What is a melt pressure process?

The melt pressure system engineered and supplied by Pyrosales are designed to measure, control, and supervise the temperature and pressure associated with plastic extrusion process. The key components needed to establish a melt pressure control system are transducers, controllers, and indicators.

What is melt pressure extrusion?

Extrusion is a process that involves plastic materials being formed to shape. This is done by first softening the material with heat. Using a drive screw, the material is forced toward and then through the opening, called a die used to shape the plastic melt. Various compounds, colourants and additives can be mixed with the plastic materials as they move along the screw path. The heated materials are shaped by the die and then cooled to retain their shape.

What are melt pressure transducers?

Transducers are used to sense pressure of the extrusion process and can be used in various parts of the process for different reasons, including:

1. For quality control purpose, a transducer should be placed in the die area. Pressure measurement in this phase indicates flow rate.
2. Transducer ahead of the screen changer which shows when a screen should be changed while making sure people and equipment are safe.
3. Transducers should be placed in various parts along the barrel for research and development purpose to monitor the pressure of the extrusion process along the melt line.
4. Pressure sensing post extrusion is also where transducers are used in equipment such as spinnerets, extrusion pumps and blowing moulding heads.

Placing pressure transducers along the machinery ensures increased safety of the extruder and the melt process.

Some application of melt pressure.

Film: Plastic film used to create packaging materials and bags. Adaptable for either slit casting or blown process, pressure monitoring can help produce thinner, more reliable film with quicker process speeds. The pressure transducer also presents fundamental process information helpful for boosting productivity and lessen start up scrap.

Wire Coating: Insulated cable and wire housing. Monitoring pressure in the cross-head die, which is where the wire is coated in the plastic, improves output quality and profits. The need to have a transducer at this process is becoming more important as system are reaching higher speeds, and therefore pressure monitoring becomes vital.

Pipe, Tubing and Profile: Plastic tubing, hose and piping to contain water, gases, or chemicals. Monitoring pressure allows for tighter tolerance, improving product quality, whilst increasing cost effectiveness, even for more multiple/complex extrusion processes.

Synthetic Fibers: Fibers used to create end products such as various textiles, brushes, rope, and twine. Placing transducers along the extrusion process helps produce higher quality consistency as well as reducing waste.

Other: Pre-processing for other plastic packaging needs, which can also be used for mixing and compounding.

What are the design features of Pyrosales instruments?

• Stainless steel construction
• Fully interchangeable with competitors
• 80% output signal for easy calibration
• 33mV/V, 6 pin connector
• Range from 0-500 to0-20000psi
• 400 deg Celsius (750 degrees Fahrenheit) rating, standard Inconel tip

Melt pressure instruments.

Rigid Stem Transducer: Interchangeable with competitors ,      Standard 3.33mV/V, 6 pin connector,     Stem (standard),     1% combined error,   80% Output for easy calibration,    400 deg Celsius (750 deg Fahrenheit) rating, standard Inconel tip. Rigid Stem Flex:  Offers the same features as the Rigid Stem transducer, with the added benefit of an 450mm stainless steel flexible armour between the housing and the stem. Is used for applications that need more thermal isolation or where installation may be difficult.

Pressure and Temperature Transducer: This model can measure pressure and temperature at the same time. Only one transducer point is needed for the installation of this device. The temperature probe can be replaced without affecting the pressure reading.

Pyrosales’ engineers have over 40 years’ experience producing specialised solutions for any temperature applications. Whether this is an infrared temperature monitoring system or a more traditional contact temperature system, we can design and supply the most effective temperature and process control equipment for furnaces, ovens, kilns, and other extreme heat applications.

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