ON-SITE DETERMINATION OF THE CONTROL LINE FOR INTEGRALLY GEARED COMPRESSORS FOR AVOIDANCE OF IMPELLER FATIGUE FAILURES

LectureIn this lecture a root cause analysis (RCA) is presented for a fatigue failure of a semi-open impeller of an integrally geared compressor. The compressor had been in service for about one year in an air separ 3rd stage impeller

ON-SITE DETERMINATION OF THE CONTROL LINE FOR INTEGRALLY GEARED COMPRESSORS FOR AVOIDANCE OF IMPELLER FATIGUE FAILURES

LectureIn this lecture a root cause analysis (RCA) is presented for a fatigue failure of a semi-open impeller of an integrally geared compressor. The compressor had been in service for about one year in an air separ 3rd stage impeller

Hepatic mitochondrial dysfunction in Friedreich Ataxia

<p>Abstract</p> <p>Background</p> <p>Mitochondrial dysfunction due to respiratory chain impairment is a key feature in pathogenesis of Friedreich ataxia. Friedreich ataxia affects the nervous system, heart and pancreas.</p> <p>Methods</p> <p>We assessed hepatic mitochondrial function by ¹³C-methionine-breath-test in 16 Friedreich ataxia patients and matched healthy controls.</p> <p>Results</p> <p>Patients exhaled significantly smaller amounts of ¹³CO₂over 90 minutes. Maximal exhaled percentage dose of ¹³CO₂recovery was reduced compared to controls.</p> <p>Conclusions</p> <p>¹³C-methionine-breath-test indicates subclinical hepatic mitochondrial dysfunction in Friedreich ataxia but did not correlate with GAA repeat lengths, disease duration or disease severity.</p

Association between solar insolation and a history of suicide attempts in bipolar I disorder

In many international studies, rates of completed suicide and suicide attempts have a seasonal pattern that peaks in spring or summer. This exploratory study investigated the association between solar insolation and a history of suicide attempt in patients with bipolar I disorder. Solar insolation is the amount of electromagnetic energy from the Sun striking a surface area on Earth. Data were collected previously from 5536 patients with bipolar I disorder at 50 collection sites in 32 countries at a wide range of latitudes in both hemispheres. Suicide related data were available for 3365 patients from 310 onset locations in 51 countries. 1047 (31.1%) had a history of suicide attempt. There was a significant inverse association between a history of suicide attempt and the ratio of mean winter solar insolation/mean summer solar insolation. This ratio is smallest near the poles where the winter insolation is very small compared to the summer insolation. This ratio is largest near the equator where there is relatively little variation in the insolation over the year. Other variables in the model that were positively associated with suicide attempt were being female, a history of alcohol or substance abuse, and being in a younger birth cohort. Living in a country with a state-sponsored religion decreased the association. (All estimated coefficients p <0.01). In summary, living in locations with large changes in solar insolation between winter and summer may be associated with increased suicide attempts in patients with bipolar disorder. Further investigation of the impacts of solar insolation on the course of bipolar disorder is needed.Peer reviewe

Aeroacoustic Phenomena In High Pressure Centrifugal Compressors - A Possible Root Cause For Impeller Failures.

Lecturepg. 103-122During the past decades studies of aeroacoustic phenomena in turbomachinery were mainly carried out by research institution. The aerospace industry was the main driver in this field since noise issues gained more and more significance. Though it has been known for some years that acoustic resonances may also lead to strong excitation sources, very little is known about the relevant physics, especially for centrifugal compressors. Failures that were observed in the field could not be explained by state-of-the-art analysis procedures, and it became from customer discussions that there is a strong need for better understanding of aeroacoustic excitation mechanisms; these were suspected to play a significant role in the root causes of failures. To improve the reliability of centrifugal compressors, especially for high-pressure applications, an extended in-house research program has been launched to better understand the involved interactions that may lead to machine failures. The current paper gives an overview on the research activities, presents the underlying theory, and gives new results that are relevant from a practical point of view. Anew aeroacoustic excitation model is presented and its successful application to explain tow impeller failures in the oil and gas industry is illustrated