Split Type Pressure Transmitter with 316L Remote Diaphragm Seal for Extreme Process Conditions
Some processes are simply too hot, too corrosive, too viscous or too cramped for an integrated pressure transmitter. The QWY-308 split type pressure transmitter separates the 316L sensing diaphragm from the electronics, connected by a capillary and fill-fluid system, so the electronics stay cool, clean and safe while the diaphragm meets the process face to face.
Why Do You Need a Split Type Pressure Transmitter?
When the process medium exceeds 150 °C, direct heat conduction through an integrated transmitter destroys its electronics within weeks. When the medium is strongly corrosive, crystallizing or viscous, it blocks and corrodes standard pressure ports. When the measuring point vibrates violently or sits in a space too small for a transmitter body, an integrated unit simply cannot be installed. And in food and pharmaceutical lines that demand CIP/SIP sterilization, steam would cook a conventional transmitter. In all these cases the answer is the same: move the electronics away from the process. A split type transmitter with a remote diaphragm seal keeps the sensor at the process and the electronics in a safe, stable location, delivering reliable measurement where integrated transmitters fail.
Working Principle: Capillary-Coupled Remote Sensing
In the QWY-308, the pressure sensor and the signal transmitter are physically separated. A remote diaphragm (flange) mounts directly at the process connection, and a capillary tube filled with silicone oil connects it to the transmitter body. Process pressure deflects the remote diaphragm, and the fill fluid transmits that deflection hydraulically through the capillary to the sensing element inside the transmitter, which converts it into a standard electrical signal. Because the capillary is long and flexible, the transmitter body can be mounted meters away on a wall, bracket or panel, away from heat, vibration and cleaning chemicals. The 316L stainless steel diaphragm provides corrosion resistance and a smooth, weldable process interface.
Structural Advantages of the QWY-308
- Heat isolation: capillary separates electronics from media temperatures above 150 °C, even up to 400 °C at the flange.
- 316L stainless steel diaphragm: resists corrosion from aggressive chemicals and allows hygienic polishing.
- Dead-corner-free design: flush or extended diaphragm leaves no pockets for viscous or crystallizing media to accumulate.
- ±0.1%FS accuracy: precision measurement preserved despite the remote configuration.
- Linearity superior to 0.25%FS: dependable signal across the whole calibrated span.
- Electronics in a safe zone: transmitter body mounts away from vibration, steam and wash-down.
- Operating temperature -20 to +85 °C: stable electronics performance in plant environments.
- CIP/SIP compatible: flange withstands harsh cleaning and sterilization cycles.
Pain Point Analysis: 4 Challenging Working Conditions
| Working Condition | Typical Failure | Why Integrated Transmitters Fail | QWY-308 Solution |
|---|
| High-temperature media (>150 °C) | Electronics overheating, drift, death | Direct heat conduction into the body | Capillary isolates electronics; flange takes the heat |
| Corrosive, viscous, crystallizing media | Blocked ports, corroded diaphragm | Direct contact with unprotected ports | 316L remote diaphragm, no dead corners, easy flushing |
| Severe vibration / tight spaces | Accuracy loss, housing damage | Transmitter body forced to mounting point | Compact flange at process; body mounted on stable bracket |
| CIP/SIP sterilization cycles | Electronics damaged by steam | Body exposed to cleaning chemicals and steam | Hygienic flange in place; electronics kept out of the cleaning zone |
Application Cases
Case 1 - Chemical Reactor Pressure
Industry: Specialty chemicals
Application: Reactor pressure control during exothermic batch reactions
Measured Medium: Aggressive chemical slurries
Range: 0-16 bar
Process Temperature: Up to 250 °C
Output Signal: 4-20 mA to DCS
Key Challenge: High temperature plus corrosive, crystallizing medium
Configuration: QWY-308 with extended 316L flange and long capillary
Installation: Flange on reactor nozzle, transmitter on nearby wall bracket
Performance Result: Stable pressure control across entire batch campaign
Customer Benefit: Safer exothermic reactions, no shutdowns from sensor failure
Case 2 - Pharmaceutical Fermenter
Industry: Pharmaceutical manufacturing
Application: Fermenter pressure and sterilization monitoring
Measured Medium: Culture broth, steam (SIP)
Range: 0-6 bar
Process Temperature: 15-135 °C (SIP peaks)
Output Signal: 4-20 mA to batch control system
Key Challenge: Repeated steam sterilization without damaging electronics
Configuration: QWY-308 with sanitary flush flange and hygienic fill fluid
Installation: Sanitary flange on fermenter, transmitter outside the clean zone
Performance Result: Reliable readings through hundreds of SIP cycles
Customer Benefit: Batch reproducibility and audit-ready hygienic compliance
Case 3 - Food Processing Line
Industry: Food and dairy
Application: Pressure monitoring on UHT and pasteurization lines
Measured Medium: Milk, juice, viscous food products
Range: 0-10 bar
Process Temperature: 90-140 °C
Output Signal: 4-20 mA to PLC
Key Challenge: Viscous product fouling and daily CIP cleaning
Configuration: QWY-308 with flush 316L diaphragm, PTFE-compatible option
Installation: Flush-mounted at pipeline tee, electronics on control panel
Performance Result: No fouling build-up, stable pressure during CIP
Customer Benefit: Consistent product quality with minimal cleaning downtime
Case 4 - Petrochemical Transfer Line
Industry: Oil and gas / petrochemical
Application: Pressure on heavy oil and polymer transfer lines
Measured Medium: Heavy crude, polymer melts
Range: 0-40 bar
Process Temperature: 200-350 °C
Output Signal: 4-20 mA to control room
Key Challenge: Extreme temperature plus high-viscosity, solidifying medium
Configuration: QWY-308 with extended diaphragm and steam-traceable capillary
Installation: Flange at line nozzle; transmitter in instrument shelter
Performance Result: Continuous measurement with no line blockage false readings
Customer Benefit: Reliable transfer operations and reduced maintenance exposure
Product Advantages
- Remote diaphragm design isolates electronics from extreme process heat
- 316L stainless steel diaphragm for corrosion resistance
- ±0.1%FS accuracy maintained in remote configuration
- Linearity superior to 0.25%FS
- Handles media temperatures above 150 °C, up to 400 °C at flange
- Dead-corner-free flush design for viscous and crystallizing media
- CIP/SIP compatible for food and pharmaceutical hygiene
- Electronics operating range -20 to +85 °C
- Flexible capillary length for installation flexibility
- OEM/ODM options: flange types, diaphragm materials, capillary length
Technical Parameters
| Parameter | Specification |
|---|
| Accuracy | ±0.1% FS |
| Linearity | Superior to 0.25% FS |
| Diaphragm Material | Stainless steel 316L |
| Transmitter Operating Temp | -20 to +85 °C |
| Flange Media Temperature | Up to 400 °C (option) |
| Fill Fluid | Silicone oil (hygienic option available) |
| Cable Material | Polythene |
| Model | SMF17 / QWY-308 |
SEO FAQ
Q1: What is a split type pressure transmitter?
A split type pressure transmitter is an instrument in which the pressure-sensing element and the signal-converting electronics are physically separated. The sensing element, usually a remote diaphragm or flange, mounts directly at the process connection, while the transmitter body is installed away from the process. The two parts are connected by a capillary tube filled with a hydraulic fluid that transmits the process pressure from the diaphragm to the sensing element. This configuration is chosen when the process conditions at the measuring point, such as high temperature, corrosion, vibration or limited space, would damage or prevent the installation of an integrated transmitter.
Q2: When should I choose a split type transmitter instead of an integrated one?
Choose a split type transmitter when the process medium temperature exceeds roughly 150 °C, because heat conducted into an integrated transmitter body will damage its electronics. Choose it for strongly corrosive, viscous or crystallizing media that would block or corrode standard pressure ports. Choose it when the measuring point suffers severe vibration or offers too little space for a transmitter body. Choose it for food and pharmaceutical processes requiring CIP/SIP sterilization, where steam and cleaning chemicals must not contact the electronics. For ordinary clean, low-temperature applications, an integrated transmitter remains simpler and more economical; the split type is the specialist solution for extreme conditions.
Q3: How does the capillary and fill fluid system work?
The capillary is a small-diameter metal tube filled with a hydraulic fill fluid, typically silicone oil. Process pressure deflects the remote diaphragm, and this deflection is transmitted through the incompressible fill fluid along the capillary to the sensing element in the transmitter body. Because liquids are nearly incompressible, the pressure transfer is virtually loss-free and linear. The length and internal diameter of the capillary, together with the fill fluid properties, determine the response speed and temperature behavior of the assembly. Our engineers match the capillary length and fill fluid to your application to minimize response lag and temperature error.
Q4: What is the maximum process temperature the QWY-308 can handle?
The electronics of the QWY-308 operate reliably in ambient temperatures from -20 °C to +85 °C, but the remote diaphragm flange can be exposed to process media temperatures well above that, up to approximately 400 °C with appropriate configuration. The capillary physically separates the hot flange from the cool transmitter body, and the fill fluid is selected to remain stable at the expected flange temperature. This is what makes the split type design indispensable for high-temperature processes such as polymer production, heavy oil transfer and high-temperature chemical reactors. Please specify your maximum process temperature when ordering so the correct fill fluid and seal materials are selected.
Q5: Can the diaphragm material be changed for very corrosive media?
Yes. The standard wetted diaphragm is stainless steel 316L, which covers the majority of industrial media. For highly corrosive media, the diaphragm and flange can be supplied in alternative materials such as Hastelloy, tantalum, or with a PTFE or PFA coating, depending on the chemical, its concentration and temperature. The remote diaphragm design makes material selection easier because only the flange and diaphragm need to be made of the exotic material, while the rest of the instrument remains standard. Send us your medium composition and we will recommend the most economical material combination that guarantees long service life.
Q6: How does the split design handle vibration at the measuring point?
Vibration is one of the main reasons to select a split type transmitter. Only the small, light flange is mounted at the vibrating process point; the heavier transmitter body is installed on a stable wall bracket or panel away from the vibration source. This protects the electronic components and sensing element from mechanical stress that would cause accuracy drift and premature failure in an integrated unit. The capillary absorbs the relative movement between the process point and the mounting location. For extremely severe vibration, additional damping and capillary protection can be provided. This makes the QWY-308 suitable for pumps, compressors and agitated vessels.
Q7: Is the QWY-308 suitable for food and pharmaceutical applications?
Yes, with the appropriate configuration. For food, dairy and pharmaceutical service, the QWY-308 can be supplied with a sanitary flush flange, a polished 316L diaphragm, and a food-grade fill fluid that is safe in the event of diaphragm rupture. The flush design leaves no dead spaces where product can accumulate and spoil, and the flange withstands the high temperatures and chemicals of CIP and SIP cleaning cycles. Because the electronics are mounted away from the cleaning zone, they are not exposed to steam or caustic wash-down. Please specify your hygienic requirements so we can provide a configuration with the correct surface finish and documentation.
Q8: What accuracy can I expect from the remote configuration?
The QWY-308 offers an accuracy of ±0.1%FS and linearity superior to 0.25%FS, which is excellent even for a remote diaphragm assembly. The remote configuration introduces small additional errors from capillary temperature effects and fill fluid expansion, which our engineers compensate during calibration by selecting the appropriate fill fluid and by factory calibration at your expected operating temperature. For best accuracy, install the transmitter so that the capillary is not exposed to strong temperature gradients, and specify your normal operating temperature so the calibration can be optimized for it.
Q9: How do I maintain and troubleshoot a split type transmitter?
Maintenance of the QWY-308 is straightforward: periodically check the capillary for mechanical damage, verify that the flange bolts are correctly torqued, and confirm that the fill fluid has not leaked, which would show up as a slow or sluggish response. If the reading drifts or responds slowly, first check for capillary damage or loose connections before suspecting the electronics. The transmitter body can be tested independently by applying a known pressure to the sensing element. For capillary or fill-fluid issues, we recommend returning the unit to the factory for professional recharging and recalibration, as field repair of the fill system requires specialized equipment.
Q10: What customization options are available for the QWY-308?
As the manufacturer, we offer extensive customization: flange types including flush, extended and sanitary designs; wetted materials from 316L to Hastelloy, tantalum and coated options; capillary lengths from short couplings to several meters; a choice of fill fluids for general, high-temperature or hygienic service; and standard 4-20 mA or other output configurations. We also support OEM and ODM projects with custom branding and documentation. With a monthly supply capacity of 100 pieces and 5-8 working days delivery, we can support both replacement projects and new plant construction schedules. Contact us with your process details for a recommendation and quotation.
Why Choose Our Split Type Pressure Transmitter?
When your process demands a remote diaphragm solution, the QWY-308 delivers the accuracy, material quality and configuration flexibility of a premium instrument at a direct-from-manufacturer price. You receive a 316L diaphragm assembly engineered for your specific temperature, media and hygiene requirements, factory-calibrated and leak-tested, with responsive engineering support behind it. Whether it is a 400 °C polymer line, a sterile fermenter or a corrosive reactor, our split type transmitter is built to keep measuring when integrated transmitters give up. Tell us your working conditions, and we will configure the right solution for you.
