Nitrogen Tool Box Talk

NITROGEN

Refresher Training / Tool Box Presentation

NITROGEN INCIDENTS

• BP had 5 fatalities from nitrogen asphyxiation in less than 2 years. These included:• 2001 Lavera Refinery, France - employee was found dead in the

bottom of hydrocracker reactor which was under a nitrogen blanket for catalyst unloading. Employee had been making a gas test at the top manhole of reactor, was overcome and fell inside.

• 2001 Texas City Refinery, US - contractor was adjusting ladder from the top manhole of a reactor being purged with nitrogen. He was overcome and fell inside and died of asphyxiation.

• 2002 Merak Polyethylene Plant, Indonesia - analyser technician died inside analyser house after analyser instrument air purges had been changed over to nitrogen.

• 2003 Belgium - fitter found dead inside decene railcar which had been purged with nitrogen in preparation for repair of leak.

NITROGEN INCIDENTS - ExxonMobil

In ExxonMobil there have also been fatalities from nitrogen asphyxiation. These include:• 1967 Port-Jerome - 2 inspectors died after entering 36” line connected

to Steam Cracker compressor KO drum. Two 2” nitrogen connections on another line were later found to be open.

• 1975 Notre-Dame-de-Gravenchon - Contractor asphyxiated by nitrogen on Butyl Plant - had entered compressor KO drum without permission

• 1977 Rotterdam Refinery - Vacuum truck driver died after entering his tank truck containing nitrogen

• 1987 Beaumont Refinery - While painter was spray painting an overhead pipeband with a breathing air line set, air bottle was somehow switched over to a nitrogen bottle.

• 1990 Chalmette Refinery - Maintenance supervisor returned to the job site and leant into manway to check something (possibly a forgotten tool). He fell into the vessel and was asphyxiated.

• 1991 Sakai Refinery - Contractor died after his breathing air line setwas inadvertently connected to a nitrogen header while sand blasting bottom of a floating roof tank

• 2001 Torrance Refinery - While working in a hyrocracker reactor to remove catalyst a contractor became stuck in a manway, becamedetached from his umbilical air supply and died

BP Texas City Fatality - 2001

• A subcontractor employee (not wearing breathing apparatus or safety harness) enters the barricaded area on top of a reactor to assist a confined space entry attendant to lift the internal access ladder.

• He is overcome by an oxygen deficient atmosphere around the manhole and falls into the reactor and is asphyxiated.

BP Texas City 2001 Near-Miss

BP Belgium Fatality - 2003 INFORMATION IS CRUCIAL!

•A railcar was identified as having a problem with a leak on the blue vent valve on top of the railcar.

• It was purged with nitrogen and despatched for repair at the railcar repair contractor warehouse.

•A fatality occurred when a contractor entered inside the railcar.

•There was no indication in the paperwork or on the railcar that it was under nitrogen atmosphere.

Nitrogen (N2) vs. Oxygen (O2)

• Nitrogen is not toxic – it exists in air at 79%.• Oxygen in the air is typically 20.8%• When nitrogen concentration increases, oxygen concentration decreases.

• Note: any compressed gas can also decrease O2 concentration in an enclosed space by replacing O2.

Transport of oxygen

O2 flows from high concentration to low concentration

Concentration of O2 in the lungs is high

Concentration of O2 in the tissues and Brain is lower.

Oxygen Osmosis*

Oxygen is transported from the lungs to cells, tissue and brain via Osmosis*Osmosis: the flow of material across a permeable membrane when there is a concentrated mixture on one side and a dilute mixture on the other - flow is from concentrated to dilute side

O2 flows from high concentration to low concentration

O2 deficient air is inhaled

Concentration of O2 in the tissues and Brain is higher than the lungs

What happens when you breathe in nitrogen?

• Reverse Osmosis• Lungs take O2 from the blood stream which in turn takes it from the brain

• Brain becomes starved of oxygen – you pass out

• You could say your brain shuts you down

• It only takes one breath!

What happens when you breathe in nitrogen?

Oxygen (%vol) Effects & Symptoms

23.5 Maximum “Safe Level”

21 Typical O2 concentration in air

19.5 Minimum “Safe Level”

15 - 19 First signs of hypoxia. Decreased ability to work strenuously. May induceearly symptoms in persons with coronary, pulmonary or circulatoryproblems.

12 - 14 Respiration increases with exertion, pulse up, impaired muscularcoordination, perception and judgment.

10 - 12 Respiration further increases in rate and depth, poor judgment,lips blue.

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

6 - 8 6 minutes – 50% probability of death8 minutes – 100% probability of death

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

Physiological Effects of Less Oxygen

How long does it take to have an effect?

• When a person enters an oxygen deprived atmosphere the oxygen level in the arterial blood drops to a low level within 5 - 7 seconds.

• Loss of consciousness follows in 10 - 12 seconds.

• Heart failure and death ensue if person does not receive any oxygen within 2 - 4 minutes.

Can you smell the invisible killer?

No!

• How are you sure it is safe to enter?

• What are your precautionary measures before entry?

• Do you have a standby attendant?

• Do you know you can be overcome by N2 just by looking into a manhole of a vessel under a nitrogen purge?

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, suffocation and death will follow in most cases.

Facts & Figures- Liquid Nitrogen

• Liquid nitrogen (boils at minus 196 deg. C or minus 320 deg. F) so can cause cold burns

• One litre liquid gives 700 litres of gas • Cold nitrogen is heavier than air so accumulates

at ground level.• When liquid N2 is exposed to air the cloudy

vapour that you see is only the condensed moisture from the air, not the N2 gas. Remember N2 gas is invisible and this is the Danger!!!.

As a gas, for:• Preparing equipment by purging hydrocarbons.• Removing oxygen from equipment before start up.• Blanketing tanks and inerting or "mothballing" equipment• For clearing /pigging lines• For off-loading tank cars / railcars• Process and laboratory analyser operations• Purge or quench for instruments.• Specific welding operations.

As a liquid:• Coolant (laboratory, freezing lines, etc.).• To store and transport gas in large quantities.

Where is Nitrogen Used?

OPEN MANHOLES ARE DANGEROUS!

PREVENT

ACCESS!

Extract from ExxonMobil Inert Entry GMG: ”The area around open manways, nozzles, and vents where nitrogen is being dischargedshould be adequately barricaded and warning signs positioned to prevent inadvertent access without BA.”

Do I have to be inside a vessel to be at risk?

• No! We have already heard of 3 fatal incidents where personnel were overcome by nitrogen while outside a vessel

• Any situation where you can breathe oxygen deficient air has the same effect. For example:– areas of poor ventilation caused by temporary enclosures, e.g., tents,

tarpaulins– inside buildings where nitrogen has been hard-piped, e.g., inside

analyser shelters– when opening process equipment in poorly ventilated areas or where

flanges are at face level– using contaminated breathing air– working with liquid nitrogen in pits or close to grade, e.g., freeze

sealing+ cold nitrogen is more dense than air so it will deplete oxygen at floor level.

Leaning down close to a liquid nitrogen spillage can cause asphyxiation

Union Carbide Hahnville, US Fatality 1998

• Two workers were examining the flange surface of a 48 inch pipe for stress cracks using UV light.

• A tarpaulin was draped over the flange to block out the light to facilitate inspection.

• The confined space created by the tarpaulin was soon filled with nitrogen which asphyxiated both men.

• One man died as a result of the exposure.

• Second survived because he collapsed face down on metal grating, which allowed sufficient oxygen to sustain his life.

Tarpaulin Created Confined Space

BP Merak Indonesia - Fatality 2002

18:00: Lost power to plant18:30: Low instrument air

pressure - switched over to back-upnitrogen

19:15: Radio announcement that IA switched to nitrogen, do not enter

Nitrogen Purge inside Analyser House

Extract from ExxonMobil GP 4-3-3 on Analyzer Houses: Instrument air that is backed up by nitrogen shall not be piped into enclosed analyzer shelters....

analyser houses (instruments being purged with N2)

22:00: Shift handovers01:35: Analyser technician called in and arrived on site02:20: Analyser technician found on floor of analyser house

Merak Polyethylene PlantSeptember 2002

Reconstruction

Be Aware of Working at Face Level on Equipment under

Nitrogen Pressure

Where ventilation is poor or space is restricted such that face is close up to flange, then breathing air should be worn

DO NOT CONFUSE AIR AND NITROGEN!

? ? 1991 Sakai RefineryContractor died after his breathing air line set was inadvertently connected to a nitrogen header while sand blasting bottom of a floating roof tank

1987 Beaumont RefineryPainter working on overhead pipeband with breathing air line set, died when air bottle was somehow switched over to a nitrogen bottle.

What else do I need to Know?

• Always use an Entry Permit and follow Confined Space Procedures when entering a vessel or any other area where ventilation is restricted

• Global Manufacturing Guideline on Confined Space Entry requires:– minimum of 19.5 % oxygen in confined space before entry– gas test for oxygen to be conducted within 2 hours of

entry and at least once per shift• Only specialised contractors should enter confined

spaces when oxygen levels are less than 19.5%– Global Manufacturing Guidelines for Inert Entry should be

followed

What else do I need to Know?

• Do not use nitrogen instead of compressed air (e.g., with pneumatic tools).

• Use different couplings for nitrogen• Never store bottles of compressed nitrogen (or any other gas)

in confined unventilated areas (e.g., a leaking 50-litre bottle at 200 barg can reduce the oxygen level in a 9 m2 room to 12%).

• Do not transport compressed nitrogen bottles in vehicle cabs• Always check the oxygen level before carrying out explosive

tests in a confined area, if nitrogen has been used.• Never touch liquid nitrogen• A chemical cartridge respirator is useless because nitrogen is

100% chemically inert.• Identify / label all equipment, utility headers, piping,

compressed gas bottles containing nitrogen.

What if I see a colleague who is unconscious?

• Call emergency services first as with all incidents

• Do not enter the area without self contained breathing apparatus. DO NOT ENTER AT ALL IF THE ATMOSPHERE IS PURE NITROGEN (vessels under nitrogen purge)

• NEVER ENTER A CONFINED AREA ALONE TO GIVE HELP

• In industry over 50% of workers who die in confined spaces are attempting to rescue other workers

Other inert gases….

ArgonBetween 1995 – 2000:

• 1 death in UK• 23 deaths in USA

Carbon Dioxide, CO2

Between 1975 – 1998:• 43 deaths, 57 injured in Western Countries

(excl. USA)• 29 deaths, 88 injured in USA

Fatal Incident• Baytown Refinery - October 1989• Contractor died from Argon

Asphyxiation• Had been applying refractory

inside FCCU Reactor cyclone• Argon purge used for welding on

cyclone dipleg had been left on and leaked through plug

Need to ensure any fixed CO2 firefighting extinguishingsystems, e.g., inside gas turbine acoustic enclosures, areALWAYS deactivated before entry

References

Global Manufacturing Guidelines• Confined Space Entry

• Inert Entry

Material Safety Data Sheets:• Nitrogen - compressed gas

• Liquid Nitrogen

Confined Space Entry

Inert Entry

NitrogenGas MSDS

LiquidNitrogen MSDS

The last word….Nitrogen is an invisible, silent killer

which demands our RESPECT!!!

Let us not forget the incidents that have occurred in the past

Our procedures and practices for confined space entry and handling nitrogen and other inert gases are

there to avoid such incidents happening to you!!