Interkristalline Spannungsrißkorrosion an Hochtemperatur-Winderhitzern. Werkstoffkundliche,fertigungs- und verfahrenstechnische Maßnahmen zur Minderung und Vermeidung der Schäden

Intercrystalline stress corrosion cracking (SCC) in high temperature hot blast stoves. After a brief survey of known cases of stress corrosion cracking and today's protective or repair measures, the results of lab tests are presented which provide new knowledge about the course of nitrate stress corrosion cracking. The lab tests are dynamic stress corrosion cracking tests allowing direct simulation of SCC-attack on structural steels under operational conditions. It thus becomes possible to specifically intervene in the mechanism of SCC. Modifying the factors material, tensile stress, and medium provides a basis for the construction of hot blast stoves not sensitive to SCC.     

Schädigung der Z-Gruppe und Hydantoinbildung bei der Alkalischen Verseifung von Z-Peptidestern

Cleavage of Z-Group and Formation of Hydantoine during Saponification of Z-Peptide Esters In the course of alkaline decomposition of the tetrapeptide ester Z-Arg(NO₂)-Gly-Phe-Phe-OMe one gets a high output of a by-product. the latter was isolated and identified by ¹³C-n.m.r. spectroscopy to be the hydantoine derivative arising from a loss of Z-group and from a cyclisation. A possibility to suppress the undesired side-reaction by addition of benzylalcohol is proposed resulting from the discussion of a probable mechanism of reaction.     

Nachbehandlung von Halbzeugen und Apparaten aus austenitischen Stählen zur Vermeidung von Spannungsrißkorrosion

After-treatment of semifinished products and equipment made of austenitic steel to avoid stress corrosion . Among the factors initiating stress corrosion, the extent and distribution of internal tensile stress are the least tractable. Unknown internal stresses are always superposed on the estimable operational stresses. If they arise from distortions or welding, the former are distributed throughout the entire cross-section. The action of tools, e.g. on turning or grinding, can also lead to high internal tensile stresses in a thin surface zone. Such stresses are of particular significance because stress corrosion is initiated on the surface. In this article, it is shown that it is usually sufficient to adequately reduce these surface-proximate internal tensile stresses, e.g. by a pickling process removing a surface layer of material, in order to eliminate stress corrosion and thus to extend the scope of austenitic steels. Should the internal tensile stresses due to distortion and welding suffice to initiate stress corrosion under particularly aggressive conditions, one can attempt to reduce the stress by suitable heat treatment; however, no impermissable change in the microstructure of the steel may occur. Finally, it is also possible to produce compressive stress in a thin surface zone by shot peening so that no stress corrosion can take place. The advantages and disadvantages of the various possibilities are illustrated with the aid of examples.     

Schälung von Rapssaat durch definierte Verformung Teil II: Untersuchungen zum Schälverhalten

Dehulling of Rapeseed by Definite Deformation, Part II: Investigations on Dehulling Behaviour In continuation of results presented in the earlier communication on the disintegration behaviour of rapeseed, the findings on the disintegration of the seed after deformation in the rolls are reported. With the aim to determine the optimum spacing between the rolls, the extent of disintegration after a single passage at constant spacing is compared with that for passages at varying spacings. If one considers that the seed meat has to be deoiled by percolative extraction, effort should be made to obtain high proportions of coarse particles of the meat. The optimum spacing which ensures high capacity, low recycling, and no thawing of the meat particles is S = 0.6 mm.     

Trennung von Triglyceriden nach Kettenlänge und Sättigungsgrad durch HPLC

Separation of Triglycerides According to Chain Length and Degree of Saturation by HPLC In routine fat analysis HPLC is efficiently used. For constant work columns with chemically bound C₁₈-groups are especially suitable. There are critical pairs of fatty acid-methylesters which however can be separated by means of elution agents basing on acetonitril. Oleic acid and elaidic acid can be separated by this way, too. By GLC triglycerides can only be separated according to the number ob C-atoms, whereas in HPLC double bounds have a great influence on the retention time, too. This is especially evident if elution agents, basing on nitrils, are used. The separation principle was determined by capillar gas chromatographic analysis of the HPLC fractions. Further on hints are given to avoid technical difficulties in the use of differential refractometers.     

Silikon als Rohstoff für Schäumer und Entschäumer

Silicone as Raw Material for Foaming and Anti-Foaming Agents The remarkable significance of methyl polysiloxanes in the field of anti-foaming agents is based on two fundamental principles, namely, low intermolecular interactions (low surface tension), and the unique variability of the polymer system which permits that by variation of molecular weight, molecular weight distribution as well as the nature and number of end groups, these agents can be made to fit into a particular type of application. The above properties have also led to the use of modified methyl siloxanes as foam stabilizers. In the latter case, a further factor enhancing the efficacy by the introduction of a solubilizing group in the modified siloxane is made use of. Examples for the same are polyether modified methyl polysiloxanes as foam stabilizers in polyurethane foams, and anionactive methyl siloxanes containing sulfate groups as foaming agents in fire extinguishing systems.     

Fixierung von Cu2+-Ionen in Matrizen aus Polyamid- und Polyhydrazidsäuren

Fixation of Cupric Ions in Matrices from Polyamide- and Polyhydrazide Acids On polymerisation of pyromellitic dianhydride with 4,4′-diamino-diphenyl ether and the dihydrazides of oxalic acid, malonic acid, adipic acid and terephthalic acid, respectively, filmforming polyamide-hydrazide-acids result. It is possible to control the reducing and mechanical properties of the polymers by variation of the mole ratio of 4,4′-diamino-diphenyl ether and acid hydrazide. Polymers with 0.3 moles of acid hydrazide and 0.7 moles of 4,4′-diamino-diphenyl ether do not reduce cupric ions, but co-ordinate them. EPR and absorption spectra show the cupric ions to co-ordinate with the hydrazide but not with the amide groups if the stoichiometric ratio polymer/Cu(II) is greater then 12. Only in foils prepared with the hydrazide of terephthalic acid the co-existence of Cu(II) complexes of the amide and hydrazide groups, respectively, is observed. Both these complex polyeders exhibit axial geometry.     

Technische Lösungen zur Schälung von Ölsaaten

Technical Solutions for the Dehulling of Oil Seeds The generation of a kernel-hull-mixture, its fractionation and the hull- seperation is elaborated for the example of sunflower seed. The use of electro-separation represents a new alternative to the traditional technology of air-sifting. The new technology enables us to make significant reductions of electric power consumption and production area. The major advantages of the SKET-solution and a prospective view of the application for further oil seeds are pointed out.     

Verbesserung von Qualität und Wirtschaftlichkeit durch Dosierpumpen in der Öl- und Fett-verarbeitenden Industrie

Improvement of Quality and Economy in the Oil and Fat Processing Industry by the Use of Metering Pumps Volumetric metering of liquids using metering pumps is discussed with special reference to the following aspects: Limits of application, requirements to be met by the metering pumps in the oil and fat industry, types of metering pumps, forms of construction, drives and gears, pump heads, cylinder packings, pump valves, influence of external conditions, installation of metering pumps and their regulation. The economic solution of tasks involving metering is shown with examples from the practice.     

Fettsäurenaufnahme des Menschen und Möglichkeiten der Beeinflussung durch die Tierernährung

Fatty acid intake of men and possibilities to influence the intake by animal nutrition. About 70% of total fat intake (≈ 100 g per person per day) are from fat of animal origin in Germany. Animal nutrition may influence fat content and fatty acid pattern in animal products. This paper summarizes the influence of feeding on fatty acid pattern of meat (pork, beef, poultry, rabbit, fish), milk and eggs. Fatty acid intake is demonstrated under consideration of fat intake of men and variation of fatty acid pattern of various fats of animal origin. Daily fat intake of men amounted to 43 g saturated, 37 g monoen and 13 g polyen fatty acids. It may vary between 38 and 46 g saturated, 33 and 45 g monoen and 11 and 17 g polyen fatty acids if variation of fatty acid pattern of animal fats is considered. By combination of lower fat intake and changed fatty acid pattern of animal products fatty acid intake may be changed to more monoen and polyen fatty acids.