Filtern
Dokumenttyp
Referierte Publikation
- ja (21) (entfernen)
Schlagworte
- Biofuels (7)
- Compatibility (7)
- Tensile properties (7)
- Sealing materials (6)
- Biodiesel (5)
- Polyethylene grades (5)
- E85 (4)
- B10 (3)
- Change in tensile properties (3)
- Mass loss (3)
Organisationseinheit der BAM
More than 400 Mt of dangerous materials are transported in Germany every year, of which 150 Mt are by road. Tank containers, tank vehicles and rail tank cars are used for the carriage of dangerous goods in large quantities. Data on the operating life of tanks are only available, in practice, to a minor degree. They are only partly published, mainly after accidents.
The BAM-List - Requirements for Tanks for the Carriage of Dangerous Goods, which has compatibility evaluations of metallic and polymeric materials, has been the basis for substance-related prototype approvals for tank containers and portable tanks designed for the carriage of dangerous goods by the BAM since publication of the first edition in 1989. These data are also used for the approval of rail tank cars and road tank cars and are used as a source of knowledge not only in Germany but also worldwide.
Tank leakages caused by tanks or rail tank cars being made of tank and sealing materials which are not resistant to the fill goods are avoided by using the material resistance data of the BAM.
Corrosion damage is among the main causes of damage. Uniform and non-uniform area corrosion without mechanical stress in aqueous substances is one of the most frequent types of corrosion during the transport of chemicals in tanks. Much damage by pitting corrosion occurs during the transport of substances containing chlorides or substances which separate chloride ions in the presence of moisture.
Operational stresses are caused by the effects of both the road and the dangerous goods being transported. Mechanical damage often results from long-term overstressing and occurs after longer operating times.
Operational failures cause damage which may appear during the service of tank containers, road tank cars or rail tank cars. The damage results from the inattention of employees when opening and closing the valves. Traffic accidents also cause damage to tanks and frames.
Many cases of damage are due to weld area cracks resulting from four basic errors in construction, material, manufacturing and operation. Manufacturing errors can be undetected and the starting point of cracks which only grow under service conditions.
Manufacturing errors result from variations in measurement and design, fittings, state of surface (hardness, abrasiveness) and mechanical surface damage (scratches, cracks). Incorrectly welded joints and errors during mechanical deformation are typical mistakes when installing the component parts. Variations in the wall thickness or combinations of different materials lead to manufacturing errors too. A lot of tanks are not used for the transport of dangerous goods before the end of their service life as they do not fulfil the revised technical safety requirements in the Dangerous Goods Regulations.
Predictions in the BAM-List based on literature data and corrosion test results are reflected in the service (operating) life. Rail tank cars made of carbon steel, for example, which are mainly used for the transport of petroleum products, can achieve a service life of 40 – 50 y.
Rail tank cars produced of austenitic CrNi- or CrNiMo-steel can reach an operating life of at least 30 y, whereby the corrosiveness of the transport substances plays an important role.
The material parameters melt flow rate (MFR), density (D), notched impact strength (NIS) at –30°C, stress crack resistance [determined with the Full Notch Creep Test (FNCT)] and resistance to oxidative degradation (Ox) have been selected for a comparison of polyethylene grades in the European standard EN 15507. These parameters have a relationship with design type tests of packagings for the transport of dangerous goods.
This paper presents the results of additional investigations to determine the impact of the pre-storage time of jerricans with 55% nitric acid at 40°C and 23°C on the marginal drop heights in drop tests at –18°C, on the MFR and on the tensile properties. Jerricans made of different polyethylene grades were pre-stored with 55% nitric acid for 21, 42 and 84 days at 40°C and for six months at 23°C.
The tests showed that the NIS values at –30°C of polyethylene grades were not comparable with marginal drop heights determined in drop tests at –18°C.
Pre-damage with 55% nitric acid for 21 days at 40°C led to an increase in the marginal drop heights of the jerricans. Altering the test regulations by increasing pre-storage time with 55% nitric acid to 42 days would be an alternative.
The test results demonstrated clearly that pre-storage of the jerricans for six months at 23°C caused a higher increase in the MFR and lower marginal drop heights for the jerricans when compared with pre-stored jerricans for 21 days at 40°C.
The aim of this work was to study the interaction between high-density polyethylene (HDPE) grades as material for dangerous goods packagings and biofuels such as E85 and biodiesel. Jerricans made of two polyethylene (PE) grades were filled with these fuels and exposed to temperatures of 20°C and 40°C for 1 year. Tensile properties (tensile strength, breaking elongation and elasticity modulus) and melt flow rate (MFR) were determined once a month, and Fourier transform infrared (FTIR) spectroscopy was used to evaluate changes in the chemical structure.
Measurements of the MFR and tensile properties of the PE grades after 1 year of exposure to E85 showed only a slightly damaging influence. An increase in the peak of 1585 cm-1 (C=C) stretching vibrations is visible in the FTIR spectra after the immersion tests with E85. Therefore, packagings made of HDPE grades are suitable for the transport of E85.
An increase in the MFR with immersion time of the grades in biodiesel was measured, in particular, after 1 year of exposure. The elasticity modulus of the PE grades was reduced with immersion time. The FTIR spectra showed a broadening of the CO peak of 1740 cm-1 and the appearance of the hydroxyl group at 3500 cm-1. Both results are explained by secondary degradation products of the PE decomposition process caused by increasing unsaturated fatty acid content in the biodiesel. In light of the above mentioned, it was concluded that HDPE grades are not suitable as packaging materials for the transport of biodiesel.
The material parameters melt flow rate MFR, density D, notched impact strength N.I.S. at -30 °C, stress crack resistance FNCT and resistance to oxidative degradation Ox (determined by the increase of MFR) have been selected for a comparison of polyethylene grades for one design type in the “European Standard EN 15507 - Transport packaging for dangerous goods - Comparative material testing of polyethylene grades”. The parameters have a systematic relationship with design type tests. The notched impact strength at -30 °C and the resistance to oxidative degradation of polyethylene grades determined with test specimens of compression moulded sheets are directly comparable with drop tests at -18 °C of design types produced of these grades after pre-storage with 55 % nitric acid for 21 days at 40 °C. The impact of the pre-storage time of jerricans with 55 % nitric acid at 40 °C and 23 °C on the marginal drop heights in drop tests at -18 °C, on the MFR and on the tensile properties tensile strength, breaking elongation and the elastic modulus were investigated. Packaging design types (jerricans) made of three polyethylene grades from different producers were pre-stored with 55 % nitric acid for 21,42 and 84 days at 40 °C as well as for six months at 23 °C. The MFR and tensile properties of test specimens taken from the design type side walls as well as the marginal drop heights of the jerricans in drop tests at -18 °C were determined.
The values of the notched impact strength at -30 °C of polyethylene grades are not comparable with the marginal drop heights determined in drop tests at -18 °C. The oxidative damaging impact of nitric acid has a greater effect on the grade with lower resistance to oxidative degradation by reducing more significantly the marginal drop heights with increasing pre-storage time.
Pre-damage with 55 % nitric acid for 21 days at 40 °C, as recommended in ISO 16101 and EN 15507 caused an increase in the marginal drop heights of most design types in drop tests when compared with design types without pre-damage. The test results demonstrated clearly that pre-storage of the jerricans for six months at 23 °C caused a higher increase in the MFR and lower marginal drop heights of the jerricans in drop tests at -18 °C compared with pre-storage of the jerricans for 21 days at40 °C.
The mechanical properties change as a result of diffusion of nitric acid into the polyethylene grades and the reaction of the nitric acid with the polymers. The percentage decrease and increase in the tensile strength, breaking elongation and elasticity modulus of test specimens taken from the design type side walls after different pre-storage times were only partly comparable with the marginal drop heights in drop tests at -18 °C.
Compatibility of high density polyethylene grades with bioethanol-gasoline blends and biodiesel
(2012)
Biofuels including ethanol and biodiesel (fatty acid methyl ester) represent an impor-tant renewable fuel alternative to petroleum-derived transport fuels. Increasing bio-fuel use would bring some benefits, such as a reduction in oil demands and green-house gas emissions, and an improvement in air quality.
Materials compatibility is a major concern whenever the fuel composition is changed in a fuel system.
The aim of this work is to study the interaction between sealing materials such as FKM (fluorocarbon rubber), EPDM (ethylene-propylene-diene rubber), CR (chloro-prene rubber), CSM (chlorosulfonated polyethylene), NBR (acrylonitrile-butadiene rubber), IIR (butyl rubber), VMQ (methyl-vinyl-silicone rubber) and FVMQ (methyl-fluoro-silicone rubber) and biofuels such as biodiesel, E85 (fuel with 85% ethanol) and B10 (heating oil with 10% biodiesel) at 70°C for 84 days. Experiments were con-ducted with tests specimens of theses elastomers to document the changes in the mass and tensile properties of these sealing materials according to ISO 1817.
The exposure tests of the elastomers in E85 at 70°C showed that the weight gain caused by swelling of the test specimens was in the range of 3% to 12%. However, the weight gain of the fluorinated elastomers was at the lower end of this range. Tensile strength and breaking elongation decreased by 22% to 61% or 13% to 77%. The lowest decrease in the tensile properties was determined for FKM, EPDM und IIR. These sealing materials were evaluated as resistant to E85 up to a temperature of 70°C.
Biodiesel absorbed water more quickly and aged faster than conventional diesel fuel. The weight loss of the elastomers varied between 9% (FKM) and 126% (CSM) in biodiesel. FKM was evaluated as resistant with a 16% reduction in tensile strength, a 2% reduction in breaking elongation and low weight loss. NBR, EPDM, CSM and VMQ were evaluated as not resistant. CSM even lost 84% of its original tensile strength and 78% of its breaking elongation.
The highest weight gain as a result of swelling was measured for CSM with 86%, for EPDM with 84% and for VMQ with 54% in B10, while the fluorine-containing elasto-mers FKM (1%) and FVMQ (3%) absorbed much less B10 and swelled less. FKM lost 23% in tensile strength and 17% in breaking elongation; FMVQ lost 29% in ten-sile strength and 36% in breaking elongation. FMVQ was, therefore, only limited in its resistance to B10.
The elastomers NBR, EPDM, CSM and VMQ were not resistant to B10 at all as the decrease in the tensile properties was significantly over 50%. NBR lost about 93% and CSM about 100% of its breaking elongation.
The conclusion of the investigations at 70°C is that FKM is the most resistant sealing material in biodiesel, E85 (fuel with 85% ethanol) and B10 (heating oil with 10% biodiesel).
Biofuels including ethanol and biodiesel (fatty acid methyl ester) represent an important renewable fuel alternative to petroleum-derived transport fuels. Increasing biofuel use would bring some benefits, such as a reduction in oil demands and greenhouse gas emissions, and an improvement in air quality.
Materials compatibility is a major concern whenever the fuel composition is changed in a fuel system. The question arises of whether sealing materials are resistant to fuels with bioethanol and biodiesel (rapeseed oil fatty acid methyl ester).
The aim of this work is to study the interaction between sealing materials such as FKM (fluorocarbon rubber), EPDM (ethylene-propylene-diene rubber), CR (chloroprene rubber), CSM (chlorosulfonated polyethylene), NBR (acrylonitrile-butadiene rubber), IIR (butyl rubber), VMQ (methyl-vinyl-silicone rubber), FVMQ (methyl-fluoro-silicone rubber) and PA (polyamide) and biofuels such as biodiesel (FAME, non-aged and 2 years aged), E85 (fuel with 85% ethanol) and B10 (heating oil with 10% biodiesel, non-aged and one year aged) compared with premium-grade fuel at 20°C, 40°C and 70°C for 84 days. Exposure experiments were conducted with specimens of these elastomers to document the changes in the mass and tensile properties of these sealing materials. Visual examination of some test specimens clearly showed a great volume increase until breakage or partial dissolution.
The sealing materials FVMQ, VMQ and PA were evaluated as resistant in E85 at 20°C and 40°C with a reduction of tensile properties limited to 15%. None of the examined materials was evaluated as resistant at 70°C with even fluorocarbon rubber losing 20% of its tensile strength in E85.
When exposed to biodiesel, elastomers were affected in two ways: firstly, by absorption of liquid by the elastomers and, secondly, by dissolution of soluble components from the elastomers into the liquid medium. Swelling was the result of the high absorption by the elastomers CR, CSM, EPDM, IIR and NBR in comparison to their dis-solution in non-aged and two years aged biodiesel. FKM, VMQ and PA were evaluated as resistant sealing materials in non-aged biodiesel at 40°C. FKM was still resistant in aged biodiesel at 40°C but only to a limited degree at 70°C.
The sealing materials CR, CSM, EPDM, IIR, NBR and VMQ were damaged to a high extent in non-aged and one year aged B10 as a result of swelling up to 70°C. FVMQ and PA can be evaluated as resistant in non-aged and one year aged B10 at 20°C and 40°C. However, FKM was evaluated as resistant up to 70°C.
The exposure tests showed that all the elastomers tested were resistant in the premium-grade fuel Super at 20°C. On increasing the temperature to 40°C, only FKM, VMQ and PA were resistant to Super. At 70°C FKM showed the best resistance.
In Germany the "BAM-List - Requirements for Tanks for the Transport of Dangerous Goods" is the basis for substance-related prototype approvals for tank Containers undertaken by the BAM - Federal Institute for Materials Research and Testing. Compatibility evaluations of selected metallic materials as well as of polymeric gasket and lining materials under the influence of approximately 7000 dangerous goods have been published in the BAM-List since 1989.
The duplex Steel 1.4362 (2304, UNS S32304) was originally developed as substitute for the austenitic grades 1.4404 (316L, UNS S31603) and 1.4571 (316Ti, UNS S31635). Due to its characteristic profile this Steel was qualified for applications requiring high strength values at concomitant adequate corrosion resistance. Because of its lower content of the alloy elements nickel and molybdenum this duplex Steel is a cost-efficient alternative to the molybdenum containing austenite. Only a limited number of corrosion test results of 1.4362 under the influence of dangerous goods published in the BAM-List were available. Therefore test specimens of this Steel were exposed to selected corrosive substances.
Due to the reduced alloy content a reduced corrosion resistance of the duplex Steel 1.4362 in acidic substances, such as formic acid, acetic acid and sulfuric acid, in comparison to the austenitic CrNiMosteels was observed. Tests in the alkaline medium showed a sufficient resistance.
Alloy 59 (NiCr23Mo16Al) with a lot of chromium, molybdenum and nickel possesses excellent resistance not only to reducing but also oxidizing chemicals. Both the Nickel alloy 59 and the superaustenitic steel alloy 31 have already been used as shell materials for tank vehicles or tank containers. Use of these alloys allows the transport of a signifi-cantly more wider variety of chemicals and, especially, waste mixtures than the use of common aus-tenitic steels. Another advantage is the extension of test intervals of for transport tanks. In Germany the 'BAM-List – Requirements for Tanks for the Transport of Dangerous Goods' is the basis for substance-related prototype approvals for tank containers designed for the carriage of dangerous goods issued by the Federal Institute for Materials Research and Testing (BAM). Com-patibility evaluations of selected metallic material groups as well as polymeric gasket and lining materials under the influence of approximately 7000 dangerous goods and water-polluting sub-stances are published in the BAM-List. Alloy 59 belongs to the group of metallic materials in the BAM-List. Due to the large number of dangerous goods in the BAM-List BAM, IKS Dresden and ThyssenKrupp VDM performed a comprehensive corrosion test programme with welded specimens of the nickel alloy 59 and the superaustenitic steels alloy 926 and alloy 31 in the period 2002 - 2010. Especially In particular alloy 59 and alloy 31 were exposed to a large number of corrosive sub-stances such as various mixtures of both nitric acid/sulphuric acid and nitric acid/phosphoric acid at 55 °C. Other corrosive test substances were different organic and inorganic halogenides, peroxyace-tic acid and molten substances. In the case of molten chemicals such as monochloroacetic acid the test temperature was increased to more than 100 °C. The test results presented in this paper are al-ready included in the 10th edition of the BAM-List and, therefore, available to the customer.
For the characterization and the comparison of polyethylene grades used for the manufacture of packaging and intermediate bulk container, the following parameters are required: melt flow rate (MFR), density (D), low-temperature notched impact strength, full notch creep test (FNCT) and increase of MFR by molecular degradation (resistance to oxidative degradation). The relationship between these material parameters determined on the basis of specimens prepared from compression-moulded sheets of polyethylene grades and the test behaviour of packaging has been investigated in several tests. The environmental stress crack resistance determined by FNCT represents the impacts from the stacking tests performed with standard liquid wetting solution (without pre-storage) and with normal butyl-acetate-saturated wetting solution (pre-storage with normal butyl acetate). Resistance to molecular degradation by the determination of MFR increase is related to the impacts in drop tests and stacking tests performed after pre-storage for 21 days with standard liquid 55% nitric acid at 40°C. The low-temperature impact strength is directly comparable with the impacts in drop tests at -18°C performed without pre-storage and after pre-storage with 55% nitric acid. A partly good relationship was found between the test results and the material parameters. Conditioning the design types with 55% nitric acid for 21 days causes an increase in the marginal drop heights of the design types in drop tests at -18°C when compared with design types without pre-storage. Post-cross-linking of the grades increases stiffness because of the acidic influence.