Creep assessment of overheated grade 9Cr steels for decision making on plant integrity

Alloy steels Gr. 91 (9Cr1MoVNb) and Gr.92 (9Cr0.5Mo1.8WVNb) are commonly used to construct supercritical and ultra supercritical boilers. The martensitic properties of both alloys require post weld heat treatment (PWHT) as mandatory process after welding. In the past experience at TNB power plants, overheating incidents had occurred during post weld heat treatment due to unintentional factors. The soaking temperature which is supposed to be controlled at 730°C to 770°C was accidentally overshot to beyond Ac1 (800°C~830°C) and Ac3 (890°C ~ 930°C). The overheated alloys experienced microstructure transformation which would have changed the hardness property and the creep strength of the alloys, making them unfit for further service. According to standard practice, the overheated components should be replaced immediately. Nevertheless, power station management, sometimes, encounters dilemma due to lack of time allowance to extend outages for further repair work. For this reason, the re-use of overheated components on temporary basis has become an important option to protect the national interest. This research is designed with the objective to gain an understanding of the metallurgical behavior of the overheated components and develop experimental creep curves as a guideline for operational decision making on this short term solution. Prior to this, TNB Research provided advices and recommendations based on practical knowledge and experience. With the presence of this research data, TNB Research can make a better judgment with a higher confidence level in problem-solving and decision making. The main purpose of this research is to investigate the microstructure transformation and creep property change as a result of possible overshoot above the normal tempering temperature (730°C-770°C) for these steels. The experimental results show that the hardness property is dependent on the type of microstructure matrix transformed at room temperature. The creep strength is proportional to the hardness property, but inversely proportional to the applied stress. As expected, the high temperature creep strength for both overheated alloys has dropped significantly as compared to the published creep master curves for new and unexposed specimens. Both Gr 91 and Gr. 92 alloys with overheated and degraded microstructure / property can be re-used for temporary service, depending on the metal temperature and applied stress level. Soft microstructure as a result of overheating at 850°C to 900°C has a very limited creep rupture time and it was considered unfit and impractical for further service, especially at design parameters for supercritical boilers, but if the parameters are compromised to subcritical level, temporary service up to 10,000 hours is possible. Hard microstructure as a result of cooling from 900°C to 1000°C shows improvement in creep life, likely attributed to tempering effect during creep exposure. The experimental creep data/curves developed for overheated Gr. 91 and Gr. 92 steels are reasonable and they are ready to serve as a reference/guideline to determine the temporary duration and operational load/stress selection. The allowance to re-use overheated components on temporary basis would have saved the downtime. Statistics from Stesen Janakuasa Sultan Azlan Shah, Manjung, the biggest coal-fired power plant in the county shows that the economic gain or return is equivalent to a few millions Ringgit Malaysia

Cost-Effectiveness in Individual Development Accounts

Because resources are limited, the benefits and costs of social-work interventions—like all interventions—must be compared with the benefits and costs of alternatives. Evidence-basedpractice should ask not only “What works?” but also “How well does it work?” and “What does it cost?” Unfortunately, evaluations of social-work practice—like evaluations in any field—rarely can measure all the relevant variables. In particular, benefits are extremely difficult to measure. Costs are simpler to measure, but even so, few evaluations measure costs. In the end, all evaluations are inevitably incomplete and so must make subjective judgments aboutunmeasured factors. The key to evaluation, then, is not certainty nor objectivity but rather explicitness. an evaluation’s usefulness rests not in its (apparent) incontrovertibility but rather in its clarity of assumptions, its explicitness about subjective judgments, and its openness to meaningful review and critique. With these goals in mind, this paper analyzes the provision ofIndividual Development Accounts with a new cost-effectiveness framework meant to help make assumptions and judgments explicit. In the specific IDA program examined, one month of services for one participant cost about $64. The mere existence of a cost figure—regardless of whether it is seen as high or low—has sparked many questions in the IDA community: How can costs be reduced without sacrificing quality? Which features of IDAs are essential? Are IDAs worth it? This sort of healthy questioning is precisely the purpose of cost-effectiveness analysis in social-work practice

Outcome of Laparoscopic Live Donor Nephrectomy and Impact of Double Renal Arteries: Results From Two Transplant Centres

ObjectiveLive donor kidney transplantation is consistently superior to deceased donor kidney transplantation. Laparoscopic donor nephrectomy (LDN) is increasingly accepted as a safe and preferred surgical option. To evaluate the outcome of LDN and the impact of multiple arteries, a retrospective review was conducted on patients in two transplant centres.MethodsFifty patients including eight with double vessels were studied. Standard left transperitoneal LDN was performed. Grafts including those with double vessels were prepared using the bench technique. Postoperative outcomes (up to 1 year) for donors and recipients were studied. The outcomes of recipients of a single or double vessel graft were compared.ResultsAll donors had an eventful recovery. No difference was found between the single and multiple vessels groups for operating time (168.21 ± 5.712 minutes vs. 197.50 ± 15.755 minutes) or hospital stay (3.21±0.165 days vs. 4.13±0.789 days). The recipient outcomes including hospital stay (10.17±0.596 days vs. 12.13 ± 1.797 days) and creatinine levels at day 7 (106.53 ± 5.583 μmol/L vs. 107.13 ± 11.857 μmol/L) and 1 year (120.21 ± 6.562 μmol/L vs. 124.75 ± 11.857 μmol/L) were similar. No ureteric stricture or graft loss was noted at 1-year follow-up. Recipient complications included lymphocoele (n = 2), haematoma (n = 3 with 2 requiring exploration), sepsis (n = 1), renal artery stenosis (n = 2 with 1 stented), repeated anastomosis (n = 1), and incisional hernia (n = 1). No differences were noted between the two groups.ConclusionOur results showed that overall donor morbidity rate was low, as reflected by the short hospital stay. Also, the overall parameters of the recipients were good. In particular, no ureteric stricture was noted, and graft survival was 100% at 1 year. The outcomes of the reconstructed group, despite the technical challenge, were similar to those of the single-vessel group

Mutation signatures implicate aristolochic acid in bladder cancer development

10.1186/s13073-015-0161-3Genome Medicine71Article number 3

Botulinum toxin and benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is a clinical condition where lower urinary tract symptoms are caused by both a physically obstructing prostate as well as tight smooth muscles around the bladder outlet. Treatment of this condition with botulinum toxin has been used since 2003, but this interest has somewhat died down after two large randomized controlled trials (RCTs) showing equivalence of results between their treatment and placebo arms. However, with review of animal studies and unexplained exaggerated effect of the placebo arms of the two RCTs, together with recent data of sustained benefits after 18 months of treatment, the place of botulinum toxin in the BPH field is probably still present

Multilevel marketing (mlm) industry : an empirical study.

The main objective of our study is to examine the Multilevel Marketing (MLM) industry in Singapore, including the perception of the public towards MLM, the views from MLM companies, the sentiments of distributors towards their companies, as well as the ethical issues concerning the industry. The results generated indicate that Singaporeans are generally negative towards MLM. Further analysis shows that purchasers, especially those who are currently using the products, have more positive perceptions than non-purchasers and purchasers who had discontinued with the products. It was also found that purchasers generally buy the products from their friends and relatives who are distributors. As for distributors, results indicate that they are generally committed to their companies and are satisfied with their jobs. Despite five years following the deregulation of MLM in Singapore, the industry still seems promising in setting new grounds for their unique method of product distribution. However, in light of the ethical concerns, recommendations have also been provided to improve the public’s perception

Government policies on foreign domestic labour : who benefits? who profits?

This paper highlights examples of the complexities of increasing reliance on foreign domestic help in the context of global migration and discusses the regulatory policies on foreign domestic labour and their impact on the employment relationship between employers and the foreign domestic workers in Singapore