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High Temperature Melt Pressure Transmitter 350°C With Heat Dissipation

Specifications

Media Temperature :

Up to 350°C (continuous); 400°C peak

Brand Name :

QINWEIYB

Packaging Details :

Carton with foam padding / wooden box

Process Connection :

1/2-20 UNF, M14x1.5, M18x1.5 (standard melt pressure threads)

Optional Accessories :

Flexible capillary with remote electronics for ultra-high temperature

Diaphragm Material :

17-4PH Stainless Steel / Inconel 718 (corrosion-resistant)

Filling Medium :

NaK (sodium-potassium) or silicone oil for high temperature

Payment Terms :

T/T,L/C,Western Union

Heat Dissipation :

Integrated finned heat sink + optional water cooling jacket

Model Number :

QW-4088HT

Measurement Range :

0~35 bar to 0~1000 bar (standard melt ranges)

MOQ :

1 Set

Supply Ability :

200 Sets/Month

Price :

Negotiable

Delivery Time :

7-12 working days

Output Signal :

4-20mA (2-wire) / 0-10V / RS485 Modbus RTU

Place of Origin :

China

Certification :

CE, ISO9001

Accuracy :

0.5%FS (0.25%FS high-precision optional)

Description

Are High Temperatures Destroying Your Pressure Sensors?

Sensors failing within weeks at high process temperatures -- standard pressure transmitters rated to 85°C die rapidly when exposed to 200-350°C melt streams, forcing you to stock excessive spare parts and schedule frequent production stops for replacement.
Measurement drift from thermal shock -- rapid temperature changes during startup/shutdown cycles cause silicon oil fill fluid expansion and contraction, creating zero drift of 5-15% between cold and hot states.
Melt material solidification in sensor cavities -- dead spaces in the sensor mounting port trap polymer melt that cools, solidifies, and creates a plugged sensing path that transmits zero pressure regardless of actual process conditions.
Product quality defects from undetected pressure variations -- inconsistent melt pressure during extrusion causes dimensional variations, surface defects, and material waste that erodes margins in competitive polymer markets.

Operating Environment Analysis

Selecting the right pressure transmitter demands a thorough understanding of your operating environment. Below is the complete application profile:

Industries Served	Plastic extrusion (film, sheet, pipe, profile), injection molding, blow molding, rubber compounding & calendering, synthetic fiber spinning, hot melt adhesive manufacturing, asphalt processing, food extrusion (snacks, pet food)
Measured Media	Polymer melts (PP, PE, PVC, PET, nylon, PC, ABS, PEEK), rubber compounds, hot melt adhesives, asphalt/bitumen, molten waxes, food dough/paste, and other high-temperature viscous fluids
Temperature Range	Media: up to 350°C continuous (400°C peak); Ambient electronics: -20°C to +85°C with heat sink protection
Pressure Range	0-35 bar to 0-1000 bar; typical melt pressure ranges are 0-350 bar for general extrusion, 0-700 bar for injection molding, 0-1000 bar for high-pressure compounding
Corrosivity	Standard 17-4PH SS diaphragm for clean polymer melts; Inconel 718 diaphragm for corrosive off-gases (PVC/HCl), fluoropolymer processing, and chemically aggressive compounds
Viscosity	High-viscosity polymer melts (500-100,000+ cP) -- sensor is specifically designed for thick, slow-flowing media that would clog narrow ports on standard pressure transmitters
Installation Conditions	Threaded directly into extruder barrel, melt pump housing, or die adapter plate; requires proper thermal insulation of electronics housing; water cooling jacket recommended when ambient >60°C near mounting location

Why Traditional Solutions Fall Short

Many procurement professionals have experienced the limitations of conventional pressure measurement approaches:

Standard Industrial Transmitters (85°C max)	Electronics and fill fluid are not rated for melt temperatures; thermal damage occurs within hours of exposure; standard stainless steel O-rings and seals degrade rapidly above 150°C.
Mechanical Bourdon Tube Melt Gauges	No electrical signal output for extrusion control systems; fill medium (mercury in older units) presents environmental and operator safety hazards; mechanical linkages wear and develop hysteresis in vibrating extruder environments.
Capillary Remote Seal Designs (without heat dissipation)	The fill fluid in the capillary still absorbs process heat; without a properly sized heat sink, the fill fluid can boil or thermally degrade within weeks, creating offset errors and eventual seal failure.
Infrared Non-Contact Temperature Measurement	Measures temperature, not pressure. Cannot replace a pressure sensor for melt pump control, screen changer monitoring, or die pressure optimization. Different measurement entirely.

QWP-4088HT: High-Temperature Melt Pressure Transmitter for Demanding Polymer Processing

The QWP-4088HT is purpose-built for the extreme conditions of polymer melt pressure measurement. It features a thick abrasion-resistant 17-4PH stainless steel diaphragm, NaK (sodium-potassium) high-temperature fill fluid, and an integrated finned aluminum heat sink that protects the electronics from process heat. The standard 1/2-20 UNF mounting thread fits directly into all major extruder barrel ports, and the 4-20mA output integrates seamlessly with extrusion control systems from B&R, Beckhoff, and all major PLC platforms.

Core Capabilities at a Glance:

350°C continuous media temperature rating -- handles standard polymer processing temperatures from polypropylene (200°C) to PEEK (380°C peak)
Abrasion-resistant thick diaphragm -- withstands glass-fiber-filled, carbon-fiber-filled, and mineral-filled engineering plastics that destroy standard thin diaphragms
NaK high-temperature fill fluid -- remains thermally stable across the entire operating range with minimal expansion/contraction, ensuring consistent zero stability during startup and steady-state operation
Integrated heat sink + optional water cooling -- finned aluminum heat sink dissipates process heat before it reaches the electronics; water cooling jacket available for ambient temperatures above 60°C
4-20mA + digital RS485 Modbus option -- analog output for direct PLC connection; RS485 Modbus RTU for multi-sensor networks with digital precision

Technical Advantages

17-4PH / Inconel 718 Diaphragm	Thick, hardened diaphragm with 3-5× the abrasion life of standard 316L in glass-filled polymer service. Inconel 718 option for corrosive off-gas environments (PVC, fluoropolymer processing).
NaK Fill Fluid System	Sodium-potassium eutectic fill fluid remains liquid and thermally stable from -10°C to 500°C. Unlike silicone oils that degrade above 300°C, NaK maintains consistent volumetric expansion characteristics ensuring minimal zero drift.
Multi-Fin Heat Dissipation	Die-cast aluminum finned heat sink with optimized thermal path reduces electronics temperature by 100-150°C versus direct mount. Enables the transmitter to operate in 350°C process conditions with electronics below 85°C.
Flush-Face Mounting Design	Zero dead volume between diaphragm and process -- no cavities for polymer to stagnate, degrade, or solidify. Eliminates false pressure readings from plugged sensing ports.
Flexible Stem + Capillary Options	Rigid stem (standard) for direct mounting; flexible capillary with remote electronics housing for installations with severe space constraints or ambient heat sources near the mounting port.

Extruder Barrel and Melt Pump Installation

The QWP-4088HT installs directly into the standard 1/2-20 UNF pressure port found on all major extruder barrels, melt pumps, and die adapters:

Step 1 -- Clean the Mounting Port	Purge the extruder with clean polymer to clear the mounting hole of degraded material and carbon deposits. The port must be completely filled with melt before sensor insertion to prevent trapped air.
Step 2 -- Insert & Finger-Tighten	Insert the sensor tip fully into the port with the diaphragm flush against the melt stream. Finger-tighten the 1/2-20 UNF threaded collar. The diaphragm must be exactly flush -- recessed or protruding installation causes measurement errors.
Step 3 -- Torque to Specification	Apply the specified torque (typically 40-50 Nm for 1/2-20 UNF) using a torque wrench. Over-torque damages the mounting threads; under-torque may cause melt leakage at operating pressure.
Step 4 -- Connect Cooling (if applicable)	For water cooling: connect 6mm OD tubing to the cooling jacket inlet and outlet ports. Maintain minimum 2 L/min flow rate. For air cooling: ensure unobstructed airflow across the finned heat sink.
Step 5 -- Electrical Connection & Zero Set	Connect the 2-wire 4-20mA cable using the M12 or DIN 43650 connector. With the extruder at operating temperature but zero pressure (screw stopped), perform a zero trim via the calibration interface.

Installation during a normal die/mold change takes approximately 20 minutes. Always install at operating temperature to avoid thermal expansion mismatch. Calibration verification recommended after the first 48 hours of operation and every 3 months thereafter in continuous production.

Real-World Application Cases

Case 1: PET Sheet Extrusion Line Pressure Optimization

Industry	Plastic Packaging -- PET Sheet Extrusion
Measured Media	PET (polyethylene terephthalate) melt at intrinsic viscosity 0.80 dL/g
Temperature	+275°C to +285°C at the die
Pressure	0-200 bar (melt pump inlet and outlet differential)
Installation Environment	Extruder barrel and melt pump housing, ambient temperature 45-55°C near the machine, continuous 24/7 production
Customer Problem	A PET sheet manufacturer producing thermoforming-grade sheet experienced 6-8% thickness variation across the web width, resulting in 5 tons of rejected sheet per month. The existing pressure monitoring used only a single pressure transducer before the melt pump with no die pressure measurement, making it impossible to identify whether the extruder, melt pump, or die was the source of the variation.
Solution	Installed 3 QWP-4088HT transmitters: one at extruder discharge, one at melt pump inlet, and one at the die entry. Trend data from all 3 measurement points was fed to the extrusion control system for coordinated pressure control.
Installation Location	Standard 1/2-20 UNF pressure ports on the extruder barrel, melt pump housing, and sheet die adapter plate
Result	Web thickness variation reduced from 6-8% to under 2%. Material waste eliminated, saving 60 tons/year of rejected sheet worth approximately $90,000. Melt pump differential pressure control optimized energy consumption, reducing extruder motor load by 7%.

Frequently Asked Questions

Q1: What is the maximum continuous operating temperature?

The QWP-4088HT is rated for 350°C continuous operation at the diaphragm with the standard heat sink. Peak exposure to 400°C is acceptable for short durations (purge cycles, startup transients) without damage. For applications exceeding 350°C continuously, the flexible capillary remote electronics option is recommended.

Q2: What fill fluid is used and why not silicone oil?

We use NaK (sodium-potassium eutectic) for high-temperature stability. Standard silicone oil fill fluids begin to thermally degrade above 280-300°C, causing polymerization, gas bubble formation, and measurement drift. NaK remains thermally stable to 500°C and has excellent thermal conductivity for fast response.

Q3: Can this transmitter handle glass-fiber-filled polymers?

Yes. The diaphragm is made from hardened 17-4PH stainless steel, providing 3-5× the abrasion resistance of standard 316L SS when exposed to glass-fiber-filled (10-40% GF) engineering polymers. For extreme abrasion applications (carbon fiber, ceramic-filled compounds), Inconel 718 diaphragm is available.

Q4: How often does the transmitter need calibration?

Recommended calibration verification is every 3 months for continuous production. In practice, QWP-4088HT transmitters typically maintain specification for 6-12 months between calibrations. The NaK fill fluid system provides significantly better long-term stability than silicone-oil-filled alternatives.

Q5: What thread sizes are available?

Standard is 1/2-20 UNF, the industry standard for melt pressure sensors. Also available: M14×1.5 and M18×1.5 metric threads. Custom thread adapters can be supplied for non-standard extruder barrel ports.

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