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As the design of the SSTS has matured, it was deemed that option 3 met the requirements of the URD/SRD and safety targets better than the other two options. A detailed safety risk assessment has now been carried out on the selected design option.

The SSTS will be built to recognised safety standards and in compliance with relevant legislation. The system has been designed in accordance with recognised good practice. A cost benefit analysis has been carried out to demonstrate that the implementation of the design changes constitutes an ALARP and tolerable position. It is recommended that all design changes are implemented by the DO.

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The main hazards associated with the system are overpressure, oil and gas leakage and noise. This risk is further increased by frequent control system failures leading to remotely operated valves opening inadvertently. In order to mitigate this to a tolerable level specific operating procedures must be followed, these include:

Enhanced (24/7) valve inspection.

Spill kits positioned at appropriate locations.

Control room manned 24/7.

Regular rehearsal of emergency procedures.

When SSTS subsystems are being maintained, the control system shall be disconnected from any automatic valves into the subsystem.

PPE required when working around the SSTS system, including: Goggles, Gloves, Safety Shoes, Overalls, Helmet.

All incidents should be reported to the DT for monitoring and tracking.

The use of appropriate PPE will mitigate risks to health from noise. Other hazards are addressed in contingency procedures. The normal operating pressure of the system is 20bar, with safety measures to prevent overpressure. The system can be isolated, manually or electrically, in the event of overpressure. Operating and maintenance procedures will be developed.

1. A description of the operational envelopes;

2. Any limitations on use or operational capability;

3. The main areas of risk e.g. Class A/B risks;

4. Relevant information that can assist the operator in balancing the operational imperative against safety risk;

5. Demonstration that operating and maintenance procedures and publications have been, or will be, developed.

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5.0 Emergency / Contingency Arrangements

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5.0 Emergency / Contingency Arrangements

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With risks identified within the SSTS hazard log, the following Emergency / Contingency Arrangements would be required to be established:

Fire fighting emergency procedures.

Evacuation procedures (Lifeboats).

MARPOL spillage recovery procedures.

Gas leak repair procedures.

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4.1 Oil SSTS Safety Requirements –

Meet requirements of DSA01.

Meet HSE Requirements.

MOD Certification requirements (DSA)

Safety related standards to be applied e.g. British Standards, Defence Standards, International Standards or overseas standards.

Meet all relevant DEFSTAN requirements

The user must be provided with a measurement of oil quantity offloaded to the tanker

The user must be able to monitor the quality of the crude oil

The user must be able to control the amount of oil in storage

Pump oil at compatible pressures when interfacing with tankers

The system shall provide for safe & environmentally compliant disposal of non oil product (Gas and Water)

The system shall be able to be isolated from the well head within 10 seconds

The system shall be able to be isolated from the tanker within 10 seconds

To be able to pump oil from storage/SSTS to tanker at required pressure safely. (<20bar>8bar)

The Target Safety Objective for the project shall be <1E-6 catastrophic repercussions per year

4.2 Key Hazards –

Flammable substances leading to fire/explosion and burn injuries

Asphyxiants

Exhaust gases, leading to respiratory illness and/or burns

Rotating machinery/hydraulic arms leading to personnel injury or death

Arcing/sparking of electrical equipment leading to explosion

Overfilling of the storage tank and overfilling and/or overpressure of tanker leading to fuel spillage/MARPOL incident.

Machinery failure (separation system) leading to lack of available water for fire suppression systems (see assumptions).

Oil Leaks leading to fire/explosion

System operating noise

4.3 Risk Management Actions

Implement an inerting system.

Replace butterfly valve with shutoff ball valve with higher rating.

Ensure design has a gas detection system in working areas.
Ensure design routes pipework away from working areas.

Prevent oil spread if tank is damaged. Procure strong tank (double skin).

Design org is responsible for implementing the above.

4.4 Residual Safety Risk

Ignition of flammable substances - Class C

Pressure systems  - Class B (Raised to B following inadvertent valve opening issue, discussed at 4.5)

Asphyxiants - Class D

System operating noise - Class C

Oil Leak - Class B (Raised to B following inadvertent valve opening issue, discussed at 4.5)

4.5 Issues of Note

Following Manufacturing Tests and Trials it has been identified that the Oil SSTS control system fails with a higher than expected frequency, which has resulted in an intolerable safety risk that remotely operable valves could open inadvertently, inadvertent opening of valve would lead to both the Pressure Systems and Oil Leak hazards increasing risk. As it is not possible to change the design, to reduce the residual risk where possible soft controls will be implemented, these are further discussed at section 6.

4.6 Regulator approvals/certificates

4.7 Counter Evidence

Option C gives the best mix of automation with safety monitoring compared to options A and B, however the butterfly valves are only rated 5 Bar above normal operating level.

4.8 Interfacing Systems

Drill Head

Fire systems

Flame boom

Control system

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3.1 Progress against the SMP –

Project Safety Committee (PSC) review conducted with Quora stakeholders identified.

Completed initial HazID

Legislation compliance assessment

Completed safety and performance elements of the URD

Populated SRD

Developed ITEAP

Agreed design option for project (Design 3)

Carried out ALARP risk analysis.

3.2 Areas of Project Risk –

Haven't fully costed the mitigations to the risks.

How will the SSTS interact with other interfacing systems.

Limited Testing and trials information at this point.

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Technical Assumptions include:

System will operate continuously

Minimum workforce required

Operate in all Weather conditions and sea states

The Safety Case pertains only to the SSTS and its interfaces with other systems. It will thus interface with other safety cases managed by the relevant DTs.

Recommendations from risk analysis will be implemented.

Where the oil rig will be situated.

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The Oil SSTS receives hydrocarbons direct from the well head into a separator which acts to remove gas which is to be released via a flame tower, water which is sent for further processing to enable use on the rig and sediment which settles out. The processed oil then passes to storage tanks or can be supplied direct to a tanker should one be waiting. Valves and a pump are used to direct flow to/from the storage capability. Metering of oil is used from storage to the tanker to provide indication of quantity passed to tanker.

Provides separation, water conditioning, oil storage, metering and transfer capability to a tanker. The High Voltage electric pump can pressurise the flow under failure conditions to 100 Bar.  Water conditioning provides water for use elsewhere on the rig, could be for fire fighting or washing etc. Water is transferred to separate storage not shown or provided as part of the SSTS.  Some valves in this solution manually operated and some are monitored and automatically operated via the control system requiring a low level of personnel to monitor system operation and perform maintenance.  The Ball valves are rated to 100 bar and the butterfly valves are rated to 25 Bar, with a closing time of 9.99 seconds (automatic valves).  The design meets all international standards. There is the capability to isolate the whole SSTS should input pressure from the well head exceed specific limits i.e. due to failure of well head system indicated to the operator separately by the well head system.  The rig overall provides fire, heat and gas leak detection.  The design has been developed taking DSA01.1 in to consideration. The Pressure Relief Valves (PRV)s are set at a level to prevent structural deformation/failure of the vessel on which it is attached.  There is no system detection of PRV operation.  The meter provides a digital readout on its body but also to the control system to indicate to the operator the amount of oil passed.  The control system records all data from the meter past and present.  By setting the two valves associated with the storage unit flow can be directed to bypass the storage, deliver oil just to the storage or deliver oil just from the storage to the tanker as required by the operator.  The Non-Return Valve (NRV) prevents flow of oil into the storage tank downstream of the ball valve.  Pressure from the well head is assumed to be maintained by interfacing system to <20bar to which the SSTS is designed however this can be isolated should the pressure increase above this by the butterfly valve. The storage tank and separator normal operating pressure is 20bar but have been proof pressure tested to 25bar. The system partially complies with the Control of Noise Regulations with peak levels no greater than 50dbA. The system is fitted with a standalone fixed fire detection and system, which alarms inside the module only