Pressure Dispensing Solvent Containers
1. Current Solvent Container Regulatory Considerations
2. Positive Pressure Containers and Pressure
3. Safety Practices Associated with Pressurized
Returnable Solvent Containers
4. The PTI-20 Returnable Solvent Cylinder
1. Current Solvent Container Regulatory
This Overview is far from complete. As far as we know there is no one
source that can be looked at in order to get a complete overview of what
is called the "limiting regulation". Every state and jurisdiction or location
does have a "limiting regulation" defined as the fire code, building code
or even company wide policy that defines the maximum flammable solvent
that can be handled or stored at that location. PTI is attempting to collect
that data - first in a state by state view and then in "specific zones"
view. We plan to share any data received with those people who participate
in the survey and work on the collection of that data.
The use of large solvent containers in the workplace is allowed by OSHA
regulation 1910.106. This regulation allows metal containers up to 60
gallons for Class 1A, 1B and 1C liquids. OSHA's code and quantities
are in fact what was listed in NFPA 30 in 1967 when that part of the
OSHA code was written.
NFPA (National Fire Protection Association)
A number of states have either directly "incorporated by reference"
some of the NFPA codes or done so indirectly by incorporating an NFPA
code which has made another NFPA code a part of its requirement to comply.
It should also be noted that a number of US government agency's have
made incorporation of specific NFPA codes mandatory at specific locations
or have even mandated agency wide compliance.
The two most relevant NFPA (National Fire Protection Association)
codes for the use of flammable liquids ar NFPA 30, Flammable and Combustible
Liquids Code and NFPA 45, Fire Protection for Laboratories Using Chemicals.
For laboratory use, NFPA 45 can limit flammable liquid containers
to 4 Liters for glass bottles and 5 gallons for metal containers (non
pressure vessel). Formulas involving room size and solvent storage cabinets
are required for storing quantities exceeding these limits. Large quantity
solvent storage is allowed in specially constructed rooms under NFPA 30.
NFPA 30 also allows solvents to be piped to the point of
use, providing that shut off valves are available at the container and
at the point of use. However NFPA 45 does not currently address piping
flammable liquids from such locations. NFPA 45’s paragraph 8-2 includes
standards that address piping flammable gases, however those definitions
do not currently include pressurized flammable solvents.
Western Fire Code (WFC)
Jurisdictions in states recognizing the WFC - and often individual
cites within a state that does not itself recognize the WFC - have adopted
all or parts of the WFC as their basic fire code. Most jurisdictions
that recognize and use the Western Building Code also mandate the Western
Fire Code. In the past companies that operate in the East – and which
sell to companies in the West have had difficulty getting- a clear picture
of what the Western Fire Codes require as to quantities of flammable
liquids in either laboratories or pilot plant operations. NFPA codes
are of no use here.
All states have incorporated one of the national building
codes such as WBC (Western Building Code), BOCA (Building Official Code
Administrators, Int.), SBCC (Southern Building Code Congress, Int.).
The maximum amount of flammable solvents is addressed by these codes.
The question then is if they take precedence or prescribe i.e. allow
another code or standard to take precedence in specific instances such
as “a laboratory”.
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2. Positive Pressure
Containers and Pressure Vessel Definitions
Positive Pressure Dispensing Container: A Pressure
Dispensing Container (PPDC) is a non-bulk vessel or cylinder which uses
a compressed gas as a propellant to discharge a liquid from the vessel.
The propellant gas may be adde3d prior to or during the discharge of the
liquid. Normally the compressed gas used as the propellant is neither
flammable or reactant.
Pressure vessels: Today, even as companies introduce
smaller than 20 liter units, most returnable solvent containers are designed
for positive pressure dispensing. Pressure dispensing introduces additional
regulatory considerations.The three types of positive pressure containers
now in the market are UN1A1/UN1A2, ASME or DOT.
The UN1A1/UN1A2 container is built to UN performance test specifications,
which are accepted by DOT (US Department of Transportation), TC (Transport
Canada) and most of the countries of the world. However, UN 1A1/2 containers
are not pressure vessels which means they are not legal for shipping
with pressures over 25 psig*. (*Flammable materials as defined in 49
CFR as Division 2.1 (Flammable Gas) are addressed by the DOT during
transportation even if they do not meet the pressure criteria of a “compressed
Some UN1A1 containers are marked with pressure ratings
exceeding 25 psig. However, by DOT regulation these ratings are only
to control the vapor pressure developed by the liquid in the container.
Only DOT specification or DOT exemption containers may be shipped under
pressure in the United States. NFPA codes (NFPA 45 (1966 Edition) 8-1.3)
require a pressure vessel for pressures over 15 psig. Many states –
such as required by California OSHA - have statewide requirements that
any pressure vessel must meet requirements of their "unfired boilers
and pressure vessel" codes. Pressure vessels are, in most jurisdictions,
either DOT (US Department of Transportation) or ASME containers.
ASME (American Society of Mechanical Engineers)
ASME containers are certified as pressure vessels by meeting strict
ASME codes for the particular pressure rating marked on the container.
NFPA 30 also addresses on-site pressure tanks which must meet ASME code.
A container "made to ASME" specifications but not marked with an ASME
registered symbol is not an ASME pressure vessel.
Note again that ASME containers are not allowed for shipping
of pressurized materials by the US DOT or Transport Canada. Therefore,
ASME containers cannot be shipped with more than 25 psig pressure -
although they can be used up to their rated pressure at the user’s location.
DOT pressure vessels (the most common are gas cylinders) are built to
DOT specifications (or an approved exemption to a listed specification)
for a rated pressure. DOT cylinders may be legally shipped and used
at pressures up to their rated pressure. The pressure at 70O F (called
the service pressure) is the maximum pressure a cylinder can be filled
to or shipped at. The shipment of flammable solvents in DOT pressure
vessels is allowed by 49CFR, paragraphs 173.101, 173.201-203 and 173.305
The NFPA allows the use of DOT pressure vessels. DOT cylinders
have been used for decades in all 50 states with non-flammable (Division
2.2), flammable (Division 2.1) and poisonous (Division 2.3) materials.
In a proposed revision to NFPA 45, the maximum size of
cylinders allowed in laboratories may be changed to be consistent with
DOT regulations. DOT, flammable liquid cylinders may be up to 100 pound
water capacity (about 45 liters).
Some companies market containers that are Factory Mutual
(FM) approved. The FM approval is not recognized in current pressure vessel
codes. In fact, in our experience, FM approval guidelines are much less
strict than ASME or DOT pressure vessel codes. The FM approval should
not be considered a substitute for these proven and mandatory codes.
FM approval may have merit for any electronic volume sensors
that may be used on the containers.
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3. Safety Practices
Associated with a (Returnable) Pressure Dispensing Container (PPDC)
The concept of positive pressure solvent dispensing has raised
safety questions in the minds of some people. Concerns about pressurized
liquids are tempered by the fact that the safe piping and dispensing of
compressed gases from cylinders is an everyday practice in hundreds of
thousands of laboratories. In fact, DOT flammable gas cylinders have been
used in laboratories for almost 100 years. We believe the concepts used
for compressed gas dispensing will also provide safe solvent dispensing.
Strong, essentially unbreakable containers can be placed
in labs, solvent cabinets or in cylinder storage areas. Solvents are dispensed
through stainless steel piping to the point of use. Valves and regulators
provide safe flow control and shut off just as with compressed gases.
One must always also consider the current problems with solvent
bottles in laboratories. Is having a person pouring a four liter bottle
of a flammable solvent into an instrument reservoir (often higher than
their heads) a safe procedure when judged against the hazard analysis
hurdle often brought out to judge a PPDC. Safe handling and storage requires
good housekeeping practices to be compliant with NFPA requirements. Some
labs exceed recommended storage limits by storing cases of solvents far
exceeding allowable limits and we have even seen the use of pressure to
dispense from bottles or plain solvent cans. The use of containers that
are not pressure vessels is both unsafe and illegal.
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4. The PTI-20 Returnable Solvent Cylinder
The Purification Technologies PTI-20 is called a cylinder
because it is the only returnable solvent container which is built of
316 stainless steel to DOT pressure vessel specifications. We selected
a DOT pressure vessel because the unit can be shipped and returned with
pressure. (Remember if the customer does not properly vent a non-DOT container,
they are the “shipper of record” and therefore liable for fines that can
run into the thousands of dollars.)
Use of DOT cylinders also allows the solvent filler to pre-pressurize
the container for dispensing and for the customer to return with residual
pressure if necessary. Possible fines are eliminated which can happen
when shipping a pressurized UN1A1 or ASME container.
The PTI-20 can be used to dispense solvents from cylinder
storage areas. The PTI-20 may also be used to dispense solvents from within
laboratory areas although it should be in a solvent cabinet. This restriction
may be eased with the revision of NFPA 45.
Purification Technologies does not recommend UN1A1 containers
for pressure dispensing unless they also meet ASME specifications. Since
UN1A1 containers are not approved pressure vessels, there are potential
safety and liability problems when used with positive pressure. A “tested
to” pressure does not mean “rated for” pressure.
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Copyright ©2004, Purification Technologies, Inc., U.S.A.
All rights reserved.