Quick Release Hooks—Safer Operation for Remote Release Systems Industry Best Practice

Remote Release consule An accident at a major LNG terminal in South Korea recently occurred where all mooring lines were unintentionally released by the jetty's Remote Release / Quick Release Hook System, allowing the vessel to drift off from the jetty.

Remote Release is not a passive system and the accidental release of quick release hooks, and thereby the vessel itself, can lead to very serious consequences.

The purpose of this article is to highlight concerns surrounding the inadequate specification of remote release systems, and the safe guards that should be considered to ensure safe and secure operation.

Currently, remote release systems are offered by most quick release hook vendor regardless of their experience or technical qualifications in providing a proven and safe system. This is primarily because there are no existing international regulations or specifications governing the design of remote release systems fitted to quick release hooks. The views presented in this article, provide the most up to date best practice which should be incorporated into any new terminal or upgrade of an existing terminal.

Ten years ago, 1 in 10 jetties had remote release installed as part of the quick release hook mooring package. Today, typically 4 out 5 oil/gas jetties being built or refurbished have remote release specified with the quick release hooks.

The fact is that more often than not, typical specifications for remote release of hooks only describe the system's function; they do not address the basic safety requirements and operational protocols within the design to ensure a Safe and best practice terminal operation. Remote Release vendors can therefore provide a system that appears to fit the operating criteria, however in the author's experience, safety aspects covering accidental release can be over-looked if the performance requirement for safety is not specified, or if there is inadequate understanding of the possible causes for uncontrolled release in daily operational requirements.

Many of the remote release systems currently available utilize very simple control logic to allow release immediately upon the release command being given from a remote panel, and without having safety interlocks in place to prevent accidental or unintentional release. The lack of status indication and fault indication can also lure the operator into making the wrong release decision.

Other systems which use digital communications as the only means to instigate and monitor the release operation could, in some circumstances, trigger a hook release.

Neither of the above commonly used design methods provide adequate safeguards for best practice Safe operation and therefore prevention of a release under a fault condition or from other possible induced effects on the control system.

Overview of Function Requirements

Quick Release Hooks are often fitted with a Remote Release control system incorporating a remote operations panel located at the jetty head or in the Marine Control Room on shore. It's basic function is to provide the facility to remotely release vessel mooring lines from the quick release hook mooring points on the berth.

There are a number of features commonly specified for the Remote Release System that may include some or all of the following requirements:

Individual release for each hook.
Release all hooks simultaneously, commonly referred to as Emergency Release.
Status indication for system pressure for electro hydraulic systems.
Imminent Release audible/visible alarm warning at a number of locations on the jetty.
Capability to release the hook from zero to full Safe Working Load.
Provide release operation under power failure or Blackout Condition.
Release hooks either from the remote panel or locally at each hook base.
Interlock to prevent the Operator from accidentally or inadvertently releasing hooks.
ESD (Emergency Shut Down) implemented Emergency Release of all hooks.
Remote Release panel installed off the jetty.
Manual hook release override over the Remote Release System.

Quick release hooks on site The following sections of this article discuss these functional requirements and the design considerations necessary to provide best practice safe operation for electric or electro hydraulic based systems that may use conventional a release console or virtual release panel.

Individual Release

The operator should have the ability to release each hook individually from the remote panel and for release requests to be held in que and in the sequence that the release buttons are pressed.

Hook release is an intentional procedure, which must have the permission of the mooring master in co-operation with the vessel. Under normal operating procedures, the vessel will have relieved the mooring line tension just prior to release taking place.

The vessel crew must be prepared to quickly haul in and stow the lines as they are released from the hooks.

Release All Hooks

The functionality to provide Simultaneous Release or Emergency Release from the remote release panel is often specified, however the consequences of releasing all lines simultaneously is not always recognized.

Over the past 3 years we have heard overwhelming concerns raised by some experienced and learned jetty Owners, Operators and vessel Masters that this feature should not be provided at the remote release panel as it is highly dangerous to personnel and can be detrimental to achieving the intended quick getaway of the vessel in an emergency situation, for the following reasons:

There is no time for vessel crew to haul in mooring lines thereby creating the hazard of the mooring lines fouling the vessel's propeller and shaft.
Mooring lines that are under considerable tension and released without warning can recoil violently, having the potential to cause serious injury to personnel either on the jetty or on board the vessel.

Status indication of each hook (Locked or Released)

Both hardwired and virtual consoles should provide individual status indication for each hooks clearly indicating whether hook is Released, Locked, Release in Progress, Release Failed or Fault Condition. This is best practice and essential to insure that Operators without visual contact have clear feedback as to the status of each hook prior to, during and after release has been achieved.

Imminent Warning of Release

In order to warn personnel on the jetty head, dolphins and on board the vessel of the imminent release of lines, several visible and audible warning stations should be installed around the jetty at strategic locations such as the loading platform and entrance to catwalk access ways.

The warning should be automatically activated once the Release Enable (or Release Arm) remote panel switch is activated.

Capacity to Release Hooks

The Remote Release Actuating System must be designed and tested to be capable of exerting sufficient mechanical force on the release mechanism of each hook to release the lines from zero to full Safe Working Load of the hook. Specifications should ensure products comply with this requirement. If systems are assembled by inexperienced vendors this simple but essential check may well have been overlooked.

Release Hooks in Blackout

To operate in a blackout condition an Electric Release System should be powered by a UPS (Uninterruptible Power Supply). In the case of Electro hydraulic Systems the mechanical energy should be provided by an accumulator and a UPS is needed to power the control system.

It is often cost prohibitive in Electromagnetic Solenoid based systems to provide blackout release as the UPS peak energy demand can be as high as 40Kw for a 20 hook system. Electric systems, using geared actuators to develop the release force require only around one tenth of this.

Local Release Operation for Hooks

Some operators prefer a local push button at the hook unit. To prevent inadvertent release, local release operation should be isolated at the remote panel. Best Practice dictates local release operating buttons should be located in a position that allows the operator protection against injury whilst commanding the release.

Interlock or Prevention of Accidental / Inadvertent Release

An extremely important design requirement for best practice is that the system should incorporate safety interlocks and control measures to prevent accidental, inadvertent or uncontrolled release. A failure of either the Remote Panel electronics or any part of the remote release control system should not be able to cause an unintended release of hooks.

ESD (Emergency Shut Down) Instigated Release of Hooks

It is sometimes specified to include a plant linked "Release All" mooring lines function. This presents many operational safety issues unique to the marine environment. It is often confused with the primary intention of ESD to shutdown equipment in an emergency. As stated earlier, release of mooring lines under load can be dangerous. For safety, the vessel and jetty personnel must be aware of this intention prior to release. When interconnecting the remote release system to the plant or Vessel ESD system, the client must consider the safety implications and consequences.

The ESD system should provide a set of normally open contacts which are closed in an ESD situation. This is inverse to the traditional closed loop found in most ESD systems, It is not satisfactory to have a system where a system fault or field wiring failure could open the loop and therefore release all the mooring lines!

Best practice systems provide an extra level of safety by an independent interlock circuit which is in addition to the release control system. This "Release Enable" isolates the output of the release controller at the mooring hook, therefore preventing the control system from outputting signals unless the "Release Enable" is independently asserted.

These new release controllers have automatic diagnostic functions which check the status of all inputs and outputs.

Remote Release Panel Location

Increasingly specifications require the Release Panel to be located into the Marine Terminal Building which may be hundreds of meter from the jetty. Ideally the remote Release Panel should be located at the jetty to provide the Operator with a high degree of visual contact with mooring crews, vessel lines and hooks.

If necessary a second Remote Panel can be installed at the Marine Terminal Building. In this arrangement interlocks over release operation should be provided between the panels to ensure that one or the other is in control of release operation. Status of hooks Locked or Released may be displayed at both locations.

Fully Manual Release of Quick Release Hooks

In addition to the remote control of the hooks, the quick release hook itself should be able to be manually released up to it's Safe Working Load without power, and independently of it's release system.

Industry Best Practice

The safety of operators and vessel crew is paramount and must be a key consideration and given the highest priority when addressing specifications for Remote Release Systems.

The authors have been involved in the design and implementation of Mooring Systems including Remote Release over the last 25 years. We consider the specification considerations discussed above to be Industry Best Practice and should be high on the priority list of all parties concerned with the mooring and monitoring of Oil and Gas Vessels.

The critical considerations highlighted and summarised in Table 1 have been tried and tested and so far been welcomed by responsible clients.

Table 1: Best Practice Safety Features for Remote Release Systems
Provide an audible visible "Imminent Release" warning at a number of locations on the jetty.
Incorporate CCTV of remote hook locations to allow remote operators to ensure it is safe to release lines
Release Lines with the co-operation of the Vessel by incorporating communications within the terminal operating procedures.
Control system to: Report hook locked, released, release in progress, release failure and fault conditions. Include self diagnostic functions Incorporate cyclic redundancy checking of transmitted data Incorporate a time dependency between the 'release activate' signal and the release commands sent via the communications system to reduce risk of a false release command.
Incorporate a separate "Release Enable" interlock / isolator separate circuit from the control system to isolate output of controllers at the hook units.
At the Quick Release Hook Provide a mechanical override to release a hook in the event of a control system failure Isolate the Hook's local release button by the separate release enable system. Ensure Hook is designed and tested with a release mechanism and release control system that can release the hook from Zero to its full Safe Working load.
Do Not link the Remote Release system to the Terminal or Ship or ESD system without a thorough understanding of the operational consequences.

Tom Toth, Technical Director at HME, has a degree in civil engineering and over 25 years experience in the marine field. He is responsible for the company's technical management and product development.

Alistair Traylen is HME's Instrumentation Director, overseeing innovation and design of electronic monitoring systems.

Harbour & Marine (HME) was established in 1971 in Melbourne and is a leading designer and supplier of mooring and monitoring systems to the oil and gas marine industry worldwide. The company has supplkied equipment to approximately 75% of LNG terminals (excl. Japan) over the past 3 years and specialises in the design of integrated jetty mooring systems drawing on both a strong mechanical and instrumentation in-house resource.

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