During my time at sea, I have found that Refrigeration is one of the least well understood systems on board ship. Generally Refrigeration Plants are ignored until they break down and then everyone panics. So I thought that I would try pass on some of the hard learnt knowledge I have acquired over 45 years at Sea.
I am starting with a brief Historical overview, and some personal experiences. Later I plan to write a simple talk through a system, followed by a more detailed talk through the system, and some trouble shooting tips.
Firstly, the word itself, Refrigeration comes from the Latin words frigerare meaning cold and Re denoting a change of state. (Initially I wrongly assumed that it had something to do with the German word “Gerat” meaning equipment, apparatus or machinery.)https://en.wikipedia.org/wiki/Refrigeratio
From early times ice was collected from Frozen Lakes and stored in Ice Houses to make cool drinks etc in the summer. https://en.wikipedia.org/wiki/Ice_house_(building
In the 19th Century, entrepreneurs developed a way of shipping ice in sailing ships from New England to hotter Countries where people were willing to pay dearly for a cold drink. They made this possible by insulating the ships Holds with straw and sawdust.
This technique was also used during the Second World War to import frozen produce across the Atlantic to England, when English Agriculture was converted to Arable farming to reduce the volume of food imports required to feed the population, freeing Merchants ships to carry war Material.www.history.com/news/the-man-who-shippe ... -the-world
Following on from this, the first mechanical refrigeration plants were developed.
In 1834, the first working vapor-compression refrigeration system was built. The first commercial ice-making machine was invented in 1854. In 1913, refrigerators for home use were invented. In 1923 Frigidaire introduced the first self-contained unit.
Later the first refrigerated cargo ships were developed.
Reefer ship - Wikipediahttps://en.wikipedia.org/wiki/Reefer_ship
The first attempt to ship refrigerated meat was made when the Northam sailed from Australia to the UK in 1876. The refrigeration machinery broke down en route and the cargo was lost. In 1877, the steamers Frigorifique and Paraguay carried frozen mutton from Argentina to France, proving the concept of refrigerated ships, ...
History of ship refrigeration • United Fruit Company ... • Types of reefers
Dunedin (ship) - Wikipediahttps://en.wikipedia.org/wiki/Dunedin_(ship
The Dunedin (1876–82) was the first ship to successfully transport a full cargo of refrigerated meat from New Zealand to England. In this capacity, it provided the impetus to develop the capacity of New Zealand as a major provider of agricultural exports.
Early refrigeration plants used water vapour, Ammonia or CO2 as Refrigerant Gases.
When I was a Cadet I sailed with a Second Engineer who had sailed with a water vapour air conditioning system.
There were problems with water not being very efficient, so it was replaced with Ammonia which was extremely corrosive and Toxic and several people died at Sea because of this, especially when people mistakenly used Brass or Copper fittings in Ammonia systems which rapidly corroded through and failed, releasing the Gas. In turn Ammonia was replaced with CO2 which, although asphyxiating was not actually poisonous, and was not corrosive, it was also cheap and widely available. However, its big drawback was the High Pressure needed to condense it.
Many different refrigerants have been used over the years, some extremely harmful to people, some harmful to the Ozone Layer and others powerful contributors to Global warming.https://en.wikipedia.org/wiki/List_of_refrigerants
On refrigerated ships built during the 1950’s, on which I sailed as a Cadet and Junior Engineer, (Particularly S.S. Patonga, which was my first ship as a Cadet and as a Junior Engineer, later renamed S.S.Strathlauderhttps://www.google.co.uk/search?tbm=isc ... =927&dpr=1
and the Strathleven, previously the Middlesex and Jelunga which I sailed on as a Junior Engineer.https://www.google.co.uk/search?q=MV+Je ... _SIaG0VwLM
The compressors, condensers and associated pipe work were rated for a working pressure of 1,360 psi (about 90 bar), which obviously meant that they were massively built, heavy and expensive. The compressors also required a lot of power to drive them. I can remember 3 big compressors each with two horizontal cylinders thundering away in the Refrigeration Flat, each driven by Large 220 Volt Variable Speed DC Motors.
The Hot, High pressure gas was cooled by Sea Water in the condensers and then the cool liquid CO2, at the same pressure, went through an expansion valve into an evaporator where it was heated up by Calcium Chloride Brine, turning it back into low pressure Superheated Gas to return to the compressor suction.
There was a system of mixing the brine so that it could be circulated at various Temperatures and the valves were colour coded “Blue Brine” was the coldest used to cool Deep Frozen Cargo Holds, Lockers and Domestic Stores, “Yellow Brine” was warmer and used to cool Chilled Cargo Holds, lockers and Veg. Rooms etc. The “Red Brine” was Steam Heated and used for defrosting when required. The “Blue” valves to and from the space were shut and the “Red” valves opened until all the ice was melted and then they were shut off and the Blue Valves re opened. There were other colour codes but I can’t remember what they were used for now. The Brine pumps were all driven by variable speed DC motors, so the pumping rates could be adjusted to suite the cooling load on the circuit.
Some Compartments were cooled by having a grid of steel pipes running all over the Bulkheads and Deck heads which had cold Brine circulating through them. I remember that one of my first jobs as a Cadet was slacking off the leaking screwed pipe couplings on the deck head, cleaning off the old sealant, wrapping the screw threads with Sail Makers Twine coated in a mixture of Red Lead Paint and Tallow (to keep it flexible) and retightened the couplings, all the time with the Brine dripping into my eyes, (not a pair of safety goggles in sight!).
Other spaces had Fan Batteries, where the cold Brine passed through something similar to the cooling units seen in modern refrigerated store rooms, but on a larger scale and a variable speed DC fan blew the air through to cool it.,
The CO2 came in large cylinders which were manhandled into a water tank, connected up to a Copper pipe leading to the compressor suction, and the cylinder valve and system valves opened so that Gas flowed from the cylinder into the compressor, as the Gas Pressure dropped, Liquid CO2 in the cylinder started to evaporate, cooling the cylinder and reducing the pressure in it, which was when the steam heating was cracked on to a heating coil in the water tank to make sure all the refrigerant was turned into Gas and sucked out of the cylinder.
The Brine could be circulated through the Brine Mixing Tank, an open steel tank, in the Brine room, where all the Brine Valves and the Brine pumps were. When the system level became low, it was topped up with water, and large sacks of Calcium Chloride were tipped into it and mixed well until the Specific Gravity was correct according to the Hydrometer, which was calibrated according to the Freezing point of the solution. Put too much Chloride in and you were throwing away money, when it eventually leaked out, too little and the Brine would freeze in the evaporators!. The contents of the Brine mixing tank were then pumped into the Brine circuit until excess Brine overflowed from the Brine Header/ expansion tank back into the mixing tank. We used to use hydrometers calibrated in the Twaddel scale.https://en.wikipedia.org/wiki/Twaddell_scale
While sailing on the Middlesex/Jelunga/Strathleven https://www.balticshipping.com/vessel/imo/5234371
there were 4 Junior Engineers, 3 watch keeping and one on Day work but no Refrigeration Engineer, because she was by this time only partly refrigerated. We were running between the Persian Gulf, Pakistan, India Sri Lanka, Malaysia, Singapore, and about 6 Ports in New Zealand and Australia. When we reached the Gulf the Senior Junior decided that because of the High Sea Temperatures we would have to increase the Gas pressure in order to make it condense and told the rest of us to shut in the compressor Gas discharge valve which we did. Which was a mistake, but he was an authoritive personality and appeared to know what he was talking about, so the rest of us failed to challenge his idea. However, throttling the gas outlet from the compressor raised the pressure in the compressor, reducing its volumetric efficiency, (and hence the mass flow) increasing the power required to drive it, and raising the Gas temperature. After the Gas had been throttled by the discharge valve the gas pressure dropped to the pressure required to make the Gas condense at Sea Temperature, while the turbulent expansion through the valve would have converted the energy released by the pressure drop into heat energy, so overall it was a very bad idea. But in those days I did not have the level of understanding of refrigeration to understand this, or the confidence to challenge other Engineers, I just accepted it, but it was a very bad idea. For anyone who doesn’t understand, the Gas flows into the condenser and the lower the condenser temperature the lower the pressure required condensing the Gas, this is automatically self regulating.
These were replaced by Halons, such as Freon 11, 12 and 22 which operated at much lower pressures. For instance Refrigerant / Freon 11 was a liquid at room temperature, and came in drums. When the Liquid level in the condenser was low, you unscrewed the filling cap on the condenser, put a funnel in the hole and poured in some Liquid Refrigerant out of the drum! Because it changed phase between liquid and Gas at Atmospheric Pressure within the normal range of atmospheric Temperatures, it was an ideal Gas for Air Conditioning systems, which could operate almost at Atmospheric Pressure and the compressors could be similar in design to a Turbocharger, making the systems cheap, light, compact and very efficient. Unfortunately Refrigerant 11 was the most Ozone depleting Refrigerant in use and was the first to be banned. The only time I came across it was sailing as Second Engineer on the Eurosun/Orient Express, where it chilled water which was supplied to air handling units distributed about the Passenger Accommodation. http://hhvferry.com/blog/?tag=eurosun
One of the York Turbo Compressors blew up while I was onboard, apparently this was a regularly recurring event, at one time one of the Sea Water tubes in the condenser had failed, flooding the Gas side of the condenser with Sea water which had caused corrosion inside the condenser and every so often lumps of rust got into the Lubricating oil system and caused the turbo compressor to fail. We had some excellent service engineers who came out and stripped the compressor down, replaced the bearings and compressor wheel, and they revealed that they had suggested several times that the owners have the condenser Chemically cleaned to remove all traces of rust and permanently solve the problem, but they always refused to pay the extra cost, preferring to rebuild the turbo compressors every 6 months.....http://www.hevac-heritage.org/electroni ... ifugal.pdf
Refrigerant / Freon 22 was widely used for small air conditioning and some refrigeration plants but could not achieve temperatures as low as Freon 12 which in my experience was probably the most commonly used for Domestic Refrigeration on ships. When Freon 12 was banned, many Freon 12 plants were converted to run on Freon 22.
These last 2 refrigerant gases could both be used in Direct Expansion systems, (DX) where liquid Refrigerant was expanded and turned to Gas in the compartment it was cooling, or in “Indirect Expansion” systems where the refrigerant cooled a secondary refrigerant, such as Brine, which in turn cooled the refrigerated space. This was possible because the Gas pressure was so much lower than CO2 that the cost of the pipe work was no longer prohibitive, however, the much greater length of gas filled pipe work, in a DX system tended to mean more leaks and a higher Gas consumption, but this was offset by having a much cheaper and simpler system to build, operate and maintain.
For instance the Floristan, (later the Strathalvie) which I sailed on for my second trip as a Cadet, had DX refrigerated lockers aft.http://www.ships-photos.net/picture/sho ... -Floristan
As did the Strathmeigle, previously the Merkara, which I sailed on as a Junior Engineer.http://www.shipsnostalgia.com/gallery/s ... ra/cat/511
While the Piako, Taupo and Westmorland which I also sailed on as a Junior Engineer, in the 1970’s all used Brine.https://www.google.co.uk/search?biw=952 ... i8#imgrc=_https://www.google.co.uk/search?biw=952 ... ipDBfBTe_Ehttps://www.google.co.uk/search?biw=952 ... gKh1knH2bA
Much later, (this century) I sailed as Chief Engineer on the Cala Piana, which was a refrigerated Cargo ship that used a DX,F22 system to cool the cargo holds. The system worked well but the Supers had the Chiefs so terrified of using F22 that they were running the system with only tiny amounts of Gas in the system. (By then Western Countries had banned the manufacture of F22 and it was only possible to buy increasingly expensive recycled Gas) However, they still make vast quantities of the Gas in China and if your ship goes there you can stock up really cheaply). This meant that more compressors were working inefficiently to hold the temperatures down, (we were carrying Bananas and supposed to be keeping the temperatures at 13.3C +/- 0.5C.)
When I joined, they were just finishing discharging a Reefer cargo, in Korea, before we got to the loading Port, (Davao in the Philippines) I started the Reefer plant to cool down the holds and found it struggling, and added a lot of Gas, which improved the performance and reported that to the Superintendant. The system had 3 condensers mounted under the Deck head of the Engine room with the liquid flowing out of them towards the sub cooler, with a “T” off to what should have been a liquid reservoir, and after the sub cooler the liquid went to the manifold supplying the various holds.( See drawing in sub cooling link) When the system was running there was never any Liquid refrigerant visible in the reservoir. As I understood it, the hot gas flowed into the condenser where it was cooled by Sea Water, the pressure in the entire system from the compressor discharge to the expansion valves was the same and determined by the temperature of the liquid Refrigerant in the condenser. So any refrigerant at a lower temperature than the condenser would be liquid and any at a higher temperature would be Gas. The reservoir was not insulated and was standing in the Engine Room so the temperature of the refrigerant inside was always equal to the E.R, air temperature, much hotter than the condenser, so the sight glass on it would always show empty because all the contents would be gas. For the vessel to act as a liquid reservoir it would have had to have a gas return pipe fitted from the top of the reservoir to the top of the condenser. Then, liquid refrigerant would have flowed into the reservoir, displacing vapour into the condenser. Some of the liquid in the reservoir would have been continually boiling off in order to maintain the temperature of the reservoir at the same Ts as the condenser, but the liquid in the condensers and reservoir would have “found their own level” i.e. gravitated level, which would have meant the condensers would have operated with a “Dry Bottom” increasing the tube area condensing the Gas, but reducing the under cooling. The Superintendant came back with a response from the previous Chief saying that there was plenty of Gas in the system when he left and that once the refrigeration plant had been shut down and the S.W. cooling left on the condenser for a few days the Liquid reservoir would fill up!!! In my opinion this was impossible and later experience on board showed that I was right. So long as the Condenser pumps were running there was never any liquid in the reservoir, however, once the pumps were stopped the condensers warmed up to the same temperature as the reservoir and the pressure increased, pushing liquid into the reservoir, compressing the Gas above it, the liquid disappeared again when the pumps were started, the condenser cooled and its pressure dropped while the gas in the reservoir expanded pushing the liquid back up into the condensers.
After thinking about the system for some time, I concluded that if it had been intended to run the system with the condensers “Dry” with all the liquid stored in the reservoir, because if it was intended to run with the liquid stored in the condensers that would provide under cooling and it would not be necessary to fit a separate sub-cooler in the line to the evaporators.https://www.guentner.asia/fileadmin/sit ... ncy_EN.pdfhttps://www.swep.net/refrigerant-handbo ... sers/asd4/
On this ship the undercooler/subcooler took some of the liquid refrigerant and evaporated it to cool the rest and returned the gas produced to the compressor suction.
Therefore there should have been a vapour return line between the top of the reservoir and the condensers, and all the liquid pipe work after the condensers should have been insulated to prevent the liquid warming up and evaporating, however it wasn’t. It appeared to be a typical case of the shipyard modifying the plant designer’s plans to reduce their costs.https://www.google.co.uk/search?biw=952 ... Z1X-hKWIzQ
I also sailed as Chief on the Amazonas and Talca which both used F22 systems.
One of them had a DX system and the delivery and return manifolds were in the Engine Room. Over many years the crew had been operating the isolating valves using wheel keys and as a result 2 problems had been caused:
1) All the valves had been over tightened, this had caused a plastic “skirt” fitted on the valve lids to ensure a perfect gas tight seal with only a small closing force had been destroyed, so none of the valves could be made gas tight
2) If a valve is operated manually, with one hand pulling and the other pushing, there is a balanced torque applied to the spindle, if a wheel key is used, all the force is applied in the same direction and in the same place, this puts a bending moment on the valve spindle, which had caused a slight bend in all the valve spindles, this in turn had worn the valve glands so that there was a very slight gas leak from every valve gland. Unfortunately it was impossible to tighten or repack the glands.
I discovered this when the 4th Engineer carried out a routine Gas Leak Test and found a leak on one of the valve, seeing a Hexagon on the top of the valve lid he assumed that this was to tighten a gland and attacked it with a hammer and spanner (wrench) unfortunately the hex was part of the casting andused to tighten the valve bonnet into the valve body, he put so much compression on the Teflon gasket between the two halves of the valve that it blew out, when I desperately tried to close all the valves to limit the gas loss I found that none of the valves were gas tight and that the only way to stop the leak was to unscrew the valve bonnet, machine a new Teflon gasket and re assemble it, it was a very expensive accident.
The only long term solution would have been to pump down the entire system, replace every valve and recharge the system, which was not going to happen!http://www.shipspotting.com/gallery/pho ... id=1299566https://www.fleetmon.com/vessels/baltic ... anguage=en
(I must say that I sailed on her after she had been released by the Pirates)
When I was Chief on the Dilmun Tern an Old Tanker trading around the Caribbean,http://www.shipspotting.com/gallery/pho ... id=1498939
we struggled with the refrigeration plant. There were 2 air cooled units in the steering flat, and they were struggling in the high temperatures, someone had put a hole in the escape hatch from the steering flat and fitted a fan inside an old 20 litre oil drum into it, to blow extra air into the compartment. This was not a good idea as it made it impossible to open the Emergency Exit hatch! I removed all the covers from the condensers and got the Motorman to carefully clean all the cooling fins with a paintbrush and Electrical cleaner. The result was that instead of the compressor continually tripping out on high pressure, the pressure became too low to push enough refrigerant through the expansion valves. The condensers were fitted with air dampers to restrict the air flow in cold temperatures and we had to close them to raise the condenser pressure to the correct level!. I also found that the “standby compressor must have been tripping out on high pressure and someone had hammered the gas pipe to the pressure switch flat to stop it cutting out!! That had worked until it had blown out the head gasket and there was no spare gasket onboard and the only gasket material on board was unsuitable, and we had no pipe onboard to replace the destroyed one.
When I was Chief on the Acina, an OBO, I joined at the same time as 2 new domestic refrigeration compressors and the Second Engineer immediately fitted the new compressors. I was told that there had been a problem before with the compressors using large quantities of oil and having to be topped up daily with oil and Gas. The old compressors had been removed and dumped before I got to investigate them, but I suspected that the oil separator had not been operating as it should. The gas suction goes through the crankcase and the entrained oil lubricates the valves, piston and cylinders, the oil and gas are discharged into an oil separator where the oil falls to the bottom and the dry gas goes out of the top and back down to the condenser. When the oil level rises, in the separator, a float valve opens and the gas pressure pushes the oil back into the crankcase. I suspected that either the manual valve between the crankcase and separator was closed, or the float valve had failed. The floats have been known to collapse if the pressure becomes too great or explode if they are exposed to a vacuum.http://www.vesseltracking.net/ship/acina-7369041
When I sailed on her she was operated by C. H. Sorensen of Norway.
When the two new compressors started running, they drew oil out of the system and had to be stopped daily to drain excess oil out of them, after a week or two the oil levels stabilised and the cold rooms were all maintaining their temperatures well except for the Veg Room which was still struggling. After checking everything else, I suspected that the evaporator was full of oil, it was a low point in the system, and we would have to remove the evaporator, drain the oil out and refit it. However, we did not have a vacuum pump and I was reluctant to release the gas out of the system to atmosphere, so I called in a Fridge Engineer who did it, he drained about 20 litres of oil out of the evaporator and when it was refitted everything worked perfectly. He also supplied and fitted new isolating valves for the compressors, which had previously been leaking from the glands. All problems solved and the plant ran perfectly without adding oil or gas and maintaining the designed temperatures, running for about 8 hours a day, as it should.
On another Ship I joined as Chief, a car carrier, the Autoline, the Old Chief assured me that the fridge plant was working perfectly, but the condenser sight glass didn’t work so that it was impossible to see a liquid level. I soon realised that the Provisions Stores were not being kept at the correct temperature and simply feeling around the condenser revealed that there was very little liquid in it, only a few mm. (The part of the condenser shell that is in contact with the Gas is hot, the part that is in contact with liquid is at the liquid coolant temperature) the compressor was running at maximum pressure, just short of cutting out, so I deduced that the problem was inadequate cooling. The Refrigerant piping and evaporators were all icing up, classic signs of undercharging with Gas.http://www.shipspotting.com/gallery/pho ... id=1798253
So we opened up and cleaned the Sea Water side of the condensers and the condenser pressure dropped right down and we were then able to charge in enough Gas to see a liquid level in the sight glass and get everything running properly again.
The Old Chief had also assured me that the AC plant was working perfectly, but that “like all AC plants you had to manually hold in the contactor for the compressor motor to get it to start”! When we eventually got into hot weather and tried to run it, we found the same problems, there was not enough Gas in the system to raise the pressure at the compressor inlet high enough for the pressure switch to start the compressor automatically, which was why they had been manually holding the contactor in. Once the compressor was running the suction pressure became high enough for the pressure switch to keep the compressor running. Again the condenser was filthy dirty and once it had been cleaned and gassed up properly the system worked reasonably well.
(One way of temporarily compensating for a dirty water cooled condenser is to lower the liquid level in the condenser which will increase the Tube area condensing the gas, reducing the gas pressure, but it will reduce the tube area under cooling the liquid, which means that more of the refrigerant will evaporate in the pipe work before reaching the expansion valve.)
I had a similar experience when I joined the PSV Northern Sea, the Chief I relieved explained to me that the Fridge plant worked perfectly, but the condenser sight glasses didn’t work and the Veg Room evaporator iced up badly and had to be defrosted every week with a hot water hose!, all perfectly normal according to him.http://www.shipspotting.com/gallery/pho ... id=2001818
I found exactly the same problems; the water side of the condenser was solid with dirt, barely any liquid in the condenser, and the icing up is the Classic symptom of the system being undercharged with gas. We cleaned the condensers, charged them up with Gas, and no more icing, and everything cooled down to the right temperatures.
On another ship that I was on, the Car Carrier Donington, there had originally been Sea Water Cooled refrigeration compressors in a special room above the ship’s Provision rooms. These hadn’t worked properly for some time and it was decided to scrap them and fit Chest http://www.shipspotting.com/gallery/pho ... id=2532259
Freezers and a chiller unit in the deck head of the Veg Room. Unfortunately the Unit for the Veg. Room ran 24/7 and never brought the room down to temperature, the Chief at the time had been given a catalogue and told to choose the correct unit, so he had gone through the procedure given to calculate the rate of heat loss of the Veg room through its walls and selected the unit that exactly matched that cooling capacity. Unfortunately it did not allow for the Cook opening the Door and letting hot air in or cooling the warm produce put into the room. My experience with correctly functioning Domestic Refrigeration plants shows that the system should be able to maintain the correct temperatures running for 20 minutes in every hour. The Chiller unit was eventually replaced with one with 3 times the cooling capacity and it worked fine. When the redundant Sea water pipes between the Engine Room and the original condensers were removed it was clear that the build up of rust on the inside of the pipes had almost completely blocked the water flow, causing the original problems.
I joined an Offshore construction ship, the Boa Roverhttp://www.shipsandoil.com/Ship%20Info% ... oa/Boa.htm
for familiarisation as Chief, in Venezuela, and I asked the Chief I was relieving why it was getting so hot in the accommodation in the afternoon and he told me that they had to defrost the A/C every afternoon to remove the Ice forming on the evaporator, I asked him why there was ice on the evaporator and he insisted that was normal. For a year I tried to convince him that there shouldn’t be ice on the evaporator and he insisted that there should be, and that every Engineer knew that the correct way to run A/C and refrigeration plants was to adjust the expansion valves until the evaporators iced up because that showed they were working “strongly” and then manually defrost them. Each time I joined I would adjust the expansion valves to give the correct superheat and each time he joined he adjusted them to make the evaporators ice up. Eventually the cylinder head valves on the A/C compressor all smashed up when he was onboard because the superheat wasn’t set correctly and liquid refrigerant went back to the compressor, inevitable really.
On my last ship, the Enea, the refrigeration plant was using one of the new environmentally friendly refrigerants, and against traditional Good Engineering Practice we had to run the plant with a vacuum at the compressor suction in order to maintain the correct temperatures in the Meat Room. My back to back Chief was replaced and when I rejoined he proudly told me that he had set up the refrigeration compressor correctly because all the pressures were wrong but then for some strange reason it would no longer keep the Meat frozen, so he had changed over to the stand by compressor and that was now running and maintaining the temperatures correctly!
. http://www.shipspotting.com/gallery/pho ... id=2001818
On my First Ship as a very Green, Second Engineer, the Birling, we loaded a cargo of coal in Gdansk, Poland. http://www.tynebuiltships.co.uk/B-Ships ... g1977.html
The Captain took advantage of the very low price of Pork there to fill the Freezer Room right up with Meat. Unfortunately, in loading the Meat the Evaporator casing was slightly bent and one of the cooling fans started to make contact with a refrigerant pipe, and later the Cook reported that the temperatures in the Meat and Veg Room were sky high. Investigation showed that there was no Gas in the system. Unfortunately the ship did not carry any spare Refrigeration Gas and although there was a spare compressor, complete with condenser, this was bolted on the Engine Room Bulkhead rather than being connected to the system. We called in a local Fridge Engineer who told us that the Freon 12 was not available in Poland or other Eastern Bloc Countries, but that he could charge the system with another Gas that would keep the temperatures down temporarily and then we would have to change the Gas when we reached a Country where F12 was available, so he did that, found and fixed the leak and we got the Gas changed in the next Port. The Super was very angry that we had called in Fridge Engineers at two Ports, but otherwise we would have lost all the Meat. If we had had some Gas on board, we could have charged up the system, found and fixed the leak and fully charged the system ourselves.
On another ship, I think it was the FD Reliable, there were two refrigeration compressors, but to my surprise both were running together! On investigation I found that one compressor was cooling the Meat Room and the other compressor cooling the Vegetable Room and there was no redundancy in the system.http://www.rosetti.it/projects/platform ... d-reliable
This ship’s plant also ran on one of the new Refrigerant Gases and I was very surprised to find instructions, supposedly given by a Refrigeration Service Engineer who had worked on the system, saying that the only way to charge up the system was by charging with Liquid Refrigerant into the Compressor suction! This surprised me as I had always understood that to charge a plant quickly, you would close the condenser outlet valve and charge liquid into the line between the condenser and the expansion valves, and for charging small amounts in a more controlled way, Gas should be charged into the compressor suction.
So I went online and bought myself a handbook of modern Refrigeration and found that some of the modern Refrigerants are blends of different gases and change state at different temperatures, so charging with Gas would mean that all of one type of Refrigerant in the storage cylinder would evaporate first, changing the balance of gases in the system and changing the characteristics of the charge. The liquids in the blend intermingle freely, so charging with Liquid ensures that the correct blend is maintained, and consequently the performance of the plant.
This was when I first came across Zeotropic and Azeotropic Gasses, which is explained in the link better than I could.https://www.swep.net/refrigerant-handbo ... rants/sd1/
I hope the information in here helps a few people to keep their Beer Cold, and avoids incidents like one that had happened previously to one ship I sailed on where the Meat was continually melting and freezing and the ship's Engineers were either unable or unwilling to get the Fridge plant working properly. Eventually the entire compliment came down with Food Poisoning and half the Officers and crew were Hospitalised, and the ship was detained in Port until the Refrigeration Plant was working properly and everyone was fit to sail the ship.
It is always better to ask a stupid question than to do a stupid thing.