Ring Type Joint Research Articles

Generalization of the tetraparametric assembly method for the optimization of bolt tightening sequences in ring-type joints

Uniform bolt load is critical to achieve leak-free service in pressure vessel gasketed joints. In a previous work, the authors presented the tetraparametric assembly method, which enabled to obtain a uniform final load distribution in a one-pass tightening sequence. The accuracy of the method was proved by finite element analysis and experimental tests. However, the tetraparametric assembly method was only developed for one-pass tightening sequences, and in some cases more than one pass can be necessary. Furthermore, the method was only validated for a particular joint geometry. In this sense, the present work generalizes the method for two-pass tightening sequences and studies the range of application.

A new methodology for the optimization of bolt tightening sequences for ring type joints

Achieving uniform bolt load distribution is critical to obtain leak-free service in pressure vessel gasketed joints used in offshore pipelines. This is a difficult task due to bolt load variations during the assembly process. In this sense, the Elastic Interaction Coefficients Method has been developed in previous works to define tightening sequences that provide the target load at the end of the sequence in one or two passes. The method is very costly because a complete sequence must be simulated and the load of every bolt must be measured after each tightening operation. The present work validates this method for Ring Type Joints and further develops a numerically and experimentally validated new methodology that provides highly satisfactory results with a significantly lower cost.

A Study on the Contact Characteristics of Metal Ring Joint Gaskets

Gaskets are usually used for the sealing of flange joints. The joint is usually composed of two flanges, a ring gasket and clamping bolts. The metal ring gasket is suitable for pipe flanges, pumps and valve joints in high temperature and high pressure environments. A very high surface stress is developed between a ring type joint gasket and the flange groove when the ring type joint is bolted up in a flange. The dimensions of flanges and ring joint gaskets for the pipe sizes that are in common use are specified in the ANSI codes. However, sometimes it is necessary to make a new design for the flange joint which is not specified in the codes, as the equipment is getting larger and larger in size. This paper presents the contact behavior of Class 600 ring joint gaskets with oval and octagonal cross sections. Five different sizes of gaskets are employed in the analysis, and one of them is newly designed on the basis of analysis results obtained from existing models. Three load steps are used to find the stress, stain and contact pressure etc., and to compare the contact characteristics among the models due to the bolt clamping force and the working surface pressure. ANSYS Workbench version15 is used to conduct the finite element analysis.

Stress Corrosion Cracking of Ring Type Joint of Reactor Pipeline of a Hydrocracker Unit

Failure of a ring type joint (RTJ) of reactor pipeline of a hydrocracker unit has been reported. Cracks were noticed on the flange as well as the ring gasket of the RTJ during inspection following a periodic shutdown of the unit. These components of the RTJ were manufactured from stabilized grades of austenitic stainless steel, namely, type 321 and 347, respectively. Study showed that the failure of the RTJ components occurred by transgranular stress corrosion cracking. It was further established that formation of polythionic acid due to presence of H2S in the process gas and H2O in the system was responsible for initiation of SCC in RTJ components. Detailed metallurgical investigation was carried out to identify the probable causes that could have been responsible for formation of polythionic acid in the process gas.

In-Situ Repair of Multiple Cracks Present in the RTJ Groove of High Pressure Hydrogen Bearing DHDS Reactor by Welding

This article describes a detailed repair procedure with necessary heat treatment involving the repair of multiple cracks in the Ring type joint (RTJ) groove of top man-way flange observed during the first internal inspection of the Reactor (25-R-01). Detailed site inspection and laboratory investigations, including visual inspection, thickness measurements, metallographic analysis, hardness testing of RTJ groove and RTJ gasket, Dye Penetrant testing, cladding disbonding testing by ultrasonic method, ferrite number measurement etc., were performed to identify the cause and mechanism of damage. Various factors like Stress corrosion cracking, Hydrogen induced cracking, sigma phase formation, have been involved with respect to the operating conditions of the equipment. In view of the above observations and ascertaining the severity of the overall damage of the Reactor, the in-situ repair methodology by welding was developed & repair jobs were successfully undertaken.

실험계획법을 이용한 STS301L 이음재의 GMA 용접 자동화에 관한 연구

Stainless steel sheets are widely used as the structural material for the railroad cars and the commercial vehicles. These kinds structures used stainless steel sheets are commonly fabricated by using the GMAW (gas metal arc welding). For fatigue design of GMA welded joints such as fillet and plug, ring type joint, it is important to obtain optimum design factor information on GMA welded joints. in this paper, analysis approach for fatigue test using design of experiment are evaluated optimum factor in GMA welded joint type and geometrical parameters of materials. Using these results, that factors applied to fundamental information for fatigue design.