Union Connection Remote Seals (S26Un) - ABB S26 Series Operating Instruction

5.10 Union Connection remote seals (S26UN)

The union connection remote seals are used exclusively for pressure measurement. The seal is available without a weld bushing,
with an optional weld bushing, or with an optional chemical tee flange. An O-ring is used to seal the process connection.
The O-ring material can be silicone rubber for temperatures up to 177°C (350°F) or PTFE for temperatures up to 204°C (400°F).
Note. The operating temperature limit for the seal can be lower than the O-ring temperature limit because of fill fluid limitations
(refer to the fill fluid parameter table in the Specification Sheet). Connect the seal as described in the applicable following section.
Seal without Weld Bushing
The seal without a weld bushing must be connected to a user supplied fitting having mating surface dimensions as shown in the
figure. Connect the seal as follows:
1. Lubricate the sealing O-ring with Silicone gasket grease.
2. Mount the O-ring on the end of the seal.
3. Insert seal into mating fitting and tighten the union connection nut to press the O-ring against the fitting surface.
Figure 28: Union connection remote seal – basic version
Seal with Weld Bushing
The remote seal with a weld bushing includes a bushing which provides the mating surface for the seal element. The bushing
must be welded to the process piping or vessel before installing the seal. Use the following procedure:
1. Weld bushing to pipe or vessel in accordance with standard industrial practices.
2. Remove protective covering from seal.
3. Lubricate the sealing O-ring with silicone gasket grease.
4. Mount the O-ring on the end of the element.
5. Insert element into mating fitting and tighten the union connection nut to press the O-ring against the fitting surface.
Figure 29: Union connection remote seal with weld bushing
26 OI/S26-EN Rev. B | 2600T Series Pressure transmitters
134 (5.34)
29 (1.14)
16 (0.6)
54 (2.12) - 16N2
2 (0.08)
10 (0.39) Full Thread
134 (5.34) 25 (1)
Union Connection
57 (2.25)
9 (0.35)
14 (0.55)
Diaphragm Surface
Welding Bushing