In offshore commercial diving, safe and reliable gas storage is essential. Whether supporting inspection, maintenance or construction activities beneath the surface, the correct choice of gas storage equipment, particularly quads, has a direct impact on operational safety, project timelines, and compliance with industry regulations.
This guide offers an in-depth look at how to choose gas storage and quads for offshore diving projects, considering certification standards, practical deployment, safety, and logistical efficiency. It also draws on iSubC’s experience supplying certified, ready-to-deploy gas quads to clients across offshore sectors.
What Are Gas Quads?
A gas quad, also known as a gas rack or T-frame, is a portable structure containing a group of high-pressure cylinders manifolded together. In offshore diving, these cylinders typically store gases such as oxygen, helium, or nitrogen, used in various diving techniques including surface-supplied diving, saturation diving, and mixed-gas operations.
Each quad is designed to simplify transport, streamline gas management, and ensure the safe storage of breathing gases in harsh marine environments.
Why Gas Quads Matter in Offshore Diving
Gas quads serve as the backbone of breathing gas supply systems on offshore projects. A well-specified quad:
- Ensures uninterrupted supply of breathing gas to divers
- Reduces the need for frequent resupply trips
- Provides a controlled and secure method of gas storage at high pressure
- Supports compliance with offshore safety regulations and vessel standards
- Enhances logistical efficiency, especially in remote or floating installations
Incorrect or poorly certified gas storage systems can lead to safety hazards, delays, and non-compliance with marine operational codes.
Understanding the Certification: DNV 2.7-1
Gas quads used in offshore environments must meet stringent requirements. One of the most recognised standards is DNV 2.7-1, developed by DNV (Det Norske Veritas), which specifies the requirements for offshore containers used in dynamic marine environments.
Key Aspects of DNV 2.7-1 Certified Quads
- Structural Integrity: DNV 2.7-1 quads are built to withstand high dynamic loads, including those encountered during crane lifting, rough seas, and offshore deployment.
- Offshore Safety: Containers are fitted with certified lifting points, secure pressure fittings, and robust protective framing.
- Standardisation: Ensures compatibility with offshore vessels, supply chains, and lifting equipment.
Choosing a DNV 2.7-1 certified gas quad means investing in equipment built for safety, durability, and compliance.
Gas Types and Storage Needs
Common Gases Used in Offshore Diving
- Air: Filtered and compressed for surface-supplied diving.
- Nitrox: Oxygen-enriched air (typically 32% or 36%) used for shallower mixed-gas diving.
- Trimix: A mixture of oxygen, helium, and nitrogen, used for deeper diving operations.
- Heliox: Helium and oxygen mix, used primarily in saturation diving.
- Pure Oxygen: For decompression chambers and treatment.
Storage Considerations
- Volume Requirements: Determined by dive depth, number of divers, gas mix, and project duration.
- Cylinder Pressure: Most offshore cylinders are rated at 200–300 bar.
- Cylinder Count per Quad: Typically 12, 16 or 18 cylinders, depending on quad design.
- Manifold Configuration: Ensures uniform pressure distribution and easy gas delivery from quad to control panel or umbilical.
Careful gas planning and appropriate quad selection help prevent gas shortages, which can jeopardise safety and delay operations.
Key Considerations When Choosing a Gas Quad
1. Certification and Safety Compliance
Offshore projects are governed by strict health and safety protocols. Always ensure:
- The quad complies with DNV 2.7-1
- All cylinders are pressure-tested and within inspection dates
- Manifolds and hoses are properly rated and tested
- Lifting certification is current and traceable
2. Portability and Handling
- DNV 2.7-1 quads are fitted with standard offshore lifting slings and forklift pockets
- Compact footprint allows deck space optimisation
- Modular design supports quick switch-out during diving shifts
Consider logistics: how easily can the quad be lifted, positioned, and accessed on a dive support vessel or offshore platform?
3. Gas Type and Pressure Rating
- Ensure compatibility with project-specific gas mixtures
- Verify maximum working pressure (MWP) of quad and cylinders
- Pressure regulators and valves must match the intended delivery pressure
At iSubC, clients can specify quads for helium, oxygen, nitrox, or custom mixes, with valves, manifolds and pressure gauges preconfigured to suit.
4. Availability and Lead Time
Delays in gas supply can halt offshore operations. iSubC addresses this by:
- Holding a large inventory of DNV 2.7-1 gas quads, ready for immediate dispatch
- Supporting international logistics for urgent mobilisation
- Offering flexible rental or purchase options depending on project length
5. Maintenance and Inspection Support
Gas quads must be periodically inspected and maintained to remain compliant and safe.
iSubC offers:
- Pre-delivery testing and inspection
- Re-certification and cleaning services
- Advice on quad lifecycle management and replacement planning
Hire or Purchase: What’s Right for Your Project?
When to Hire
- Short-term projects (days to a few months)
- Limited deck space or frequent equipment change-outs
- Budget-conscious clients who want to avoid capital expenditure
When to Purchase
- Long-term use or regular diving operations
- Projects with highly customised gas configurations
- Clients who require permanent equipment integration into their systems
iSubC provides both options, offering flexible hire packages and competitive purchase pricing on new or used certified quads.
How iSubC Supports Offshore Clients
With a commitment to safety, stock availability, and offshore expertise, iSubC is trusted by clients in oil and gas, renewables, defence, and civil marine sectors.
Services include:
- Ready-to-deploy gas storage units
- Custom manifold setups
- Certification and inspection support
- Global logistics coordination
- Technical advice from experienced commercial diving professionals
Final Thoughts
Choosing the right gas storage and quads for offshore diving projects is not just a matter of convenience, it is a critical decision that affects diver safety, operational continuity, and compliance.
By selecting DNV 2.7-1 certified equipment and partnering with a supplier who understands offshore demands, project teams can operate with greater efficiency and confidence.
If you are planning your next offshore dive campaign, contact iSubC for advice or to request a quote. With in-stock equipment and expert support, we help keep your operations safe, compliant, and on schedule.
