Pressure Grouting

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Pressure grouting is used for grouting jacket legs in deep water where fixed pipework becomes uneconomical from a fabrication point of view. It does not require the use of grout seals.

Pressure grouting is a highly skilled two-stage process involving pressurised annuli and carefully controlled grout pumping.

The pile is inserted through the jacket leg, and driven into the seabed. Shim plates are then welded into position between the pile and the top of the jacket leg to provide an airtight seal.

The jacket leg has two valves fabricated onto it above sea level: one inlet for pressurised air and grout, and one outlet for air.

To start with, the outlet valve is closed and an air pump is connected to the inlet valve to pressurise the annulus. This displaces the air downwards and out of the annulus.

When the pressure at the top of the annulus equals that at its bottom (and therefore the seabed), the annulus should be dry. The grout hose is connected to the inlet valve and grout is injected at a steady, highly controlled speed. At this time, the air outlet valve is opened to enable the pressurised air to escape so that the combined pressure of the air and grout inside remains equal to that at the seabed, eliminating grout leakage.

Once half of the annulus has been filled, the grout is left to cure to provide a solid plug for when the remaining grout is injected.

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