Waterfront Shipping Company Limited

Hazards of a Nitrogen Generation Plant Onboard a Ship

- What you need to know to be safe -

Nitrogen (N2)

The Silent Killer….

*Film footage courtesy of BP

Nitrogen (N2)

First, the good news:

Nitrogen is part of the life cycle and, as humans, we need some nitrogen to stay alive – PROVIDED we get it in the right quantities.

Breathable air consists of 21% oxygen, 79% nitrogen with some other trace amounts of assorted gases.

Nitrogen (N2)

It is a naturally occurring part of the atmosphere and comprises approximately 79% of the air that we breathe.

It is essential to life as it forms a constituent part of the human DNA and as such, forms part of our genetic code.

Nitrogen is a colourless, odourless and tasteless gas.

Nitrogen (N2)

Nitrogen (N2)

Next, the bad news:

Every year people die in nitrogen-rich / oxygen-deficient atmospheres because of ignorance, attitude and a failure to adhere to safe work practices.

It can and will kill you if you get it wrong.

Nitrogen will surprise you only once – SO BE AWARE

Within the last 5 years for example, BP has experienced 24 incidents involving nitrogen that resulted in 5 fatalities.

Nitrogen (N2)

Legal

IMO through SOLAS mandates that chemical tankers with cargo tanks in excess of 3,000 M3 must have their tanks inerted.

Ships with cargo tanks under 3,000 M3 are not required to inert the tanks at this time, but may be required to do so depending on the cargo they are carrying and the terminals at which they will be calling.

Due to past incidents, IMO is now looking at the possibility for all new and existing chemical ships under 20,000 mts dwt to have inert gas systems onboard.

Definition

Inerting

Filling the cargo tanks and associated piping systems with a gas or vapour that will reduce the oxygen content to 8% or below and will not support combustion nor react with the cargo and will maintain that condition.

Legal and Maintenance

SOLAS requires the installation of devices that will not allow the reverse flow of inert gas back into the machinery spaces.

These devices may be either a deck water seal, or a block valve in the inert gas line of any inert gas system.

The regular maintenance of these items is to be adhered to rigorously in order to prevent the flow of inert gas back into the machinery spaces.

When performing maintenance on the N2 plant it is equally important

to ensure that the plant is totally gas-free before work commences.

Nitrogen – Flammability

As an inert gas, nitrogen does not support combustion. It is this property that makes it ideal for use on ships that require inert atmospheres in their cargo tanks to eliminate any chance of fire and/or explosion.

The National Fire Protection Association (NFPA) has assigned a flammability rating to nitrogen of ‘zero’ (0), in other words, it is not combustible – it will not burn.

In addition, it is deemed to be a “clean” gas that will not contaminate or interact with the cargo.

Nitrogen – Tank Entry

Tank Entry Hazards and Awareness

Nitrogen – Tank Entry

Nitrogen is slightly lighter than air at ambient temperature, so it will tend to rise towards the upper levels in a space.

You need to be aware of this should you ever need to open the main access hatches (or any tank opening) of the cargo tanks when they are full of cargo and the ullage space above the cargo contains nitrogen.

It is possible that some of the N2 couldmove up and out of the hatch access and if you are in the way …… !!!

So, do a risk assessment

Nitrogen – Tank Entry

Wear the appropriate PPE and a gas detection sensor at all times and follow procedure by using a checklist.

When an inerted tank is maintained at a positive pressure, personnel should be aware of some additional hazards.

For example, this pressure must be adequately reduced before opening any access to the tanks, such as the main access hatches, ullage ports and tank washing hatches.

Nitrogen – Tank Entry

• How do you know the tank is safe to

enter?

• Have you completed a checklist?

• What precautions do you take before entry?

• Do you have a portable gas detector that will ‘beep’ if the O2 level falls

below 19%?

• Do you have a man on stand-by at the tank access hatch?

• Do you know that you can be overcome by N2 just by looking into the open tank access hatch without wearing breathing apparatus?

Can you see or smell the invisible killer?... No!

Nitrogen – Tank Entry

Check, check, check!!!!

Nitrogen – Physiological Effects

Physiological Effects – Oxygen Deficiency

% Oxygen Effects & symptoms

23.5 Maximum ‘safe level’ (23.5% is often the high level alarm setting on most O2 detectors)

21 Typical O2 concentration in breathable air

19.5 Minimum ‘safe level’ (19% is often the low level setting on most O2 detectors)

15-19 First signs of hypoxia. Decreased ability for strenuous work. May induce early symptoms in persons with coronary, pulmonary or circulatory problems

12-14 Respiration increases with exertion, pulse rate increases, impaired muscular coordination, perception & judgement

10-12 Respiration further increases in rate and depth, poor judgement, lips turn blue

8-10 Mental failure, fainting, unconsciousness, ashen face, blueness of lips, nausea, vomiting, inability to move freely

6-8 6 minutes exposure – 50% probability of death

8 minutes exposure – 100% probability of death

4-6 Coma in 40 seconds, convulsions, respiration ceases, death

What happens when you breathe in nitrogen? The brain becomes starved of oxygen You pass out in approximately 10 to 12 seconds The brain shuts down It only takes ONE BREATH

What if I hold my breath? Holding your breath causes the oxygen in your blood to be used up.

If you then inhale the inert atmosphere (N2), suffocation and death will follow in most cases.

Nitrogen – Physiological Effects

Physiological Effects Death by Nitrogen

Exposure to an atmosphere with a low concentration of oxygen (O2) does not necessarily produce any recognizable symptoms before unconsciousness occurs.

The onset of brain damage and death can follow in as little as 2 to 4 minutes.

If oxygen deficiency is not sufficient to cause unconsciousness, the mind nevertheless is liable to become apathetic and complacent.

Even if the victim notices these symptoms and attempts to escape, the physical exertion will just aggravate the weakness of both mind and body to the extent that escape is probably not going to happen.

Ugly news !

Nitrogen is listed a a natural asphyxiant. In other words, in areas where N2

is abundant and the level of O2 is insufficient to support life, nitrogen will

block the body’s autonomous response to inhalation. Basically, you are

not able to breathe in and……………….

YOU WILL DIE!

Remember that…

I am… InvisibleI am… SilentI have no… Smelland

I am a… KILLER

You do not want to meet this fellow

Thank you to BP for the use of their material.

SOSO