Melt pressure sensors for high-temperature polymers

The Italian multinational group specialised in the design and production of sensors, industrial process control systems, electric drives and automation components, Gefran, upgraded its range of Melt transducers and pressure transmitters for high temperatures, designed to meet the highest safety standards, while fully respecting the environment.

Two are the main manufacturing technologies at the base of the Melt sensors by Gefran: these can be either fluid-free, following a silicon piezoresistive operating principle (Impact - I series sensors), or work by means of filling fluids through a strain gauge system (K, W, M series). These sensors, available in four designs - rigid stem, flexible stem, flexible with thermocouple, and exposed tip - guarantee a precise installation whenever it is necessary to measure the pressure and possibly the temperature of the fluid, both in traditional extrusion systems and in potentially explosive areas.

In this scenario, Gefran was the first Company to design a sensor with Atex, SIL2 and PLd, certifications, as well as a Hart digital communication protocol, dedicated mechanical flanges, and a fluid-free transmission system. This is the HIX Series (Hart - Impact - Atex), designed for use in potentially explosive environments and with the typical advantages of the Impact sensors by Gefran. More specifically, thanks to a contact membrane up to 15 times thicker than the traditional versions, the pressure is transmitted directly to the sensitive element, which features a micro-worked silicon structure (Mems). The HIX series, with a current output signal, withstands temperatures of up to 350°C and covers a pressure range from 0...10 bar to 0...1.000 bar, making it the ideal choice for the extrusion of low-viscosity plastics. Another advantage of this solution is the quick installation, thanks to the ready-to-use flanges offered by Gefran.

There are also additional models with a construction principle based on the hydraulic transmission of pressure and on the transfer of mechanical stress through filling liquids with a low coefficient of compressibility. More in detail, the K series is characterised by a mixture of Sodium + Potassium (NaK) which allows the sensor to withstand up to 538°C. The W series is characterised by an FDA-approved diathermic oil filling, which is typically used in the production of plastics for medical or food products. Finally, the M series uses mercury as a transmission fluid and it is employed in all circumstances approved by European Directive 2011/65/UE - RoHS II, in environments with temperatures of up to 400°C.

The full range of Melt pressure transmitters comes in a SIL2 and Pld certified version. Furthermore, the K, W, M models can also be equipped with a HART serial communication (HKE, HWE, HME models), while models HWX, HMX - which are Atex EXia certified - are particularly suitable for polymer production plants in potentially explosive environments. Finally, the broad range of Gefran Melt sensors also includes digital output series IO-Link, 1.1.3 version, which make the Gefran offer unique on the market.