Expansion Joints - Type MFD | Macoga

Macoga MFD Expansion Joints

Macoga MFD are metallic expansion joints of the universal unrestrained type with flanged ends. The assembly consists of two bellows connected by an intermediate pipe. The welded-end variant in the same family is designated MWD.

Operation and Allowable Movements

The MFD type is designed to absorb a combination of basic pipe movements, primarily used where significant lateral displacement is required. Lateral capability depends on the angular flexibility of each bellow and the length of the intermediate pipe.

Allowable movements:

• Axial movement
• Lateral movement in one or multiple planes
• Angular movement in one or multiple planes

Pressure Thrust and Anchoring

The MFD does not absorb pressure thrust. The piping system must include properly calculated main anchors and alignment guides. Installation is not recommended where supports have not been verified for section modulus, operating pressure, displacement, and piping loads.

Typical Applications

• Steam and hot water lines
• Thermal oil and process gases
• Exhaust gases and auxiliary industrial circuits
• Piping with lateral offset
• Locations requiring flanged disassembly

Selection must consider DN, PN/Class, temperature, lateral travel, operating cycles, bellow material, gasket type, and media compatibility.

MFD vs MFG / MFL

• MFG: Single bellow, mainly axial absorption
• MFD: Two bellows, universal unrestrained, high lateral displacement
• MFL: Two bellows with tie rods, absorbs pressure thrust

Installation and Inspection

Not intended for misalignment correction. Prior to installation, verify nameplate data, flow direction (with internal sleeve), gaskets, anchors, and guides. Protect bellows from impact, scratches, arc strikes, and weld spatter. Remove yellow transport bars before pressure testing; use chloride-free water for hydrostatic tests.