insulating materials: • Granular insulation – Composed of small nodules that contain voids

7D3ME - UniKL MIMET Classification of insulating materials: • Cellular insulation – Composed of small individual cells produced from glass, rubber or plastic

7D4ME - UniKL MIMET Classification of insulating materials: • Reflective insulation – Composed of parallel thin sheets of foil having high thermal reflectance

Students activity : 1. Move into several group. 2. Each group need to find and discuss on below question : What are the most Common Problems Found in Ship’s Refrigeration System? Each group will only choose 1 question. The answers must consist of problem and solution. It will be present during class session.

Topic 3 : Aircond and Ventilation System LMD 25603 Marine Auxilliaries Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2020

Air Conditioning System• Ships travel the world and are therefore subject to various climatic conditions. • The crew of the ship must be provided with reasonable conditions in their work place regardless of the weather. • Temperature alone is not a sufficient measure of conditions acceptable to the human body. • Relative humidity in conjunction with temperature more truly determines the environment for human comfort.

cont' • The Maintenance of controlled atmosphere according to the requirements in a space is known as “Air conditioning’’. The controlled atmosphere which gives maximum comfort to the human beings is known as comfort air conditioning. • The controlled atmosphere which is required for the manufacturing process is known as industrial air conditioning. • Comfort air conditioning is further subdivided into summer air conditioning and winter air conditioning. The air cooling and dehumidification used in summer is known as summer air conditioning and heating and humidification used in winter is known as winter air conditioning.

What is air conditioning ? Typical Aircond system onboard ship • It is the control of temperature and humidity in a space together with the circulation, filtering and refreshing of the air. What are the objectives of air conditioning on ships ? • To extract excess heat • To raise air temperature when required • To add moisture as required • To reduce moisture content as required • To maintain sufficient oxygen and air flow • To remove dust *Comfortable temperature range is about 22 °C and relative humidity (RH) about 60% (usually 40 ~ 70%) Relative Humidity It is the ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure.

WHAT IS HUMIDITY? Humidity is a measure of the amount of water vapor in the air. Relative humidity measures the amount of water in the air in relation to the maximum amount of water vapor (moisture). The higher the temperature, the more water vapor the air can hold. Relative humidity is what your morning weather reporter would refer to. Humidity is a natural part of our atmosphere, it comes from the amount of water vapor in the air. Water vapor enters the atmosphere by evaporating from the large bodies of water on the Earth’s surface including lakes, oceans, and seas. It is an integral part of the water cycle, as water vapor is continuously generated by evaporation and removed by condensation. When the temperature is higher, the air can hold more water vapor, meaning that the warmer the climate, the higher the humidity level can be. For example, a densely saturated amount of air may contain 0.9oz of water per cubic meter at 86F, but only 0.2oz of water per cubic metre of air at 46°F3.



A picture of a hygrometer. There are actually two hygrometers aboard, one is located on each side of the bridge.

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Topic 4 : Heat Exchangers Malaysian Institute of Marine Engineering Technology (MIMET) Marine Auxiliaries / WAS / Jan 2020

Heat exchanger is an equipment which reduces the temperature of a medium by transferring temperature of that medium to another, when both the mediums are separated by a solid membrane or wall like structure. Exchanging of heat in a heat exchanger can be in between- liquid and liquid, gas and liquid, liquid and gas etc. For heat transfer basically three patterns of flow are used for construction of a heat exchanger.

1. A counter flow or countercurrent shell and tube heat exchanger’s construction is in many ways identical to that of a parallel flow shell and tube heat exchanger. The main difference is that the tubeside fluid enters the exchanger at the opposite end of the shellside fluid. This results in the two fluids running against each other rather than in the same direction. 2. A parallel flow pattern, also referred to as a cocurrent flow, is one in which the shellside and tubeside fluids flow in the same direction. This is widely seen in double-pipe heat exchangers and can be replicated in shell and tube heat exchangers as well

3. A crossflow heat exchanger is designed so that the two fluids flow perpendicular to one another. This is typically utilized when one fluid is a liquid and the other is a gas, as in a car radiator in which hot water flowing left and right is cooled by air moving up or down, Bright Hub Engineering explained. Crossflow exchangers are also common in steam condensers, in which a liquid transforms into a gas by the end of the process.

By having the two liquids pass on either side of a conducting surface. e.g Inside the tube and outside the tube. 1. The heat from the hot liquid passes to the cold liquid through the conducting surface, i.e. the tube wall, is at a temperature between the two. 2. The two liquids flowing in opposite directions, i.e. counter flow or contra flow. This arrangement provides a fairly constant temperature difference between the two liquids and therefore the maximum heat transfer for the available conducting surface area. example of plate type heat exchangers

Conduction, convention and radiation heat transferring process

There are divided into two groups :- 1. Shell and tube type 2. Plate type.

 In the shell and tube design,a tube bundle or stack is fitted into a shell (Figure 7.4).  The end plates are sealed at either end of the shell and provision is made at one end for expansion.  The tubes are sealed into the tube plate at either end and provide a passageway for the cooling liquid.  Headers or water boxes surround the tube plates and enclose the shell.