603 大口径閉止フランジ締結体の密封特性に与えるガスケット特性の影響(フランジガスケット締結体の力学と密封性能評価I)

Leakage from large diameter flanges had occurred several times in a new 1360 t/d ammonia plant. One such incident resulted in a large fire. The causes of this incident are examined.

This paper describes the design, analysis and testing of "The Split Clamp", a device which can be used for strengthening any flanged connection. For a given space envelope, the split clamp connection is significantly stronger than any conventionally used flange or clamp connection. A split clamp device was designed and built for a modified 11"-5,000 psi API flange. This prototype assembly was tested to 20 ksi internal pressure and to1.1 million ft-lbs bending moment with various torque values on the flange bolts. Finite Element Analysis(FEA) was also conducted and the results were compared. INTRODUCTION API flange bolted connections have traditionally been used to fasten several forged body components together for many subsea wellhead and completion systems. As equipment is i nsta11 ed in ever deeper waters, the bending moment associated with drilling or completion risers grows. Recently, many subsea equipment assemblies have used large diameter high pressure flanges (e.g., a 13-5/8-IOK flange on a 4" × 2"-5K working pressure tree) to withstand high bending moments on tree end connections. These larger flanges have diameters much larger than what is usually needed for the rest of the forged body. This results inspecially shaped forgings or larger and heavier forgings which are expensive. The split clamp devices were originally designed for use on deep water (3,200 - 5,800 ft) guideline less subsea completion trees being installed offshoreBrazil. Riser Analysis [1] was conducted to determine the bending moment on the guide1i ne1ess tree end flanges. It was determined that when tie 9-5/8" completion riser is subjected to the environmental conditions shown in Table 1, the maX1mum bend1ngmoment on the connection at the base of tree canbe as high as 1.1 million ft-)bs. The bending moment capacity of an API 68 1l"-5K flange at 5,000 PSl internal pressure is 350,000 lbs [2] and that of a 6BX I3-5/8"-10K flange is 800,000 ft-lbs. This necessitated significantly stronger end connect10ns, on the trees, than the above specified API flanges which are typically used on subsea trees. The split clamp device increased the strength of the connection without increasing the overall size of the subsea tree composite block valve. DESIGN The split clamp device (see Figure 1) is designed for insta11 action on any flanged connection. It consists of a split ring (see Figure 2) and annular outer ring. The device is assembled by firstthreading the outer ring over the lower half (threaded) of the flange connection. Next, flangehalves are made up with the AX type gasket 1ns1de. The flanges are made up and preloaded with the flange bolts in the same manner as conventiona1 flanges, except the preload value is higher than recommended for a conventional flange. The two halves of. the split ring are then mounted and bolted together in agroove around the upper half of the flange connection.

A new technology for manufacturing large sealing flange is presented. It involves bending combined with welding and finishing machining at the construction site. The innovation in this method is that the preliminary machining of the section, using a heavy-duty vertical lathe, is replaced by precision bending. Therefore large diameter flange can be manufactured at very low cost. Bending of a specimen with an E-cross-section was investigated by numerical simulation and experiment. The mechanism of lateral deformation was analyzed and the method to overcome it was given. This technology was successfully used for manufacturing a large flange which used in a large wind tunnel.

With the recent increase of a safety and environmental concern, the tightness of gasketed flanged connections becomes an important issue. In estimating the tightness of gasketed flanged connections, the sealing behavior of gaskets must be known. Currently, methods to test the sealing behaviors have been established in the North America, Europe and Japan. However, the relationships between the gasket data and the tightness of gasketed flanged connections have not been examined systematically. This paper consists of two parts: gasket data concerning sealing behavior and tightness of gasketed flanged connections. Firstly, several sheet gaskets were tested based on the test method JIS B 2490 in order to grasp tightness of gaskets. Secondly, tightness tests were carried out using blind flanges with the tested gaskets by JIS B 2490. Both the results were compared and discussed to highlight the relationship between them. It is shown that the tightness of bolted flanged connections is largely affected by the sealing behavior of gaskets. Based on the results, a simplified method to estimate the tightness of flanged connections is proposed.

The considerable diversity of locomotor behavior within the suborder Prosimii largely is due to differences in locomotion between families. Within families, locomotion is relatively homogeneous, although some species, such as Otolemur crassicaudatus among the galagids and Hapalemur simus and Lepilemur spp. among the lemurids, differ from other species in their family. This paper describes the locomotion of a captive colony of red-bellied lemurs, Eulemur rubriventer (following the classification of Simons and Rumpler [1988] who place all species of Lemur other than Lemur catta in the genus Eulemur), another species whose movements differ markedly from other members of its family, the Lemuridae. Features that distinguish the locomotion of E. rubriventer from other lemurids are the high frequency of leaping, low frequency of climbing and suspension, and the use of head-downward vertical climbing in this species. Leaping is the most common form of locomotion in E. rubriventer. Horizontal, rather than vertical supports, are preferred during leaping. Although the frequency of climbing in this study is relatively low, the large brachioradialis flange, robust hallux, and claw-like nails of E. rubriventer suggest that clinging and climbing on large diameter vertical supports (lacking in the enclosures used in this study) may be an important component of locomotion in wild E. rubriventer and may reflect a gummivorous or insectivorous dietary adaptation. While the locomotion of E. rubriventer differs from all prosimians yet studied, the general pattern of locomotor behavior seen in this species is most similar to other species of the family Lemuridae.

Subsea installations of large diameter flanged connections can prove to be costly and dangerous. The use of Taper-Lok connectors for subsea make-up of tie-ins and manifold connections during the installation of the BP Bombax Pipeline Project provided safer and faster connection make-up times, damage resistance, reduction of weight and one time, leak free installation. This paper will outline the reasoning behind the use of the Taper-Lok connection for this project and the areas of cost savings associated. Introduction The subsea pipeline portion of the BP Trinidad Bombax Project called for flanged connections to be used in 20-inch, 26-inch and 48-inch sizes. These were to be provided in Weld Neck, Swivel, Blind Flange and Misalignment designs. The need for ease of make-up at depths of 300 feet, in waters with limited visibility, high current loads and heavy weight considerations were driving forces in the connections to be used. Due to stringent BP policies, safety during installation was a major consideration, as well. Discussions began in mid March of 2001 regarding the manufacturing of the required connections. Preliminary design requirements were developed and the Taper-Lok engineering phase began in early April. Taper-Lok offers a full range of product groups. All product groups have features, which are common elements, and several of the products offer additional, unique features and time saving devices. Design Criteria and Requirements General. Operating Conditions.External Hydrostatic Pressure = 300 feet water depthOperating Max. Seawater Ambient Temp. = +80 deg FMin. Blow Down Temp. = +14 deg FMax. Internal Operating Pressure = 1480 psigHydrostatic Test Pressure = 1.5 times operating pressureOperating Temp. = 150 deg F Taper-Lok was selected due to the following inherent design features:Sealing Integrity;Self Alignment During Make-Up;Size and Weight Reduction;Safety During Installation;Forgivingness of Sealing Surfaces;Misalignment Capabilities.Annulus Test Port Capability.Meets or exceeds the requirements of ASME Section VIII, Division 1 and 2, API 6A, ANSI, and MSS flange design standards.Self-Energized/Pressure Energized, Reusable, Seal Ring.Smaller/Lighter Bolts Flange Requirements. Size Description Qty. 48" Weld Neck Flanges 12 48" Swivel Flanges 8 48" Blind Flanges 11 26" Weld Neck Flanges 16 26" Swivel Flanges 11 26" Blind Flanges 13 20" Weld Neck Flanges 11 20" Swivel Flanges 4 20" Blind Flanges 7 48" 5°?Misalignment Connectors 2 26 10°Misalignment Connectors 3 Total 98 Various Sizes Studs with 2 Nuts ea. 2,700 +

To consider special demands, two gaskets floating between the flange faces are used for example in flanged connections of pressure vessels, valves, pumps etc. Tightness control can be one of the reasons to choose this design. The inner (primary) gasket has to tighten the internal pressure; the outer (secondary) gasket tightens possible leakage of the primary gasket. By the use of two identical gaskets in the same plane the procedure for the tightness proof is the same as in connections with one gasket. In many cases there are used two gaskets with different characteristics (deformation and tightness characteristics) in two tightening planes. The behaviour of this connection depends not only on the gasket characteristics but also on the tolerances of axial dimensions. The distribution of prestress on both gaskets is determined by the elastic-plastic deformations of both gaskets and tolerances of axial dimensions of the connection. The decrease of gasket stress in operation depends on the plastic deformations of both gaskets in operation, too. Depending on the demanded tightness class, the possible gasket stress during assembly and the gasket stress in operation determine the selection of suitable gaskets (with necessary gasket characteristics). It is necessary to take into account the internal pressure and possible pressure between primary and secondary gasket, too. In the paper the design of gaskets for this type of connection is discussed. Originally, it was used: - nickel ring as primary gasket, - asbestos packing as secondary gasket. Both gaskets have suitable deformation characteristics for the existing type of connection. The secondary gasket has low stiffness for the adjustment of an optimal stress on the primary gasket after prestressing. The primary gasket has a good relaxation behaviour. However, the nickel ring needs a very high local stress to achieve suitable tightness behaviour. This stress leads to plastic deformation of the flange surface during assembly, too, and this can induce leakage after the next assembly (with new rings) as operation experience showed. The use of asbestos packing is not allowed any more due to health reasons. This invoked a redesign of this gasket. The paper deals with gasket proofs and gasket characteristics for selection of suitable gaskets. Calculations of gasket stress distributions of both gaskets (elastic-plastic deformations) are presented. The analysis of the stress distribution allows reviewing the tightness class in operation incl. relaxation behaviour of the connection. Other recommendations are listed like the increase of connection safety by a reduction of bolt stiffness (better relaxation behaviour of the connection and higher bolt elongation), more accurately bolt elongation measurement, new assembly procedure, etc. Main target of the re-design is life time extension of connection, too.