A new type of melt-pressure sensor from Dynisco Plastics, Franklin, Mass., is said to be the first such device to sense pressure directly, without using mechanical structures or liquid-fill media. Called Vertex and suited to all types of extrusion, this approach reportedly results in faster response and better control. At the same time, the sensor is said to be significantly more robust for longer service life and lower cost of ownership.
Melt pressure is registered at the tip of the sensor directly through a single diaphragm. Direct measurement eliminates errors that can arise in sensors with complicated internal structures, transmission fluids, and moving push rods. The Vertex diaphragm is reportedly much thicker than diaphragms in other sensors, and is made of tough Inconel 718 alloy, which provides a higher level of corrosion resistance than stainless steel. For added protection against abrasion and corrosion, the tip has a diamond-hardened coating. The sensor wall structure also has been fortified to handle side stresses. The device is covered by a 4-yr warranty.
Faster processes and controls demand faster sensing measurements, and so the Vertex sensor is many times faster than traditional sensors. Accuracy, as defined under the ISA-S37.1 standard, is pegged at ±0.25% full scale over standard pressure ranges of 1500 to 10,000 psi.