Expansion Joints - Type MWD | Macoga

Macoga MWD Expansion Joints

Macoga MWD are metallic expansion joints of the universal unrestrained type with welded ends. The assembly consists of two bellows connected by an intermediate pipe. The corresponding flanged version in this series is the MFD.

Operation and Movements

The MWD type can absorb a combination of axial, lateral, and angular movements, but is primarily used for large lateral displacements. Lateral capability depends on the angular deflection of each bellow and the length of the intermediate pipe.

Permitted movements within design limits:

• axial movement,
• lateral movement in one or more planes,
• angular movement in one or more planes.

Pressure Thrust and Anchoring

The MWD does not absorb pressure thrust. The piping system must include main anchors and alignment guides, designed for pressure, effective area, thermal movement, and pipeline loads. Installation without a full support and restraint analysis is not recommended.

Typical Applications

• steam and hot water lines,
• thermal oil,
• process gases,
• flue gases,
• piping with lateral offset,
• industrial networks requiring permanent welded connections.

Selection should verify DN, pressure class, temperature range, lateral travel, cycle life, bellow material, possible internal sleeve, and media compatibility.

MWD vs MWA / MWL / MFD

• MWA: single bellow, mainly axial movement absorption.
• MWD: two bellows, universal unrestrained, large lateral displacement.
• MWL: two bellows with tie rods, absorbs pressure thrust.
• MFD: same function as MWD, but with flanged ends.

Installation and Inspection

MWD is not intended for misalignment correction. Protect bellows from impacts, scratches, arc strikes, and weld spatter. Yellow transport bars must be removed after final installation and before pressure testing; for hydrostatic tests, use chloride-free water.