2H offshore are a global engineering contractor specialising in the design, structural analysis and integrity of riser and conductor systems. These are used in the drilling and production of offshore oil and gas.
Annulus tests are an annual requirement to confirm the integrity of the outer sheath of a flexible riser. The outer sheath is the riser’s only barrier to keep seawater from the annulus that house the riser’s carbon steel structural support components.
A test can be conducted either by pressurising the annulus to approximately 1.5 barg or by drawing a vacuum in the annulus of negative 0.5 barg and holding that pressure to confirm the integrity of the outer sheath.
An Alicat MB series portable mass flow meter forms part of 2H Offshore’s portable flexible riser annulus test kit.
When pressurising the annulus the flow meter is used to measure the flow rate of nitrogen going into the annulus or to measure the flow rate to return the annulus to gauge pressure when drawing a vacuum.
In both cases the built in flow totaliser on the Alicat flow meter allows 2H offshore to calculate the free space within the annulus and confirm that the space has not been filled with liquid.