Dog-type lockout and position indicator assembly

1. A drilling riser tensioner ring assembly, comprising:

an annular tensioner ring body having a central opening for receiving a tubular riser component and an outer surface having an outer cylindrical portion concentric with the central ring;

a plurality of bores integrally formed in the tensioner ring body, each of the bores extending radially through the tensioner ring body from the central opening to the outer surface relative to an axis of the central opening;

a plurality of hydraulic passages within the tensioner ring body, each of the hydraulic passages extending to one of the bores for delivering hydraulic fluid pressure to the bore;

a plurality of actuators, each of the actuators having a piston with a seal mounted thereto and carried within a respective one of the bores, the pistons being movable in response to fluid pressure applied to the bores via the hydraulic passages between an outer disengaged position and an inner engaged position in engagement with the riser component;

a plurality of lockdown supports, each of the lockdown supports being mounted in a fixed position to the outer surface of the tensioner ring body radially outward from a respective one of the pistons, relative to the axis; and

a plurality of lockdown members, each mounted to a respective one of the lockdown supports radially outward from a respective one of the pistons, each of the lockdown members being movable between retracted and extended positions relative to a respective one of the lockdown supports, such that movement of each of the lockdown members to the extended position while a respective one of the pistons is in the engaged position causes the lockdown member to abut an outer end of the piston and prevent the piston from moving to the disengaged member to abut an outer end of the piston and prevent the piston from moving to the disengaged position, wherein the piston is movable between the engaged and disengaged positions while the lockdown member is in the retracted position.

2. The assembly according to claim 1 , wherein:

each of the lockdown supports has a lockdown opening through which one of the lockdown members extends, each of the lockdown openings being threaded; and

each of the lockdown members is threaded so that rotation of the lockdown member moves the lockdown member between the retracted and extended positions.

3. The assembly according to claim 1 , further comprising:

a position indicator mounted to each of the pistons for movement therewith; and

each of the position indicators has an outer end extending through an aperture in a respective one of the lockdown supports.

4. The assembly according to claim 3 , further comprising:

a collar mounted to each of the pistons; and

wherein each of the position indicators is mounted to a respective one of the collars.

5. The assembly according to claim 1 , wherein each of the lockdown supports comprises a cap having a cylindrical sidewall secured to the outer surface of the tensioner ring body and a base in alignment with and spaced radially outward from a respective one of the pistons.

6. A drilling riser tensioner ring assembly, comprising:

an tensioner ring body having a central opening with an opening axis and an outer surface with a cylindrical portion concentric with the central opening;

a tubular riser component that lands within the central opening;

a plurality of bores integrally formed in the tensioner ring body, spaced around the central opening, and extending radially from the central opening to the outer surface of the tensioner ring body;

a piston carried within each of the bores, each of the pistons having a dog on an inner end for engaging the riser component, each of the pistons being movable along a bore axis between inner and outer positions in response to fluid pressure applied to the bore containing the piston;

a plurality of lockdown supports, each having a flat base mounted in a fixed position to the outer surface of the tensioner ring body radially outward from a respective one of the pistons relative to the bore axis, the base having a aperture;

a plurality of lockdown members, each extending through a respective one of the apertures radially outward of a respective one of the pistons, each lockdown member being manually movable from a retraced position to an extended position relative to the base, each of lockdown members having an inner position and the lockdown member in its extended position, each of t he pistons being freely movable in response to fluid pressure in the bore while a respective one of the lockdown members is in the retracted position; and

a position indicator coupled to each of the pistons for movement therewith and extending alongside a respective one of the lockdown members to indicate the position of each of the pistons.

7. The assembly according to claim 6 , wherein each of the apertures comprises a threaded hole that receives a respective one of the lockdown members in threaded engagement.

8. The assembly according to claim 6 , wherein:

each of the lockdown members is located on the bore axis of a respective one of the bores; and

each of the position indicators is located alongside and parallel with a respective one of the bore axes.

9. The assembly according to claim 8 , wherein each of the position indicators protrudes through a hole in a respective one of the bases.

10. The assembly according to claim 6 , further comprising:

a collar mounted to each of the pistons; and

wherein each of the position indicators is mounted to a respective one of the collars alongside the bore axis.

11. The assembly according to claim 6 , wherein the bores further comprise a plurality of upper bores and a plurality of lower bores.

12. The assembly according to claim 6 , wherein the tensioner ring assembly further comprises a plurality of eyelets adapted for receiving a cable.

13. A drilling riser tensioner ring assembly, comprising:

an annular tensioner ring body having a central opening for receiving a tubular riser component and an outer surface with a cylindrical portion concentric with the central opening;

a plurality of bores integrally formed in the tensioner ring body, each of the bores extending radially through the tensioner ring body from the central opening to the outer surface relative to an axis of the central opening;

a plurality of hydraulic passages within the tensioner ring body, each of the hydraulic passages extending to one of the bores;

a plurality of pistons, each of the pistons carried within one of the bores and being movable in response to fluid pressure applied to the hydraulic passages between an outer disengaged position and an inner engaged position with the riser component;

a plurality of lockdown assemblies for selectively securing the pistons in the engaged position, each of the lockdown assemblies comprising:

a lockdown support mounted in a fixed position to the outer surface of the tensioner ring body and having a base with a threaded aperture radially outward from one of the pistons, relative to the axis; and

a lockdown screw secured to the threaded aperture and being movable by rotation between an extended position with an inner end in abutment with an outer end of a respective one of the pistons and a retracted position with the inner end spaced radially outward from the outer end of the respective one of the pistons.