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SIGTTO cargo-handling guidance for the ship/shore interface

Fri 09 Mar 2018 by Mike Corkhill

SIGTTO cargo-handling guidance for the ship/shore interface
SIGTTO’s new manifold document covers LNG bunkering for the first time

The Society of International Gas Tanker and Terminal Operators (SIGTTO) is publishing three sets of guidelines early in 2018 that focus on equipment and operations that come into play when a gas carrier is berthed at a terminal and cargo is being pumped between ship and shore. 

The first deals with ship manifolds; the second provides guidance on how to avoid the generation of excessive surge pressures when emergency shutdown (ESD) systems are activated; while the third features safe working practice guidelines for ships and terminals handling LPG and chemical gases. 

The Second Edition of Recommendations for Liquefied Gas Carrier Manifolds is a joint SIGTTO/Oil Companies International Marine Forum (OCIMF) publication. The document, which updates the 2011 edition, provides recommendations on the layout, strength and fittings for gas carrier manifolds. 

With the new edition, SIGTTO and OCIMF have sought to bring together in one document the manifold arrangements and cargo strainer guidelines for LPG and LNG carriers in order to promote improved standards of safety and efficiency in ship operations. Shore compatibility is an essential element of safe operations and the new guidance will also assist in planning the position of loading and discharging facilities on new jetties.

Among the key changes in the latest version of the manifold publication are: 

  • New sections covering small-scale LNG.
  • The bunkering manifold provisions have been extended to include LNG bunkering as an option. 
  • A new approach to laying down the recommendations on manifold design is introduced through the specification of the pipe schedule (denoting the wall thickness of the pipework); allowable loads on manifold support arrangements; minimum mechanical properties of material used; and the pressure rating of flange reducers and spool pieces.
  • Clarified presentation flange dimensions and face finish to conform to the ASME B 16.5 standard. 

The new Guidelines for the Alleviation of Excessive Surge Pressures on ESD for Liquefied Gas Transfer Systems publication has been prepared by SIGTTO to assist relevant ship and shore staff in avoiding the generation of excessive surge pressures and momentum change in cargo transfer systems on activation of ESD devices or other events. The document’s description of the generation of surge pressures features both a high-level overview and a more detailed technical explanation so that it is applicable to surge experts and novices alike. 

The publication’s practical guidance and recommendations are aimed specifically at personnel with responsibilities for gas carrier and terminal loading and unloading systems. They have been developed to assist in achieving the following goals:

  • Recognise the potential hazards of surge pressure.
  • Understand the factors that affect or create surge pressures.
  • Review the engineering and operating procedures of the cargo transfer system.
  • Understand aspects of surge pressure control on the other side of the ship/shore interface to enable mutual understanding of safe transfer procedures.
  • Understand the potential benefits of a linked ship/shore ESD system in mitigating surge pressures.

The first edition of the Ship/Shore Interface for LPG/Chemical Gas Carriers and Terminals guidance document recognises the technological advances that have been made over the past two decades and supersedes a 1997 SIGTTO publication entitled Ship/Shore Safe Working Practice for LPG and Chemical Gas Cargoes, which is now withdrawn.

SIGTTO has prepared this document to identify the potential hazards that can arise at the LPG/chemical gas ship/shore interface; to provide safe working practice guidelines through reference to industry publications; to minimise the risk of incidents occurring; and to help raise overall safety awareness at the interface. 

The publication describes risk assessment and hazard identification techniques that can be used by gas carrier staff and terminal operators.

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