Heave compensation is motion compensator technology applied to minimizing the vertical movement of a load supported by lifting gear mounted on a heaving platform. Techniques include

active heave compensation Active heave compensation (AHC) is a technique used on lifting equipment to reduce the influence of waves upon offshore operations. AHC differs from Passive Heave Compensation by having a control system that actively tries to compensate for any m ...

and

passive heave compensation Passive heave compensation is a technique used to reduce the influence of waves upon lifting and drilling operations. A simple passive heave compensator (PHC) is a soft spring which utilizes spring isolation to reduce transmissibility to less th ...

—the two traditional types of heave compensation—as well as

balanced heave compensation Balanced heave compensation (BHC) is a heave compensation technology engaging the principle of a balanced-arm lamp for offshore Motion compensator, motion compensation. Working principle The technical working principle can be summarized as conve ...

. Devices that perform heave compensation are known as heave compensators.

Description

Heave compensation is move compensator technology used to minimize the movement of a load in one direction. This direction is often vertical, as for a load supported by lifting gear mounted on a heaving platform. In

offshore drilling Offshore drilling is a mechanical process where a wellbore is drilled below the seabed. It is typically carried out in order to explore for and subsequently extract petroleum that lies in rock formations beneath the seabed. Most commonly, the ter ...

, heave compensation is used to reduce the impact on the drill system from motions, including those of

waves United States Naval Reserve (Women's Reserve), better known as the WAVES (for Women Accepted for Volunteer Emergency Service), was the women's branch of the United States Naval Reserve during World War II. It was established on July 21, 1942, ...

and the vessel.

Types

There are two traditional basic types of heave compensation are

and

Balanced heave compensation Balanced heave compensation (BHC) is a heave compensation technology engaging the principle of a balanced-arm lamp for offshore Motion compensator, motion compensation. Working principle The technical working principle can be summarized as conve ...

is also used, and differs from the two traditional approaches.

Active heave compensation

Active heave compensation Active heave compensation (AHC) is a technique used on lifting equipment to reduce the influence of waves upon offshore operations. AHC differs from Passive Heave Compensation by having a control system that actively tries to compensate for any m ...

has a control system that uses power to drive the lifting gear to keep the load stabilized along the vertical axis to compensate for any movement of the platform specific point, using power to gain positional accuracy.

Passive heave compensation

Passive heave compensation Passive heave compensation is a technique used to reduce the influence of waves upon lifting and drilling operations. A simple passive heave compensator (PHC) is a soft spring which utilizes spring isolation to reduce transmissibility to less th ...

uses a relatively soft spring which isolates the load from most of the vertical force variation to reduce transmissibility of transient loads.

Balanced heave compensation

converts the non-linear force of a gas spring or hydro-pneumatic spring into an adjustable, substantially linear force supporting the load.

Compensators

A ''heave compensator'' is a kind of motion compensator. Whereas most motion compensators will compensate for movement in all directions, the heave compensator will compensate for movement in only one direction, for instance, for vertical movement. In practice, the words ''motion compensator'' and ''heave compensator'' are used interchangeably. Sensor technologies being used are inertial sensors and GNSS (example: iMAR Navigation) or image processing. The simplest motion compensator is the

anchor An anchor is a device, normally made of metal, used to secure a vessel to the bed of a body of water to prevent the craft from drifting due to wind or current. The word derives from Latin ', which itself comes from the Greek (). Anch ...

chain of a

ship A ship is a large watercraft, vessel that travels the world's oceans and other Waterway, navigable waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research and fishing. Ships are generally disti ...

. Not only does the anchor prevent the ship from drifting, but the chain itself dampens the movement of the ship due to undulating motion of the waves. Generally, motion compensators are implemented as springs. For very large forces (dozens to hundreds of tonnes), the springs are implemented as gas springs:

hydropneumatic Hydropneumatic devices (or hydro-pneumatic devices) are systems that operate using water and gas. The devices are used in various applications. Description A hydropneumatic device is a tool that functions by using water and gas. ''Hydropneumati ...

devices — a plunger cylinder buffered by a volume of gas. Examples of heave compensators include: *

Drill string compensator A drill string compensator decreases the influence of the heave of a drilling vessel on the drill bit. Drill string compensators are also known under the more general name: heave compensator. Drill string compensators are used onboard drill ships ...

s * Riser tensioners * Conductor tensioners * Guideline tensioners More advanced heave compensated systems are often specified as systems with

or combinations of these. A new approach to advanced heave compensation systems is offered by

, increasing safety while lowering energy consumption and spring adjustment times.

References

{{reflist Mechanisms (engineering)