Time filter

Source Type

Peters M.,Dow Deutschland Anlagengesellschaft mbH
Institution of Mechanical Engineers - 12th European Fluid Machinery Congress | Year: 2014

Most of the referenced vertical cooling water pumps are equipped with sleeve type bearings, which are lubricated by water. Different bushing materials are in use, e.g. rubber, plastics, bronze or sometimes ceramic. In most cases the pump itself is feeding a small side stream of water to the bearing. If the water contains abrasive material, like silt or sand, wear of the shaft sleeve or the bushing will take place. The mean time between failure of this pump is most of cases less than 5 years. Reducing or eliminating wear on these bearings, will result in higher MTBF values of the whole pump. In addition, the bearing material should be robust and not brittle to handle unstable running conditions. This report describes a bearing modification which is suitable for vertical cooling water pumps which handle fresh-, brackish- and salt-water with a certain amount of silt and sand. In February 2011 the first pump was retrofitted, followed by a second in April 2011 with a third pump modified in 2012. No pump has failed so far. The goal is to run the pumps with these bearings at least 10 years without failure. © The author(s) and/or their employer(s), 2014. Source

Mischnick P.,TU Braunschweig | Unterieser I.,TU Braunschweig | Voiges K.,TU Braunschweig | Cuers J.,TU Braunschweig | And 2 more authors.
Macromolecular Chemistry and Physics | Year: 2013

Hydroxyethylmethyl celluloses (MSHE 0.15-0.26, DSMe 1.49-1.82) and hydroxyethyl celluloses (MSHE 1.89-3.03) are analyzed with respect to their substituent distribution in the polymer chains. The cellulose ethers are peralkylated and partially hydrolyzed, and are analyzed by electrospray ionization-ion trap-mass spectrometry (ESI-IT-MS). The randomness of the partial hydrolysis is proven. Quantitative evaluation of their mass spectra becomes possible after labeling the oligosaccharides at the reducing end. Reductive amination with o-aminobenzoic acid gives better results than hydrazone formation with cationic Girard's T reagent. Syringe pump infusion gives more-accurate results compared with liquid chromatography (LC)-ESI-MS. Profiles of the substituent distribution in the oligosaccharide fractions of DP 2-DP 7 are compared with the theoretical random distribution of glucosyl units in the chain. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Lueske J.,Dow Deutschland Anlagengesellschaft mbH | Kar K.,Dow Chemical Company | Piras L.,Dow Chemical Company | Pressler J.,Dow Chemical Company
Chemical Engineering and Technology | Year: 2015

Stirred-tank reactors (STR), in which gas and liquid phases make intimate contact for mass transfer, are quite common in chemical processes. Mechanical agitation enhances the mixing performance and the oxygen transfer capability in bio-STR, but they cannot be aerated at high rates because of impeller flooding. Another type of reactor widely used in bioprocessing is the airlift bioreactor, which consists of a draft tube and operates with an internal airlift loop. In this work, the mass transfer characteristics of a draft tube-impeller agitation system (combination of a conventional airlift and a stirred bioreactor) were investigated in a large-scale tank. The draft tube design configuration shows superior mass transfer performance compared to a conventional down-pumping agitation system consisting of a Rushton turbine combined with a pitched-blade turbine. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Cuers J.,TU Braunschweig | Rinken M.,Dow Deutschland Anlagengesellschaft mbH | Adden R.,Dow Wolff Cellulosics GmbH | Mischnick P.,TU Braunschweig
Analytical and Bioanalytical Chemistry | Year: 2013

Three hydroxypropyl methylcellulose samples (HPMC1-3, DSMe = 1.45, 1.29, and 1.36; MSHP = 0.28, 0.46, and 0.84) were analyzed with respect to their methyl and hydroxypropyl substitution pattern in the polymer chains. Ionization yield of HPMC oligomers in electrospray ionization ion trap mass spectrometry (ESI-IT-MS) is strongly influenced by the hydroxypropyl pattern. Therefore, a sample derivatization procedure, as well as suitable measurement conditions that enable relative quantification were elaborated. Analysis was performed by negative ESI-IT-MS after per(deutero)methylation, partial depolymerization, and reductive amination with m-aminobenzoic acid. Measurement parameters like solvent, trap drive, and voltages of the ion transportation unit were studied with regard to the suitability for quantitative evaluation. Using direct infusion of the samples, strong influence of trap drive and octopole settings was observed. Optimized measurement conditions were used for the determination of the HP pattern of the permethylated samples by direct infusion. The methyl pattern was determined from the perdeuteromethylated samples by high-performance liquid chromatography-electrospray tandem mass spectrometry. For HPMC1, substituents were both found to fit the random distribution model. The other two samples showed pronounced heterogeneity which could be interpreted in more detail by extracting methyl subpatterns depending on the number of HP groups. [Figure not available: see fulltext.] © 2013 Springer-Verlag Berlin Heidelberg. Source

Kerkhof K.,University of Stuttgart | Schwenkkros J.,Dow Deutschland Anlagengesellschaft mbH | Barutzki F.,GERB Schwingungsisolierungen | Gurr-Beyer C.,Buro fur Baudynamik
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2010

Safe operation, availability and lifetime assessment of piping are of utmost concern for plant operators. This paper presents the first results of the European research project IRIS (Integrated European Industrial Risk Reduction System) [1]. One important IRIS goal is to identify risk reduction methods to avoid high cycle fatigue at a large vertical pipe system. The piping system is supported by a tall structure fixed at the base. As a result, the steel building stiffness decreases with height. Furthermore large piping-elbow forces act at the top of the building, which lead to large vibration amplitudes. Since both piping system and supporting structure exhibited these large vibration amplitudes, dampers or shock absorbers placed between them would prove ineffective. Therefore, special vibration absorbers were developed for such piping systems. The paper presents the design process, starting with an extensive system investigation up to the passive multi-axial vibration absorber design parameters. The aim was to establish a good basis for the risk reduction of vibration induced emergency conditions by use of vibration absorbers. This included: •Laboratory tests with a mock-up pipe system, where the first design ideas for new passive vibration absorbers were investigated. •Vibration measurements were carried-out to investigate the current state of the vibration behavior. •The piping system was inspected; strain gauges were used to identify stress concentrations at welds and other notches due to ovalization. •Finite element calculations were performed, first as a combined beam and shell model for the pipe without the support structure. •A detailed model for the combined steel construction and pipe system was created. •Modal-updating was done to fit the calculated model to the experimental modal analysis data. •Load simulations were created to describe the mass flow excitation. •Harmonic frequency analysis was performed. •On the basis of these calculations design parameters for the passive vibration absorber were determined. Finally, a solution for the design of the two passive vibration absorbers will be presented. © 2010 by ASME. Source

Discover hidden collaborations