REMOVABLE CLOSURE DEVICE

Abstract: A pile guide has a removable ring gate (26) which restrains a pile within braces (24) of the pile guide. When in the closed position, the ring gate (26) is secured to the guide by means of a pivotable arm (30). To release the pile and/or to convert the guide to an open pile guide, a cable secured to the arm (30) is pulled to pivot the arm (30) fracturing a weld (35) securing the arm (30) to the respective brace (24) and a weld (33) securing the pin (41) of the arm (30) to a fixed pin (41) of the guide, on which fixed pin the ring gate (26) is engaged. This thereby releases the ring gate (26) from the pile guide and releases restraint on the pile.

Description: The invention relates to the art of pile driving and more specifically to a pile guide. Pile guides are used on such structures as offshore jackets for securing a pile to the structure and thereafter guiding the pile as it is being driven so as properly to align skirt piles, follower piles, and/or the hammer during pile driving operations. In the case of closed pile guides, such follower and skirt piles can be preloaded onto the structure before it is launched giving a significant cost saving over having to load elongate and unwieldy piles in the ocean. However, should additional lengths of the skirt pile be necessary or should more follower pile lengths be needed, the cost savings associated with preloading is consumed by the pains-taking process of threading these additional lengths through the closed guides. Open pile guides, on the other hand, are considerably easier to reload in the field but by being open, the cost savings of preloading onto the structure is not available. Convertible-type pile guides which are closed during jacket launching and positioning and then opened prior to pile driving permit the advantages of preloaded piles to be combined with the advantages of open pile guides. Such convertible guides often are designed as hinged clamps that are held closed by bolts, hydraulically activated rams, or both. Clamps held closed only by bolts are less expensive to fabricate than hydraulic devices but they entail the expense of offshore divers when the time comes to remove the bolts. Hydraulically activated clamps reduce or eliminate the need for divers but their fabrication cost is very high. In the past, the high cost of bolted or hydraulic type convertible pile guides often offset the cost savings of combining preloaded pilings with the open pile guide method of pile installation. Patent Specification US-A-4110993 discloses apparatus for driving piles into the sea bottom which enables the required hoisting height of a pile follower by a crane to be reduced. Two semi-circular claws are provided, a fixed one secured at one end to the free end of a pivotable horizontal arm and a rotating one secured at one end to the other end of the fixed claw and having an integral lever at said one end that can be acted on by a cable to pivot the rotating claw about the fixed claw. When closed the claws together form a circular guide and when open the lever extends across the space between the claws. The claws can be opened by pulling on the cable or closed by rotating the arm to cause the lever to abut the pile follower. According to the invention there is provided a pile guide comprising: a fixed support surrounding a portion of a pile; a removable ring gate surrounding the remaining portion of the pile to restrain the pile against the support; and a removable closure device comprising: at least one connecting assembly connecting the ring gate to the support, the or each connecting assembly comprising an elongate pivotable arm characterised in that said pivotable arm is fixedly attached adjacent one end thereof to both the ring gate and the support; and operating means are provided to apply a force to the other end of the pivotable arm to to break the attachment between the ring gate and the support thereby releasing the ring gate from the support and the restraint on the pile. Such a pile guide can combine the cost savings of preloading with the ease of re-loading and permit inexpensive and reliable conversion of a closed pile guide to an open pile guide. The removable closure device includes the connecting assembly removably securing the ring gate to the pile guide. When the pivotable arm is pivoted it releases and removes the ring gate from the pile guide thereby transforming the previously closed pile guide into an open pile guide. The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which: Figure 1 is an illustration of an offshore structure showing a skirt pile, a follower pile, and an above water hammer, all of which are typically used in conjunction with a closed pile guide; Figure 2 is an illustration of an offshore structure showing a skirt pile and an underwater hammer which are typically used in conjunction with an open pile guide; Figure 3 is a plan view, partially broken away, of a pile guide according to the invention; Figure 4 is a fragmentary plan view of part of Figure 3 to a larger scale showing one end of a ring gate retained by a pivotable arm; Figure 5 is a fragmentary sectional view taken on lines 5-5 of Figure 4 showing attachment of the pivotable arm to the pile guide; Figure 6 is a fragmentary sectional view taken on line 6-6 of Figure 4; Figure 7 is a fragmentary sectional view taken on line 7-7 of Figure 3; and Figure 8 is a fragmentary sectional view taken on line 8-8 of Figure 4. Referring initially to Figure 1, there is shown an offshore structure 10 with a skirt pile 12 and a follower pile 14 supported within pile guides 16. An above water hammer 18 drives the piles 12, 14 through the guides 16, which in all likelihood, would be of the closed variety since the piles would, for cost savings, be preloaded onto the structure 10 prior to its launching. Should any additional lengths of follower pile 14 be needed they would be threaded through the closed guides 16 from above. Figure 2 shows an underwater hammer 20 driving a skirt pile 12 through guides 16. In this instance, the guides 16 would be of the open variety since the hammer 20 would pass through the guides 16 as the skirt pile 12 becomes embedded. In the embodiment of the invention shown in Figure 3, a pile guide 16 surrounds a pile such as a skirt pile 12. The pile guide 16 includes a fixed support 22 that incorporates a pair of outwardly extending braces 24. The fixed support 22 is configured to nestle or support the skirt pile 12 between the braces 24. A ring gate 26 spans between the braces 24 and restrains the skirt pile 12 against the fixed support 22. The ring gate 26 is removable from the fixed support 22 and is held in place by connection assemblies 28. Each of the connection assemblies 28, which, as shown, connects one end of the ring gate 26 to its respective brace 24, includes a pivoting arm 30 held by hinge brackets 32. Figures 4 to 8 illustrate, in greater detail, one of the connection assemblies 28. As shown, the hinge brackets 32 are secured to the ring gate 26 such that when the arm 30 is pivoted to an upright position, the arm 30, the hinge brackets 32, and the ring gate 26 each become released from the respective brace 24. A weld bead 33 connects a pin 40 fixed in the pile guide 16 to a hinge pin 41 integral with the arm 30 and engaged in the hinge brackets 32 while legs 34, welded as shown to the brace 24 via a weld 35, retain the arm 30 in its stored horizontal position, thereby also securing the ring gate 26 to the brace 24 and around the pile 12. To break the welds 33 and 35 and to release the ring gate 26, a cable 36, which is connected to an eyelet 38 at the free end of the arm 30, is pulled thereby pivoting the arm 30 in the hinge brackets 32 to a more vertical position. Once the arm 30 is no longer secured to the brace 24, the arm 30 can be lifted upward via the cable 36 bringing with it the ring gate 26 and the hinge pin 41 and the hinge brackets 32. The ring gate 26 is lifted up over the pin 40 in the brace 24 before being released. The pin 40, when the ring gate 26 is secured around it, acts as a shear pin both to absorb any horizontal force transmitted through the ring gate 26 and to restrain the pile 12 in place. During operation, a pile, such as a skirt pile 12, is loaded into the fixed support 22 between the braces 24. Each end of the ring gate 26 is then slipped over its respective pin 40 so as to restrain the pile 12 in place. The pivoting arm 30, which secures the ring gate 26, is then positioned so that the attached legs 34 can be welded to the brace 24 and the hinge pin 41 can be welded to the pin 40. Such welding secures the ring gate 26 in place. The pile guide 16 is now a closed pile guide restraining the preloaded pile 12 against the structure 10 prior to launching. Whenever a pile 12 is to be released or whenever a pile guide 16 is to be converted into an open pile guide, the cable 36 is pulled thereby pivoting the two arms 30 to a more upright position while breaking the welds 35 securing the legs 34 to the braces 24 and breaking the welds 33 securing the pins 40 to the hinge pins 41. Once the welds 33, 35 are broken, the cable 36 lifts the connected ring gate 26 from around the two pins 40 thereby releasing the pile 12 from the fixed support 22. The pile guide 16 thus has been converted from a closed-type guide to an open-type guide enabling additional piles easily to be positioned within the guide and enabling an underwater hammer to pass through the guide during the hammering operation. The cable 36 generally extends along the length of the pile that is being restrained with much slack in the line. Oftentimes, in the case of multiple pile guides supporting a single pile, the same cable will be secured to a plurality of pairs of pivoting arms. This is accomplished by installing slack in the line between the various pivoting arms. Thus, as the slack is taken out by, say, a winch, only one ring gate is released at a time. Additionally, just above each pile guide, the cable branches to two lines so that at each pile guide, both of the pivoting arms 30 thereof are activated at the same time.

Claims: 1. A pile guide (16) comprising: a fixed support (22) surrounding a portion of a pile (12); a removable ring gate (26) surrounding the remaining portion of the pile to restrain the pile (12) against the support (22); and a removable closure device comprising: at least one connecting assembly (28) connecting the ring gate (26) to the support (22), the or each connecting assembly (28) comprising an elongate pivotable arm (30) characterised in that said pivotable arm (30) is fixedly attached adjacent one end thereof to both the ring gate (26) and the support (22); and operating means (36, 38) are provided to apply a force to the other end of the pivotable arm (30) to break the attachment between the ring gate (26) and the support (22) thereby releasing the ring gate (26) from the support (22) and the restraint on the pile. 2. A pile guide according to claim 1, wherein the pile is nestled against the support (22) between spaced extending braces (24). 3. A pile guide according to claim 2, wherein the ring gate (26) spans between the braces (24). 4. A pile guide according to claim 3, wherein the pivotable arm (30) is removably coupled to one of the braces (24). 5. A pile guide according to claim 4, wherein the or each connecting assembly comprises a pin (40) projecting from one of the braces (24), extending through the ring gate (26) and coupled to the pivotable arm (30) so that the pivotable arm (30) retains the ring gate (26) engaged on the pin (40). 6. A pile guide according to claim 5, wherein there are a pair of the connecting assemblies (28) secured one to each of the opposite ends of the ring gate (26). 7. A pile guide according to claim 6, wherein the operating means comprise a cable (36) secured to said other end of each of the pivotable arms (30). 8. A pile guide according to any one of claims 5 to 7, wherein the pivotable arm (30) is coupled to the pin (40) and to one of the braces (24) by welds (33, 35) and the welds (33, 35) are broken by pivoting movement of the pivotable arm (30) caused by the operating means (36, 38).

Inventors: CALKINS, DENNIS EARL, HANEY, JAMES ALLAN
Applicants: MCDERMOTT INCORPORATED
Application year: 1988
Main classification: E02D13
IPC codes: E02D13, E02B17