Overview; Seal System - ABB S26 Series Operating Instruction

3 Overview

3.1 Seal system

The S26 Series Seal System is a protective device used to isolate transmitters from the process fluid.
When used without diaphragm seals, these transmitters are generally connected to process piping or process vessel by impulse
lines. The process fluid leaves its enclosure, fills the impulse lines, and enters the body of the transmitter. For certain applications,
it is necessary to prevent the process fluid from leaving its enclosure. The seal system provides a flexible diaphragm seal between
the process fluid and a liquid filled capillary tube connected to the body of the transmitter. The diaphragm isolates the process
fluid while the filled capillary tube hydraulically transmits the process pressure to the transmitter body.
Some reasons why an isolating seal is required are:
— The process fluid is highly corrosive. Remote seals offer a much wider choice of corrosion resistant materials compared to
conventional transmitters.
— The process fluid has solids in suspension or is highly viscous and can clog impulse lines.
— The process fluid can solidify in impulse lines or inside the transmitter body.
— The process fluid is too hazardous to enter the control area where the transmitter is located.
— The process temperature exceeds the recommended maximum or minimum limits for the transmitter.
— The application is interface level or density measurement. Remote seals offer the required constant and equal specific gravity
of the pressure transfer fluid on the high and low sides of the transmitter.
— The transmitter body must be located away from the process for easier maintenance.
The S26 series is available in a variety of seal element types. They provide process connection to ANSI, JIS or EN pipe flanges,
wedge flow elements, chemical tees, and threaded pipe fittings. Extended diaphragm remote seals are suitable for connection to
2-inch, 3-inch or 4-inch flanged tank nozzles or flanged tees permit the seal diaphragm to be located flush with the inside of a
tank or pipe. Sanitary and sanitary aseptic type seals meet the stringent requirements of sanitary food, dairy, pharmaceutical, and
Biotech applications. All sanitary seals comply with 3A Sanitary Standard No. 74-02. These remote seal systems feature unique all
welded construction (see in Figures 1 and 2). This construction assures reliable operation over a wide range of operating
temperatures and pressures. It is especially important in preventing air leakages when the system is operating under vacuum
conditions.
1 Transducer isolation diaphragm | 2 Welding capillary | 3 Filling capillary | 4 Capillary tube | 5 Element stem | 6 Element flange | 7 Process diaphragm |
8 Welding | 9 Weld ring / gasket surface
Figure 1: Seai system components
1
2
4
3
6
2
5
2600T Series Pressure transmitters | OI/S266-EN Rev. B 7
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8
9