Designing and Manufacturing Custom Metal Diaphragm Sensing Elements for Critical Applications

Fulton Bellows designs and manufactures custom metal diaphragm sensing elements for critical applications when extremely accurate pressure versus deflection curves are required.

Diaphragm sensing elements are used on many types of controls. The diaphragm capsules are made of stamped corrugated metal diaphragms that are welded together to form a convolution or capsule. Diaphragm capsules are suitable for applications requiring larger displacements and lower linear travel. Changing the depth of the corrugation and thickness of material may adjust the range, linearity characteristic curves and even stress level.

Three types of diaphragm capsules are available: vapor filled, and liquid filled for temperature applications, and open-ended for pressure sensing applications. Liquid filled capsules operate hydraulically, while vapor fill and open-ended sensing elements operate pneumatically.

Fulton Bellows manufactures custom design diaphragm capsules in medium to large volume on completely automated assembly stations using laser welding techniques.

Automation ensures a consistently high quality, long lasting capsule, but limits the number of designs available at low cost. Parts may be attached by laser, resistance and plasma arc welding; silver soldering, brazing or mechanical crimping.

The service life of a corrugated metal bellows is the number of stress cycles endured until the first leak, where movement from starting position through the bellows range and returning to starting position is regarded as one stress cycle. The laser welded diaphragm capsule can withstand 250,000 stress cycles, based on typical applications and conditions.

The main factors affecting cycle life are:


Amplitude of elastic deflection (reciprocating movement)

Working pressure

Pre-stress (distribution of elastic movement)

Stress cycle frequency

Pressure surge (shocks, pulsation)

Thermal shock


Faulty installation

The designer should therefore have a general idea of the cycle life required for the application.


Custom configurations and fittings available

Consult factory for other options

Medium to high volume quantities

To learn more about our metal diaphragm sensing element capabilities, contact us today.