SE457524B - PARTICLY DROPABLE PLATFORM WITH BODY FOR REDUCING AND / OR LIMITING THE SLOPE OF THE PLATFORM - Google Patents

Description

457 524 or arrange for additional ballast and other measures which substantially increase the weight of the partially submersible platform usually result in the transit freeboard being reduced.

The main object of the present invention is to provide means which reduce and / or limit the inclined floating position of the partially submersible platform, said means not entailing the above-mentioned disadvantages and in particular not entailing any significant weight gain or deterioration of the movement pattern of the platform in its partially submerged state.

The object of the present invention is to provide a solution which does not have the above-mentioned disadvantages. The device proposed according to the invention for a semi-submersible body, which consists of a working or residential deck, two or more elongate floating bodies and at least three pillars, is intended to limit an inclined floating position caused due to leakage. The characteristic of the invention is that the parts of the floating bodies ("floating body ends") lying outside the pillars which connect the floating bodies to the deck are designed so that the volume center of a floating body end is above the volume center of the total floating body end and the floating body end , intact condition (= uniformly loaded floating position) is completely below the waterline. Additional embodiments of the invention are described in the subclaims.

U.S. Pat. No. 3,874,314 discloses a partially submersible platform of the type initially described. The partially submersible platform according to this patent specification consists of four floating bodies, a working platform and of pillars extending between the floating bodies and the working platform. However, the partially submersible platform does not have additional means for reducing and / or limiting an inclined floating position as proposed in the present invention. 4.57 524 The magazine "Schiff und Hafen", issue 2, 1981 describes partially submersible platforms intended for use in water with ice.

The floating bodies are lifted at the front and have nose-like superstructures, which obviously, like an icebreaker, are to be driven up onto the ice and break it. Magazines "Ship & Boat International", July / August 1977, p. 79 and 85 and "New Ships / Die Neubauten", volume 2, p. 42, 43 and 46 show partially submersible platforms in which the pillars shown at the ends of the floating bodies i. The partially submerged symmetrical state of the platform protrudes considerably above the water surface and in this way serves to ensure the required stability in the upright floating position (ie in the intact state). U.S. Pat. No. 3,771,481 and its Continuation-in-part application 27478 disclose a partially submersible platform having side-by-side half-pillars which are intended to provide sufficient stability in the intact state at shallow to medium depths, i.e. until The arrangement shown does not allow reduction and / or limitation of the inclined floating position of the partially submersible platform because the half-pillars have not reached the surface when the inclined position is 150. The dominant upward conditions in a platform of this known kind is shown in the accompanying Figure 1.

In a preferred embodiment of the invention, the upwardly generating volumes are constituted by upward force chambers mounted on the floating bodies.

The invention will be described in more detail below in connection with the accompanying drawings, in which Fig. 1 shows the upward force conditions prevailing in the device according to U.S. Pat. No. 3,771,481, 457,524. Fig. 2 shows the manner in which the inclination limiting means according to the invention affect the stability curve. a partially submersible platform, and Figs. 3a, 3b show an embodiment of a platform equipped with the inclination limiting means according to the invention, Fig. 3a being a sectional view along the line IIIa-IIIa in Fig. 3b and Fig. 3b is a sectional view taken along the line IIIb-IIIb in Fig. 3a.

Figures 3 show that a partially submersible platform of the type having a working platform 3, on which at least one working and / or residential deck is arranged, is carried by two floating bodies 1 via three pillars 2, two of these pillars extending between the working platform 3 and one of the floating bodies 1 and the third extends between the working platform and the remaining floating body. Transverse struts can be arranged in a conventional manner between the floating bodies in order to stabilize the construction against mechanical loads.

As can be seen in particular from the sectional views in Figs. 3a and 3b, the two floating bodies 1 have a substantially rectangular cross-sectional shape and have at their ends 1 'upwardly sloping hull surfaces.

Upwardly generating chambers 4 are attached to the outermost ends 1 'of the floating bodies 1 outside the area bounded by the columns.

Since the force-generating chambers 4 are mounted on the upper surfaces of the floats 1, the volume center points of the end portions 1 'of each float 1 will be at the point denoted by S1' + 4 »while the volume center of the whole float is at the point denoted by S1 + 4. which in turn is at the distance h below the point Sl »+4. As can be seen from Fig. 3b, the upwardly generating chambers 4 widen outwardly at their upper surfaces, whereby the volume center of each 457,524 upwardly generating chamber is closer to the upper surface of the upwardly generating chambers than the upper surface of associated floating bodies 1.

The partially submersible platform is normally towed out to sea and then partially submerged or submerged by water filling rooms located in the floats 1 or pillars 2. In the normal partially submerged position, in which the work platform 3 is preferably horizontal, the waterline 5 can be considered to lie at the dashed line 5. If a leak should occur, e.g. in a watertight space 7 in the aft pillar 2 of the partially submersible platform, the platform will tend to heel over, whereby it is conceivable that the water line lies at the line shown by 6a. In this position, the front upwardly generating chamber 4 will be located above the water surface and therefore no longer contribute to the upward force acting on the platform from other upwardly generating chambers. The result is that the resulting upward center of force is displaced away from the central vertical axis of symmetry through the platform and reduces the heeling angle. The magnitude of this reduction is, of course, due to the prevalent shape of the force-generating chambers and to the heeling motion induced by the leak.

If the leak were to occur instead in the front pillar 2, the waterline would tend to follow line 6b, in which case the rear upwardly generating chamber 4 rises above the water surface and the upward force it or the previously located upwardly generating chambers will tend to compensate for the heeling motion occurring as a result of the leak.

Should a leak occur in the central pillar 2, the two upwardly generating chambers of the floating body to which the remaining two pillars 2 are connected would tend to move out of the water so that they no longer contribute to the upward force of the platform. The upward force from the two submerged upwardly generating chambers 4 on the floating body 1 to which the central pillar 2 is attached will then generate a moment which tends to counteract the heeling moment due to the leakage in the central pillar 2.

The effects produced by the upwardly generating chambers are shown graphically in Fig. 2. The curve in Fig. 2 clearly shows the displacement in the straightening moment with resp. without superstructures as a function of the heeling angle. It will be appreciated that the change in heeling angle due to these superstructures amounts to several degrees and that this may be critical in terms of platform safety.

In the curve shown in Fig. 1, which shows the dominant upward force conditions in a construction according to U.S. Pat. No. 3,771,481, conventional designations are used in this context, where KB is the distance from the keel to the upward center of gravity, the center of gravity and MB are the distance from the unstable to the stable upward center of gravity.

Claims (3)

457 524 PATENT CLAIMS A device for a semi-submersible body, consisting of a working or residential deck (3), two or more elongated buoyancy bodies (1) and at least three pillars (ZL), which device is intended to limit a sloping buoyancy caused by leakage, characterized in that the shape of the outer portions of the floating bodies ("floating body ends") lying outside the pillars (2), which connect the floating bodies to the deck, is designed so that the volume center of a floating body end (4) is above the volume center of the total floating body and the floating body end in submerged, intact condition (= uniformly loaded floating position) is completely below the waterline. Device for improving existing semi-diving bodies according to claim 1, characterized in that one or more lifting bodies (4) are arranged at all floating body ends (1 utanför lying outside the pillars (2), which lifting bodies (4) generate upward force and in the submerged uniform loaded floating position are completely submerged, which lifting bodies or volume is so selected that the volume center point (S1- + 4) for the floating body end changed in this way is above (h) the volume center ~ point (S1 + 4) for the total floating body. Device according to claims 1 and 2, characterized in that the volume center point of a floating body end (1 ') is at least 30% above the volume center point of the total floating body.