Sealing Performance Evaluation of Pipe Flange Connection Under Elevated Temperatures

ABSTRACT Since a lot of pipe flange connections are exposed to elevated temperature during operation, it is important to evaluate the sealing performance of the connections under operational temperature. In this study, the sealing performance of pipe flange connection was experimentally evaluated by measuring the amount of gas leakage at room temperature (RT), 100 ℃ and 200 ℃ in addition to internal pressure. Non-asbestos graphite gaskets were used in the experiment. The nominal size of the pipe flange used during the experimental study was 3 inch. The eight bolts and nuts were tightened according to ASME PCC-1 and the Japanese method (HPIS). During assembly, the axial bolt force was individually measured with strain gauges attached to each bolt. The scatter in the axial bolt force during the assembling process was examined and compared between the ASME and the HPIS. In addition, the gasket contact stress distribution of each assembly process was calculated by finite element method under elevated temperature and internal pressure. In the FE study, experimentally measured physical properties such as elastic modulus and thermal expansion were used. The amount of leakage was estimated from the contact gasket stress distribution obtained by FE analysis. The estimated axial bolt forces were compared with those of experimental ones. PVP2007-26401 Copyright © 2007 by ASME 1 INTRODUCTION Pipe flange connections with gaskets in chemical plants, electric power plants and other plants are usually exposed to internal pressure under elevated temperature environment. For the applications, the thermal effects such as thermal expansion or thermal stress should be included in the design. The sealing performance evaluation under thermal condition is especially an important issue to avoid unexpected leakage. In order to predict the sealing performance of the pipe flange connection, gaskets, under elevated temperature, it is necessary to examine the characteristics of the connections under thermal conditions. Many investigations, looked at the sealing performance, the contact stress at the interfaces, a variation of the axial bolt force and creep behavior of flange joints, and were performed by looking at the mechanical behavior of pipe flange connections with gaskets [1]- PVRC (Pressure Vessel Research Council) proposed the tightness parameter "T p " and the new gasket constants "G b ", "a" and "G s " [8]-[12]. The council also proposed the procedure to evaluate the sealing performance and the method to determine the initial clamping bolt force (bolt preload) by using the new gasket constants and the tightness parameter T p . The sealing performance under elevated temperature can be evaluated with the HOTT (Hot Operational Tightness Test In the HOTT, the new gasket constants and the tightness parameter are obtained under uniform contact gasket stress distributions in the gasket tests. However, the assumption is not practical enough. It is impossible to avoid the scatter of axial bolt force in assembling process. The sealing performance evaluation and leakage rate measurement in actual bolted flange connections by using the new gasket constants is, therefore, the remaining issue. In this paper, the stress-strain curve of the gasket was experimentally measured at elevated temperature as well as room temperature and used in FE analysis for evaluating the contact gasket stress under elevated temperature. The scatter of the axial bolt force was also experimentally measured and used in the FE analysis. The sealing performance from experiment, FE analysis and PVRC method was compared and discussed

Impact of Regional Factors on Births and Wives' Continuation in Employment - Panel survey of consumers by the Institute for Research on Household Economics (Japanese)

This thesis examines regional disparities in fertility rates, and analyzes the influence of regional factors on birth trends and continuation in employment. For this analysis, while controlling for individual attributes such as type of work, age, and academic career, by combining microdata and attribute data for the region in which individuals reside, we investigate how differences between regions with regard to the living environment and other factors affect women's birth behavior and continuation in employment. With regard to regional factors, we focus on housing conditions, commuting time, the government's family policies, and the economic climate. In order to consider the concurrence of birth behavior and continuation in employment by wives, we used a bivariate probit model to make estimates, and our findings were that there are correlations between the birth rate of the second child and whether the home is rented or owned, and between the birth of the first child and the father's commuting time and the capacity of daycare centers.

Wireless Power Transfer System for Hyperthermia Therapy

Hyperthermia therapy attracts attension as a low-inversive target treatment for deep-positioned cancer. One of the hyperthermia therapies is hgh-frequency induction heating type by using nano-mgnetic materials and magnetic implants. A tumor with injected magnetic materials is heated by hysteresis loss and eddy-current loss under high frequency magnetic fields with a few handred kHz and a few mT. To generate magnetic fields at the deep position of body, we proposed double pancake type exciting system that consists with two flat coils at both sides of body. This paper discusses a wireless exciting system to generate AC magnetic fields rather than transmit energy to load. The experimantal results proved that a wireless transmission enables us to excite two pancake coils and generate magnetic fields in deep position like series-connected coils

Fluctuation of Resonance Frequency of Applicator Having Wireless Power Transmission for Hyperthermia Therapy

One of the hyperthermia therapies is hgh-frequency induction heating type by using nano-mgnetic materials and magnetic implants. A tumor with injected magnetic materials is heated by hysteresis loss and eddy-current loss under high frequency magnetic fields with a few handred kHz. To generate magnetic fields at the deep position of a body, we proposed a double pancake type exciting system with wireless power transmission. Since this system is constituted by two tuned resonant circuits, the characteristic is sensitive to the change of parameters. This paper discusses the fluctuations of resonance frequency depending on the change of a distance between the exciting and induced coils and resonance capacitor. As a result, we recognized the fluctuation range of the resonance frequency for a tuned exciting power source

Control of Exciting Frequency to Pancake Type Applicator Having Wireless Transmission for Hyperthermia Therapy

The hyperthermia as one of low-invasive therapies was taken notice of in aging society. There is a magnetic generating coil system, an applicator, as one research issue of the engineering developments in the medical treatment system. The proposed applicator system with the wireless transmission can be set a patient to operating bed easily and the gap between two flat coils can be adjusted to the breast thickness of a patient. But on the other hand, the distance between coils changes a mutual inductance and influences the characteristics of circuit and magnetic fields. This paper estimates the characteristics on the variation range of electric parameters by change of the size of exciting coils, and proposes the control methodology of the parameter fluctuation by a control of exciting frequency. The feasibility and performances of the apparatus were discussed by the simulation and the experiment

Structural and dynamic behavior of lithium iron polysulfide Li₈FeS₅ during charge–discharge cycling

Lithium sulfide (Li₂S) is one of the promising positive electrode materials for next-generation rechargeable lithium batteries. To improve the electrochemical performance of electronically resistive Li₂S, a Fe-doped Li₂S-based positive electrode material (Li₈FeS₅) has been recently designed and found to exhibit excellent discharge capacity close to 800 mAh g⁻¹. In the present study, we investigate the structural and dynamic behavior of Li₈FeS₅ during charge–discharge cycling. In Li₈FeS₅, Fe ions are incorporated into the Li₂S framework structure. The Li₂S-based structure is found to transform to an amorphous phase during the charge process. The delithiation-induced amorphization is associated with the formation of S-S polysulfide bonds, indicating charge compensation by S ions. The crystalline to non-crystalline structural transformation is reversible, but Li ions are extracted from the material via a two-phase reaction, although they are inserted via a single-phase process. These results indicate that the delithiation/lithiation mechanism is neither a topotactic extraction/insertion nor a conversion-type reaction. Moreover, the activation energies for Li ion diffusion in the pristine, delithiated, and lithiated materials are estimated to be in the 0.30–0.37 eV range, which corresponds to the energy barriers for local hopping of Li ions along the Li sublattice in the Li₂S framework

Radiotherapy for mucosa-associated lymphoid tissue lymphoma of the ocular adnexa

Objectives: We investigated the results of radiotherapy for mucosa-associated lymphoid tissue (MALT) lymphoma of the ocular adnexa. Methods: Twenty-one patients with MALT lymphoma of the ocular adnexa were treated with radiotherapy alone at a dose ranging from 30 to 54Gy. The disease arose from the conjunctiva in 15 patients (9 with bilateral involvement), and from the retrobulbar space in 6 patients (1 with bilateral involvement). Results: All patients with MALT lymphoma achieved a CR or unconfirmed CR (CRu). The 5-and 10-year overall survival rates of all patients with MALT lymphoma were 100% and 90%, respectively. The 5-and 10-year cause-specific survival rates were 100% and 100%, respectively. In all patients with delayed toxicity, the radiation dose was more than 40Gy. Conclusions: Excellent local control and survival can be achieved for patients with MALT lymphoma of the ocular adnexa using radiotherapy alone