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- Bergström, Gunnar, et al.
(author)
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Direct burial of district heating pipe bends – A limited casing pipe temperature ap-proach
- 2003
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In: Euroheat & Power - English Edition.
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Journal article (other academic/artistic)abstract
- The direct burial of district heating pipe bends, i.e., without the use of expansionabsorbing elements, has reportedly frequently been done withoutany observed pipe-line damage. This in spite of current design principles,predicting so large stresses on a directly buried L bend that the techniqueshould be avoided. A reason for the lack of correspondence between practicalexperience and design theory is the difficulties in formulating relevantcriteria for tolerable stresses and deformations in the pipe. Conservative designlimits are traditionally used, particularly regarding allowable stresses inthe PUR foam.An alternative method for design with respect to the PUR foam may bedeveloped based on the idea that the deformation of the PUR foam, and thusalso the displacement of the steel pipe relative to the casing pipe, must belimited only to avoid overheating of the polyethylene. The factors influencingthe deformation of the PUR foam is mainly a question of the temperatureinduced steel pipe displacement versus the stiffness and strength of thebackfill material. When the loading properties of the PUR foam and thebackfill material are known, the relationship between the steel pipe displacementand the PUR foam deformation is defined. Thus also a relation betweena specified thermal motion of the steel pipe and the resulting maximumtemperature on the casing pipe is established. This makes it possible touse the maximum casing pipe temperature as a design value.The conclusion using this approach is that the laying of bends directly inthe ground should be possible with normal backfill materials and compactionconditions. Certain care must be taken, though, when bends are laid invery stiff and strong backfill, where high reaction pressures may develop. Ingeneral, the risk for pipeline damage is minimised if directly buried bendsare laid in only moderately compacted backfill.
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| 4. |
- Östrand, Fredrik, et al.
(author)
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Stereoisomeric composition of the sex pheromone of the pine sawfly Microdiprion pallipes (Hym., Diprionidae)
- 2003
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In: Chemoecology. - : Springer Science and Business Media LLC. - 0937-7409 .- 1423-0445. ; 13:3, s. 155-162
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Journal article (peer-reviewed)abstract
- The basic chemical structure of the sex pheromone of the pine sawfly Microdiprion pallipes (Fallen) has earlier been identified as the propionate ester of (2S,3S,7 R/S,11 R/S)/(2R,3R,7 R/S,11 R/S)-3,7,11-trimethyl-2-tridecanol. We now report the results from further investigations on the male response to individual stereoisomers and to blends of stereoisomers, both in electroantennographic (EAG) recordings and in field trapping experiments. We also present our attempts to determine the stereochemistry of the compounds present in females of M. pallipes. By comparing gas chromatograms and mass spectra obtained from natural extracts with those from synthetic compounds it was found that the females contain one or more of the four (2S,3S,7 R/S,11 R/S)-3,7,11-trimethyl-2-tridecanol isomers (SS++-1). The active pheromone component is the corresponding propionate ester 2. In EAG experiments, males responded most strongly to five propionate ester samples, namely two four-isomer blends: SS++-2 and SR++-2, and three individual stereoisomers: SSSR-, SRRR- and SRSR-2. In a series of field trapping experiments it was found that males were attracted to the SR++-2 four-isomer blend and to the individual isomer SSSR-2. Based on the EAG-recordings and field responses of males and the stereoisomers found in the females, we suggest that the propionate ester of (2S,3S,7S,11R)-3,7,11-trimethyl-2-tridecanol (SSSR-2) is used as a main component of the sex pheromone in M. pallipes. Apparently the males react to other stereoisomers in addition to that or those produced by the females.
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