A secondary sealing element and spring backing in the dynamic part of rotating and stationary metal bellows seals (cf. bellows mechanical seals and metal bellows). Unlike a rolled bellows, the laminated bellows – known also as diaphragm bellows – consists of profiled metal discs, which are welded together at their inner and outer diameters in a number to suit the given case of application. In their axial cross section these discs resemble truncated cones, two of them welded together forming a disc pair. Laminated bellows are similar to rolled bellows as regards function, but they are able to compensate far greater axial, angular and lateral movements relative to their installation dimensions. Laminated bellows are preferred for use in metal bellows mechanical seals on account of their low spring rate, minimal hysteresis, high hydraulic responsiveness and short overall length compared with rolled bellows. Further applications:

• as compensators in pipelines, e. g. to compensate thermal expansion, or as low-stress connectors on sensitive apparatus
• as e.g. volume compensators or pressure pickups in measuring and control systems
• for glandless sealing of valve stems in fittings
• as an elastic element in lifting pistons
• as e.g. vibration absorbers or assembly compensators in machine construction.

Welding discs using the micro plasma pulse technique (MPPT)

Cross section of a weld