Covid19 pandemic has affected almost every part of the world. Some countries were able to contain the virus while others were not so lucky. During the first wave of pandemic India served as an example in front of first world countries like America but during the second wave, Indian infrastructure failed miserably. The variant found in India was dangerous. It was resulting in instant deaths. People were struggling to get a hospital bed and around 400 thousand cases were being reported every day. Thus arises the problem of oxygen and as a result the transportation of Medical grade oxygen for the patients through cryogenic tankers.
Many Indian lost their lives. Corona Virus was the culprit but the faulty infrastructure was much more responsible. India struggled with the shortage of oxygen. Now, the more surprising thing is that India was producing much more oxygen than what the situation demanded. So why was there a crisis? The reason is transportation. India lacked in the transportation of oxygen.
Understanding the difficulty:
Let’s first understand how oxygen is transported. Medical grade oxygen is commonly transported in oxygen cylinders directly to the hospital. After the Covid19 crisis, there was a significant rise in the oxygen demand due to obvious reasons. So to transport a large amount of liquid oxygen cryogenic tankers are used. These cryogenic tankers are heavily insulated. To liquefy any gas we have to maintain a very low temperature. For liquefaction of gases, at least temperature of -90 degree Celsius is to be maintained and in the case of liquid oxygen it is -183°C (-130°F). Now, during the entire process of transportation, we have to maintain this temperature and here cryogenic tankers come into play.
These vacuum-insulated tank’s double-wall consist of two concentric vessels, one is an austenitic steel wall present in the inner tank and an outer jacket in carbon steel with an anti-corrosion primer on top and a special environmentally-friendly top coat. The interspace between the inner and outer tank is evacuated(vacuum is created) and filled with insulating powder (perlite). An adsorbent is also added to maintain the vacuum in the insulation interspace. This is similar to thermos and vacuum flasks that we use in everyday life to keep liquid hot or cold. This unique structure makes the transportation of gases possible. If anyhow temperature increases then the entire tanker will explode due to expanding gas. That’s why it is so hard to manufacture and maintain such transport vehicles.
As liquid/cryogenic oxygen has a boiling point of -183°C (-130°F), the temperature must be kept extremely low to maintain liquid oxygen .Now that we understand what is a cryogenic tank and what’s its use let’s take a look into the current capacity of India and the problem.
Another important aspect regarding Cryogenic tankers/containers is that you will not find any corners in them. Most of the containers/tankers are cylindrical in shape because curved edges helps reducing the pressure at a particular point as in cryogenic containers gases are stored in highly compressed form.
Liquid oxygen physical and chemical properties :
- Molecular Formula O2
- Molecular Weight 31.999
- Boiling Point @1 atm -297.4°F (–183.0°C)
- Freezing Point @1 atm -361.9°F (–218.8°C)
- Critical Temperature -181.8°F (–118.4°C)
- Critical Pressure 729.1 psia (49.6 atm)
- Density, Liquid @BP, 1 atm 71.23 lb/scf (1141 kg/m
- Density, Gas @ 68°F (20°C), 1 atm 0.0831 lb/scf (1.33 kg/m3)
- Specific Gravity, Gas (air=1) @ 68°F (20°C) 1 atm 1.11
- Specific Gravity, Liquid (water=1) @ 68°F (20°C) 1 atm 1.14
- Specific Volume @ 68°F (20°C), 1 atm 12.08 scf/lb (0.754 m3/Kg)
- Latent Heat of Vaporization at BP 91.7 Btu/lb (213 Kj/Kg)
- Expansion Ratio, Liquid to Gas, BP to 68°F (20°C) 1 to 860
- Solubility in Water @ 77°F (25°C), 1 atm 3.16% by volume
The total number of tankers available right now for oxygen transportation is around 1400 and other tankers for transportation of Nitrogen and Argon is 1000. Now, the problem is that tankers used for transportation of one gas are a little different from tankers used in another gas. So we can’t use Nitrogen and Argon tankers without modifying them to suit the needs. No one had ever anticipated that demand will rise to such an extent. Earlier only 10% of total oxygen produced was used for medical purpose rest of it was used in industries. Now around 90% of total oxygen produced is diverted to hospitals but 1200 containers are not enough. Other tankers are being modified to suit our need. So total capacity will rise to around 1800 tankers. Also, some cryogenic tankers are being imported from different countries. So the situation will improve shortly.
Why aren’t people investing in cryogenic tankers? The answer is because they are a game of loss. Once the pandemic is over there will be no use for these tankers. We already have enough tankers to meet our requirement so once this pandemic is over these tankers will become absolute junk. Cost of maintenance and manufacturing these tanker trucks is quite high. No sane person or company will invest a significant chunk of their capital on these tankers which will serve no need other than a little publicity in name of charity.
Role of Indian Railway:
INDIAN RAILWAY played a huge role in the transportation of oxygen across the country. The speed limit for tankers is 40km/hr. as they contain highly inflammable gas and believe me this speed is not at all-sufficient. So Indian railway came up with a plan. They loaded oxygen tankers on a freight train and send them across various states. They named it ‘Oxygen Express’. Now, this move may not seem so significant as they were using those same tankers which could have been delivered via road but it is. The average speed on road is 40km/hr but on the train is 60km/hr. That means that truck which used to reach in 3 days can reach in just 2 days and at a much lesser cost of transportation. Indian Railways have always proved its worth in times of need like this.