Gefran melt pressure transducers & transmitters for plastic extrusion, injection moulding & blow moulding applications.
Find a pressure sensor here for use on highly viscous media at high temperatures.
Pressure sensors for measuring hydraulic and plastic melt pressures on plastic injection & moulding machines.
Contents
Sensor Technology
Filling Fluid With Extensimetric Technology
The operating principle is based on hydraulic transmission of pressure by means of filling fluids with low coefficient of compressibility: mercury (M series), FDA-approved diathermic oil (W series), and sodium-potassium NaK mix (K series), defined as a substance Generally Recognized As Safe (GRAS).
Therefore, the entire structure is built to transfer the pressure exerted by the medium on the contact diaphragm to the transduction part, i.e., measurement diaphragm with the strain gauge, keeping it away from the heat source. The strain gauge then transduces the physical pressure quantity into an electrical signal.
Entirely Fluid Free Piezoresistive Technology
Innovative IMPACT sensors (I series) are pressure transmitters without transmission fluid: medium pressure is transferred directly to the silicon sensitive element by means of a thick diaphragm.
Physical stress is transduced by a Wheatstone bridge with 4 piezoresistors
Gefran’s IMPACT series, with proprietary technology, provides:
- High strength (up to 35 times stronger that traditional sensors)
- High response speed
- Extremely easy installation thanks to a modular sensor
- High safety standards (conformity to Machinery Directives and RoHS)
Pressure Measurement at High Temperatures
Gefran melt sensors are pressure/temperature transducers and transmitters that measure Melt medium
pressure in high temperature environments (up to 538°C).
Melt pressure can be measured in four main process temperature ranges:
Fill Types
Melt pressure sensors incorporate a fluid filled capillary to isolate the thermally sensitive electronic components from high temperature media.
Mercury Filled
The M series mercury filled high temperature pressure transducers and transmitters for use on plastic melt injection moulding machines. These sensors have a mercury filled capillary tube to isolate the sensing element from media temperatures up to 400°C/750°F.
Oil Filled
The W series oil filled high temperature pressure transducers and transmitters for use on plastic melt injection moulding machines where the use of mercury filled device is prohibited. These sensors have mercury free oil filled capallary to isolate temperatures up to 315°C/600°F.
NaK (Sodium Potassium) Filled
The K series NaK (Sodium Potassium) filled high temperature pressure transducers and transmitters for use on plastic melt injection moulding machines where a higher media temperature is required up to 538°C/1000°F. These sensors have a NaK fill which is GRAS (Generally Considered As Safe) substance, which is safe to use in the manufacture of food & drink products.
Fill Free
Improved stability and extended lifetime sensors with a dry sensing element. The IMPACT series incorporate a Silicon On Insulator (SOI) sensing chip which has very high temperature tolerance making it possible to locate it very close to the plastic melt thus improving stability of measurement. Since there is no need for a thin isolation diaphragm to transmit pressure through the fluid fill, the extra thickness of the diaphragm improves resistance to abrasion over time. The IMPACT series is capable of operating on media temperatures up to 350°C/660°F.
Product Series Types
Gefran melt pressure sensors are generally available in four versions: rigid stem, flexible sheath, flexible with
thermocouple, and exposed tip (except for the IMPACT series).
Product Selection Guide
Features & Approvals
Mercury Free Solutions
Sensitive to environmental issues, and in full harmony with the RoHS Directive (2011/65/EU), Gefran offers a wide range of sensors Melt pressure mercury-free, both by filling with oil (FDA approved), NaK (GRAS substance) or fluid free (IMPACT).
GTP+
The new GTP+ coating, the result of Gefran research, guarantees longer melt sensor life thanks to:
- Greater hardness
- Resistance to high temperatures
- Low coefficient of friction
Auto-Zero Function
All Gefran amplified Melt pressure sensors (M/W/K/I series) have the Auto-Zero functions, which eliminates signal variations linked to a thermal effect, before putting the system under pressure.
Auto-Compensation
With the SP option (internal auto-compensation), M/W/K series transmitters cancel the effect of variation of pressure signal caused by variation of Melt temperature.
In this way, the read error caused by heating of the filling fluid (typical in filled sensors) is reduced to a minimum.
In IMPACT, technology, digital electronics automatically compensate for drift due to thermal effect.
Atex and Factory Mutual
MX/HMX, WX/HWX or IX (Atex) and MF or WF (Factory Mutual) Gefran transmitters are certified based on their respective protection and safety requisites, and can work in potentially explosive atmospheres.
Performance Level “C” (PL”C” EN13849-1)
IMPACT is available in the IMPACT PL”c” version, IMPACT PL”c”, to the safety requisites of the recent machinery Directive 2006/42/CE and EN1114 specific for extruders.
IMPACT PL”c” features intelligent electronics with Auto Diagnostics to detect possible faults. An integrated relay in the electronics changes state in case of overpressure or if the setpoint is exceeded. Increased safety on the IMPACT PL”c” is completed by full conformity to Namur NE21 and NE43 recommendations.
Even the full range of MELT pressure transmitters with filling fluids (e.g. sodium-potassium) is available in Performance Level ‘c’ version.
The benefits are tangible and immediate: higher safety levels for machineries (i.e. conformity with the
Machinery Directive and with the standard for extruders’ safety) and less risk for operators above all.
Applications
Gefran Melt Pressure Sensors Brochure
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