© ISO 2017 Petroleum products — Gum content of fuels — Jet evaporation method Produits pétroliers — Teneur en gommes des carburants — Méthode d’évaporation au jet INTERNATIONAL STANDARD ISO 6246 Third[.]
INTERNATIONAL STANDARD ISO 6246 Third edition 2017-03 Petroleum products — Gum content of fuels — Jet evaporation method Produits pétroliers — Teneur en gommes des carburants — Méthode d’évaporation au jet Reference number ISO 6246:2017(E) © ISO 2017 ISO 6246:2017(E) COPYRIGHT PROTECTED DOCUMENT © ISO 2017, Published in Switzerland All rights reserved Unless otherwise specified, no part o f this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission Permission can be requested from either ISO at the address below or ISO’s member body in the country o f the requester ISO copyright o ffice Ch de Blandonnet • CP 401 CH-1214 Vernier, Geneva, Switzerland Tel +41 22 749 01 11 Fax +41 22 749 09 47 copyright@iso.org www.iso.org ii © ISO 2017 – All rights reserved ISO 6246:2017(E) Contents Page Foreword iv Introduction v Scope Normative references Terms and definitions Principle Reagents Apparatus Assembly of air-jet apparatus Assembly of steam-jet apparatus Calibration 10 Samples and sampling 11 Procedure 12 Calculation of gum content 13 Expression of results 14 13.1 Aviation fuels 13.2 Non-aviation fuels 13.3 All fuel types Precision 14.1 General 14.2 14.3 Repeatability, r Reproducibility, R 15 Test report Bibliography 10 © ISO 2017 – All rights reserved iii ISO 6246:2017(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies) The work o f preparing International Standards is normally carried out through ISO technical committees Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters o f electrotechnical standardization The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part In particular the different approval criteria needed for the di fferent types o f ISO documents should be noted This document was dra fted in accordance with the editorial rules of the ISO/IEC Directives, Part (see www.iso org/directives) Attention is drawn to the possibility that some o f the elements o f this document may be the subject o f patent rights ISO shall not be held responsible for identi fying any or all such patent rights Details o f any patent rights identified during the development o f the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso org/patents) Any trade name used in this document is in formation given for the convenience o f users and does not constitute an endorsement For an explanation on the voluntary nature o f standards, the meaning o f ISO specific terms and expressions related to formity assessment, as well as in formation about ISO’s adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso org/iso/foreword html This document was prepared by ISO/TC 28, Petroleum products and related products of synthetic or biological origin This third edition cancels and replaces the second edition (ISO 6246:1995), which has been technically revised and aligned with ASTM D381[1] It also incorporates the Technical Corrigendum ISO 6246:1995/Cor 1:1998 The changes incorporate modern methods for temperature measurement and clarification o f various measurement limits Some process steps on the rounding of results are added The precision in the ormer edition was based on very old data using samples that did not contain components found in modern gasoline, such as oxygenated compounds and deposit control additives New precision estimates from a 1997 joint ASTM/EI study[3] are included Unwashed and washed gum results for nonaviation fuels can now be expressed to the nearest 0,5 mg/100 ml This study and additional work in ASTM[4] and CEN in 2014[5] have led to broadening of the scope to modern gasoline (blends) f iv © ISO 2017 – All rights reserved ISO 62 46: 017(E) Introduction T he tr ue s ign i fic ance o f th i s te s t me tho d for de term i n i ng gu m in mo tor gas ol i ne is no t fi rm ly e s tabl i s he d I t s b e en proven th at h igh gu m content c an cau s e i nduc tion- s ys tem dep o s its a nd s ticki ng of intake valves, and in most cases, it can be assumed that low gum content will ensure absence of i nduc tion- s ys tem d i ffic u ltie s T he u s er shou ld , however, re a l i z e that the te s t i s no t o f its el f correlative to i nduc tion- s ys tem dep o s its T he pri ma r y pur p o s e o f the te s t, a s app l ie d to mo tor ga s ol i ne, i s the me a s urement o f the oxidation pro duc ts forme d in the s ample prior to or duri ng the comp aratively m i ld cond ition s o f the te s t pro ce du re Si nce many ki nd s o f mo tor gas ol i ne a re pu rp o s ely blende d with non-volati le oi l s or add itive s , the hep ta ne e xtrac tion s tep i s ne ce s s a r y to remove the s e from the evap oration re s idue s o that the deleterious material, gum, can be determined With respect to aviation turbine fuels, large quantities o f gum are i nd ic ative o f contam i nation o f fuel b y h igher b oi l i ng oi l s or p a r tic u late matter and genera l ly refle c t p o or nd l i ng prac tice s i n d i s tribution down s tre am o f the refi ner y © ISO 2017 – All rights reserved v INTERNATIONAL STANDARD ISO 6246:2017(E) Petroleum products — Gum content of fuels — Jet evaporation method WARNING — The use of this document can involve hazardous materials, operations and equipment This document does not purport to address all of the safety problems associated with its use It is the responsibility of users of this document to take appropriate measures to ensure the sa fety and health o f personnel prior to application o f the document, and fulfil statutory and regulatory requirements for this purpose Scope T h i s c u ment s p e c i fie s a me tho d for de term i n i ng the e xi s tent gu m content o f avi ation fuel s a nd the gum content of motor gasoline or other volatile distillates It includes the determination of products f f additives For determination of gum content in automotive ethanol (E85) fuel, no precision data is available (see 14.1) For non-aviation fuels, a procedure for the determination of the heptane-insoluble portion of the residue is also described conta i n i ng e th anol (up to a volu me rac tion o %) and e ther-typ e ox ygenate s and dep o s it control CAUTION — This method is not intended for the testing of gasoline components, particularly those with a high percentage of low-boiling unsaturated compounds, as they can cause explosions during evaporation Normative references T he fol lowi ng c u ments are re ferre d to i n the tex t i n s uch a way th at s ome or a l l o f thei r content s titute s re qu i rements o f th i s c u ment For date d re ference s , on ly the e d ition cite d appl ie s For u ndate d re ference s , the late s t e d ition o f the re ference d c ument (i nclud i ng a ny amend ments) appl ie s ISO 3170, Petroleum liquids — Manual sampling ISO 3171, Petroleum liquids — Automatic pipeline sampling ISO 3696, Water for analytical laboratory use — Specification and test methods ISO 4259, Petroleum products — Determination and application of precision methods of test ISO 4788, Laboratory glassware — Graduated measuring cylinders ASTM E2251-14, Standard specification for liquid-in-glass ASTM precision liquids data in relation to thermometers with low-hazard BS 2000, IP standard thermometers Terms and definitions For the pu r p o s e s o f th i s c u ment, the fol lowi ng term s and defi n ition s apply ISO and IEC maintain terminological databases for use in standardization at the following addresses: — IEC Electropedia: available at http://www.electropedia org/ © ISO 2017 – All rights reserved ISO 6246:2017(E) — ISO Online browsing platform: available at http://www.iso org/obp 3.1 existent gum evaporation residue (3.2 ) o f aviation fuels without any further treatment 3.2 evaporation residue material that remains a fter controlled heating under a flow o f air or steam 3.3 unwashed gum content 〈non-aviation fuel〉 evaporation residue (3.2 ) o f the product under test without any further treatment 3.4 solvent-washed gum content 〈non-aviation fuel〉 residue remaining a fter the evaporation residue (3.2) has been washed with heptane and the washings discarded Principle A measured test portion o f fuel is evaporated under controlled conditions o f temperature and flow o f air or steam The resulting residue is weighed and may be subject to further treatment by solvent washing and further weighing Reagents During the analysis, unless otherwise stated, use reagents o f recognized analytical grade Water, where specified, shall be o f a quality equivalent to grade o f ISO 3696 5.1 Heptane , CH (CH ) CH , o f minimum 99,7 % purity 5.2 Toluene, C H CH 5.3 Acetone , CH COCH 5.4 Gum solvent, a mixture of equal volumes of toluene (5.2) and acetone (5.3) 5.5 Air supply, filtered, at a gauge pressure o f not greater than 35 kPa 5.6 Steam supply, free o f oily residue and at a pressure o f not less than 35 kPa 5.7 Detergent cleaning solution The type o f detergent and conditions for its use shall be established in each laboratory The criterion for satis factory cleaning shall be a matching o f the quality o f that obtained with chromic acid cleaning solution on used beakers (fresh chromic acid, h soaking period, rinsing with water and drying) Apparatus 6.1 Balance , capable of weighing to of the nearest 0,1 mg © ISO 2017 – All rights reserved ISO 6246:2017(E) Figure , individually permanently marked It is expedient to arrange the beakers in sets, the number in each set being the number of beaker wells in the evaporating bath The lowest-mass beaker in each set should be reserved for use as the tare 6.2 Beakers , capacity 100 ml, tall form, as illustrated in 6.3 Cooling vessel , tightly covered vessel such as a desiccator without desiccant for cooling the beakers before weighing NOTE 6.4 The use of a desiccant can lead to erroneous results Evaporation bath , either a solid metal block bath or a liquid bath, electrically heated and constructed in accordance with the general principles shown in Figure , having wells and jets for two or more beakers The rate o f air/steam flow at the temperature o f test from each outlet jet when fitted with the conical adaptors with 500 µm to 600 µm copper or stainless steel screens shall be 000 ml/s ± 150 ml/s A liquid bath, i f used, shall be filled to within 25 mm o f the top with a suitable liquid Maintain the bath temperature either by means o f thermostatic controls or by refluxing liquid o f suitable composition WARNING — I f a liquid-filled evaporation bath is used, care shall be taken to ensure that the flash point o f the liquid used is at least 30 °C higher than the highest bath temperature expected 6.5 Flow indicator, 6.6 Sintered glass filter funnel , 6.7 Steam super heater 6.8 Temperature sensors 6.9 Graduated cylinders , each outlet capable o f indicating a total flow o f air or steam equivalent to 000 and 250 µm 232 °C ± °C ml/s for capacity 150 ml, with a maximum pore diameter between 150 µm , capable of delivering to the bath inlet the required amount of steam at , liquid in glass thermometer conforming to the requirements in ASTM E2251-14 or IP 73C o f BS 2000, or another temperature sensor or systems, or both, o f at least equivalent accuracy and precision over a temperature range from –5 °C to 400 °C ISO 4788 6.10 Forceps 6.11 Oven capacity 50 ml or 100 ml and l, forming to the requirements o f , stainless steel, spade-ended , capable of being maintained at 150 °C ± °C Assembly of air-jet apparatus Assemble the air-jet apparatus as shown in Figure With the apparatus at room temperature, adjust the flow o f air to a rate o f 600 ml/s at one o f the outlets, with the remaining conical adaptors in position Check the other outlets individually under the same conditions for uni form air flowrate within 7.1 the range of 600 ml/s ± 90 ml/s NOTE A total reading on a flow indicator (calibrated under ambient conditions) corresponding to 600 ml/s ± 90 ml/s at each outlet will, in normal circumstances, ensure a flowrate o f 000 ml/s ± 150 ml/s at a temperature o f 155 °C ± °C, provided that the back pressure across the flow indicator is not greater than kPa In order to set the apparatus in operation, heat the bath until the temperature reaches 160 °C to 165 °C, and then introduce air into the apparatus until the reading established in accordance with 7.1 7.2 © ISO 2017 – All rights reserved ISO 6246:2017(E) is obtained on the flow indicator Measure the temperature in each well with the temperature sensors (6.8) placed with the thermometer bulb (or equivalent sensing device) resting on the bottom of a beaker (6.2 ) in the well Do not use any well having a temperature that differs from 155 °C by more than °C for standard tests Dimensions in millimetres Key 10 11 12 13 air supply cotton or glass wool filter flow indicator thermometer and thermometer well (optional) thermometer removable adaptor copper or stainless steel screen, (500 - 600) µm thermo-regulator metal, black bath beaker super heater steam trap steam supply Figure — Apparatus for determining gum content by jet evaporation Assembly of steam-jet apparatus Assemble the steam-jet apparatus as shown in Figure 8.1 WARNING — The sample and solvent vapours evaporated during the performance of this test p r o c e d u r e c a n b e e x t r e m e l y f l a m m a b l e o r c o m b u s t i b l e a n d h a z a r d o u s f r o m t h e i n h a l a t i o n standpoint To control such vapours and reduce the risk of thermal explosion and intoxication, national health and safety regulations are to be applied In order to set the apparatus in operation, heat the bath until the temperature reaches 000 ml/s ± 150 ml/s per outlet is obtained Regulate the temperature of the bath within the range 239 °C ± °C and that of the super heater to provide a well temperature of 232 °C ± °C Measure the temperature with the temperature sensor (6.8) placed with the thermometer bulb (or equivalent sensing 8.2 232 °C Operate the super heater, and slowly admit dry steam into the apparatus until a flowrate o f © ISO 2017 – All rights reserved ISO 6246:2017(E) device) resting on the bottom of a beaker (6.2 ) in the well Do not use any well having a temperature that di ffers from 232 °C by more than °C for standard tests Adjust the apparatus to give a steam flowrate o f 000 ml/s for the outlet under test Check the remaining outlets for uni form steam flow Make necessary changes to individual outlets i f the rate varies by more than 150 ml/s o f steam, record the flowmeter reading and use this setting for subsequent 8.3 testing Calibration Calibrate the flowmeter by successively condensing the steam from each outlet and weighing the total quantity o f water recovered To accomplish this, attach a copper tube to a steam outlet jet and extend the tube into a l cylinder (6.9 ) that has been filled with crushed ice and then weighed Exhaust the steam into the cylinder for approximately 60 s Adjust the position o f the cylinder so that the end of the copper tube is immersed in the water to a depth of less than 50 mm to prevent excessive back pressure Weigh the cylinder The gain in mass represents the amount o f steam condensed Calculate the steam flowrate, S, as given in Formula (1): S = where S (m cs − m ice ) ⋅ 000 k⋅t (1) is the flowrate o f the steam, in ml/s, at 232 °C; cs is the mass, in g, o f the cylinder with the condensed steam; m ice is the mass, in g, o f the cylinder and ice; m k is the mass (0,434 g) o f 000 ml o f steam at 232 °C at atmospheric pressure; t is the condensing time, in s 10 Samples and sampling Samples for testing by the procedures described in this document shall be taken by the procedure described in ISO 3170, ISO 3171 or in accordance with the requirements of national standards or regulations for the sampling of the product under test 11 Procedure 11.1 Wash the beakers (6.2) including the tare, with the gum solvent (5.4) until free of gum Rinse thoroughly with water and immerse in detergent cleaning solution Remove the beakers from the cleaning solution by means o f forceps (6.10) and handle only with forceps therea fter Wash the beakers thoroughly, first with tap water and then with distilled water, and dry in the oven (6.11), controlled at 150 °C, for at least h Cool the beakers for at least h in the cooling vessel (6.3 ) placed in the vicinity of the balance (6.1) NOTE For the comparison o f cleaning e fficiency, visual appearance and loss in mass on heating the glassware under test conditions can be used Detergent cleaning avoids the potential hazards and inconvenience related to handling corrosive chromic acid solution The latter remains as the reference cleaning practice and as such can function as an alternative to the preferred procedure of cleaning with detergent solutions © ISO 2017 – All rights reserved ISO 6246:2017(E) WARNING — Chromic acid is a health hazard It is toxic, a recognized carcinogen as it contains Cr(VI) compounds, is highly corrosive and potentially hazardous when in contact with organic materials When using chromic acid cleaning solution, protective measures in accordance with national health and safety regulations, such as eye protection and protective clothing, are essential Never pipette the cleaning solution by mouth After use, not pour cleaning solution down the drain, but neutralize it with great care owing to the concentrated sulfuric acid present, and dispose of it in accordance with standard procedures for toxic laboratory waste (chromium is highly dangerous to the environment) Non-chromium-containing, strongly oxidizing acid cleaning solutions are also highly corrosive and potentially hazardous when in contact with organic materials, but not contain chromium which has special disposal problems Select the required conditions for testing aviation and motor gasoline or aircraft turbine fuel from Table and set the apparatus in operation following the procedures of 7.2 or 8.2 as appropriate If an f well temperature 11.2 external p reheater is us ed, regulate the temp erature o the (vap o rizing) medium to give the s p ecified tes t Table — Test conditions Sample type Vaporizing medium Aviation and motor Air gasoline Aircraft turbine fuel Steam Operating temperature °C Bath Test well 160 to 165 150 to 160 232 to 246 229 to 235 11.3 Weigh the test beakers against the tare beaker to the nearest 0,1 mg When a single-pan balance is used, weigh the tare beaker as a blank Record the mass of each beaker 11.4 I f s us p ended o r s ettled s o lid matter is p res ent, mix the co ntents o f the s amp le co ntainer tho ro ughly I mmediately filter a quantity o f the s amp le, at atmo s p heric p res s ure, thro ugh the s intered glas s (6.6 ) Treat the filtrate as s p ecified in 11.5 to 11.7 inclusive funnel f 6.9), add 50 ml ± 0,5 ml of the sample to each beaker except the tare, using one beaker for each of the fuels to be tested 6.4) The elapsed time between placing the f air, replace the conical adaptor as each individual beaker is placed in the bath When using steam, allow the beakers to heat for to before replacing the conical adaptor, which shall be preheated in the steam stream prior to attaching to the outlet Centre the conical adaptors above the centre of the f f gum values to be in error 11.5 B y means o the graduated cylinders ( Place the fi l le d b e a kers , a nd the ta re i n the evap oration b ath ( fi rs t a nd l as t b e a kers i n the b ath sh a l l b e a s shor t as p o s s ible When evap orati ng s ample s b y me an s o l iquid s u r ace Ta ke c a re to avoid s pla sh i ng when i ntro duc i ng the j e t o a i r or vap ou r, as th i s cou ld cau s e M nta i n the temp erature and rate o f flow a nd a l low the te s t p or tion s to evap orate for ± 0, S ample s te s te d s i mu ltane ou s ly s l l have s i m i lar evap oration cha rac teri s tic s NO TE I n cer ta i n c a s e s , dupl ic ate te s ti n g i s advi s ab le to che ck i f the te s t me tho d’s rep e atab i l ity i s me t At the end of the heating period, transfer the beakers from the bath to the cooling vessel (6.3) f with 11.3 Record the mass of the beakers 11.6 Place the co o ling ves s el in the vicinity o f the b alance o r at leas t h Weigh the b eakers in acco rdance © ISO 2017 – All rights reserved ISO 6246:2017(E) 11.7 Segregate beakers containing residues from products for which the heptane-insoluble portion of the gum is also required to be determined, and follow 11.8 to 11.12 The remaining beakers may be returned for cleaning and reuse For non-aviation fuels that have unwashed results that are