S26 · ABB diaphragm seals
ABB combines technical data, dimensions, fill-fluid selection and instructions in one PDF.
ABB S26 diaphragm seals · remote and direct mounting
ABB pressure transmitters with diaphragm seals
Diaphragm seal systems isolate the transmitter from the process fluid, supporting corrosive, viscous, dirty or hot fluids and level configurations requiring direct mounting or remote capillaries.
Selection principle
Size the diaphragm seal as part of the measurement system
Seal type alone is not enough. Overall performance depends on the sensor, diaphragm diameter and stiffness, fill fluid, temperature, capillary and installation configuration.
ABB · With diaphragm seals
ABB datasheets and manuals
Download PDFs for your model. IT or EN identifies the language. Select manuals to match the instrument's communication protocol.
PGD100 / PAD100
PGD300 / PAD300
PDD300
PGD500 / PDD500
P-300/P-500 family manual and S26 documentation.
PGD500 and PDD500 datasheets on request. Contact us
266CRH / 266CRT / 266JRH / 266JRT
Performance
What changes when a diaphragm seal is added?
Assess three aspects of the system, beyond the transmitter's nominal accuracy.
ABB best practice
How to size a diaphragm seal system
Mounting
Direct mounting or remote capillary?
Direct-mounted diaphragm seal
- Lower fill-fluid volume
- Less sensitivity to temperature changes
- Generally faster response
- Compact installation
- Fewer variables from a remote system
Remote diaphragm seal with capillary
- Transmitter away from the measurement point
- Access requirements
- High process temperature
- Tank or pipe geometry
- Configurations with one or two remote seals
A long capillary affects more than accuracy.
More fill fluid increases sensitivity to temperature changes and may lengthen system response time. Consider sunlight and temperature differences along the route during selection.
Fill fluid
Fill fluid is part of the selection
Availability depends on seal type and configuration. Listed temperatures are catalogue fluid values and do not replace a complete application assessment.
-40 ... +250 °C
A standard choice for many industrial applications.
-85 ... +250 °C
Silicone option for lower ambient or process temperatures, depending on configuration.
-10 ... +375 °C
For high-temperature applications, subject to pressure and installation checks.
-100 ... +100 °C
For very low-temperature applications.
Oxygen service
Inert fluid listed in ABB's catalogue for oxygen service, where available.
Food applications
FDA-approved options offered in dedicated food-application configurations.
Vacuum service
Remote seals in vacuum applications
Vacuum requires a dedicated assessment
For vacuum applications, ABB recommends an all-welded construction and installing the transmitter at least 30 cm below the lower seal connection. Fill fluid, maximum temperature and minimum pressure must be assessed together.
ABB S26
Diaphragm seals come in many forms
The S26 family includes a wide range of geometries and connections to suit the process.
Seals with an integral flange and flush or extended diaphragm.
Rotating-flange configurations for greater installation flexibility.
Compact versions installed between compatible flanges or process connections.
Threaded connections for applications and lines that do not require a flange.
Tri-Clamp, V-band and other hygienic configurations for food and pharmaceutical applications.
Dedicated configurations for particular material, geometry or process requirements.
Level
Tank applications
Open tank
A typical configuration connects the high-pressure side to the bottom of the tank and references the low-pressure side to atmosphere. A diaphragm seal can isolate the process side where required.
Two remote seals
Closed tanks, or applications requiring both measurement points to be isolated from the process, can use two seals. Diaphragm, capillary and fill fluid should be symmetrical on both sides.
ABB range
Transmitters with diaphragm seals
The platform depends on measurement type, performance level and seal configuration.
| Family | Description | Status |
|---|---|---|
| PGD100 / PAD100 | P-100 platforms with diaphragm seals, according to measurement type. | Available |
| PGD300 / PAD300 / PDD300 | P-300 industrial platforms with diaphragm seals. | Available |
| PGD500 / PDD500 | P-500 high-performance platforms with diaphragm seals. | Upcoming |
ABB models covered:
ABB PGD100ABB PAD100ABB PGD300ABB PAD300ABB PDD300ABB PGD500ABB PDD500
Multivariable transmitters with remote seals
266CRH / CRT and 266JRH / JRT
For applications requiring both multivariable functions and process isolation through remote seals.
266CRH / 266CRT
266C family versions with remote diaphragm seals. Combine differential pressure, absolute pressure and temperature with mass flow and compensated-level functions.
CRH: 0.075% · CRT: 0.04%
266JRH / 266JRT
266J family versions with remote diaphragm seals, combining differential pressure, absolute pressure and temperature measurement while leaving calculations to an external system.
JRH: 0.075% · JRT: 0.04%
ABB replacements
266 series with diaphragm seals: replacement and migration
The model alone is insufficient to migrate a sealed 266 configuration correctly. The full code, serial number or nameplate is needed to identify seal type, material, capillary, connection and fill fluid.
ABB 266HRHABB 266DRHABB 266NRHABB 266GRTABB 266MRTABB 266ART
Why is there no universal one-to-one replacement table?
The diaphragm seal is a substantial part of the transmitter configuration. Two instruments from the same base family may need different replacements because of their connections, materials, capillary lengths, fill fluids, temperatures and mounting arrangements.
ABB · With diaphragm seals
Datasheets and manuals for earlier series
Original documents for identifying installed versions. Check the full code and protocol on the nameplate.
266HRH / 266DRH / 266NRH
266GRT / 266MRT / 266ART
264DC / 264HC / 264NC · direct-mounted seals
264DC: differential/gauge; 264HC: gauge; 264NC: absolute. 2007 and 2003 editions.
264DR / 264PR / 264HR / 264VR / 264NR · remote seals
264DR: differential; 264PR/HR: gauge; 264VR/NR: absolute. 2008 and 2006 editions.
621ES / 624ES · remote seals
621ES: differential, gauge and absolute. 624ES: gauge and absolute.
621ES / 624ES · direct-mounted seals
621ES: level, differential and gauge. 624ES: gauge and absolute.
611ES · flanged differential pressure
Dedicated datasheet for the flanged variant of the 600T EN series.
621L / 621N · flanged level measurement
1998 datasheet for identifying installed level measurement versions.
Hydrogen service
H-Shield / H-Shield+ to reduce hydrogen permeation
The challenge
Hydrogen molecules can permeate the diaphragm and, over time, compromise measurement stability and reliability, particularly under demanding pressure and temperature conditions.
ABB's solution
ABB offers H-Shield/H-Shield+ diaphragm coatings with high permeation resistance. Selection requires checks on hydrogen purity, temperature, pressure, seal material and transmitter configuration.
Do you need to measure hydrogen pressure? Include hydrogen concentration or purity, process pressure and temperature in the form. We will assess the most suitable diaphragm configuration.
Applications
When diaphragm seals are particularly useful
Request a quotation
Send your existing configuration
Nameplates and installation photographs are particularly useful for transmitters with diaphragm seals.
Please provide the full model code, serial number or a clear nameplate photograph. If available, also attach photographs of the seal and installation point.
Technical FAQ
Diaphragm seals, capillaries and ABB S26 FAQ
When is a direct-mounted seal preferable?
Where geometry and access permit, direct mounting reduces the variables introduced by the seal system. Overall performance still depends on sensor range, diaphragm diameter, fill fluid and thermal conditions.
How can thermal error in a seal system be reduced?
Select a sensor with an upper range limit close to the application span, use the largest compatible diaphragm, keep the capillary as short as practical and choose a fill fluid suited to temperature and pressure conditions.
Why does temperature affect a remote seal?
Fill-fluid expansion within the closed transmitter, capillary and seal volume can cause zero shift. Its magnitude also depends on diaphragm stiffness and actual installation conditions.
Does a diaphragm seal increase response time?
Yes. The delay depends on sensor range, number of seals, configuration, fill-fluid viscosity, temperature and capillary length.
Should dual remote seals have equal capillary lengths?
The same diaphragm size, capillary length and fill fluid are recommended on both sides of the transmitter.
How should a vacuum application be handled?
ABB recommends carefully assessing fill fluid, temperature and absolute pressure. For vacuum service it specifies an all-welded construction and the transmitter at least 30 cm below the lower seal connection.
Which fill fluids are available for S26 systems?
Depending on configuration, options include standard, high-temperature and low-temperature silicones, inert fluids for oxygen service and approved fluids for food applications.
Which ABB S26 seal types are available?
The S26 series includes fixed and rotating flanges, threaded connections, sanitary or aseptic designs, wafer seals and special configurations.
How do you identify a replacement for an older 266DRH or 266HRH?
We need the full code, serial number or a nameplate photograph. The model alone does not identify the connection, material, capillary, fill fluid and other options.