Lens Metal Expansion Joints

RoundTec metal expansion joints effectively absorb the compression-extension and/or angular movements occurring along the channel by allowing the parallel faces of the U-profiled joints that constitute them to undergo positive or negative angular changes. On the other hand, the central pipe between the U-profiled convolutions takes on the role of absorbing lateral movements along the channel.

The cumulative total of channel movements, including factors such as channel dimensions, line pressure, fluid temperature, is compiled and calculated according to the AD2000 B13 standard to obtain an appropriate design. Based on this design, one or more convolutions are combined with the central pipe to create the final product.

Depending on environmental conditions, a portion of the loads accumulated on the convolutions of the metal expansion joint can be transferred to the pipeline using components, thereby extending the service life of the metal expansion joint. These components, often including limit stops, pantograph shears, hinges, universal joints (gimbals), are custom-designed according to the type and magnitude of the movement the compensator needs to absorb.

RoundTec compensators are categorized based on manufacturing types as NO-WELD and ONE-WELD.

ONE-WELD lens type metal compensators are composed of U-shaped bellows, obtained by joining two separate parts with integral cross-sections at their apex through circumferential welding.

Lens type metal compensators, through the integrated design of parts welded together, ensure superior durability, enhancing their ability to withstand effects such as thermal expansion, impact, and displacement. These compensators find extensive use across a wide range of industrial applications, delivering long-lasting performance attributed to the precision and accuracy achieved through spinning and pressing.

The diversity of lens type metal compensators, coupled with various connection options, offers flexibility and applicability. These compensators provide tailored solutions to different industrial needs through customized design and assembly options. Ultimately, lens type metal compensators, crafted with innovation and exceptional engineering, play a pivotal role in elevating the efficiency and durability of industrial systems.


• Large production capacity from DN 200 to DN 8000
• Sheet thickness option up to 10mm
• Unlimited pitch (knuckle) height. (See: AD2000 Calculations)
• Manufacturing with one or more nodes.
• Flanged, swivel flange or welded flange connection option.
• Limit rod, gimbal, universal joint features can be added according to the ambient operating conditions.

NO-WELD lens-type metal compensators, presented as an exceptional feat of engineering, are meticulously crafted using a seamless bellows profile, eliminating the necessity for any circumferential welding on the expansion joint. This unique manufacturing technique ensures that the expansion joint profiles remain untouched by the hardness induced by heat during welding, thereby preserving their inherent flexibility. As a result, these expansion joints enjoy significantly prolonged lifespans; NO-WELD lens-type compensators offer an average usage life that is 20% to 30% longer than their ONE-WELD counterparts manufactured withcircumferential welding. This innovative approach, abolishing the effects of weld-induced hardening, elevates the service life of the expansion joints, delivering an amalgamation of exceptional performance and unwavering reliability.


• Wide production capacity ranging from DN 1000 to DN 12000.
• Sheet thickness options from 2mm to 4mm.
• Maximum span (convolution) height of 222mm. (See: AD2000 Calculations)
• Single or multiple convolutions.
• Connection options include flanged, swivel flange, or welded end connections.
• Additional features such as limit rods, shear stops, hinges, gimbals and universal joint characteristics can be added based on operating conditions.

PolyTec metal expansion joints effectively absorb the compression-extension and/or angular movements occurring along the channel by allowing the parallel faces of the U-profiled joints that constitute them to undergo positive or negative angular changes. On the other hand, the central pipe between the U-profiled convolutions takes on the role of absorbing lateral movements along the channel.

PolyTec metal compensators, which have a very wide production range in terms of dimensions, are produced from rectangular geometry to hexadecagon geometry. According to the operating conditions of the compensator and the expected cycle life, the appropriate form is selected from 6 different corner types.

Depending on environmental conditions, a portion of the loads accumulated on the convolutions of the metal expansion joint can be transferred to the pipeline using components, thereby extending the service life of the metal expansion joint. These components, often including limit stops, pantograph shears, hinges, universal joints (gimbals), are custom-designed according to the type and magnitude of the movement the compensator needs to absorb.