Liquid Oxygen Tanker Leaks: What Are the Risks and How Should We Prepare?

Dear all,

We use and store liquid oxygen in our plant, which comes in oxygen tankers. What can happen if oxygen leaks? What are the hazards associated with it? Do we need any special PPE or precautions for its containment? What actions can be taken in such cases? If anyone has some SOP or instructions regarding the same, kindly share.

Regards,
Hansa Vyas

What's the quantity of O2 being stored? What's the location of the tanks - outdoor or indoor? Provide specific details so that any of our forum members can assist you.

Thank you.

This is the short answer.

On top of the fire risk and explosion, especially if it comes into contact with any oil product, or the risk of leaks and people smoking outside or hot exhaust from vehicles.

In addition to being a class 2 gas, store it away from ignition sources and oxidizers. Secure it with a double chain to prevent falling. Store oxygen away from flammable gases. Check connections regularly to avoid leaks.

The next step is to pull the MSDS sheet and read about the risk problems and fire risks, as well as what your local government codes and standards state.

Because oxygen is colorless, odorless, and tasteless:

- Oxygen enrichment cannot be detected by the normal human senses!

Being heavier than air, oxygen can accumulate in low-lying areas such as trenches, pits, or underground rooms, especially in cases of cryogenic liquid spillage. Leaks can lead to oxygen enrichment, i.e., an increased fire hazard.

Leaking connections, flanges, and fittings connected to an oxygen source are hazardous, causing the oxygen concentration in the surrounding area to increase. Insufficient ventilation increases the risk. All equipment, whether newly assembled or after maintenance, must be thoroughly leak-tested before being put into service.

A spill of liquid oxygen creates a dense cloud of oxygen-enriched air as it vaporizes. The clothing of personnel entering the cloud will become enriched with oxygen. When liquid oxygen impregnates the soil containing organic material, e.g., wood, asphalt, etc., a dangerous situation arises as the organic material is liable to explode when impacted. Liquid oxygen filling locations are areas where oxygen enrichment is likely to occur.

Only certain materials are suitable for use in oxygen service.

Most materials - including metals! - will burn in pure oxygen or in oxygen-enriched atmospheres, even if they cannot be ignited in air. Oils, grease, and materials contaminated with these substances are particularly hazardous in the presence of an oxygen-enriched atmosphere, as they can ignite extremely easily and burn with explosive violence.

Oxygen enrichment of the atmosphere, for example, during cryogenic liquid filling, shock impact with combustible material, improper use of oxygen, incorrect operation and maintenance of oxygen systems, and use of materials not compatible with oxygen service can lead to hazardous situations.

Oxygen-enriched atmosphere can occur in pits, trenches, low enclosed areas, underground ways, sewers, in ASUs, cylinder filling plants, around tanker filling, around vents, leaks, and other areas.

In such areas:

- DO NOT SMOKE
- Do not use naked flames or weld
- Wear adequate fire-resistant or cotton garments and underclothing.
- Smoking is forbidden in locations susceptible to oxygen enrichment.

BOTTOM LINE: IF IT IGNITES OR CATCHES ON FIRE, YOU ARE GOING TO HAVE A BLEVE (BOILING LIQUID EXPANSION VAPOR EXPLOSION) BECAUSE THE TANK IS A COMPRESSED GAS DESIGN, EVEN IF THE ESCAPE HATCHES WORK.

Dear Tgpenny,

Thank you very much for the great explanation. Actually, a few days ago, a liquid oxygen-carrying tank leaked just outside our plant. I was aware of the fire hazard, but your explanation was very good.

I am also curious to know about its health hazards and what personal protective equipment (PPE) are required to stop this leakage. If you could provide information on this as well, it would be great.

Thanks and regards,
Hansa Vyas

Dear Hansa,

Please go through the following excerpt from one of our earlier discussions. It's from Mr. Keshav Pillai:

"As a health hazard, it has been discovered that the delivery of higher concentrations and high pressure of O2 can cause hypoxia from pulmonary damage, as well as visual damage and central nervous derangement."

I am also unsure about any personal protective equipment (PPE) requirements in such a situation of O2 leakage... Let's wait for others' opinions...

Thank you.

With any gas leak, oxygen or not, the following is always true in safety:

DO NOT switch on or off any electrical appliances.
DO NOT smoke.
DO NOT use naked flames.
DO NOT use intercoms or door entry systems – they can cause sparks.
DO NOT use a phone in the property – it can cause sparks.
DO NOT use mobile phones.
DO NOT flick any electrical switches – they can cause sparks.
DO open windows and doors to allow the gas to disperse.
DO turn off gas at the meter.

Oxygen gas in cylinders is used by many people at work and sometimes at home. It is used in welding, flame cutting, and other similar processes; for helping people with breathing difficulties; in hyperbaric chambers as a medical treatment; in decompression chambers for people who work in compressed air or in deep-sea diving; for food preservation and packaging; in steelworks and chemical plants.

The air we breathe contains about 21% oxygen. Without oxygen, we would die in a matter of minutes. It may be hard to believe, but oxygen can also be dangerous. The dangers are fire and explosion.

Oxygen gas is a colorless, odorless, non-toxic cryogenic liquid or colorless, odorless, oxidizing gas. Contact with oxygen liquid, its cold vapors, or cold piping can cause frostbite and cryogenic burns to exposed tissue. Liquid releases will quickly vaporize to gas.

The chief physical hazard associated with releases of the gas is its oxidizing power, which can greatly accelerate the burning rate for both common and exotic combustible materials. Emergency personnel must practice extreme caution when approaching oxygen releases because of the potential for intense fire.

The primary health hazard at atmospheric pressure is respiratory system irritation after exposure to high oxygen concentrations. Maintain oxygen levels in the air above 19.5% and below 23.5%. While up to 50% oxygen can be breathed for more than 24 hours without adverse effects, high concentrations in open air accelerate combustion and increase the risk of fire and explosion of combustible or flammable materials.

Effects of acute exposure:

Eye contact: Can cause frostbite (liquid form).
No adverse effects from gas.
Skin contact: Can cause frostbite (liquid form).
No adverse effects from gas.
Inhalation: May cause breathing difficulty.
Prolonged exposure to high oxygen levels (>75%) can cause central nervous system depression: signs/symptoms can include headache, dizziness, drowsiness, poor coordination, slowed reaction time, slurred speech, giddiness, and unconsciousness.
May cause coughing and chest pain.
May cause lung damage.
May cause soreness of the throat.
Ingestion: Not a likely route of exposure.
Effects of chronic exposure: None known.
Reproductive effects: Oxygen deficiency during pregnancy has produced developmental abnormalities in humans and experimental animals.

Skin contact: Remove contaminated clothing.
Treat for frostbite if necessary by gently warming affected areas.
Consult a physician.
Eye contact: Immediately flush eyes with plenty of water for at least 15 minutes.
Consult an ophthalmologist.
Inhalation: RESCUERS SHOULD NOT ATTEMPT TO RETRIEVE VICTIMS OF EXPOSURE TO THIS PRODUCT WITHOUT ADEQUATE PERSONAL PROTECTIVE EQUIPMENT. At a minimum, Self-Contained Breathing Apparatus should be worn.
Remove victim(s) to fresh air, as quickly as possible. If not breathing, qualified personnel should administer artificial respiration. Get medical attention.
Keep the person warm and at rest.
Ingestion: No first aid should be needed.
Not considered a potential route of exposure.
Flammability: Oxidizer.
Conditions of flammability: Contact with flammable materials.
Vigorously accelerates combustion.
Extinguishing media: Use appropriate extinguishing media for surrounding fire.
Special procedures: Self-contained breathing apparatus required.
Firefighters should wear the usual protective gear.
Cool fire-exposed containers with water spray.
Personnel should be evacuated, if necessary, to upwind area.
Remove containers from the fire area if without risk.
Sensitivity to mechanical impact: Avoid impact against the container.
Explosive power: Closed containers may rupture or explode due to pressure build-up when exposed to extreme heat.
Leak/Spill: Evacuate all non-essential personnel.
Stop the leak without risk.
Keep combustible materials away from the spill.
Ventilate. Eliminate all sources of ignition.
Allow to evaporate to the atmosphere.
Do not walk on or roll equipment over the spill.
Wear gloves and goggles.
Ventilate the area. Monitor the surrounding area for oxygen levels.
Handling procedures and equipment: Never allow any unprotected part of the body to touch uninsulated pipes or vessels that contain cold fluids. The extremely cold metal of the container will cause moist flesh to stick fast and tear when one attempts to withdraw from it.

Protect system components against physical damage. Check all hoses and transfer equipment before filling them with the liquid. Replace any worn or cut hoses before use.

Liquid Oxygen is extremely cold and is under pressure. A complete hose failure can result in a large release of Oxygen and violent movement of the hose and associated equipment, which may cause severe injury or death. Special care must be taken when depressurizing and disconnecting hoses.

Use adequate ventilation.
Avoid inhalation.
Never work on a pressurized system.
If there is a leak, close the upstream valve, blow down the system by venting to a safe place, then repair the leak.

For bulk liquid shipments:

Oxygen, refrigerated liquid
UN 1073
Class 2.2 (Non-Flammable Gas) with subsidiary risk 5.1 (Oxidizer)
Oxygen behaves differently from air, compressed air, nitrogen, and other inert gases. It is very reactive. Pure oxygen, at high pressure, such as from a cylinder, can react violently with common materials such as oil and grease. Other materials may catch fire spontaneously. Nearly all materials, including textiles, rubber, and even metals, will burn vigorously in oxygen.

Even a small increase in the oxygen level in the air to 24% can create a dangerous situation. It becomes easier to start a fire, which will then burn hotter and more fiercely than in normal air. It may be almost impossible to put the fire out. A leaking valve or hose in a poorly ventilated room or confined space can quickly increase the oxygen concentration to a dangerous level.

The main causes of fires and explosions when using oxygen are:

oxygen enrichment from leaking equipment;
use of materials not compatible with oxygen;
use of oxygen in equipment not designed for oxygen service;
incorrect or careless operation of oxygen equipment.

Risk assessment:

Employers are legally required to assess the risks in the workplace and take all reasonably practicable precautions to ensure the safety of workers and members of the public. A careful examination of the risks from using oxygen should be included in the risk assessment.

Beware of oxygen enrichment:

Oxygen enrichment is the term often used to describe situations where the oxygen level is greater than in air. Oxygen is colorless, odorless, and tasteless. The presence of an oxygen-enriched atmosphere cannot be easily detected by the human senses.

The main danger to people from an oxygen-enriched atmosphere is that clothing or hair can easily catch fire, causing serious or even fatal burns. For example, people can easily set their clothing and bedding on fire by smoking while receiving oxygen treatment for breathing difficulties.

Smoking should be forbidden where oxygen is being used.

Oxygen enrichment is often the result of:

leaks from damaged or poorly maintained hoses, pipes, and valves;
leaks from poor connections;
opening valves deliberately or accidentally;
not closing valves properly after use;
using an excess of oxygen in welding, flame cutting, or a similar process;
poor ventilation where oxygen is being used.

Consequently, the main ways to prevent oxygen enrichment are to keep oxygen equipment in good condition and to take care when using it. Good ventilation will also reduce the risk of oxygen enrichment.

Oxygen enrichment can also result from the misuse of oxygen. Never use oxygen for:

cooling or refreshing the air in confined spaces;
dusting benches, machinery, or clothing.

If oxygen enrichment from an oxygen leak is suspected, the oxygen supply should be turned off. Cigarettes and open flames should be extinguished. The room should be well-ventilated, and the source of the leak identified and repaired. It is possible that oxygen may contaminate any clothing in the area. If this is suspected, the clothing should preferably be removed and taken outside for airing and ventilating.

Confined spaces:

Some of the most serious oxygen-related incidents have involved damaged oxygen hoses leaking into confined spaces, where welding and burning operations were taking place. The workers’ oxygen-enriched clothing caught fire, causing serious or fatal injuries.

Gas cylinders should not be taken into confined spaces; the gas can be fed in by using hoses. The hoses should be removed from the confined space when work is finished or suspended, such as at the end of each day. Where this is not practicable, the hoses should be disconnected from the gas supply at the cylinder or manifold.

Where the risk from oxygen enrichment is high, such as in a confined space or a poorly ventilated room, the use of oxygen monitoring equipment is advisable.

Never use materials incompatible with oxygen:

Some materials react explosively if they come into contact with pure oxygen at high pressure. Other materials may catch fire spontaneously. Such materials are incompatible with oxygen.

Equipment designed for oxygen service is made from materials and components that have been tested and proved to be compatible and are safe for the purpose. The reasons for a particular design and choice of material are not always obvious. Using substitute materials or components, which appear to be similar but are not proven to be oxygen compatible, is extremely dangerous and has caused many accidents.

You need to take care when replacing:

O-rings and gaskets: There are hundreds of different types of rubber and elastomer, and most are not compatible with oxygen.
Metal components: Many

Safety Risks on any compressed gases on your worksite

What are the three major groups of compressed gases?

There are three major groups of compressed gases stored in cylinders: liquefied, non-liquefied, and dissolved gases. In each case, the pressure of the gas in the cylinder is commonly given in units of kilopascals (kPa) or pounds per square inch gauge (psig).

Gauge pressure = Total gas pressure inside the cylinder - atmospheric pressure

Atmospheric pressure is normally about 101.4 kPa (14.7 psi). Note that a compressed gas cylinder with a pressure gauge reading of 0 kPa or 0 psig is not really empty. It still contains gas at atmospheric pressure.

Liquefied Gases

Liquefied gases are gases that can become liquids at normal temperatures when they are inside cylinders under pressure. They exist inside the cylinder in a liquid-vapor balance or equilibrium. Initially, the cylinder is almost full of liquid, and gas fills the space above the liquid. As gas is removed from the cylinder, enough liquid evaporates to replace it, keeping the pressure in the cylinder constant. Anhydrous ammonia, chlorine, propane, nitrous oxide, and carbon dioxide are examples of liquefied gases.

Non-Liquefied Gases

Non-liquefied gases are also known as compressed, pressurized, or permanent gases. These gases do not become liquid when they are compressed at normal temperatures, even at very high pressures. Common examples of these are oxygen, nitrogen, helium, and argon.

Dissolved Gases

Acetylene is the only common dissolved gas. Acetylene is chemically very unstable. Even at atmospheric pressure, acetylene gas can explode. Nevertheless, acetylene is routinely stored and used safely in cylinders at high pressures (up to 250 psig at 21°C).

This is possible because acetylene cylinders are fully packed with an inert, porous filler. The filler is saturated with acetone or another suitable solvent. When acetylene gas is added to the cylinder, the gas dissolves in the acetone. Acetylene in solution is stable.

What are the pressure hazards associated with compressed gas cylinders?

All compressed gases are hazardous because of the high pressures inside the cylinders. Gas can be released deliberately by opening the cylinder valve or accidentally from a broken or leaking valve or from a safety device. Even at a relatively low pressure, gas can flow rapidly from an open or leaking cylinder.

There have been many cases in which damaged cylinders have become uncontrolled rockets or pinwheels and have caused severe injury and damage. This danger has happened when unsecured, uncapped cylinders were knocked over, causing the cylinder valve to break and high-pressure gas to escape rapidly. Most cylinder valves are designed to break at a point with an opening of about 0.75 cm (0.3 inches). This design limits the rate of gas release and reduces cylinder velocity. This limit may prevent larger, heavier cylinders from "rocketing," although smaller or lighter cylinders might take off.

Poorly controlled release of compressed gas in chemical reaction systems can cause vessels to burst, create leaks in equipment or hoses, or produce runaway reactions.

What are the fire and explosion hazards associated with compressed gases?

Flammable Gases

Flammable gases, such as acetylene, butane, ethylene, hydrogen, methylamine, and vinyl chloride, can burn or explode under certain conditions:

Gas Concentration within the Flammable Range: The concentration of the gas in the air (or in contact with an oxidizing gas) must be between its lower flammable limit (LFL) and upper flammable limit (UFL) [sometimes called the lower and upper explosive limits (LEL and UEL)]. For example, the LFL of hydrogen gas in the air is 4 percent, and its UFL is 75 percent (at atmospheric pressure and temperature). This means that hydrogen can be ignited when its concentration in the air is between 4 and 75 percent. A concentration of hydrogen below 4 percent is too "lean" to burn. Hydrogen gas levels above 75 percent are too "rich" to burn.

The flammable range of a gas includes all of its concentrations in the air between the LFL and UFL. The flammable range of any gas is widened in the presence of oxidizing gases such as oxygen or chlorine and by higher temperatures or pressures. For example, the flammable range of hydrogen in oxygen gas is 4 to 85 percent, and the flammable range of hydrogen in chlorine gas is 4.1 to 89 percent.

Ignition Source: For a flammable gas within its flammable limits in the air (or oxidizing gas) to ignite, an ignition source must be present. There are many possible ignition sources in most workplaces, including open flames, sparks, and hot surfaces.

The auto-ignition (or ignition) temperature of a gas is the minimum temperature at which the gas self-ignites without any obvious ignition sources. Some gases have very low auto-ignition temperatures. For example, phosphine's auto-ignition temperature of 100°C (212°F) is low enough that it could be ignited by a steam pipe or a lit light bulb. Some compressed gases, such as silane and diborane, are pyrophoric - they can ignite spontaneously in the air.

Flashback can occur with flammable gases. Many flammable compressed gases are heavier than air. If a cylinder leaks in a poorly ventilated area, these gases can settle and collect in sewers, pits, trenches, basements, or other low areas. The gas trail can spread far from the cylinder. If the gas trail contacts an ignition source, the fire produced can flash back to the cylinder.

Oxidizing Gases

Oxidizing gases include any gases containing oxygen at higher than atmospheric concentrations (above 23-25 percent), nitrogen oxides, and halogen gases such as chlorine and fluorine. These gases can react rapidly and violently with combustible materials such as the following:

organic (carbon-containing) substances such as most flammable gases, flammable and combustible liquids, oils, greases, many plastics, and fabrics

finely-divided metals

other oxidizable substances such as hydrazine, hydrogen, hydrides, sulfur or sulfur compounds, silicon, and ammonia or ammonia compounds.

Fires or explosions can result.

The normal oxygen content in the air is 21 percent. At slightly higher oxygen concentrations, for example, 25 percent, combustible materials, including clothing fabrics, ignite more easily and burn much faster. Fires in atmospheres enriched with oxidizing gases are very hard to extinguish and can spread rapidly.

Dangerously Reactive Gases

Some pure compressed gases are chemically unstable. If exposed to slight temperature or pressure increases, or mechanical shock, they can readily undergo certain types of chemical reactions such as polymerization or decomposition. These reactions may become violent, resulting in fire or explosion. Some dangerously reactive gases have other chemicals, called inhibitors, added to prevent these hazardous reactions.

Common dangerously reactive gases are acetylene, 1,3-butadiene, methyl acetylene, vinyl chloride, tetrafluoroethylene, and vinyl fluoride.

What are the health hazards associated with compressed gases?

Many compressed gases are toxic or very toxic. They could cause various health problems depending on the specific gas, its concentration, the length of exposure, and the route of exposure (inhalation, eye or skin contact). Contact between the skin or eye and liquefied gases in liquid form can freeze the tissue and result in a burn-like injury.

What is the danger of an inert gas?

Inert gases, such as argon, helium, neon, and nitrogen, are not toxic and do not burn or explode. Yet they can cause injury or death if they are present in sufficiently high concentrations. They can displace enough air to reduce oxygen levels. If oxygen levels are low enough, people entering the area can lose consciousness or die from asphyxiation. Low oxygen levels can particularly be a problem in poorly ventilated, confined spaces.