HAZID and HAZOP for LNG are two important methods used in the oil and gas industry to identify potential hazards and analyze the operability of processes. For LNG bunkering operations, conducting HAZID and HAZOP studies can help identify risks and ensure safety measures are in place to prevent accidents.
These studies involve examining each step of the bunkering process to identify potential hazards, analyzing the consequences of these hazards, and proposing measures to mitigate the risks.
HAZID for LNG bunkering
It is important to involve a team of experts and stakeholders in these studies to ensure a comprehensive analysis and identification of potential hazards in LNG bunkering operations.
Objectives
The principal objectives of the HAZID should identify:
- hazards and how they can be realised (i. e. the accident scenarios);
- the consequences that may result;
- existing measures/safeguards that minimise leaks, ignition and potential consequences, and maximise spill containment;
- and recommendations to eliminate or minimise risks.
Scope
As a minimum the HAZID should include the scope as described in Bunkering risk on Liquefied natural gas ships assessment and safety zones“LNG bunkering risk assessment and hazard classification”. It may be complemented with an HAZOP (Hazard and Operability) assessment after all safeguards have been implemented.
Process
The HAZID process should be carried out in accordance with a recognised process using appropriately experienced subject matter experts. It is recommended that professional guidance is sought to ensure that the process is carried out to an adequate and appropriate level of detail.
The outcomes of the HAZID include hazard rankings and recommendations for additional safeguards and analysis. This may include detailed analysis or studies to establish that the measure in place meet the acceptance criteria agreed by the Administration.
Technique
To facilitate the HAZID process, the bunkering process may be divided into smaller steps each of which are then addressed systematically.
It is recommended that the following list is used to structure the HAZID exercise for LNG bunkering:
- preparation (compatibility, testing, mooring);
- connection;
- inerting of relevant pipe sections;
- cooling down;
- transfer start;
- transfer at nominal flow;
- transfer stop including topping-up;
- draining & purging;
- inerting;
- disconnection;
- commissioning;
- security.
Guidewords
To guide and help the HAZID workshop process, the following guidewords may be used:
| Leakage | Loss of containment (piping, valves) |
| Rupture | Cryogenic leaks (minor, major) |
| Corrosion | Hose damage |
| Impact | Hose rupture |
| Fire/Explosion | Major structural damage |
| Structural integrity | Gas leak |
| Mechanical failure | Gas dispersion |
| Control/electrical failure | Gas in air intake |
| Human error | Potential fire & explosion |
| Manufacturing defects | Cooling down operation wrong |
| Material selection | Excessive transfer rate |
| Flange or connector failure | Hydraulic Power Unit failure |
| BOG management during bunkering | Communication failure |
| Control failure | Black out |
| ESD valves control failure | Relative motions of vessels |
| ERC actuator failure | SIMOPS |
| ERC spring failure causing not closing | Unexpected venting |
| Harsh weather |
HAZOP for LNG bunkering operations
Definition
The HAZOP study is a structured and methodical examination of a planned process or operation in order to identify causes and consequences from a deviation to ensure the ability of equipment to perform in accordance with the design intent.
Read also: Equipment and cargo system of LNG onshore terminals
It aims to ensure that appropriate safeguards are in place to help prevent accidents. Guidewords are used in combination with process conditions to systematically consider all credible deviations from normal conditions.
Process
The HAZOP should be realised with a focus on the LNG bunkering, storage and delivery to the engines. The operational modes for the receiving ship to be considered are:
- start-up;
- normal Operations;
- normal Shutdown;
- and Emergency Shutdown.
Scope
The HAZOP should review the following cases but not limited to:
- joining together of the emergency shutdown systems of the Bunkering Facility, Receiving Ship and transfer system;
- emergency procedures in the event of abnormal operations;
- leakage from hoses;
- overpressure of the containment system;
- emergency unmooring;
- emergency venting of LNG or vapour;
- additional protection for the ship’s hull in case of fuel leakage in way of the manifolds;
- emergency shut down and quick release protocol;
- requirements for outside assistance such as tugs;
- loss of power.
The following should be analysed:
- connection;
- inerting of relevant pipe sections;
- cooling down;
- transfer start;
- transfer at nominal flow;
- transfer stop including topping-up;
- draining;
- inerting;
- disconnection;
- fatigue, stress and human errors.
It is recommended that emergency disconnection at the receiving ship’s manifold should be addressed by the Risk Assessment in the Liquefied Natural Gas Bunkering Operations, Hazard Identificationbunkering operations risk assessment in order for any potential impact of the system within the receiving ship’s bunker station lay-out to be identified and additional mitigation or support utilities to be incorporated as appropriate.
Both HAZID and HAZOP processes will produce a list of recommendations and an action plan. These action plans will address each recommendation developed and provides a means for tracking the hazards for assessment and implementation.