The fundamental reason for measuring flash point is to assess the safety hazard of a liquid with regard to its flammability and then classify the liquid into a recognized hazard group.
Classifying the flammability of fuels and
other materials by their flash point value has been an established practice
for more than 100 years. Today mandatory international and national regulations
are set by bodies such the UN, IATA, EPA, EU, and Health and Safety executives.
The fundamental reason for measuring flash
point is to assess the safety hazard of a liquid with regard to its flammability
and then classify the liquid into a recognized hazard group. This classification
is used to warn of a risk and to enable the correct precautions to be taken
when manufacturing, storing, transporting or using the liquid. Flash point
requirements are listed in regulations and product specifications.
What is flash point?
The flash point of a fuel is essentially the lowest temperature at which
vapours from a test portion combine with air to give a flammable mixture and
‘flash’ when an ignition source is applied.
Specifications quote flash point values for quality control purposes as
well as for controlling the flammability risk. The lower the flash point
temperature the greater the risk. A change in flash point may indicate the
presence of potentially dangerous volatile contaminants or the adulteration
of one product by another.
The measurement of flash point is defined
in test methods that are maintained by standardization bodies such as the
Energy Institute in the UK, ASTM in the USA, CEN in Europe and ISO internationally.
Over the last few years the focal point for flash point test methods has
become the CEN/ISO Joint Working Group on Flash Point.
Which flash point test?
In general flash point is measured by apparatus named ‘open cup’ or ‘closed
cup’. ‘Open cup’ tests are required in some specifications and regulations,
and are intended to mimic conditions in open spaces whereas ‘closed cup’ tests
are closer to most situations, where space is restricted. ‘Closed cup’ tests
are more usually specified as the test results are less affected by laboratory
conditions and give a more precise and lower (safer) result. There are 4
major ‘closed cup’ flash point tests which are specified nationally and internationally
for testing fuels and other materials: Pensky-Martens, Small Scale (Setaflash),
Abel and Tag.
The table below gives some examples
where the Small Scale test is specified or mandated.
|Material to be tested||Test method||Who says so|
|Aviation turbine fuel||Abel, Tag, Small Scale||ASTM D1655 and Def Stan 91-91|
|Gas turbine fuel||Pensky-Martens, Small Scale||ASTM 2880|
|Diesel fuel||Pensky-Martens, Small Scale||ASTM D975|
|Kerosines||Tag, Small Scale||ASTM D3699|
|Biodiesel (100% FAME)||Small Scale||EN14213 and EN14214|
|Transport regulations||Small scale, Other closed cups||UN, IATA, regulatory bodies|
|General ignitability||Small Scale||EPA 1020 A and B|
|Fuel oil|| Pensky-Martens A and B, Small
|Naphthas||Tag, Small Scale||ASTM D3734 and D3735|
|Raw Tung Oil||Small Scale||ASTM D12|
|Water borne paints||Small Scale||ISO 3679, ISO 3680|
|Waste products||Small Scale||European Waste Directive|
The Small Scale (Setaflash) Closed Cup test
is specifically identified by the following test methods: ASTM D3278, ASTM
D3828, IP303, IP523, IP524, EPA 1020 A and B, ISO 3679 and ISO 3680.
Why is the Small Scale accepted universally?
The Small Scale test method and the uniquely approved Setaflash Tester have
been in use for over 30 years, primarily for a one minute test with 2 ml of
sample to carry out a flash no-flash test, and more recently for automatic
flash point determinations.
During these 30 years, comparative tests
and collaboration with bodies such as the Institute of Petroleum, ASTM D01
and D02, British Railways, Commission of the European Communities, National
Research Council Canada, BSI, UK Ministry of Defence, Transport and Road
Research Laboratory, Paint Research Association and the major international
oil refiners, may be summarized by the following well recorded statements;
‘ASTM evaluation studies of the Setaflash
Tester demonstrate the excellent correlation between the Setaflash and the
Tag Closed and Pensky-Martens Testers. In addition ‘the repeatability and
reproducibility of the Setaflash are definitely better than values found
using Pensky-Martens’ and ‘the precision of the Setaflash is equivalent or
slightly better than the Tag Closed Tester’.
This performance and proven equivalence for
specific materials has resulted in the adoption of the Small Scale test
method in a wide range of product specifications and regulations. Today
Setaflash Testers are in daily worldwide use by thousands of laboratories
to test hundreds of different liquids.
The Setaflash family
The Setaflash Tester has evolved into a modern family of manual and automated
instruments incorporating automatic temperature control and flash detection.
A version with an electric ignitor has also been announced. In addition an
open cup tester is available for mandated combustibility testing.
Is the Small Scale test the
International transport regulations allow
the use of a number of so called ‘non-equilibrium’ closed cup tests such
as the Pensky-Martens, Tag or Abel to assess ‘flammability’ criteria. However,
if a result is within 2°C of a defined limit, the use of an equilibrium
test is mandated. In this instance the Small Scale test or another equilibrium
test is the referee. Under these circumstances the Setaflash is usually
selected because its one minute test is preferable to the 2 hours taken
by other equilibrium tests.
In product specifications it will be made
clear which test method is the referee.
Choosing which flash point method can be
difficult, however a new CEN/ISO document, Petroleum products and other liquids
– Guide to flash point testing, gives advice and will be available in 2005.
The concept of the Small Scale test eliminates
the possibility of heating the test sample above the test temperature, avoids
the loss of volatile constituents, is the fastest test available, has excellent
available precision and an in depth history of comparative tests and equivalent
results. From these facts it is clear that the Small Scale test is The Definitive
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