CEN/TR 16389:2012

SLOVENSKI STANDARD
oSIST-TP FprCEN/TR 16389:2012
01-maj-2012
*RULYD]DPRWRUQDYR]LOD3DUDILQVNRGL]HOVNRJRULYRLQL]KRGLãþD]DKWHYDQLK
SDUDPHWURYPHMQLKYUHGQRVWLLQGRORþHYDQMD
Automotive fuels - Paraffinic diesel fuel and Background to the parameters required and
their limits and determination
Kraftstoff für Kraftfahrzeuge - Paraffinischer Dieselkraftstoff und Kraftstoff-Mischungen -
Hintergrund zu den erforderlichen Parametern, den entsprechenden Grenzwerten und
deren Bestimmung
Carburants pour automobiles - Gazole paraffinique - Historique sur la définition des
paramètres requis, de leurs limites et de leurs déterminations respectives
Ta slovenski standard je istoveten z: FprCEN/TR 16389
ICS:
75.160.20 7HNRþDJRULYD Liquid fuels
oSIST-TP FprCEN/TR 16389:2012 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST-TP FprCEN/TR 16389:2012
oSIST-TP FprCEN/TR 16389:2012
TECHNICAL REPORT
FINAL DRAFT
FprCEN/TR 16389
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
March 2012
ICS 75.160.20
English Version
Automotive fuels - Paraffinic diesel fuel and blends -
Background to the parameters required and their respective
limits and determination
Carburants pour automobiles - Gazole paraffinique - Kraftstoff für Kraftfahrzeuge - Paraffinischer Dieselkraftstoff
Historique sur la définition des paramètres requis, de leurs
und Kraftstoff-Mischungen - Hintergrund zu den
limites et de leurs déterminations respectives erforderlichen Parametern, den entsprechenden
Grenzwerten und deren Bestimmung

This draft Technical Report is submitted to CEN members for Technical Committee Approval. It has been drawn up by the Technical
Committee CEN/TC 19.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to
provide supporting documentation.

Warning : This document is not a Technical Report. It is distributed for review and comments. It is subject to change without notice and
shall not be referred to as a Technical Report.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprCEN/TR 16389:2012: E
worldwide for CEN national Members.

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FprCEN/TR 16389:2012 (E)
Contents Page
Foreword .3
1 Scope .4
2 Normative references .4
3 Summary of the XTL-HVO taskforce work .4
4 Record of the work to date .5
4.1 Context .5
4.2 Paraffinic diesel fuel and FAME blending Task Force .6
4.3 Planning .6
5 The draft paraffinic diesel fuel specification .7
5.1 Parameters included .7
5.2 Considerations on the parameters .8
5.2.1 Cetane number .8
5.2.2 Density .9
5.2.3 Flash point . 10
5.2.4 Viscosity . 11
5.2.5 Distillation characteristics . 12
5.2.6 Lubricity . 13
5.2.7 Total aromatics content . 14
5.2.8 Sulfur content . 15
5.2.9 Contamination . 15
5.2.10 Copper strip corrosion . 16
5.2.11 Oxidation stability . 16
5.2.12 FAME . 17
5.2.12.1 FAME content . 17
5.2.12.2 FAME contamination issues . 17
5.3 Parameters considered and not included in the draft specification . 18
5.3.1 Poly-cyclic aromatic hydrocarbon and olefin content . 18
5.3.2 Elastomer compatibility . 19
5.3.3 Cetane index . 20
6 Conclusions . 20
7 Acknowledgement . 20
Bibliography . 21

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Foreword
This document (FprCEN/TR 16389:2012) has been prepared by Technical Committee CEN/TC 19 “Gaseous
and liquid fuels, lubricants and related products of petroleum, synthetic and biological origin”, the secretariat of
which is held by NEN.
This document is currently submitted to the Technical Committee Approval.
This document presents all decisions that led to the proposed draft of FprCEN/TS 15940 in order to support
the enquiry ballot. This document includes all decisions that have been taken following comments and further
investigations leading to the effective publication of the specification for paraffinic diesel from synthesis (XTL)
or hydrotreatment (HVO).
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1 Scope
This document explains the requirements and test methods for marketed and delivered paraffinic diesel from
synthesis (XTL) or hydrotreatment (HVO) and of blends thereof with fatty acid methyl esters (FAME) according to
European fuel specifications. It provides background information to judge the (approval of the) final text of the
standard and gives guidance and explanations to the producers, blenders, marketers and users of paraffinic
automotive diesel.
NOTE 1 This document is directly related to the pending development of FprCEN/TS 15940 and should be updated
once further publications take place.
NOTE 2 For the purposes of this document, the term “% (m/m)” and “% (V/V)” are used to represent the mass
fraction, µ, and the volume fraction, φ, respectively.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN 590, Automotive fuels – Diesel – Requirements and test methods
prEN 14214:2011, Liquid petroleum products — Fatty acid methyl esters (FAME) for diesel engines —
Requirements and test methods
CWA 15940, Automotive fuels — Paraffinic diesel from synthesis or hydrotreatment —Requirements and test
methods
3 Summary of the XTL-HVO taskforce work
Following the 68th CEN Technical Board meeting, CEN/TC 19 had been requested to check eventually existing
conflicts between the scope of work as proposed for Workshop 61 on "Automotive fuels - Blends of paraffinic
diesel from synthesis (XTL) or hydrotreatment (HVO) and fatty acid methyl esters (FAME) - Requirements and
test methods". At a CEN/TC 19/WG 24 meeting on 30 November 2010, the consensus was that there was a
possible conflict between EN 590 and the Workshop 61. The advice to both the proposers and CEN/TC 19 was to
take upon the work on XTL/HVO. A TF under WG 24 was established in order to address the matter and also
allowing specific paraffinic diesel fuel and engine experts to exchange information.
On 13 December 2010, the workshop 61 proposers had a teleconference with the TC Chairman and Secretary on
the way forward for the agreed upon TF under WG 24. In the spirit of harmonisation, they thought it advisable that
the already existing CWA 15940 should also be revised. That document had been developed in 2007 – 2009 by a
CEN Workshop 38 and was meant for dedicated fleet usage. As already in 2010, XTL product were already
reaching the EU and certain fleets had expressed interest in purchases on the basis of CWA 15940, the CWA
would need to stay in place until any revisions had been completed.
Hence, a proposal to accept the idea of Workshop 61 as an active work under CEN/TC 19, followed by a revision
of CWA 15940 was balloted. At the plenary meeting of May 2011, CEN/TC 19 accepted the two proposals for new
work. In view of the time pressure, the paraffinic diesel - FAME blends needed to be specified via a CEN/TS.
The work on the specifications was developed during a series of Paraffinic diesel fuel and FAME blending Task
Force (TF XTL-HVO) meetings between May and November 2011, and is presented by means of this Technical
Report. The draft technical specification, now referenced by the identification FprCEN/TS 15940, comprises a set
of properties and limit values to define an adequate quality of the paraffinic diesel fuel and recommendations for
precautions to be taken.
Revision pending
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Discussion in the TF started with the task to handle only blends with FAME; CWA 15940 was to remain for the
short term as an assurance for the industry for a non-FAME containing product. This meant that the actual
situation from 0% to 7% as in EN 590 was copied. Because CWA 15940 allowed limited FAME blending for
lubricity, the TF concluded that distinguishing (for instance via classes) between no FAME and up to 7%
FAME would be highly artificial. Therefore, a suggestion to CEN/TC 19 was made to draft the CEN/TS as a
replacement of CWA 15940 and to use it for up to 7% blending.
It should be noted that the draft standard has been considered on the basis of the FAME blend component
specification prEN 14214:2011 (FAME) and the last version of the EN 590 (diesel) standard. Revision discussion
on those documents has been included in the discussions. However FprCEN/TS 15940 still contains some
pending issues, which are noted as such in the text of this Technical Report.
Many of the test methods proposed by the test methods experts are being examined to determine their
applicability to paraffinic fuel and to determine if their precision is sufficient to support the limit values proposed.
This activity is being undertaken in several other CEN working groups where the specialists in methods are
present.
4 Record of the work to date
4.1 Context
From an environmental perspective, paraffinic diesel is a high quality, clean burning fuel with virtually no sulfur
and aromatics. Paraffinic diesel fuel can be used in existing diesel engines, substantially reducing regulated
and unregulated emissions. In order to have the greatest possible emissions reduction, a specific calibration
may be necessary. Paraffinic diesel fuel will also offer a meaningful contribution to the target of increased non-
petroleum/renewable content in transportation fuel pool.
As some production processes result in a fuel containing cyclo-paraffins, next to n paraffins and iso paraffins,
they show different cetane number compared to other paraffinic diesel fuels. Hence, two classes, showing
improved ignition quality compared to regular diesel fuel, have been defined. Both are intended for use in
dedicated diesel vehicle fleets.
Worldwide, energy policy makers are increasingly keen to move away from petroleum-based fuels to more
diverse or renewable sources of energy for reasons of environmental protection, energy security and
continued economic development. Amongst the available solutions are the synthetic paraffinic fuels, already
discussed in a CEN workshop WS 38, which led to the workshop specification CWA 15940. Typical production
processes, covered by that workshop, are:
1) Fischer Tropsch synthesis (XTL),
2) Hydrotreatment of vegetable oils (HVO), and
3) Conversion of olefins to distillates (COD).
The WS 38 activity in 2007 to 2009 covered the requirements and test methods for the B0 variants of
paraffinic fuels (where B0 indicates no addition of FAME components). However, against the background of
the EU Renewable Energy Directive (RED, 2009/28/EC [1]) and also the latest EN 590 regular diesel
specification which allows B7 FAME blends, there is now a pressing requirement to allow for Bx variations of
those paraffinic fuels, which are not already classified as being from renewable resources.
Allowing a Bx variant of paraffinic diesel up to B7, in the same way that the EN 590 specification allows for
refinery diesel up to B7, would have the following advantages:
a) Gives flexibility of synthetic diesel supply within EU against the backdrop of both the Renewable Energy
Directive and the Fuels Quality Directive (2009/30/EC [2]), which demand total fuel supply contains
certain percentages of bio-components, to decrease fossil energy usage.
b) Brings a synthetic diesel CWA specification totally in line with the EU refinery diesel specification EN 590.
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The original intention of CEN/TC 19 was to redraft the CWA into a CEN Technical Specification for the FAME
blend up to 7%, based on the publication of EN 14214 and EN 590. The aim of the TF was to keep the
specification simple and straightforward, allowing blends to be introduced in the market for dedicated vehicles
or fleets. The original idea was to ensure basic car functionality, for which the existing CWA succeeded. From
the beginning it was felt advantageous for the market to first draft a FAME blend specification and thus not
immediately replace the CWA. However, because technically one could not sufficiently distinguish the two and
any "no-FAME" guarantee could only be given in a purchase contract, it was decided to continue on the path
of replacing the CWA by a specification for paraffinic diesel fuel in general, assuming it could be blended up to
7 % (V/V) of FAME.
This document is the report on the work to date carried out by the TF XTL-HVO towards establishing a
European Technical Specification for paraffinic diesel – FAME blends.
4.2 Paraffinic diesel fuel and FAME blending Task Force
CEN, requested CEN/TC 19/WG 24 to convene a task force and begin work on a draft paraffinic diesel fuel
and FAME blend standard. A call was made to the industries concerned for experts to participate in the TF
XTL-HVO. The experts that have contributed to the work during the years are listed in Table 1.
Table 1 — Membership of the taskforce
Name Organisation Country
Andras Hollo MOL MSZT
Andreas Eklund EcoPar SIS
Benoit Engelen Total NBN
Gérald Crépeau PSA AFNOR
Jörg Ullmann Robert Bosch DIN
Jose Gomez-Martinech Cepsa AENOR
Ludivine Pidol IFP AFNOR
Markku Kuronen Neste Oil SFS
Pascal Manuelli Total AFNOR
Piet Roets Sasol TC19
Richard Clark Shell NEN
Róbert Auer MOL MSZT
Sören Eriksson Preem SIS
Thierry Chapus IFP AFNOR
Thomas Wilharm ASG Analytik-Service DIN
Ulrich Nowak MB Holding UPEI
Wolfgang Dörmer BP Europe SE Global Fuels Technology DIN
Wolfgang Lueke * Shell NEN
The task force has met on the following occasions:
0) 24 October 2010, Brussels, kick-off meeting WS 61
st
1) 6 May 2011, Brussels, 1 meeting
nd
2) 7 June 2011, Brussels, 2 meeting
rd
3) 21 July 2011, Paris, 3 meeting
th
4) 7 September 2011, Brussels, 4 meeting
th
5) 7 November 2011, Brussels, 5 meeting

4.3 Planning
The initial planning of the paraffinic diesel fuel specification was: CEN/TS enquiry text to be provided to
WG 24 in November 2011, enquiry ballot to start in February 2012, comments to be handled July 2012 and
the final text to be delivered to CEN/CMC in October 2012.
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The draft paraffinic diesel fuel specification
5.1 Parameters included
The original CWA had been established for dedicated vehicle use, although it was at that time felt that there would
be no need to exclude other uses as long as someone would guarantee the engine functioning. The first scope of
work given to the task force was to present a specification for captive fleets. At the third meeting that limitation
was accepted and it was suggested copying the captive fleet description of the B30 TF. As it presented some
further understanding difficulties towards the original CWA scope, that was reformulated into: "This document
specifies requirements and test methods for marketed and delivered paraffinic diesel fuel blended with fatty acid
methyl ester (FAME) up to a level 7 % (V/V), for use in diesel engine vehicles. Paraffinic diesel fuel originates from
synthesis or hydrotreatment processes."
All parameters discussed in this document are either based on the paraffinic nature of the XTL and HVO (and
thus of importance for the replacement of CWA 15940) and on the introduction of FAME complying with
EN 14214 as a blending component (thus specific to the Bx-blend specification).
The parameters chosen by the TF are those presented in Table 1 (general requirements) and in 5.7 (seasonal
th
requirements) of FprCEN/TS 15940:2012. After the 4 meeting, all-but-two of the parameters were agreed upon
in full consensus, where the seizure and cavitation prevention needed further clarification from outside the
taskforce. All the test methods applicability had been checked within CEN/TC 19 or are under improvement
process (like EN 116). An overview of the assessment is presented in Table 2, the last three columns. These
respectively present an idea on the applicability of the test method as is, where a test method revision is needed
to incorporate paraffinic diesel fuel in the scope or where an assessment by a full Round Robin study is required.
NOTE 1 For exact references to the test methods, see FprCEN/TS 15940.
NOTE 2 For not included parameters see 5.3.
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Table 2 — Test methods' assessment
Property Unit Test method
Applicability Precision Assessment
not needed
available
Cetane number EN ISO 5165 X X
a
EN 15195 X X
Density at 15 °C kg/m EN ISO 3675 X
EN ISO 12185 X
Flash point °C EN ISO 2719 X
Viscosity at 40 °C mm /s EN ISO 3104 X X
Distillation °C or EN ISO 3405 X
% recovered
b
Lubricity, corrected wear scar µm EN ISO 12156-1 X X

diameter (wsd 1,4) at 60 °C
FAME content % (V/V) EN 14078 X X
Total aromatics content % (m/m) EN 12916 X X
SIS 155116 X X
c
Sulfur content mg/kg EN ISO 20846 X X
c
EN ISO 20884 X X
Carbon residue % (m/m) EN ISO 10370 X X
(on 10 % distillation residue)
Ash content % (m/m) EN ISO 6245 X
Water content mg/kg EN ISO 12937 X
b
Total contamination mg/kg EN 12662 X X
Copper strip corrosion rating EN ISO 2160 X
(3 h at 50 °C)
Oxidation stability g/m EN ISO 12205 X
h EN 15751 X
b
CFPP °C EN 116 X X
Cloud point °C EN 23015 X
b
Cetane index EN ISO 4264 [3]  X
a
Depending on the outcome of the work of CEN/TC 19/WG 35
b
Method under revision
c
Depending on the outcome of consultation of CEN/TC 19/WG 27

5.2 Considerations on the parameters
5.2.1 Cetane number
Cetane number is a measure of the compression ignition behaviour of a fuel; it influences cold startability,
exhaust emissions and combustion noise. The cetane number is measured on a test engine or determined by
DCN equipment and reflects the combination of the natural self-ignition properties and the effects of cetane
improver additives.
The choice of 2 different classes originates from the aspect of the differences between the processes that
result in different chemical composition. The processes are the low-temperature and high-temperature
Fischer-Tropsch (LTFT and HTFT). Because, a higher cetane number is an advantage for some applications,
the specific distinction between regular diesel class (minimum cetane of 51) and a high-cetane fuel (minimum
70) has been incorporated in the CEN/TS.
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As the composition of LTFT GTL is highly paraffinic, the linear paraffins of these diesel fuels have very high
cetane numbers, in excess of 73. Generally, a high cetane number leads to a reduction in white smoke, noise,
engine misfire, emissions and improve cold starting in some engines, especially in engines without pilot
injection. HTFT GTL will in general be produced with a cetane between 52 and 65. A clear cut for the LTFT
and HVO processes was 70, it being a clear identification of the products advantage. The number has been
based on good experience, also looking at the test method's precision. In earlier discussions in the CWA a
maximum cetane had been considered by the OEMs, but such would at this stage be difficult to correctly
measure.
In the CWA 15940 the goal was to clarify that the product had an improved cetane. Therefore originally a
minimum of 55 had been included. The OEMs wished to have a certain band in order to tune the engine
where possible. The original band was 55 to 70. Because 55 was really borderline for the HTFT producers,
the minimum was lowered to 51 and the maximum to 66 in order to preserve the band width.
At the fourth meeting, of the new TF, the classes were reviewed. Based on the test method precision the two
classes cannot correctly be distinguished. With the four points gap, it might happen that a producer has a
correct product for the high cetane class, but cannot constantly measure 68 due to the test method
imprecision. At such moment the producer would not be be allowed to sell a correct product. The taskforce
agreed to remove the middle ground and to delete the maximum on class B (regular cetane).
The effective correlation between DCN and CN for regular diesel and paraffinic diesel fuel is still under study.
Pending further clarification within CEN/TC 19, the limits need to be assessed again.
5.2.2 Density
Paraffinic diesel fuel density is often lower than a diesel fuel in the field. FAME density is higher than that of
fossil diesel fuel, with the specific values depending on fatty acid composition and purity. Most batches of
FAME contain only about ten different molecules with densities usually within a very narrow range.
Contamination can significantly affect FAME density, so this property can be used to indicate contamination
by some unwanted compounds and to monitor fuel quality.
The diesel fuel injection is controlled volumetrically or by timing of the solenoid valve. Variations in fuel density
(and viscosity) result in variations in engine power and, consequently, in engine emissions and fuel
consumption. Therefore, in order to optimise engine performance and tailpipe emissions, OEMs prefers both
minimum and maximum density limits be defined in a fairly narrow range. Moreover, the (volumetric) injection
quantity is a control parameter for other emission control systems like the exhaust gas recirculation (EGR).
Variations in fuel density therefore result in non-optimal EGR-rates for a given load and speed point in the
engine map and, as a consequence, influence the exhaust emission characteristics.
Car makers prefer a narrow range of density for a good driveability. For durability a minimum limit and for
exhaust emission a maximum limit is important, therefore the range should be maximum 40 points.
Generally, FAME is known to have density values in the region of 0,880 kg/l, which are higher than the density
values of paraffinic diesel fuels such as LTFT diesel. Therefore, it is expected that the blending of most FAME
fuels with paraffinic diesel fuels will increase the density of the resulting blends. Work carried at Sasol on
blends of FAME and (LTFT) paraffinic diesel confirmed that the density of the resulting blends is higher than
the paraffinic diesel (see Table 3 and Figure 1).
At the fifth TF meeting, information was presented by one producer that density ranges for some production
facilities will be just below the 770 kg/m lowest limit of class A. In order not to unnecessarily exclude any
actual paraffinic diesel process routes, the group agree to lower the limit to 765 kg/m . As this differs from
earlier ranges, it may create additional validation needs.
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Table 3 — Density exammples (in kg/m ) for paraffinic diesel FAME bleends
Diesel FAME blends
% (V/V) FAME
FAME blend 0,00 0,5 1,0 5,0 7,0 10,0 220,0
stock density
881,1 769,5 770,1 770,7 775,5 777,6 781,4 7793,2
879,4 769,5 770,1 770,7 774,8 777,7 781,2 7792,9

Key
♦ soy X-axis FAME content (% (V/V) )
■ rapeseed Y-axis density at 15 °C (kg/mm )
Figure 1 — Dennsity of paraffinic diesel and FAME blends
5.2.3 Flash point
The flash point temperature is the minimum temperature at which the fuel will ignite (flashh) on application of an
ignition source under specified conditionns. It is used to classify fuels for transport and storage according to
hazard level; minimum flash point tempperatures are (legally) required for proper safetyy and handling of the
fuel. Flash point varies inversely with thee fuel’s volatility, and FAME’s flash point can decrease rapidly as the
amount of residual alcohol increases.
Flashpoint is a legal requirement for dieesel grade fuels. Flash point of a diesel fuel is ddefined as the lowest
temperature at which fuel vapours abovee the liquid will ignite upon exposure to an ignitionn source. As the flash
point of a diesel fuel is associated withh the light (lower boiling) material, a diesel fuel with too much light
material (shorter carbon chain length moolecules) will have a low flash point and it will be hhazardous to handle.
Generally, the flash point of neat FAMEE (soya, rapeseed and palm) fuels is higher thaan that of LTFT GTL
diesel and conventional crude-derived diesel fuels. As a result, all the FAME/LTFT GGTL blending studies
carried out indicated higher flash points ffor the blends.
The parameter is needed for safety aand transport reasons and due to legal requirrements. Flash point
requirement would be "above 55°C", likee in EN 590.
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5.2.4 Viscosity
Kinematic viscosity is an inherent property of diesel and FAME’s different feedstocks that affects injector
lubrication and fuel atomization. Kinematic viscosity for paraffinic type fuels is similar than in mineral diesel.
FAME fuel blends generally have improved lubricity; however, their higher viscosity levels tend to form larger
droplets on injection which can cause poor combustion and increased exhaust smoke under certain operating
conditions. At FAME blending levels up to 7 % by volume, the suggested limits provide an acceptable level of
fuel system performance for the finished fuel blends and allow blending without changing the viscosity of the
base paraffinic diesel fuel.
Viscosity is a measure of a fuel’s resistance to flow and affects the performance of diesel fuel pumps and
injection systems. Viscosity is related to fuel spray atomisation and it is thus required that a fuel should have
good viscosity characteristics to avoid incomplete combustion which could be associated with poor
atomisation of the fuel. If the viscosity is too low, the injection spray is too soft and will not penetrate far
enough into the cylinder and loss of power will occur. Low viscosity has also an influence on sliding by
changing hydrodynamic contacts, e.g. bearings of camshafts, rollers, etc. Also mixed contacts, e.g. piston in
cylinder, can be adversely affected. Moreover, leaking in pressure scaling contacts is increased resulting in
additional heat generation in the system and in reduced quantity injection. The risk of cavitation is also
increased.
High viscosities on the other hand can reduce fuel flow rates, especially at low ambient temperatures,
resulting in insufficient fuel flow and affecting cold start. The pressure build-up in non-pressure controlled
systems like unit injectors is also increased imposing additional stress on system components. The viscosity
of paraffinic diesel is similar to petroleum diesel fuel available in the market. The viscosity of FAME is high if
compared with paraffinic diesel and increases the viscosity of paraffinic diesel when blended. A blending study
with two types of FAME has shown that the viscosity for all the paraffinic diesel blends increased with
increasing FAME concentration. Table 4 and Figure 2 below give the results of a blending study.
Table 4 — Viscosity at 40 °C, of paraffinic diesel FAME blends
Blend percentage 0,00 0,50 1,00 5,00 7,00 10,00 100,00
% (V/V)
FAME 1 viscosity 2,24 2,25 2,26 2,32 2,37 2,44 4,11
mm²/s
FAME 2 viscosity 2,24 2,26 2,27 2,35 2,39 2,47 4,46
mm²/s
Key
A FAME 2 X-axis FAME content in % (V/V)
B FAME 1 Y-axis viscosity in mm²/s
Figure 2 — Viscosity at 40 °C of paraffinic diesel and different FAME blends
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5.2.5 Distillation characteristics
5.2.5.1 Distillation curve
The distillation curve of diesel fuel indicates the amount of fuel that will boil off at a given temperature. The
curve can be divided into three parts:
 the light end, which affects startability;
 the region around the 50 % evaporated point, which is linked to other fuel parameters such as viscosity
and density; and,
 the heavy end, characterised by the T90, T95 and final boiling points, which affects emissions and engine
oil dilution.
Blending FAME to the paraffinic fuels increases the heavy end part. Blending studies carried out by Sasol
have demonstrated that the paraffinic diesel and FAME blends were below 360 °C, which is the maximum T95
of EN 590.
5.2.5.2 Cavitation risk
At the second meeting, the occurrence of paraffinic products with an initial boiling point lower than 160 °C was
tabled. An IBP limitation by the flash point, like originally assumed for normal diesel, was not always observed.
Apparently some paraffinic fuels used in the market have a flash point in line with EN 590, but a lower IBP.
Such may lead to increased cavitation and to a possibility for excessive damaging diffuser and throttle in the
high pressure fuel injection equipment. The risk is more prominent for passenger vehicles than for heavy duty
engines.
For a general use of paraffinic fuels in the European market the FIEMs require an IBP at minimum 160 °C
tested via EN ISO 3405. Because the test method has a rather large imprecision for IBP (5 °C) and the
requirement as such should better be discussed at the level of general diesel requirements, the TF agreed at
that meeting to include a caution statement apart from the specification table. This statement should alert
producers that have a restricted range of fuels and less control on their distillation, resulting in a lower
safeguard to prevent low IBP to occur in their product.
At the third meeting the FIE producers recalled that the existing European vehicle fleet had been validated for
IBP > 160 °C. In some expert's view it would be difficult to exclude all minor components with an IBP below
160 °C. The difficulties around the required distillation cut, method imprecision and writing a specification
around experimental rather than real commercial plants, were discussed. From a lab perspective, it was
proposed executing a RR on the IBP test for paraffinic diesel first. Using the 5 % distillation point was
discussed, but the FIEMs felt such to be not sensitive enough towards the cavitation risk.
A cautionary statement from the point of view of the FIEMs was to make sure that fuels with a low IBP would
be excluded from the market. Although the IBP assessment is difficult, the FIEMs felt that the risk should be
minimised from the beginning. The FIEMs requested that this cautionary statement shall contain a note that
fuels with an IBP < 160 °C shall not be used already for reasons of customer protection. The group did not
accept this unequivocal safety advice.
An indicative votes was called. The first vote was on the introduction of an IBP limit of 160 °C minimum,
monitoring of the IBP values and subsequent removal of the IBP requirement if proven to be not necessary.
This vote received only one vote in favour (negatives and abstentions were not determined). Secondly, it was
voted on the option, to note and monitor the IBP values and to decide on a minimum IBP requirement at a
later stage when it is shown that a minimum IBP requirement is needed. The second vote received 1 negative,
few positives with most abstaining. Following the voting results, a paragraph on “Cavitation prevention” was
added to the draft specification text.
At the fourth meeting, the impact on the refinery to assure an IBP of 160 °C was discussed. While the SGS
nd
market fuel survey presented at the 2 meeting indicated that all regular diesel fulfilled this requirement
another third party survey indicated that 7 % of the fuels would not fulfil such a requirement (while reaching
oSIST-TP FprCEN/TR 16389:2012
FprCEN/TR 16389:2012 (E)
the viscosity limits). In order to check for climatic dependency, the data would be made country-specific. Some
producers did not feel that paraffinic fuel was largely different than regular diesel and that setting a limit would
present large restriction to all the producers as they need to aim at a guaranteed limit. However, CONCAWE
would be requested to present a view point on the IBP in the market. Also a request to the FIEMs was made
to present data on the actual validation of the equipment.
Following the TFs study, it was assumed that a certain small percentage of EN 590 fuels with an IBP below
160 °C is present at the general European diesel fuel market. The exact share varies from fuel to fuel survey
and cannot exactly be quoted. For the EN 590 fuel market, the effect of such fuels on a higher cavitation rate
is limited, since vehicles are refuelled constantly with different EN 590 qualities. Fuels with lower IBPs are only
statistically applied in accordance with their occurrence and their volatile components are diluted by the
previous or following filling that is still in the vehicle tank or will be refilled at the next tank stop. Compared to
the EN 590 fuel market, the case for paraffinic fuels is different. If fuels with an IBP below 160 °C are used
under fleet operation condition (under disregard of the cautionary statement), the vehicle is refilled with the
same fuel low in IBP for a fairly longer period and thus imposing an additional risk of cavitation that is not
covered by the broad vehicle field validation with standard EN 590 diesel. The TF is further investigating the
impact of lower IBPs on the durability of the fuel injection equipment.
5.2.6 Lubricity
5.2.6.1 Requirements
The lubricating components of the diesel fuel are believed to be the heavier hydrocarbons and polar fuel
compounds. Diesel fuel pumps, without an external lubrication system, rely on the lubricating properties of
diesel fuel to ensure proper operation.
Refining processes to remove sulfur tend to simultaneously reduce diesel fuel components that provide
natural lubricity. As diesel fuel sulfur levels decrease, the risk of inadequate lubrication is raising. If paraffinic
diesel is used as such it needs a different, effective lubricity additive in order to protect from wear and seizure.
The ASTM SL-BOCLE test was discussed in this context. It was not certain whether the usual correlation for
aromatic diesel fuels (an SL-BOCLE for a 460 µm HFRR result would mean 3 500 g) was also valid for
paraffinic fuels.
5.2.6.2 Seizure protection
At the first meeting two criteria regarding fuel lubricity were presented as relevant for the fuel injection
equipment manufacturers:
1. Wear, which is representative for continuous (and mostly easily detectable) change in geometric
dimensions of sliding parts and for which the test method and limit are HFRR (EN ISO 12156-1) and a
corrected wear scar diameter (WSD) at 60 °C < 460 µm, and
2. Seizure load, which is representative for a sudden and unpredictable failure and for which the test
method and limit are: SL-BOCLE (ASTM D 6078) and a load > 3500 gram.
There is fair correlation between wear and seizure load found for conventional crude oil based diesel fuels. In
non or low aromatic fuels this correlation can get lost despite lubricity additivation depending on the type of
additive applied. Depending on chemistry, only the risk of wear but not that of seizure will be reduced.
Recalling the long term use of Sasol CTL and Swedish MK I fuel, the group discussed whether problems have
ever been observed in the market with paraffinic fuels. Arctic grade additives used in Sweden were assumed
to have a corrective impact in respect to wear and seizure protection.
At the second meeting Nesteoil showed results of additive impact studies. The impact of FAME was
discussed, plus if the conclusion that the matter was solely of paraffinic nature. Based on the fact that no
issues had been observed in the market, but that some paraffinic diesel fuel obtained in the market had shown
deficiencies, it was agreed to include a warning notice in the specification.
At the following meeting Bosch proposed to include the SL-BOCLE test in the table of requirements. Some
experts thought that this would give the impression that paraffinic fuel would be of lesser quality in general
than regular diesel. Next issue was that the SL-BOCLE test was rather imprecise and some experts discussed
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FprCEN/TR 16389:2012 (E)
about what the effective test would be and how many labs in Europe could effectively execute it. The FIEMs
are not allowed disclosing their results of FIE systems runs on paraffinic fuels because they are bound to
confidentiality agreements they have been required to sign by the paraffinic fuel producers. Thus, it was not
possible to discuss the actual discrepancy between good and bad seizure protection ability in the context of
existing bench test results. The SLBOCLE-level of 3500 g was indicated by Bosch as a correlation to the
actual HFRR limit in Europe. The group felt that appropriate safeguard against seizure should be highlighted
to the fuel supplier and vehicle user. Seizure results in a sudden and unpredictable failure of fuel injection
equipment and in an immediate stop of the vehicle. In the end, the group agreed to include an informative
clause on seizure. The text was established at the third meeting and included in the standard. At the fourth
meeting it was agreed that further explanation would be presented in an informative annex to the specification.
That annex was concluded upon at the fifth meeting.
5.2.7 Total aromatics content
Aromatics are molecules that contain at least one benzene ring. The fuel aromatic content will affect
combustion, flame temperature, particulates and PAH emissions and therefore, NOx emissions.
At the second meeting, the group agreed that there is no test method available that is precise enough to
determine a paraffinic hydrocarbon content.
At the second meeting it was tabled that the usual HPLC-test, EN 12916, was not applicable at the low levels
aimed at. Swedish experience with SS 155116 (excluding the dilution step) was debated.
A typical XTL/HVO diesel is highly paraffinic with traces of aromatics (< 0,03 %). The highly paraffinic nature
results in a fuel that has a higher hydrogen–to-carbon (H/C) ratio compared to petroleum diesel fuels.
Generally, paraffins have a lower density than aromatic hydrocarbons and consequently, the density of the
highly paraffinic XTL/HVO diesel is lower than that of the conventional diesel (0,78 kg/l compared to
0,82 kg/l – 0,85 kg/l for petroleum diesel fuels). The presence of aromatics in conventional diesel results in a
higher density fuel. Aromatics may also have an influence on additive solubility. The composition of the
paraffinic diesel has been shown to result in significant improvements in diesel exhaust raw emissions, with
reduction in regulated emissions of between 21 % and 56 % when compared to a petroleum diesel, and
between 15 % and 27 % when compared to a low emission diesel fuel.
At later meetings, the necessity to set a requirement was discussed. It would merely be a marketing limit and
not a real technical requirement. OEMs can use a low aromatic content guarantee to present a dedicated
maintenance plan for the captive fleets, because the impact on the catalyst is lowered. In the past, the CWA
discussion had been that the lack of a precise enough analytical method to determine the 99 % paraffinic
content led to the decision to limit the aromatics and olefins. The fuel producers position is that wit
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