WO1991000236A1 - Method for compensating movement and force variations of a subsea load hanging from a floating vessel - Google Patents

Method for compensating movement and force variations of a subsea load hanging from a floating vessel Download PDF

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Publication number
WO1991000236A1
WO1991000236A1 PCT/FI1990/000161 FI9000161W WO9100236A1 WO 1991000236 A1 WO1991000236 A1 WO 1991000236A1 FI 9000161 W FI9000161 W FI 9000161W WO 9100236 A1 WO9100236 A1 WO 9100236A1
Authority
WO
WIPO (PCT)
Prior art keywords
subsea
lifting force
heave compensation
floating vessel
passive
Prior art date
Application number
PCT/FI1990/000161
Other languages
French (fr)
Inventor
Pertti Pale
Knut Hansen
Original Assignee
Rauma-Repola Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rauma-Repola Oy filed Critical Rauma-Repola Oy
Publication of WO1991000236A1 publication Critical patent/WO1991000236A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C13/00—Other constructional features or details
    • B66C13/02—Devices for facilitating retrieval of floating objects, e.g. for recovering crafts from water

Definitions

  • This invention relates to a method for compensating movements or force variations by means of a passive pneumo- hydraulic heave compensation system when carrying a subsea load hanging from a floating vessel subject to movement caused by waves.
  • Passive heave compensation using passive springs
  • Active heave compensation using measurements, feed backs and operating units
  • a limitation of the passive heave compensation is that due to friction and hysteresis in hydraulic systems, the load to mass ratio has to be rather low.
  • heave compensation of a diving bell is effective with a passive system as the load may be some 20 kN and the mass may be some 6 tons.
  • heave compensation of a valve unit of 6 tons weighing in water 50 kN does not work with a hydraulic passive heave compensation system.
  • the method according to this invention is characterized in that in order to reduce the hysteresis of the compensation system, the subsea mass is lightened by adding a constant lifting force to the subsea mass.
  • the lightening of the load of the subsea mass can be done as follows : 1) by addition of buoyancy to the subsea load, e.g. air bag or air tank or floating material
  • the lightening is carried out with a constant lifting force.
  • the constant lifting force should be at least 15 % of the original subsea load to gain a good compensation capability of the total system (passive heave compensation plus constant lifting force).

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Jib Cranes (AREA)

Abstract

A method for compensating movements or force variations by means of a passive pneumo-hydraulic heave compensation system when carrying a subsea load hanging from a floating vessel subject to movement caused by waves. In order to reduce the hysteresis of the compensation system, the subsea mass is lightened by adding a constant lifting force to the subsea mass.

Description

Method for compensating movement and force variations of a subsea load hanging from a floating vessel
This invention relates to a method for compensating movements or force variations by means of a passive pneumo- hydraulic heave compensation system when carrying a subsea load hanging from a floating vessel subject to movement caused by waves.
There are three well known methods to compensate movement or force variations of subsea loads hanging from floating vessels:
Passive heave compensation (using passive springs) Active heave compensation (using measurements, feed backs and operating units)
Load compensation and telescopic joints when the load is supported from the sea floor.
A limitation of the passive heave compensation is that due to friction and hysteresis in hydraulic systems, the load to mass ratio has to be rather low. E.g. heave compensation of a diving bell is effective with a passive system as the load may be some 20 kN and the mass may be some 6 tons. But heave compensation of a valve unit of 6 tons weighing in water 50 kN does not work with a hydraulic passive heave compensation system.
This invention introduces a method for the purpose of utilizing passive heave compensation in the case when the subsea load hanging from a floating vessel is heavy in relation to its mass, i.e. the load to mass ratio is some 0.8 g (g = 9.8 m/s2) .
The method according to this invention is characterized in that in order to reduce the hysteresis of the compensation system, the subsea mass is lightened by adding a constant lifting force to the subsea mass.
The lightening of the load of the subsea mass can be done as follows : 1) by addition of buoyancy to the subsea load, e.g. air bag or air tank or floating material
2) or by small active heave compensation in parallel with the passive heave compensation system. In both cases the lightening is carried out with a constant lifting force. In practice the constant lifting force should be at least 15 % of the original subsea load to gain a good compensation capability of the total system (passive heave compensation plus constant lifting force).

Claims

1. A method for compensating movements or force varia¬ tions by means of a passive pneumo-hydraulic heave compensation system when carrying a subsea load hanging from a floating vessel subject to movement caused by waves c h a r a c t e r i z e d in that in order to reduce the hysteresis of the compensation system, the subsea mass is lightened by adding a constant lifting force to the subsea mass .
2. A method according to claim 1, c h a r a c t e r ¬ i z e d in that the constant lifting force is obtained by adding buoyancy to the subsea load.
3. A method according to claim 2, c h a r a c t e r ¬ i z e d in that the buoyancy is added by at least one of the following: gas bag, gas tank or floating material.
4. A method according to claim 1, c h a r a c t e r ¬ i z e d in that the constant lifting force is obtained by using active- heave compensation in parallel with the passive heave compensation system.
5. A method according to any of claims 1 to 4, c h a r ¬ a c t e r i z e d in that, the lightening is carried out by a constant lifting force of at least 15 % of the original subsea load.
PCT/FI1990/000161 1989-06-28 1990-06-18 Method for compensating movement and force variations of a subsea load hanging from a floating vessel WO1991000236A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI893145 1989-06-28
FI893145A FI893145A (en) 1989-06-28 1989-06-28 FOERFARANDE OCH ANORDNING FOER FLYTTNING AV ETT UNDER VATTENYTAN BEFINTLIGT LASS.

Publications (1)

Publication Number Publication Date
WO1991000236A1 true WO1991000236A1 (en) 1991-01-10

Family

ID=8528679

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI1990/000161 WO1991000236A1 (en) 1989-06-28 1990-06-18 Method for compensating movement and force variations of a subsea load hanging from a floating vessel

Country Status (2)

Country Link
FI (1) FI893145A (en)
WO (1) WO1991000236A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8297597B2 (en) 2007-09-19 2012-10-30 National Oilwell Varco Norway As Method for lift compensation

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3359741A (en) * 1966-03-11 1967-12-26 Arthur J Nelson Deep water support system
DE1506784A1 (en) * 1967-05-03 1970-04-02 Draegerwerk Ag Diving bell
WO1983003815A1 (en) * 1982-04-29 1983-11-10 Zf-Herion-Systemtechnik Loading device for loads movable with respect to a water body
EP0228050A2 (en) * 1985-12-28 1987-07-08 Menck Gmbh Compensation device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3359741A (en) * 1966-03-11 1967-12-26 Arthur J Nelson Deep water support system
DE1506784A1 (en) * 1967-05-03 1970-04-02 Draegerwerk Ag Diving bell
WO1983003815A1 (en) * 1982-04-29 1983-11-10 Zf-Herion-Systemtechnik Loading device for loads movable with respect to a water body
EP0228050A2 (en) * 1985-12-28 1987-07-08 Menck Gmbh Compensation device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8297597B2 (en) 2007-09-19 2012-10-30 National Oilwell Varco Norway As Method for lift compensation
NO336258B1 (en) * 2007-09-19 2015-07-06 Nat Oilwell Varco Norway As Method and device for lift compensation.

Also Published As

Publication number Publication date
FI893145A0 (en) 1989-06-28
FI893145A (en) 1990-12-29

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