Oxygen System Safety
The purpose of this document is to give our Cleaning for Oxygen Service customers
more information on the reason for the services we perform and to enlighten others
who have interest in our services. Through this document we will give information
on how Oxygen System fires may occur and why Cleaning for Oxygen Service
lowers these risks.
Scrupulous cleaning is the most fundamental fire-safety measure applied to Oxygen
Systems. Oxygen is a fire hazard in itself, because it promotes combustion. We all
know that if you remove normal atmospheric air (roughly 21% Oxygen) by covering
or “smothering a fire” it will extinguish. If you increase the Oxygen concentration,
you greatly increase the fire hazard. Many items that will not burn in “normal
atmospheric air” will easily burn in an oxygen enriched atmosphere. Materials that
are combustible in “normal atmospheric air” will ignite easier and burn hotter, as
well as faster, if higher concentrations of Oxygen are present. That is why Oxygen
systems require special cleaning and care to remove the ignition sources. Ignition
sources that are of no consequence in “regular atmospheric air”, in an Oxygen
enriched environment, may ignite with explosive consequences.
The ignition chain begins when a very small amount of energy is released inside an
Oxygen System and ignites a low ignition material or a particle that is small in mass
with a larger surface area. Once the small item is ignited, heat that is generated
from that source will ignite larger materials with higher ignition temperatures,
which in turn generates more heat until the fire itself is self-sustaining. There are
three common methods of ignition from poorly cleaned oxygen equipment. These
are friction, mechanical impact and particle impact.
Merriam-Webster Dictionary defines friction as , A. The rubbing of one object
against another & B. The force that resists relative motion between two objects in
contact. So basically, when two solid materials rub together they create heat which
may ignite other materials.
When one object strikes against another forcefully, heat which may cause ignition
is produced at the point of impact. In an Oxygen System, many risks are involved
and this is a great one. Many instances may occur that would cause a mechanical
impact ignition. For example purposes consider the following; a mechanical
component may break off, or a large piece of debris may strike a surface that is
pressurized with oxygen, producing heat upon impact. If the surface has not been
cleaned properly and meticulously, contaminates such as oils, lubricants or any
other hydrocarbon material may ignite and the results could be the Ignition
sequence could be started. The Compressed Gas Association defines harmful
contamination as both organic and inorganic materials such as oils, greases, paper,
fiber, rags, wood, coal dust, solvents, weld slag, rust, sand and dirt. Any of these
items could cause the ignition chain to begin.
Small particles such as bits of weld slag, scale, filings, chips and even some lint
material can be carried along with a flowing stream of oxygen. Most often Oxygen
systems supply at high velocities. When the particulates strike a surface inside the
system, impact energy is released as heat. Because of the small mass of these types
of contaminates, the particles become hot enough to ignite larger materials.
HOW CLEANING FOR OXYGEN SERVICE LOWERS THE RISKS
Most items that are to be cleaned may appear in a clean and ready to use state.
This is deceiving to a person without knowledge of the nature of oxygen
contaminates. Just because a particular object is “brand new” does not mean that it
is clean and ready for use in an oxygen system. During the production process the
item may be exposed to any of the above mentioned contaminates. When ignition
sources are removed from the item to be cleaned it greatly reduces the risks
involved in handling oxygen. Several different methods may be used to clean for
oxygen service dependant upon the material of which the item is constructed and
the contaminates involved. Below are the main methods used at CELCO for
cleaning and a brief description.
The advantage for using this method is the non-flammability of the solvent (Water
and Surfactant). During this process, usually agitation of the Surfactant water
mixture is an aid in removing contaminates. Ultrasonics play a large role in the
aqueous cleaning procedures used at Central Electropolishing Co., Inc. (CELCO).
Ultrasonics have the ability to penetrate areas normally unreachable by other
When Aqueous cleaning is not an option due to the design of the item being
cleaned, solvent cleaning is used. Solvent cleaning may be accomplished by
various methods including immersion, spraying, and wiping. CELCO is extremely
environmentally conscience about the solvents that are used during this process.
The Acid cleaning procedure removes oxides and other contaminates by immersion
in a suitable acid solution, usually at room temperature.
Acid cleaning can be used post aqueous cleaning to remove any oxidation caused
by the cleaning process.
CHOOSING A SPECIFICATION
CELCO has it’s own in house specification. We can perform Oxygen Cleaning to
most any Industry Standard and Company Specific Standards upon review of the
specification. CELCO assesses the components upon arrival for contaminates and
problem areas. We use visual white light inspection (and Ultra Violet Light
inspection if necessary), to determine the degree of contamination and the optimum
method for removal. When the Oxygen Cleaning Process is complete, the cleaned
items are packaged as required by specification to protect the integrity of the
cleaning. A certification is sent back to the customer with the cleaned items stating
that the parts are Cleaned for Oxygen Service, Tested and Packaged per the
customer’s choice of specifications.
Central Electropolishing Co., Inc. has a great respect for the risks involved with
handling oxygen . We strive to provide our customers cleaning for oxygen service
that surpasses all others.