Preview of Hazards of Nitrogen and Catalyst Handling
Preview of Hazards of Nitrogen and Catalyst Handling
Preview of Hazards of Nitrogen and Catalyst Handling
Hazards of
Nitrogen and
Catalyst Handling
A collection of booklets
describing hazards and
how to manage them
This booklet is intended as a safety supplement to operator training courses, operating
manuals, and operating procedures. It is provided to help the reader better understand
the ‘why’ of safe operating practices and procedures in our plants. Important engineering
design features are included. However, technical advances and other changes made
after its publication, while generally not affecting principles, could affect some
suggestions made herein. The reader is encouraged to examine such advances and
changes when selecting and implementing practices and procedures at his/her facility.
While the information in this booklet is intended to increase the store-house of knowledge
in safe operations, it is important for the reader to recognize that this material is generic in
nature, that it is not unit specific, and, accordingly, that its contents may not be subject to
literal application. Instead, as noted above, it is supplemental information for use in
already established training programmes; and it should not be treated as a substitute for
otherwise applicable operator training courses, operating manuals or operating
procedures. The advice in this booklet is a matter of opinion only and should not be
construed as a representation or statement of any kind as to the effect of following such
advice and no responsibility for the use of it can be assumed by BP.
This disclaimer shall have effect only to the extent permitted by any applicable law.
Queries and suggestions regarding the technical content of this booklet should be
addressed to Frédéric Gil, BP, Chertsey Road, Sunbury on Thames, TW16 7LN, UK.
E-mail: gilf@bp.com
All rights reserved. No part of this publication may be reproduced, stored in a retrieval
system, or transmitted, in any form or by any means, electronic, mechanical,
photocopying, recording or otherwise, without the prior permission of the publisher.
Published by
Institution of Chemical Engineers (IChemE)
Davis Building
165–189 Railway Terrace
Rugby, CV21 3HQ, UK
IChemE is a Registered Charity in England and Wales and a charity registered in Scotland
(SC 039661)
Offices in Rugby (UK), London (UK), Melbourne (Australia) and Kuala Lumpar (Malaysia)
First edition 2002; Second edition 2003; Third edition March 2004;
Fourth edition September 2004; Fifth edition 2006; Sixth edition 2009
Nitrogen is very often used in the chemical or oil industries as a ‘safety’ tool.
However, nitrogen has proved that it can be as deadly as any other gas handled
in our plants. In this booklet you will find various descriptions of serious
incidents involving nitrogen.
This booklet was created to help share knowledge and improve the
understanding on the basic principles for safe use of nitrogen. Due to the
serious nature of the incidents along with the widespread use of nitrogen in our
industry, BP published a comprehensive ‘nitrogen information pack’ to
complement this booklet.
I strongly recommend you take the time to read this book carefully. The
usefulness of this booklet is not limited to operating people; there are many
useful applications for the maintenance, design and construction of facilities.
Please feel free to share your experience with others since this is one of the
most effective means of communicating lessons learned and avoiding safety
incidents in the future.
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Contents
Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
1 Safe use of nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Properties of nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Uses and hazards of nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Hazards of open manholes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.5 Hazards of temporary confined spaces . . . . . . . . . . . . . . . . . . . . . . 10
1.6 Hazards of piping under nitrogen purge . . . . . . . . . . . . . . . . . . . . . . 13
1.7 Hazards of inerting equipment leaving a site . . . . . . . . . . . . . . . . . . 14
1.8 Hazards of confusing nitrogen with air . . . . . . . . . . . . . . . . . . . . . . . 15
1.9 Hazards of trapped pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.10 Hazards of liquid nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
1.11 Hazards of explosimeter use in nitrogen atmospheres . . . . . . . . . . 24
1.12 Hazards of contaminated nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . 25
1.13 General advice and safe practices . . . . . . . . . . . . . . . . . . . . . . . . . . 28
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H A Z A R D S O F N I T R O G E N A N D C AT A LY S T H A N D L I N G
1
Safe use of nitrogen
1.1 Introduction
The atmosphere we live in, the air we breathe every day consists of 79%
nitrogen, 21% oxygen and traces of other gases. But only oxygen is vital and
essential to human beings for respiration/survival. Without sufficient oxygen,
i.e. if oxygen level falls below 16%, we will die of asphyxiation.
Nitrogen gas behaves somewhat like a diluent or buffer gas in the atmosphere.
Nitrogen in itself is inert, stable, non-reactive and non-toxic, but too much nitrogen
reduces the oxygen content in the atmosphere, creating an invisible condition
that can kill. If the earth was without nitrogen but filled with just oxygen, then
fires would burn out of control and steel structures would quickly rust away!
Therefore, nitrogen is an effective diluent or buffer gas that we can’t live without,
yet too much of it would deprive us of vital oxygen, which can lead to asphyxiation
and even death within seconds.
Nitrogen is widely used for various purposes in refineries and petrochemical
plants, for example, to provide an inert atmosphere, to purge a vessel of
hydrocarbons, for blanketing and padding storage tanks in order to prevent
explosions and fires.
Nitrogen is odourless and colourless. It can kill without warning. Therefore, it is
known as the invisible killer that has caused many fatalities in the refineries
worldwide.
It is one of the most dangerous gases found in refineries and chemical plants.
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H A Z A R D S O F N I T R O G E N A N D C AT A LY S T H A N D L I N G
Swimmers are acutely aware that inhaling water causes sudden, uncontrollable
coughing. This is a powerful stimulus that helps a swimmer resist the body’s
breathing reflex even after being submerged for a long time. But nitrogen, which
is odourless, tasteless, and colourless, provides no stimulus to voluntarily resist
the breathing reflex. In a highly emotional and physically demanding
emergency, it is extremely unlikely that a person would hold their breath.
Furthermore, workers may be unaware of another dangerous complication—
inhaling nitrogen or other inert gas suppresses the brain’s breathing reflex
response. The breathing reflex is controlled primarily by the amount of carbon
dioxide in the blood rather than the shortage of oxygen.
Normally, the ability to voluntarily hold one’s breath is eventually overwhelmed
by the brain’s respiratory control centre, which is triggered by the increased
carbon dioxide concentration in the blood, combined with a drop in the blood’s
pH (acidity). If high-purity nitrogen or other inert gas is inhaled, the body may
simply stop breathing, as carbon dioxide accumulation in the blood is
insufficient to stimulate the breathing reflex.’
NOTE: There is also a risk of suffocation with all compressed gases (for
example—argon, CO2, helium, etc.), which either replaces the oxygen or con-
sumes it. This risk also exists in situations where there is a large consumption of
oxygen (fires, and rusting in ballast tanks of a ship or water tanks, etc.).
Nitrogen (N2) is a very common and extremely dangerous gas that you
may be exposed to at a refinery or chemical plant. You must always be
on your guard.
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H A Z A R D S O F N I T R O G E N A N D C AT A LY S T H A N D L I N G
What is an asphyxiant?
A chemical (gas or vapour) that can cause death or unconsciousness by
suffocation. Simple aphyxiants such as nitrogen, displace oxygen in air.
They become especially dangerous in confined or enclosed spaces.
Chemical asphyxiants, such as carbon monoxide and hydrogen sulphide,
interfere with the body’s ability to absorb or transport oxygen to the tissues.
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H A Z A R D S O F N I T R O G E N A N D C AT A LY S T H A N D L I N G
Initial gas testing should be performed from outside the space by inserting a
probe or piece of flexible tubing. However, ensure that the contractor or
employee performing gas testing is adequately protected with breathing
apparatus and accompanied by a second person.
ACCIDENT A subcontractor
employee (not wearing breathing
apparatus or safety harness) entered
the barricaded area atop a reactor to
assist a confined space entry
attendant in lifting the internal access
ladder. He was overcome by an
oxygen deficient atmosphere around
the manhole and fell into the reactor.
Without the vital oxygen to sustain
respiration, it is very unlikely that
anyone could exit the reactor alive!
continued…
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H A Z A R D S O F N I T R O G E N A N D C AT A LY S T H A N D L I N G
ACCIDENT A fixed bed reactor was filled with catalyst under a nitrogen
blanket. At the start of a new shift the operator went to inspect the reactor top
alone. When he failed to return, a colleague went to look for him and
eventually saw him lying on top of the catalyst in one of the reactors. He put
his head inside an oxygen deficient atmosphere, knowing all the hazards, but
for a moment ignored them.
Good practice
A device was developed for placing across manholes and other openings to
confined spaces which may contain an oxygen deficient atmosphere. The
device can be locked into place to prevent unauthorized removal and physically
prevents access. Removal would only be allowed as a condition of a confined-
space entry permit.