Pressure vessel head seal

Type S is a floating head type. As the tubes heat up, they expand. As they expand, the floating head moves back and forth, but the pressure seal is not at the sliding joint. The pressure seal is at the fixed shell Joint in the outer head, which contains the pressure. The floating head floats free inside the pressure vessel as the tubes move. Types P and W are floating heads where the movement of the head effects the seal between either the shell-side or tube-side fluid and atmosphere. 

Pressurised water nuclear reactors require metals that will have a high degree of corrosion resistance to pure water at around 300°C. Laboratory testing of materials for this application have included potentiostatic polarisation experiments designed to clarify the active-passive behaviour of alloys as well as to establish corrosion rates. Since pressure vessels are used for this work, it is necessary to provide sealed insulated leads through the autoclave head . 

Magnetically coupled drive mechanisms have a set of inner magnets located atop the impeller shaft that extends down into the pressure vessel. This inner magnet assembly is positioned so that it can be rotated within and be encapsulated by a small pressure vessel chamber. This chamber is made of nonmagnetic material and is attached and sealed to the head of the reactor vessel. This chamber is then surrounded by another set of matching magnets located in an... 

Seal port D, and lower the head assembly into the body of the pressure vessel, and effect the pressure seal by progressively tightening opposite pairs of the eight bolts K. 

Fig. 8.2 A high-pressure vessel (G in Fig. 8.1) used for microdisc electrophoresis. The electrophoresis cell (a) is fitted into a stand (b) which is screwed onto the interior of the sealing-closure head. The electric leads (c) are soldered on inverted steel cones allowing connections through the plug to the power supply. The insulating shell of the cones is made of Teflon.

The RPV is a vertical, cylindrical pressure vessel of welded construction, with a removable top head, and head flanges, seals and bolting. The vessel also includes penetrations, nozzles, shroud support, and venturi shaped flow restrictors in the steam outlet nozzles. 

The closure head of the reactor pressure vessel accomodates the control rod drive mechanism nozzles, the in-core instrumentation nozzles, the RPV water level control nozzles and the venting nozzle. The RPV body and closure head are joined together by means of studs and nuts. During refuelling, the RPV closure head is removed, together with the platform, closure head insulation, control drive mechanisms and the seal rings. 

Reactivity control is maintained by movement of control rods and by burnable poisons in the fuel. The reactor pressure vessel (RPV) is a vertical, cylindrical pressure vessel, with a removable top head, and head flanges, seals and bolting, and with venturi-shaped flow restrictors in the steam outlet nozzles. The RPV is 6 m in diameter, with a wall thickness of about 158 mm with cladding, and 24.5 m tall from the inside of the bottom head to the inside of the top head. The RPV height permits natural circulation driving forces to produce sufficient core coolant flow by increasing the internal flow path length. 

Let s consider now a system with dynamic pressures and a constant elevation. A classic example of this would be where a pump feeds a sealed reactor vessel, or boiler. The fluid level in the reactor would be more or less static in relation to the pump. The resistances in the piping, the Hf and Hv, would be mostly static although they would go up with flow. The Hp, pressure head would change with temperature. Consider Figure 8-14. 

Because of the size and the pressure of the vessel, austenitic stainless steel could not be used throughout, but must be applied on the inner surfaces of the ferritic material. This has been done by explosion plating of a 4 mm cladding on the base material prior to rolling the cylinder and forming the hemispherical head. For the flat cover and the sealing faces weldcladding was applied. 

Figure 76. Liquid film shaft seal with nlindrkwl hushing lor a high-pressure centrifugal compressor a) Shaft b) Bearing c) Pressure side d) Ambient side e) Floating seal rings f) Sea) oil surge vessel g) Sea) oil h) Lube oil i) Drain to gas-oil separaior k) Drain lo lube oil tank l) Elevation for seal oil head...

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