Last Updated on September 28, 2022 by Amit Abhishek
Refrigerants like R11, R410A, R1234ze, R717 are used in various refrigeration system on board ship for chilling, freezing, air conditioning, provisional cooling and to maintain temperature inside a hold.
According to IMO 2014 report more than 90% of all merchant fleet use HCFC/HFC as their primary refrigerant. About 1-2% still use CFC like R11 or R12 and the rest use neutral refrigerant like CO2, Ammonia and propane.
Some of the major quality concerns regarding the refrigerant remains; moisture, stability of refrigerant, its critical temperature, toxicity, damage to environment, cost and ease of use.
- Desirable Properties of Refrigerant
- Refrigerants Used on Ship
- Montreal Protocol & Phasing Out of CFC & HCFC.
- Reasons for refrigerant leak on ships
- Quality Issue: Moisture & Oil Content
Desirable Properties of Refrigerant
- The refrigerant should have a low boiling point so they can easily evaporate in the evaporator coil.
- It should be Non Corrosive.
- The refrigerant should have a low condensing pressure. So the effort put on compressor should be low and simpler design less possible leaks can be used.
- It should not be toxic.
- The latent heat of refrigerant should be high minimizing quantity of refrigerant needed in the system.
- Should be stable i.e non flammable and non explosive.
- Should have high critical temperature.
- Easy leak detection possible.
- The refrigerant must be compatible with crank case oil, metal, seals and gaskets i.e does not react with metal or become inoperable with a small mix of oil or damage components.
- Should be environment friendly.
- Having low specific volume ( refrigerant vapor ) helps keep the system compact and easy to operate.
- Should be cheap, easily available and safe for long term storage.
Refrigerants Used on Ship
According to MARPOL, Annex VI Regulation 12 – the use of ozone depletion substances (ODS). The installation of CFC or Halon was prohibited on ship, new installation of HCFC is also prohibited after January 1 2020.
So no more Chloro Fluoro carbons (CFCs) such as R11 & R12 on ship these days. Even you will not see R22 in many ships as their use needs to be drastically reduced and then phased out.
To be honest they were much cheaper than their alternative used today and show great performance. But since they damage our environment they were slowly phased out.
According to IMO report for total use of HCFC/HFC in merchant ships 2014, a large amount of ship 70% use R22 ( HCFC ), 26% use R134a ( HFC ) and just 4% use R404A ( HFC ) at the time.
Today newer ships do not come with HCFC’s and there is a greater push for faster phase out of R22 in recent time. Many Parts of the world now only allows for the use of HFC refrigrant like R134a, R407C, R404A, R507.
Refrigerant For Provision Cooling
The refrigerants used for provision cooling on a cargo ship use primarily 3 refrigerant; R404A ( 62% ), R407C ( 33% ), R422A ( 5% ); based on report on “Refrigeration Units in Marine Vessels” by Nordic Council of Ministers.
While tankers only use R404A as their primary refrigerant passenger ship use a variety of refrigerant like R134a ( 3% ), R404A (78% ), R407C (17% ), R422A ( 1% ), R507A (1% ).
The share of R22 during 2007–2012 was almost 70% that has gone down to as much as 8% in 2016-2018 and nearly 0% for newer ships by 2021.
Further the amount of charged refrigerant has decreased on average per ship i.e from 121 kg on average per passenger ship between 2007-2012 to 113 kg on average in 2013-2016.
For cargo ship it fall from 204 kg per ship to 30 kg per ship between 2007 to 2016. Similarly the average charged refrigerant had fall from 18 kg on tankers to 7 kg in the time.
Refrigerant For Air Conditioning
Based on UNEP Report 2016 about 70% of all fishing vessels still use R22. Further on large merchant ships R407C and R404A is used primarily for air conditioning.
Further, the use of R134a and R407C has increase from 16% and 36% respectively to 45% ( R134a ) and 47% ( R407C ) between 2007-2016 for non-tanker merchant vessels.
On tanker ships the use of R404A has fell from a whopping 74% to just 16% in the same time. While the use of refrigerant R407C has gone up from 16% to 84%.
A large part of the world ( except the developing economies ) have already banned the use of R22 by 2020 while the rest of the world needs to phase it out by 2030.
The share of R22 during 2007–2012 was 9% for air conditioning system used on merchant vessels. That too now have fallen down to less than 1% by 2016.
Further the amount of charged refrigerant has decreased on average per ship i.e from 626 kg to 513 kg in passenger ships, 70 kg to51 kg in tankers but have increase from 204 kg to 211 kg in other cargo ships.
For Refrigeration in Fishing Vessels
The main use of refrigeration in commercial fishing vessel for chilling or freezing the catch. But they also have air conditioning in major places including accommodation for crew and bridge.
Based on report on “Refrigeration Units in Marine Vessels” by Nordic Council of Ministers, 91% of fishing vessels registered in Europe were using HFC like R22 and the rest CFC like R11 and R12 in 1993.
This then change to 82% of fishing vessels using HFC like R22 , a 14% were using R717 systems while the rest using a range of different HFC’s by the year 2007.
Today, Using R22 based refrigeration-systems in fishing vessels is prohibited in large part of the world. Even refill of existing units is been banned within Europe.
The traditionally used R22 is now been replaced with R717 or R744 for the RSW systems. While other refrigeration system use refrigerants like 134a, R404A and R507A.
Montreal Protocol & Phasing Out of CFC & HCFC.
Montreal Protocol is an international environmental treaty, finalized in 1987 to protect ozone layer by reducing dependency / phasing out of ODS ( ozone depleting substance ).
Between 1972 and 1977, several studies confirmed the negative impact of CFC and HCFC gases on ozone layer.
Since CFC refrigerants were used since 1950; the more damaging CFC R12 ( with ODP of 1 ) were replaced by R22 ( ODP / Ozone depleting potential of 0.055 ). The R22 is also to be completely phased out by 2030.
R-22 has been completely phased out in the EU since 1 Jan 2015 and in other developed economies in 2020 ( Non-Article 5 Parties ). Beyond which time the Remaining R-22 is to exported to the developing countries.
In third and final phase of replacing R22 with other suitable refrigerants; all other economies ( that does not banned the production and use of R22 by 2020 ) needs to do so by 2030.
Need For Shift To More Clean Refrigerants
With around 90% of world trade being carried by ships, there is at least 150,000 ships ( of different types from general cargo to tankers ) in operation at all times.
Further there is 211 kg of HFC charged just into the air conditioning and further 30 kg of charge in refrigeration system for provision cooling in cargo ships ( large containers / Bulk / Ro-Ro ships ).
While tankers use much less refrigerant in total the average charge of HFC per ships is not less than 120 kg. Which accounts for 18000 metric ton or 18000000 kg of working refrigerant.
Now based on data published by Nordic Council of Ministers website in 2018, the average annual leakage rate for Swiss vessels ( cargo + passenger ships ) vary between 10-20% for 2008-2016.
Thus a significant amount of refrigerants leak each year from the ships worldwide. Even under best case you can not reduce leaks to less than 3%; which still can cause a lot of damage if its CFC or HCFC.
This is why there is a need for faster phasing out of the HCFC with better alternatives that are efficient, compatible with existing systems and does not damage ozone layer.
Reasons for refrigerant leak on ships
- Leaks during maintenance.
- Permanent exposure of the system to ships vibration.
- The ongoing motion, or operation of the system over long time leads to damage or leakage in piping.
- Many a times ships crew does not repair the leak instead simply top off the refrigerant.
- Pin hole leaks caused due to corrosion over time.
- Damage to piping due to improper care or sludge formation.
- Wear and tear.
- Manufacturer fault i.e sloppy connection or joints.
Quality Issue: Moisture & Oil Content
When oil from compressor enters into the refrigerants it leads to an increase in pressure drop and decrease in heat transfer. Thus the efficiency of the unit go down.
To counter that most units with reciprocating compressors use oil separator in the line, which remove any oil mixture from the flowing refrigerant.
Another major quality issue is the moisture content in the system. Moisture in refrigeration system can leads to situation such as freeze-up, corrosion and sludge formation.
A freeze-up is a situation where the water freeze-up to form small water crystals in the system. Then they slowly accumulate around the inlet of the expansion valve choking the flow of the refrigerant.
Further the moisture form acid when it reach to the refrigerant causing corrosion. If remain unchecks it will slowly eat away the piping forming many pin hole leaks in the system.
Similarly when emulated with the compressor oil it forms sludge that blocks tiny passage and strainers. In extreme cases it may reduced the lubrication properties inside the compressor cylinder.
Leading to wear and tear and sometimes serious compressor damage.
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