THE “CURRENT-DRIVEN” MARINE GROWTH PREVENTER (MGP-C)
The MGP-C is a single ring product with the addition of hydro-dynamically designed cup fins. The fins are set at an angle to propel both longitudinal and rotational movements of the product. The MGP-C can be employed on vertical, vertical diagonal and horizontal members in all water depth under suitable current regime.
The MGP-C is a single-ring apparatus powered by current forces and its own buoyancy. The MGP-C can also be used on tubular between the mean sea level and the first bracing level in ocean areas where current speeds are from moderate to strong and there are frequent changes in the direction of current flow.
The single ring MGP-C is made up of components identical to those of the multiple-rings MGP-W with additional cup fins designed to capture ocean current forces. The fins are collapsible to maximise the net rotational force and set in a slight angle to provide both rotational and transitional forces for the apparatus movement around and along the tubular to be protected.
Two cup sizes are available to suit the structural clearance; the orientation of the member to be protected and the prevailing current regimes. Large cups are specified on all vertical members such as conductors, caissons and risers and vertical diagonal members whenever possible. Larger cup fins maximise the effect of current forces and enable products to operate in low to medium current environments. MGP-C with small cup fins is specified on all members in areas with restrictions; such as, inside anode areas, barge bumpers etc.
On vertical and vertical diagonal members, current actions rotate and move the apparatus downward along the member to be protected. When current speed reduces or the direction of current flow changes, the apparatus resurfaces under its own buoyancy. On horizontal members, changes in the direction of current flow rotate and move the apparatus longitudinally along the member to be protected.
The minimum current speed required for the operations of the MGP-C on vertical members is 1 knot while the minimum current speed required for vertical diagonal and horizontal members is 0.5 knots, depending on the relative direction between the current flow and the member orientation.
The range of MGP-C produced by IEV includes: