Elastic sensing elements – non-metallic diaphragms In industrial pressure instruments, non-metallic diaphragms are most commonly fabricated from which material to provide flexibility and chemical compatibility?

Introduction / Context:
Pressure transducers and gauges often employ diaphragms to convert pressure into displacement. While metals are widely used, non-metallic diaphragms are advantageous for specific media, cost, and flexibility. Choosing the right polymer affects sensitivity, hysteresis, temperature performance, and chemical resistance.

Given Data / Assumptions:

• We are considering general-purpose industrial instruments (pneumatic and electronic) where elastomeric flexibility is desirable.
• Chemical exposure is moderate; extreme corrosives may require special linings.
• Manufacturability and durability are important.

Concept / Approach:
Synthetic rubbers (e.g., neoprene, nitrile, silicone, Viton) are widely used as non-metallic diaphragms due to excellent elastic compliance, fatigue resistance under small deflections, and reasonable chemical compatibility. They can be molded with convolution patterns to increase sensitivity. Teflon (PTFE) offers outstanding chemical resistance but is relatively stiff, exhibits cold flow (creep), and is less elastic, so it is more often used as a lining or coating rather than the primary diaphragm for general service. Bakelite (a thermoset) and thick paper lack the required elastic properties and fatigue resistance for reliable diaphragm action.

Step-by-Step Solution:

Verification / Alternative check:
Manufacturer datasheets list elastomeric diaphragms as standard offerings; PTFE is typically offered as a liner for corrosive services with separate support.

Why Other Options Are Wrong:

• Teflon: Chemically resistant but not the most suitable as a sole elastic diaphragm due to creep and stiffness.
• Bakelite / Thick paper: Not elastic membranes; unsuitable for cyclic deflection.

Common Pitfalls:
Assuming the most chemically resistant material is automatically the best diaphragm; mechanical properties dominate for sensing performance.

Final Answer:
Synthetic rubber