Rosemount 1199, Справочное руководство

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Reference Manual
00809-0100-4002, Rev BB
November 2012
2-7
Rosemount 1199
Fill Fluid Selection
When the process is under vacuum conditions, the fill fluid can vaporize at a
lower temperature than when it is under normal atmospheric or greater
pressure. Each fill fluid has a specific Vapor-Pressure curve. The
Vapor-Pressure curve indicates the pressure and temperature relationship
where the fluid is in a liquid or a vapor state. Proper seal operation requires
the fill fluid to remain in a liquid state. For vacuum applications, specify fluids
with a premium combination of vapor-pressure curve and high temperature
limits like Silicone 704 or Silicone 705.
DIAPHRAGM WELD
TYPES
Weld-type is factory-determined as best for the seal typed specified. PFW and
FFW seals have ordering options that specify welding options.
Solid Faceplate Design
The solid faceplate design is used when diaphragm and upper housing
material are the same or when the weld is not wetted. This design is:
• The most efficient design to build and is the typical standard.
• TIG weld is used in solid faceplate design; this weld is wetted.
Seam Weld Design
This design is used when the upper housing material is different from the
diaphragm material. The seam welded design has a hermetic weld at the
inner diameter of the diaphragm and a TIG weld at the outer edge. The
diaphragm floats on the upper housing over the gasket surface area and
could tear if a metallic gasket were used.
• Not used with wire-wound metal gaskets
Upper Housing
Material A
Material A
TIG Weld point
Diaphragm
Upper Housing
Diaphragm
Material A
Material B