Expansion Joints - Type MWK | Macoga

Macoga MWK Expansion Joints

Macoga MWK are metallic expansion joints of the double articulated type, featuring two bellows, an intermediate pipe, and weld ends. The flanged version is designated as MFK. These assemblies are designed for lateral movements in any direction and angular movement in a single plane.

Operation and Load Management

The MWK incorporates a double hinge system that absorbs pressure thrust. As a result, main anchors for pressure thrust are not required, unlike unrestrained axial types. However, properly calculated supports and guides are necessary to accommodate pipe weight, thermal displacement, lateral loads, and vibration.

Permitted Movements

• Axial movement: Not intended for regular operation.
• Lateral movement: Permitted in one or multiple planes.
• Angular movement: Only in a single plane.
• Multi-plane angular movement: Not supported.

Typical Applications

Used in steam, hot water, thermal oil, process gas, and industrial piping systems where line geometry creates lateral offset and pressure thrust cannot be absorbed by main anchors. Suitable for applications requiring compensation of thermal expansion and vibration in accordance with EN 14917 and EJMA standards.

MWK vs MWY

• MWK: Double articulated; lateral movement in any direction, angular in one plane.
• MWY: Double hinged; lateral and angular movement in a single plane.
• MFK: Same as MWK but with flanged ends instead of weld ends.

Installation and Inspection

MWK joints are not intended for misalignment correction. Prior to installation, verify nameplate data, flow direction (if internal sleeve is present), bellow condition, and absence of foreign objects. Protect bellows from impact, scratches, arc strikes, and weld spatter.

Before pressure testing, remove yellow transport bars. For hydrostatic testing, use chloride-free water. Periodic inspection should include checks for leakage, pressure loss, vibration, external corrosion, loose mechanical parts, and particle accumulation in bellows convolutions.