Fusitive Emmision Test
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Fugitive Emission Testing of a valve under practicalconditions
By Colin Zegers
FE Type approval tests orvalvesType approval tests for valves are
established to check the usefulness ofvalves with seat and sealing-components.
Some type approval tests specify the test
temperature(s), pressure(s) and
operational cycles. Known FE type
approval tests in Europe are TA Luft
regulation in Germany,
ISO15848-1 (worldwide) and SPE 77/300
(the current specication regarding Shell
Type Acceptance Testing).
TA Luft requires testing at practical
conditions where the test temperature
and operational cycles are not strictlyprescribed. For example: a valve with a
TA Luft certicate tested at ambient
temperature with 10 operational cycles, is
only guaranteed for these conditions. Such
valves have been sold with a guaranteed
TA Luft certicate and some of them
were built in a plant with a temperature
application of -25C and hundreds of
cycles per day with serious consequences.
The international ISO15848-1 standard
requires fugitive emission testingand operational cycles at specied
temperature steps, the
number of cycles is specied by the
recommended endurance class.
Following these type approval tests, the
SPE 77/300 is the only type approval
test that species all aspects of a valve:
functionality, external leakage and
seat leakage at the entire specied
temperature
range. A type approval test of a valve
could result in a perfect fugitive emissionrate, however it could be a disaster in
practice concerning seat leakage when
seat testing is not part of the type
approval test.
Besides the type approval testing of valves
one can choose more reliability by only
mounting sealing material in their valves
which has been previously approved
during testing at the entire guaranteedtemperature range. An example of a type
Fugitive emission testing(in practice)
In this article, the author
describes the testing o
valves with regards to ugitive
emissions in practical situations.
Examples, experiences and
possible solutions are presented
and explained in detail aswell as some general terms
are pointed out or better
understanding.
Fugitive emissionsFugitive emissions are emissions of gases or vapours from pressurized equipment due to
leaks and various other unintended or irregular releases of gases, mostly from industrial
activities. As well as the economic cost of lost commodities, fugitive emissions contribute
to air pollution and climate change. When it comes to safety and environment, valves
and appendages should always be extremely reliable. Research has shown that leaking
and faulty valves are responsible for the majority of fugitive emissions in (petro) chemical
plants. Due to this fact it is obvious that valves need to perform to the highest standards.
According to the ESA (European Sealing Association) the rate of fugitive emission in the
USA has been estimated to be in excess of 300,000 tonnes per year. The rate of fugitiveemissions from European reneries ranges from 600 to 10000 tonnes of VOC (Volatile
Organic Compounds) are per year.
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Damaged soft seat during type approval test
under cryogenic conditions
Wear of graphite stem seal during a FE test of a double block and bleed valve Leak rate determining using the snifng hood method
test for packings is the API 622 (valve
packing type testing).
Difcult choices
Unfortunately, some valve manufacturersmake their choice for sealing material for
a certain valve application without paying
attention to possible test reports. They
are therefore only focused on details of
sealing material published on a website,
brochure or folder, in good faith.
Sealing material for valves can be gaskets,
seals, o-rings and (soft)seats. Applying
these materials in their valves, is actually a
leap of faith and can therefore lead to a
high risk in practice.
Too often these materials are sold fora PT range (pressure temperature)
without ever having been tested at these
conditions. In some cases these materials
are not even sufcient for applications
other than low pressure and ambient
temperature. Valves to be type approval
tested with these sealing materials
can pass a test very easily, however
sometimes they do not come further
than a helium pre-test. In the past valves
have been tested for a project, where
the valves were equipped with a speciallow temperature o-ring. Unfortunately
we had to test these valves at ambient
temperature only. All valves passed the
ambient tests perfectly. Once built in
the plant and exposed to the practical
conditions of -40C all valves failed.
During all tests, we are not only focused
on fugitive emissions from seals or gasketsbut also on emissions from the entire valve
body. Sometimes it can happen that the
leakage of a gasket, is via thread or bolting
(the way of the least resistance) and not
through a gasket. It is even a possibility
that a valve is leaking through a body!
Also alarming is the fact that during
random retests, some valves are foreseen
with a test report showing us that this
valve is tested with a certain leak rate A.
However a retest shows that the leakage
rate is rate C or even worse. Sometimesit needs even a stem seal replacement by
a different type or brand seal to meet the
maximum allowable leak rate required by
the end-user.
One reason for the different test results
observed, might be that during previous
tests, the required hold duration is not
respected. A general observation of many
international standards teaches us that the
dened hold duration for general testing
and fugitive emission testing is often too
short.
Most leakages will appear, only after aminutes hold duration instead of a hold
duration of seconds.
Many times a hydrostatic body test of
15 seconds is too short for most valves
(according to API 598 and ISO 5208, the
hydrostatic test duration for a 2 valve is
15 seconds). Especially for higher ratings,
class 600 and higher, the hold duration
should be minutes instead of seconds. The
performance of valves in practice should
be guaranteed longer than a service of 30
seconds.
Certifcate and test reportA certicate of a type approval test tells
us something about the performance of
the valve at cer tain test conditions . The
associated test report is actually a more
important manual for the practice how to
deal with a valve. In this review you can
About the test laboratoryIn our test laboratory, annually hundreds of type approval- and production tests are
performed under controlled conditions for standard specications as well as by yourown specic project demands. The test conditions can var y from deep vacuum to a
pressure of 1500 barg gas with temperatures of -196C to 800C (and over) during
high temperature tests or re safe tests. The required operational cycles can be
performed with computer-controlled actuators. All measured data can be recorded
by a log and registration system so that reporting of tests is fairly simple. Burst tests
can be executed in bunkers in perfectly safe conditions. For almost all valve related
products it is possible to offer a one-stop solution to all NDT and NDT-related
services needed to qualify your product through the highest standards. These
services involve among others:
Radiography (X-ray) Modication / revision of valves
Ultrasonic Testing (US) Hydrostatic Testing
Magnetic Testing (MT) Blasting/degreasing/spray painting Dye Penetrate Testing (PT) Disassembly-assembly
PMI (Positive Material Identication) Hardness Testing
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Leakage of a bonnet gasket via thread of a bonnet bolt O r ing leakage due to low temperature test ing body -40 degC,
Test set up of a ISO 15848 type approval test
(vacuum method)
Emission (leakage) in practice renery
nd all necessary information, such as test
temperatures, the necessary torque for
the gland bush bolts needed to meet the
minimum requirements to start the test,
including some possible adjustments ofthe gland bush bolts during the test. This
information is essential to guarantee a
proper valve operation in practice and the
valve performance in relation to fugitive
emission.
FE production tests or valvesTwo well known production tests are
described in the international standard
ISO 15848-2 and Shell MESC SPE 77/312.
These two requirements specify a test
with a reduced number of operationalcycles at ambient temperature. Also the
test pressure (depending on the revision
77/312 and tightness class) is reduced for
these two tests.
Fugitive emission in practiceEven though the quantities of leaked gases
may be small, leaks of gases that have
serious health or environmental impacts
will always cause a signicant problem.
Research has proven that fugitive
emissions of valves and (its) anges can bea signicant proportion of total emissions
in (petro-) chemical plants (average 65%
of the total fugitive emission, see www.
europeansealing.com. Fugitive emission
is normally one third of the total organic
emission. Besides the impact of these
emissions the real costs resulting from
the emissions are far higher because
of the invisible/indirect costs. Energy
losses, costs of repair, damage to image,
environmental penalties and claims are
potential examples. Our company isspecialized to carry out leak testing of
industrial installations after a shut down or
overhaul.
The cause of leaks we nd during leak
testing these installations could have
several reasons: wrong gasket, gasket
installed incorrectly, loose bolts/nuts and
sometimes a gasket or bolts have noteven been tted! However during some
tests it is remarkable that a high tracer-gas
background in the plant can be measured.
This can be caused by high leaker stem
seals of valves, where leak rates of more
than 10 cc/second per stem seal are no
exception.
Obviously, a type approval test for valves
is needed to see whether the valve
should be able to withstand the required
conditions. Besides the FE tests during the
type approval tests and production tests,the measurement of fugitive emission in
practice is equally important.
Example:A valve has a shaft with a 20 mm diameter.
The maximum leak rate according to TA-Luft
is: 6.28E-6 atm.cc / sec, 3.52E-7 atm.cc /
sec according to ISO 15848-1 rate A(H) and3.52E-6 atm.cc / sec according to SPE 77/312
(Shell). This means that every leakage of 10
cc / sec in practice represents the same leak
rate as more than 1.5 million TA-Luft valves, 28
million rate A ISO valves and 2.8 million rate A
Shell valves!
Routine inspections of process equipment
with gas detectors can be used to identify
leaks and estimate the leak rate in order to
decide on appropriate corrective action. Proper
routine maintenance of equipment reduces the
likelihood of leaks.To ensure a minimum of fugitive emission
for valves, at least every dynamic application
should be regularly checked for leakage to
guarantee the required performance according
to fugitive emission.
About the authorMr Colin Zegers has been involved in the eld of leak testing
with specialty valve testing for almost 12 years now. The Dutch
independent test facility and service provider is able to test
versatile products like: valves, appendages, vessels, heat exchangers
and gaskets for functionality, emission, endurance, leakage and
(re)safety. The test facility is a one-stop shop for testing newly
manufactured products, prototypes and revised valves also onsiteleak testing, project super vision and consultancy can also be provided. You can
contact Colin Zegers at [email protected]
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