A diaphragm seal (or remote seal) is used to protect pressure transmitters from corrosive, high-temperature, or viscous fluids. It isolates the process fluid from the transmitter by using a flexible diaphragm and a fill fluid to transmit pressure.
Why Use a Diaphragm Seal?
✅ Protects the transmitter from corrosive, high-temperature, or viscous fluids.
✅ Prevents clogging in applications with sludge, slurry, or crystallizing fluids.
✅ Allows remote mounting to keep the transmitter away from extreme conditions.
✅ Reduces thermal effects by using a stable fill fluid.
Types of Diaphragm Seals:
1. Direct Mount Diaphragm Seal
- The seal is directly attached to the pressure transmitter.
- Provides a compact design and fast response time.
- Best for low-pressure applications and when the transmitter can be mounted close to the process.
✅ Application: Clean liquids, low-viscosity fluids, and low-temperature processes.
2. Capillary Tube Diaphragm Seal
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The diaphragm is connected to the transmitter via a flexible capillary tube filled with a transfer fluid.
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Allows the transmitter to be installed away from extreme conditions (e.g., high temperature, vibrations).
- Slower response time due to the capillary length.
✅ Application: High-temperature processes, remote installations, and systems with vibrations.
Summary:
- Diaphragm seals protect transmitters from harsh process conditions.
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Direct mount seals offer a compact and fast-response solution for clean fluids.
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Capillary tube seals allow remote installation and protect against extreme temperatures and vibrations.
| Model | FDS 91 |
| Type | Diaphragm Seal |
| Size | 1″, 2″, 3″, 4″ |
| Rating | 150# ~ 1500# |
| Diaphragm Material | SS316, Hastelloy-C, Tantalum |
| Flange Material | SS316, Hastelloy-C |
| Filled Oil | Silicon, HT Silicon |
| Capillary Length | Direct or 1 ~ 25m |
| Mother Transmitter | STEX Series |
Other options and technical specifications are mentioned in the attached PDF catalog.