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An HRSG power plant in Pennsylvania was experiencing failure of expansion joints at the pipe penetrations of the boiler casing. Over 100 joints had failed or had begun showing signs of temperature-related damage in only a few months after initial startup.

The expansion joints consisted of a single layer of Teflon/glass fabric clamped to the casing and the piping with stainless steel band clamps. As the fabric was not insulated, it deteriorated; repeated thermal cycling caused relaxing of the band clamp, which allowed the joint to come loose from the pipe and casing.

Zepco's new design incorporates an adapter flange on the casing and pipe that allows the expansion joint to be bolted in rather than band clamped. The expansion joint belt is engineered to withstand 1100°F temperatures. Insulation on the steam piping is designed to allow the pipe to move through a layer of stationary insulation independent of the piping; this reduces the radiant heat transmitted to the expansion joint.

Typically, expansion joints in this application experience large axial extension movements. The Zepco joints are designed and installed with up to 8" of extra material pre-compressed into the breech opening to allow for this extension movement.

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