Summary
Clove oil can be used as an anaesthetic in the handling of marine and freshwater fish. Few studies report on its use for periods up to 48 h, for example, under long‐distance transport conditions. This study tested the effect of different clove oil concentrations for 1–48 h on recovery and survival of the cichlid Haplochromis obliquidens, an ornamental fish species endemic to Lake Victoria. Haplochromis obliquidens were anaesthetized for 1 h using 5–25 μl L−1 clove oil. There was no correlation between clove oil concentration and post‐anaesthesia recovery time (P = 0.15). On average, fish recovered within 9.5 ± 2 min, and no fish died within 24 h after recovery. Results from exposure of fish to 18–20 μl L−1 clove oil for up to 48 h suggested a narrow margin of safety as this concentration range induced mortality. At 18 μl L−1 recovery times ranged from 3 to 43 min between 24 and 36 h exposure, while fish exposed longer than 36 h recovered within 1–10 min, or within 1–2 min after 44–48 h. At the end of a 48‐h transport experiment total ammonia levels were higher in transport water containing anaesthetized fish than for non‐anaesthetized fish (1.65 ± 0.19 and 0.54 ± 0.08 mg L−1 NH + NH3, respectively). The combined use of clove oil and the selective ammonium ion exchanger zeolite was considered feasible as ammonia levels could be reduced by up to 82% compared to control bags without zeolite.
The prevention of torsional vibration-induced fatigue damage to turbo-generators requires determining natural frequencies by either field testing or mathematical modelling. Torsional excitation methods, measurement techniques and mathematical modelling are active fields of research. However, these aspects are mostly considered in isolation and often without experimental verification. The objective of this work is to compare one dimensional (1D), full three dimensional (3D) and 3D cyclic symmetric (3DCS) finite element (FE) methodologies for torsional vibration response. Results are compared to experimental results for a small-scale test rotor.It is concluded that 3D approaches are feasible given the current computing technology and require less simplification with potentially increased accuracy. Accuracy of 1D models is reduced due to simplifications but faster solution times are obtained. For high levels of accuracy model updating using field test results is recommended.
This paper presents a case study dealing with the assessment of cracking observed at steam turbine blade attachment holes, and subsequent use of an innovative repair solution based on a friction processing technique, friction hydro-pillar processing (FHPP). This was performed with a bespoke welding platform developed specifically for repair of radially cracked or incorrectly drilled blade attachment holes in LP turbine rotors. The paper initially outlines a fracture mechanics analysis of observed in-service cracking aimed at assessing critical defect sizes to support repair or replacement scenarios. It then briefly discusses development of the FHPP process before focusing on characterisation of the residual stresses resulting from the welding process and their amelioration by heat treatment; a necessary part of the procedure approval for turbine refurbishment.
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