Tensioning apparatus and method

• US 20040115024A1
• Filed: 06/06/2003
• Published: 06/17/2004
• Est. Priority Date: 12/16/2002
• Status: Active Grant

• Current Assignee: Siemens Energy Incorporated (Siemens AG)
• Original Assignee: Siemens Westinghouse Power Corporation
• Inventors: Gosling, Martin Charles
• Granted Patent: US 7,066,699 B2
• Time in Patent Office: Days
• US Class Current: 411/14.5
• CPC Class Codes: B23P 11/022 by using pressure fluids
• CPC Class Codes: B25B 29/02 Bolt tensioners
• CPC Class Codes: F16B 31/043 Prestressed connections tensioned by means of liquid, grease, rubber, explosive charge, or the like hydraulic bolt tensioners B25B29/02
• CPC Class Codes: Y10S 411/917 Nut having tension feature

Abstract

A system (150) and method of tensioning a bolt (44) across a flange assembly (42). A tensioning apparatus (40) includes the bolt and an unthreaded nut (48) connected to the shank member by an interference fit. The interference fit may be selectively relaxed by applying a fluid pressure to a groove (54) between the nut and the bolt. A tensioner (58) is energized by a pressure to pre-load the bolt by pulling on the bolt while pushing on the nut while the interference fit is sufficiently relaxed to allow relative movement between the nut and the bolt. The tensioner is sized to achieve the required pre-load in the bolt at the same working fluid pressure that is necessary to relax the interference fit on the stretched bolt, thus permitting a single pressure source (148) to be used for both functions. Once the pre-load is established, the interference fit is reestablished by releasing pressure to the nut to secure the nut in position for maintaining the closure force across the flange assembly after the tensioner is removed. Because the nut does not need to rotate, the pre-load may be applied directly through the nut without the use of a bridge, thereby eliminating the need for overstressing of the bolt to accommodate seating of the nut once the tensioner is relaxed.

Claims

1. A tensioning apparatus comprising:

a shank member;

an annular member comprising an opening sized to receive the shank member with an interference fit;

a fluid passageway for delivering a pressure between the shank member and the annular member for expanding the opening to relax the interference fit;

a tensioner responsive to a pressure to apply a force to tension the shank member;

wherein a first pressure is required in the fluid passageway to relax the interference fit when the shank member is relaxed, and a second pressure lower than the first pressure is required in the fluid passageway to relax the interference fit when the shank member is tensioned; and

wherein

the tensioner is selected to provide a desired tensioning force to the shank member at the second pressure so that a single pressure source may be used to provide pressure to the fluid passageway and to the tensioner to achieve a desired pre-load in the shank member.

2. The tensioning apparatus of claim 1, further comprising:

a pump;

a first valve connected between the pump and the fluid passageway; and

a second valve connected between the pump and the tensioner.

3. The tensioning apparatus of claim 1, wherein the tensioner further comprises:

a piston disposed within a cylinder to define a pressure chamber;

a first of the piston and cylinder connected to the shank member for applying the force to tension the shank member and a second of the piston and cylinder connected to the annular member for applying a reaction force through the annular member.

4. The tensioning apparatus of claim 3, further comprising:

a pump;

a first valve connected between the pump and the fluid passageway; and

a second valve connected between the pump and the pressure chamber.

5. The tensioning apparatus of claim 4, wherein the pump, first valve and second valve comprise a pressure supply, and further comprising a controller for remotely operating the pressure supply.

6. A tensioning apparatus comprising:

a shank member;

an annular member comprising an opening sized to receive the shank member with an interference fit;

a fluid passageway for delivering a pressure between the shank member and the annular member for expanding the opening to relax the interference fit;

a tensioner responsive to a pressure to apply a force to tension the shank member; and

a single pressure source fluidly connected to the fluid passageway and to the tensioner for tensioning the shank member with the interference fit relaxed.

7. The tensioning apparatus of claim 6, wherein the single pressure source further comprises:

a pump;

a first valve connected between the pump and the fluid passageway; and

a second valve connected between the pump and the tensioner.

8. The tensioning apparatus of claim 6, wherein the tensioner further comprises:

a piston disposed within a cylinder to define a pressure chamber;

a first of the piston and cylinder connected to the shank member for applying the force to tension the shank member and a second of the piston and cylinder connected to the annular member for applying a reaction force through the annular member.

9. A tensioning apparatus comprising:

a shank member;

an annular member comprising an opening sized to receive the shank member with an interference fit;

a means for expanding the opening to relax the interference fit; and

a means for applying a tensile force to the shank member and a reaction force equal in magnitude and opposed in direction to the tensile force to the annular member.

10. The tensioning apparatus of claim 9, further comprising a means for providing a single pressure to both the means for expanding and the means for applying a tensile force.

11. The tensioning apparatus of claim 10, wherein the means for providing a single pressure comprises:

a pump;

a first valve connected between the pump and the means for expanding; and

a second valve connected between the pump and the means for applying a tensile force.

12. The tensioning apparatus of claim 9, wherein the means for expanding further comprises:

a hole formed through the annular member from an outside surface to an inside surface defining the opening; and

a groove formed along the inside surface and in fluid communication with the hole.

13. The tensioning apparatus of claim 12, wherein the means for expanding further comprises:

a plurality of circumferential grooves formed along the inside surface; and

at least one axial groove formed along the inside surface interconnecting the circumferential grooves.

14. The tensioning apparatus of claim 9, wherein the means for expanding further comprises:

a hole formed along an axis of the shank member; and

a circumferential groove formed on an outside surface of the shank member in fluid communication with the hole.

15. A method of tensioning a shank member comprising:

providing an annular member having an opening receiving a shank member with an interference fit there between;

expanding the opening with a first pressure to relax the interference fit;

applying a second pressure to a tensioner to tension the shank member;

releasing the first pressure to reestablish the interference fit to retain the shank member tension when the second pressure is relaxed.

16. The method of claim 15, further comprising:

selecting the tensioner to apply a desired tension to the shank member at the first pressure; and

providing the first pressure and the second pressure from a single pressure source.

17. The method of claim 15, further comprising installing the tensioner to apply a tension force against the shank member and to apply a reaction force equal in magnitude and opposite in direction to the tension force to the annular member.

18. The method of claim 15, further comprising releasing the shank member tension by applying a third pressure to re-expand the opening to again relax the interference fit.