System for compensating heaving for an element hooked onto movable equipment

Patent metadata

Field	Value
Publication number	US-10214974-B2
Application number	US-201515520365-A
Country	US
Kind code	B2
Filing date	Aug 28, 2015
Priority date	Oct 20, 2014
Publication date	Feb 26, 2019
Grant date	Feb 26, 2019

Abstract

The present invention relates to a motion compensation system for an element hanging from a mobile unit, the system comprising two blocks, at least two articulated arms, a compensation cylinder and a cable. According to the invention, at least one characteristic length of the articulated system (for example: the length of a link or the distance between two sheaves of two articulated arms) is adjusted according to the motion to be compensated for.

First claim

The invention claimed is:

1. A motion compensation system for an element hanging from a mobile unit, said system comprising a first block and a second block for hanging said element, said first block being connected to said mobile unit by at least two articulated arms, each articulated arm comprising an idler sheave connected to said mobile unit, an intermediate sheave, a first link between said idler sheave and said intermediate sheave, and a second link between said intermediate sheave and said first block, said system comprising a cable fastened to retaining means and running through the idler sheave and the intermediate sheave of each of said articulated arms and through said first and second blocks, said system further comprising at least one compensation cylinder linked to said first block and to said mobile unit, and a means for adjusting at least one characteristic length of said articulated arms according to motion of said mobile unit, the at least one characteristic length is at least one of a horizontal distance between the axis of first block and the axis of idler sheave, a length of the first link or the second link, a vertical distance between a lower position of an axis of a sheave of the first block and the axis of the idler sheave.

2. The system as claimed in claim 1 , wherein said adjusted characteristic length is length that minimizes an error function defined by a formula of the form:

E
=

Fm
-
Fa

Fm

⁢

⁢
with

⁢

Fm
Q

=

1
+

[

sin
⁡

(

θ
+
φ

)

+

sin
⁡

(
β
)

-

sin
⁡

(

θ
+
σ
-
φ

)

sin
⁡

(

θ
-
φ

)

⁢

sin
⁡

(
θ
)

]

⁢

1
N

+

U
Q

⁢

a
⁢
nd

⁢

a
=

(

Q
+
U

)

⁢

V
0
γ

(

V
0

+

(

De
-

De
0

)

⁢
S

)

γ

,

with:
φ: angle between the axis of the first link and the horizontal,
θ: angle between the axis of the second link and the horizontal,
β: angle between the cable and the axis of the first link,
σ: angle between the cable and the axis of the second link,
Fm: mechanical force on the compensation cylinder,
Q: weight of the hanging element,
U: constant related to the design of the system, corresponding to the sum of the weight of the first block, of the compensation cylinder rocks and of the articulated arms,
Fa: pressure variation in the compensation cylinder,
De: compensation cylinder stroke, with De 0 the initial stroke,
V 0 : reference volume of the compensation cylinder,
N: number of sheaves,
S: section of an accumulator equipping said compensation cylinder,
Γ: gas constant,
E: error function.

3. The system as claimed in claim 1 , wherein said idler sheave is connected to said mobile unit by a controlled means of adjustable length.

4. The system as claimed in claim 1 , wherein at least one of said links comprises a hydraulic, pneumatic or electric cylinder controlled in position.

Assignees

• Ifp Energies Now

Inventors

• Mabile Claude

Classifications

• E21B19/09

  specially adapted for drilling underwater formations from a floating support using heave compensators supporting the drill string · CPC title

• B66C13/02 Primary

  Devices for facilitating retrieval of floating objects, e.g. for recovering crafts from water (handling live-boats B63B; salvaging, or hauling-out on slipways, waterborne vessels B63C; winding mechanism controls B66D1/52) · CPC title

• E21B19/002

  specially adapted for underwater drilling (E21B19/09, E21B19/143 take precedence) · CPC title

• B66D1/52

  for varying rope or cable tension, e.g. when recovering craft from water · CPC title

• B66C13/52

  Details of compartments for driving engines or motors or of operator's stands or cabins · CPC title