Selection of the appropriate diaphragm material for melt pressure transducers and transmitters

The selection of the right membrane material for pressure sensors depends entirely on the circumstances under which the sensor is used. It is important to note whether the sensor comes into contact with the material and what properties this material has.

This can be determined more precisely based on the classifications of the individual polymer components. The classifications are:

Thermoplastics
Elastomers
Thermoplastic elastomers
Thermosets

The processing of thermoplastics and elastomers includes extrusion, injection molding and compression molding. Pressure measurement and control is essential in all of these methods.

Following materials and coatings are available for selection of membrane construction:

15-5PH stainless steel with Dymax coating	·Provides durability and abrasion resistance ·Default on most sensor models
Hastelloy	Provides corrosion resistance ·Not recommended for prolonged use in high temperatures
Inconel 718	Provides abrasion and corrosion resistance ·Recommended for use in temperatures up to 750°F or higher
Dymax	·Durable protective surface coating Abrasion resistance
Borofuse	Best abrasion resistant coating available ·Can only be used on Inconel
Titanium Nitride	·Abrasion and adhesion resistance ·Can be used on most membrane materials
Titanium aluminum nitride	·Improved abrasion and adhesion resistance Standard for Dynisco Echo sensors (membrane material Inconel)

Examples:

a) The application uses polypropylene:

The standard membrane for the respective pressure sensor is recommended. The standard Dynisco cone is Dymax coated 15-5PH stainless steel. This withstands abrasive material flow well and is reliable in most extrusion environments.

b) The application uses elastomer (TPE):

This material adheres to the standard membrane. To prevent adhesion while limiting the material's ability to deform the cone, a titanium nitride coating is recommended.

c) The application uses fluoropolymers (PTFE):

PTFE has corrosive properties so a standard diaphragm would not last long due to oxidation. Hastelloy may be suggested here.

Melt Presssure Transmitter – Vertex Sensor

No fill material
RoHS compliant for sustainability programs
Robust, thicker Inconel diaphragm is coated with DyMax®
Optional Type J or K thermocouple is available to provide a melt temperature signal as well as a 4-20 mA temperature output
Equipped with a 1/2-20 UNF for installation in standard transducer mounting holes
- Also available to install 1/2-20 UNF units into a Button Seal application
Diaphragm composition of Inconel 718 coated with the abrasion resistant properties of DyMax®
Sealed, welded shell and electrical connection available if washdown capability is needed for food or mechanical applications (not available if thermocouple option TCx is selected)
Available with thermocouple temperature output
250-10,000 PSI pressure range capability
HART digital communication available
Direct measurement tip is a simple and elegant design with a more robust diaphragm
Direct measurement of process reduces errors transferred by complicated internal support structures, transmission fill materials, or moving push rods
Designed to work with universal pressure indicators