Siam Poly Fiber Case: Temperature Transmitter for Polyester Melt Spinning 280-295 Degree C Measurement
Published On: August 27, 2026
1. Client Profile
Siam Poly Fiber Co., Ltd. is a polyester filament producer in Rayong, Thailand, operating a 120 t/day POY and FDY spinning plant. The plant runs continuous polymerization with melt direct spinning, and its quality team linked filament breakage (end breaks) and denier variation directly to melt temperature stability at the extruder, manifold and spin beam.
2. Application Background
In polyester (PET) fiber production, the polymer melt temperature at the extruder, manifold and spin beam directly determines spinning stability and fiber quality. A variation of even a few degrees changes melt viscosity and can cause filament breakage, uneven denier and off-spec yarn. This case describes the temperature transmitter arrangement used on a typical chemical fiber spinning line and the specification points that matter most to buyers.
3. Real Operating Conditions
| Measurement Point | Typical Temperature | Medium / Environment |
|---|---|---|
| Extruder melt | 280-290°C | PET melt, high viscosity, approx. 80-150 bar |
| Manifold / spin beam | 285-295°C | PET melt, corrosive decomposition products |
| Spin pack | 285-295°C | High pressure, small bore |
The environment contains oligomer vapors and acetaldehyde, with high ambient heat around the melt lines.
4. Customer Pain Points
- Melt temperature fluctuation causes frequent filament breaks (end breaks), reducing line efficiency and increasing waste.
- Slow or drifting sensors hide real temperature gradients between manifold branches, producing inconsistent yarn quality.
- Standard sensors fail quickly at around 290°C in contact with melt, raising spare-part cost and downtime.
- Calibration of installed sensors is difficult without interrupting production.
5. Engineering Selection
- Pt100 RTD (QW-SLS63, Class A or better, 3-wire or 4-wire) with a small-diameter 316L thermowell for fast response in the melt stream.
- For extended tips in melt contact, use a hardened or coated thermowell to resist abrasion and oligomer attack.
- Intelligent integrated transmitter (QW-SLS65) with 4-20 mA output and digital communication for remote configuration and diagnostics.
- Connection cables rated for continuous 300°C exposure near the spin beam.
6. Recommended Qinwei Instruments for This Application
| Model | Description | Applied At |
|---|---|---|
| QW-SLS63 | Class A Pt100 RTD per IEC 60751, 3-wire or 4-wire | Melt temperature at extruder, manifold and spin beam |
| QW-SLS65 | Intelligent integrated transmitter, 4-20 mA with digital communication | Loop conversion with remote configuration and diagnostics |
| QW-SLS68 | Intelligent LCD temperature transmitter with HART protocol | Manifold branches where operators need readable local values |
| QW-SLS70 | PT100 integrated temperature transmitter, easy install | Quick-connect spare assemblies for spin pack change |
7. Installation Logic
- Mount sensors so the sensing tip is fully immersed in the melt flow rather than in a stagnant pocket, to measure the true process temperature.
- Keep insertion depth consistent across manifold branches so branch-to-branch readings are comparable.
- Use high-temperature sealing and correct torque on connections; insulate the mounting boss to avoid heat-loss errors at the tip.
- Where the spin pack is changed regularly, use quick-connect terminations so sensors can be swapped during a pack change without rewiring.
- Verify readings against a portable reference at each scheduled maintenance stop.
8. Application Results
- Stable melt temperature control reduces end breaks and improves denier uniformity, directly raising first-quality yield.
- Class A Pt100 accuracy makes branch-to-branch temperature differences visible, allowing operators to balance the manifold.
- Longer sensor life and quick-connect design cut the time and cost of each maintenance intervention.
9. Why Choose Qinwei Instruments
Xi'an Qinwei Instrument Factory (brand QINWEIYB) has manufactured industrial temperature instrumentation since 2010 and exports 50%-60% of its output, supported by 500-800 employees. For chemical fiber lines, Qinwei delivers Class A Pt100 elements per IEC 60751, small-diameter 316L thermowells for fast melt response, and complete sensor-plus-transmitter loops calibrated together for true end-to-end accuracy. With MOQ from 1 set, 5-8 working days delivery and OEM/ODM capability, Qinwei helps spinning plants standardize spares and cut maintenance cost.
10. Purchase Decision Guide
Buyers should specify: accuracy class and wire configuration (Class A 4-wire Pt100 is recommended), thermowell material and tip design for melt contact, response time (time constant), connection size (for example 1/2 inch NPT or flanged), operating temperature rating above 300°C, output signal, and calibration traceability. Confirm that the sensor can be supplied with a matching transmitter calibrated as a complete loop.
