Expansion Joints - Type MFK | Macoga

Macoga MFK Expansion Joints

Macoga MFK are metallic expansion joints of the double articulated type with flanged connections. The assembly consists of two bellows, an intermediate pipe, and a double hinge system, designed to absorb lateral displacements in any direction and angular movement in a single plane. The welded-end version is designated as MWK.

Operation and Load Management

The articulated system of the MFK absorbs pressure thrust, eliminating the need for main anchors to counteract pressure forces. Pipe guides and supports remain necessary to manage pipe weight, lateral loads, thermal expansion, and vibration.

Permitted movements:

• Lateral: in one or multiple planes
• Angular: in a single plane
• Axial: not permitted
• Multi-plane angular: not permitted

Typical Applications

Used in steam, hot water, thermal oil, flue gas, and process gas lines where flanged connections are required and lateral offset must be absorbed without transferring pressure thrust to main anchors.

MFK vs MFC / MFY

• MFK: Double articulated; lateral movement in any direction, angular in one plane.
• MFC: Gimbal type; angular movement in any plane.
• MFY: Double hinged; lateral and angular movement only in one plane.

Selection Criteria

Selection must consider DN, PN/flange class, design pressure, temperature, lateral displacement, rotation angle, operating cycles, bellows material, possible internal sleeve, gasket type, and media compatibility.

Installation and Inspection

MFK joints are not intended for correcting misalignment. Verify nameplate data, flow direction (if internal sleeve is present), gasket positioning, guides, and anchors. Protect bellows from impact, scoring, arc strikes, and weld spatter. Remove yellow transport bars before pressure testing; use chloride-free water for hydrostatic tests.