NO344824B1

NO344824B1 - Clamp connector

Info

Publication number: NO344824B1
Application number: NO20171880A
Authority: NO
Inventors: Arve Tvitekkja
Original assignee: Aker Solutions As
Priority date: 2017-11-24
Filing date: 2017-11-24
Publication date: 2020-05-11
Also published as: GB2570202B; GB2570202A; GB201819082D0; NO20171880A1

Description

CLAMP CONNECTOR

The invention relates to a clamp connector, and more particularly, to a clamp connector with clamp segments hingedly connected to each other.

BACKGROUND

Clamp connectors are used in various industries and for various purposes, among others in process piping applications in the oil and gas industry and the petrochemical industry. Clamp connectors are used for e.g. connecting pipelines and flowlines to either structures or to other pipelines or flowlines. Due to high pressure and the risk of misalignment, clamp connectors, especially subsea connectors, are often designed to experience high stresses.

Clamp connectors come in various designs, with one or more bolts for tightening the clamp. Some large size clamp connectors have a bolt hingedly connected to the connector by means of bearings. Friction is associated with bearings, and as the clamp is subject to both internal and external forces, the friction will induce additional stress on the clamp and on the bolt in particular. When a clamp is tightened, it is commonly tightened as much as the design allows.

Documents useful for understanding the field of technology include US 4225160 A, US 5645303 A, GB 2485626 A, GB 2488372 A, US 3797079 A and WO 0005527 A1.

In order to save weight and materials, or in order to maximise the strength and operational reliability of a clamp connector, there is a need in the art for improved clamp connector designs. The present invention has the objective to provide such an improvement.

SUMMARY

In accordance with an embodiment, there is provided a clamp connector comprising first and second clamp segments. The first and second clamp segments are hingedly connected to each other. A tensioning bolt connects the first and second clamp segments via rotatable elements, the rotatable elements each having an axis of rotation which is substantially perpendicular to a longitudinal centre axis of the tensioning bolt. At least one axis of rotation has an offset from the longitudinal centre axis such as not to intersect the longitudinal centre axis. The at least one axis of rotation is offset from the longitudinal centre axis in a direction away from a clamp jaw defined by the first and second clamp segments.

According to another embodiment, there is provided a clamp connector where both axes of rotation have an offset from the longitudinal centre axis.

According to another embodiment, there is provided a clamp connector where the offset is the same for both axes of rotation.

According to another embodiment, there is provided a clamp connector where the offset is different between the axes of rotation.

According to another embodiment, there is provided a clamp connector where the at least one axis of rotation is offset from the longitudinal centre axis in a direction towards a clamp jaw defined by the first and second clamp segments.

According to another embodiment, there is provided a clamp connector where the first and second clamp segments are connected to each other via at least one clamp segment.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics will become clear from the following description of embodiments, given as non-restrictive examples, with reference to the attached schematic drawings.

Figure 1 is a front view of a single bolt clamp connector.

Figure 2 is a detail view of section A from figure 1. The detailed view illustrates a rotatable element and the bolt.

DETAILED DESCRIPTION

The following description may use terms such as “horizontal”, “vertical”, “lateral”, ”upper”, “lower”, “inner”, “outer”, “forward”, “rear”, etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader’s convenience only and shall not be limiting.

The following description is related to figure 1, which shows a clamp connector 1 provided with a tensioning bolt 2. The tensioning bolt 2, also known as a jack screw, drive screw or stud bolt, connects a first clamp segment 3 and a second clamp segment 4. The tensioning bolt 2 could thus be any type of connection means, adapted for connecting and adjusting the length between two clamp segments. The connection clamp 1 could also comprise more than one tensioning bolt, as is known in the art. In this embodiment, a third clamp segment 5 connects the first and second clamp segments. The clamp connector 1 in the shown embodiment thus has three clamp segments which can rotate relative to each other, but it could comprise more or fewer clamp segments. The clamp connector could comprise only two clamp segments, the first and second segments 3,4 being connected directly to each other by means of a hinged connection, or comprise four or more such segments.

The clamp segments 3,4,5 define a clamp jaw 11 and are connected by hinge elements, such as hinge pins. A first hinge element 6 connects the first clamp segment 3 to the third clamp segment 5. A second hinge element 7 connects the second clamp segment 4 to the third clamp segment 5. The hinge elements 6,7 thus create hinged connections. Such connections are well known in the art and provide a clamp connection with several clamp segments which distribute a clamping force evenly around a circumference

The first clamp segment 3 is connected to the tensioning bolt 2 by a first rotatable element 8. Such a rotatable element 8 can be a trunnion nut or other means known in the art. The first rotatable element 8 can rotate relative to the first clamp segment 3 because of a rotational bearing, such as a ball bearing, traverse bearing, or by other means known in the art. Similarly, the second clamp segment 4 is connected to the tensioning bolt 2 by a second rotatable element 9. The rotatable element 9 can also rotate relative to the second clamp segment 4 by means of e.g. a rotational bearing.

As the tensioning bolt 2 is tightened, the first and second clamp segments 3,4 are forced closer to each other, in effect reducing the diameter of the clamp connector 1 and the clamp jaw 11. The clamp connector 1 will thus provide a secure connection of whatever device(s) it is clamping, e.g. a pipe connection. This method of operating a connection clamp is commonly known in the art.

Figure 2 illustrates in more detail a portion of the first clamp segment 3, the first rotatable element 8 and a portion of the tensioning bolt 2. The clamp connector 1 has an eccentric design which can be seen more clearly in this figure. The longitudinal centre axis 10 of the bolt 2 is not intersecting and is not coincident with a first axis of rotation 12 of the first rotatable element 8 and a second axis of rotation 13 (see figure 1) of the second rotatable element 9 (not shown in figure 2, see figure 1). The first axis of rotation 12 is offset a distance e away from the bolt centre axis 10, as can be seen indicated in figure 2.

The first and second axes of rotation 12,13 of the first and second rotatable elements 8,9, respectively, are in one embodiment equally spaced apart from the bolt centre axis 10, i.e. the minimum distance from the first axis of rotation 12 to the bolt centre axis 10 is equal to the minimum distance from the second axis of rotation 13 to the bolt centre axis 10.

However, the distance e from the axes of rotation 12,13 to the centre axis 10 of the tensioning bolt 2 need not be equal for the two rotatable elements 8,9. If there is a difference in friction between the first rotatable element 8 and the second rotatable element 9, this can be compensated by different distances e. Also, a different size of the first rotatable element 8 and the second rotatable element 9 (and hence a difference in size of the corresponding rotatable bearings) can be compensated by different distances between the first axis of rotation 12 and the bolt axis 10 and the second axis of rotation 13 and the bolt axis 10.

The two axes of rotation 12,13 are oriented substantially perpendicular to the longitudinal centre axis 10 of the tensioning bolt 2. In figure 3, the first axis of rotation 12 is positioned below the bolt axis 10. The axis of rotation 12 of the first rotatable element 8 are thus offset from the longitudinal centre axis 10 in a direction away from the clamp jaw 11 defined by the first and second clamp segments 3,4.

In clamp connectors where a tensioning bolt is connected to rotatable elements, the friction in the rotatable element is proportional to the friction coefficient between the rotatable element and the clamp segment and the tightening force in the tensioning bolt. This is shown in the following equation where the bending moment Mb in the tensioning bolt is calculated (the variables are also indicated in figure 2):

where

R is the frictional force in the rotatable element

r is the radius of the rotatable element

F is the tightening force in the bolt

e is the distance from the centre axis of the rotatable element to the centre axis of the bolt

µ is the friction coefficient between the rotatable element and the bearing

Thus, in order to eliminate the bending moment the distance e is therefore calculated and taken into account when designing the connection clamp 1. The distance e could be in the order of about 3mm, but will vary between one connection clamp design to another, according to clamp size, force/pressure ratings, friction, and other variables.

In one embodiment, if a typical friction coefficient is 0.1, the distance e can be 10% of the radius of the rotatable element or bearing. If the friction coefficient is about 0.2, the distance e can be about 20% of the radius of the rotatable element or bearing.

Advantageously, the offset distance e will reduce the bending moment of the bolt, and this clamp design can be beneficial for all types of clamp connectors, and will provide a higher utilization of the clamp components, and the tensioning bolt in particular, during tensioning of the clamp. An effect of this is that the strain on the tensioning bolt is reduced compared to connection clamps of conventional design, such that either the bolt can be tensioned more, or alternatively the tensioning bolt can be designed with a smaller radius or cross section, and still sustain the same tension as the bolt in a clamp connection with a conventional design.

In a conventional clamp connector, the centre axis of the bolt is coincident with the centre axis of the rotatable elements. During make-up of such a conventional clamp connector for e.g. tie-in, the bolt is subject to a bending moment due to friction between the rotatable elements and the clamp segments. This bending moment causes high stress in the bolt and in worst case plastic deformation. This represents a limitation of the capacity of the entire clamp and could contribute to fracture in the worst case. According to embodiments of the present clamp connector 1, this bending moment is reduced or eliminated.

Also during tensioning of a conventional clamp connector, the bolt can somewhat bend because of the bending moment induced on it. Because the bolt in a conventional clamp connector is bent when it has been tensioned, it can over time (e.g. due to vibrations and relaxation) somewhat straighten out and cause the clamp connector to undesirably relax. Such unintentional relaxing is common but highly undesirable. In embodiments of the present clamp connector 1, such bending and subsequent relaxing is reduced or eliminated.

While the invention has been described with reference to the embodiment(s) mentioned above, it is to be understood that modifications and variations can be made without departing from the scope of the present invention, and such modifications and variations shall remain within the field and scope of the invention.

Claims

1. A clamp connector (1) for a pipeline, comprising:

first and second clamp segments (3,4), the first and second clamp segments (3,4) being hingedly connected to each other;

a tensioning bolt (2) connecting the first and second clamp segments (3,4) via rotatable elements (8,9), the rotatable elements (8,9) each having an axis of rotation (12,13) which is substantially perpendicular to a longitudinal centre axis (10) of the tensioning bolt (2);

where at least one axis of rotation (12,13) has an offset (e) from the longitudinal centre axis (10) such as not to intersect the longitudinal centre axis (10);

where the at least one axis of rotation (12,13) is offset from the longitudinal centre axis (10) in a direction away from a clamp jaw (11) defined by the first and second clamp segments (3,4).

2. A clamp connector (1) according to the preceding claim, where both axes of rotation (12,13) have an offset (e) from the longitudinal centre axis (10).

3. A clamp connector (1) according to any preceding claim, where the offset (e) is the same for both axes of rotation (12,13).

4. A clamp connector (1) according to claim 2, where the offset (e) is different between the axes of rotation (12,13).

5. A clamp connector (1) according to any preceding claim, where the at least one axis of rotation (12,13) is offset from the longitudinal centre axis (10) in a direction towards a clamp jaw (11) defined by the first and second clamp segments (3,4).

6. A clamp connector (1) according to any preceding claim, where the first and second clamp segments (3,4) are connected to each other via at least one clamp segment (5).