Offshore, marine, oil and gas, energy, and industrial process projects require equipment that can operate safely and reliably under demanding conditions. Skid-mounted and modular process equipment used in these sectors must often comply with strict project specifications, international standards, offshore lifting requirements, marine transportation criteria, hazardous area classifications, and third-party certification expectations.

Among the most recognized verification and certification bodies in the offshore and marine industries, DNV plays an important role in assessing design, manufacturing, testing, lifting, transportation, and operational safety. For skid-mounted and modular equipment, DNV approval or certification may be required by project owners, EPC contractors, offshore operators, marine contractors, or regulatory frameworks.

DNV-approved skid and modular equipment design is not only about manufacturing a strong steel frame. It is a complete engineering and quality process that considers structural integrity, process performance, lifting safety, transportation loads, material traceability, welding quality, inspection, testing, documentation, and long-term operational reliability.

DNV-approved skid and modular equipment refers to equipment packages that are designed, manufactured, inspected, tested, and documented in accordance with applicable DNV standards, recommended practices, service specifications, or project-specific DNV verification requirements.

Depending on the equipment type and application, the DNV scope may involve:

• Design review
• Structural analysis
• Lifting design verification
• Material certification
• Welding procedure review
• Manufacturing inspection
• Non-destructive testing review
• Load testing
• Functional testing
• Marine transportation review
• Certification of offshore containers or portable offshore units
• Final documentation review
• Issuance of DNV certificate or verification statement

For modular process equipment, DNV involvement is usually project-specific. The exact approval route depends on whether the package is considered a portable offshore unit, offshore container, lifting frame, skid package, process module, pressure-containing equipment, or marine transportation item.

DNV approval provides independent verification that the equipment has been designed and manufactured according to recognized technical requirements. This is especially important for offshore and marine projects where failure can create serious safety, environmental, operational, and financial consequences.

DNV approval helps project stakeholders confirm that the equipment is suitable for demanding conditions such as:

• Offshore lifting
• Marine transportation
• Platform installation
• FPSO and FSO operation
• Harsh marine environments
• Dynamic loading
• Repeated handling
• Limited maintenance access
• Hazardous area operation
• High safety-critical process duties

For EPC contractors and operators, DNV approval reduces technical risk and improves confidence during procurement, transportation, installation, and operation.

DNV-approved or DNV-reviewed modular equipment can be used across a wide range of offshore and marine applications. These packages may be installed on offshore platforms, FPSOs, FSOs, FLNG units, drilling units, offshore support vessels, marine terminals, and coastal industrial facilities.

Typical applications include:

• Process skids
• Separator packages
• Filter separator skids
• Coalescer vessels
• Scrubber systems
• Knock-out drums
• Pig launcher and receiver packages
• Chemical injection skids
• Fuel gas conditioning packages
• Produced water treatment packages
• Heat exchanger skids
• Pressure reducing and metering skids
• Hydraulic power units
• Utility skids
• Drain vessels
• Sampling and analyzer shelters
• Offshore containerized equipment
• Portable offshore units
• Modular process packages

In offshore projects, these systems are often designed as compact, integrated, ready-to-install packages to reduce offshore work and simplify project execution.

A standard industrial skid may be suitable for onshore operation, but offshore and marine applications require additional design considerations. A DNV-approved or DNV-reviewed skid must be evaluated not only for normal process operation but also for lifting, transportation, installation, environmental exposure, and safety.

A standard skid design may focus mainly on:

• Equipment support
• Piping arrangement
• Basic structural stability
• Process performance
• Ease of installation

A DNV-approved offshore skid may additionally require:

• Certified lifting points
• Structural verification under lifting loads
• Dynamic load factors
• Transportation load assessment
• Sea fastening considerations
• Material traceability
• Weld inspection records
• Load testing
• Marking requirements
• Third-party inspection
• Complete manufacturing documentation
• Project-specific certification dossier

This difference is critical. Offshore equipment may be lifted multiple times, transported by sea, exposed to dynamic loads, and installed in limited spaces. Therefore, the skid must be engineered as a complete offshore package, not only as a support structure.

The structural frame is one of the most important parts of any skid or modular package. It must safely support all equipment during fabrication, testing, transportation, lifting, installation, and operation.

Structural design should consider:

• Dry weight
• Operating weight
• Test weight
• Center of gravity
• Lifting arrangement
• Pad eye design
• Frame stiffness
• Transportation loads
• Sea fastening loads
• Dynamic factors
• Wind loads where applicable
• Maintenance loads
• Equipment support reactions

For DNV-related projects, structural calculations may need to be submitted for review. The frame must be designed to resist all relevant load cases without excessive deformation, overstress, or instability.

Lifting is a critical part of offshore equipment handling. A modular package may be lifted during workshop handling, load-out, sea transportation, offshore installation, maintenance, or relocation.

• A proper lifting design should include:
• Lifting lug or pad eye design
• Sling angle evaluation
• Shackle compatibility
• Load distribution
• Center of gravity calculation
• Lift point arrangement
• Structural reinforcement
• Load testing requirements
• Lifting plan support
• Marking of lifting points

Incorrect lifting design can create serious safety risks. For offshore applications, lifting points are not simple attachments; they are safety-critical components that must be designed, fabricated, inspected, and tested properly.

Offshore and marine facilities have limited deck space. Therefore, modular equipment must be compact while still allowing safe operation and maintenance.

A well-designed skid layout should provide:

• Optimized equipment arrangement
• Minimum footprint
• Safe access to valves and instruments
• Maintenance clearance
• Filter element removal space
• Manway access
• Drain and vent accessibility
• Safe routing of piping
• Clear lifting and handling points
• Proper weight distribution

The design must balance compactness with maintainability. A skid that is too compact may create long-term operational problems if operators cannot safely access critical components.

A DNV-approved modular package must still perform its main process function correctly. Structural approval alone is not enough. Process design must be fully integrated with mechanical, piping, instrumentation, and safety requirements.

Depending on the equipment type, process design may include:

• Flow rate calculation
• Pressure drop evaluation
• Separation efficiency
• Residence time
• Filtration performance
• Coalescing efficiency
• Heat transfer performance
• Chemical dosing rate
• Operating pressure and temperature
• Relief and venting requirements
• Drainage philosophy
• Control philosophy

The process performance of the package must be compatible with project requirements and downstream equipment protection.

Many modular packages include pressure vessels, filter housings, separators, scrubbers, heat exchangers, or pressurized piping systems. These components must be designed according to applicable pressure vessel and piping codes.

• Typical considerations include:
• Design pressure
• Design temperature
• Corrosion allowance
• Material grade
• Joint efficiency
• Nozzle reinforcement
• Flange rating
• Gasket and bolting selection
• Hydrostatic test pressure
• NDT requirements
• Pressure relief requirements
• Code stamping or certification where applicable

For offshore and marine projects, pressure-containing equipment may also require additional client, class, or third-party review.

Material selection is critical for DNV-approved skid and modular equipment. Materials must be suitable for both the process medium and the external marine environment.

• Common material considerations include:
• Carbon steel
• Low temperature carbon steel
• Stainless steel
• Duplex stainless steel
• Super duplex stainless steel
• Nickel alloys
• Non-metallic linings
• Rubber lining
• GRP or FRP lining
• Coating systems
• Galvanized structures
• Corrosion-resistant fasteners

Material certificates and traceability are usually essential for DNV-related projects. The selected material must meet mechanical, corrosion, temperature, and certification requirements.

Welding quality is one of the most important aspects of DNV-approved equipment manufacturing. Welds must be performed according to approved welding procedures by qualified welders.

The manufacturing process may require:

• Welding procedure specifications
• Procedure qualification records
• Welder qualification records
• Welding consumable control
• Fit-up inspection
• Visual inspection
• NDT
• Dimensional inspection
• Weld maps
• Repair records
• Heat treatment records where applicable

For offshore equipment, welding is not only a fabrication activity. It is a controlled quality process that directly affects structural safety and pressure integrity.

Offshore and marine environments are highly corrosive. Salt spray, humidity, seawater, UV exposure, and temperature changes can accelerate corrosion. Therefore, corrosion protection must be carefully specified.

• Corrosion protection may include:
• High-performance coating systems
• Surface preparation by abrasive blasting
• Primer, intermediate, and topcoat layers
• Stainless steel or duplex components
• Internal linings
• Insulation and cladding
• Hot-dip galvanizing for selected parts
• Cathodic protection where applicable
• Sealing of crevices and water traps

Coating quality is particularly important because offshore maintenance is costly and difficult. Surface preparation, environmental conditions, dry film thickness, adhesion, and final coating inspection must be properly controlled.

Modular process equipment often includes integrated instrumentation and control components. These systems must be suitable for the operating environment and hazardous area classification.

Instrumentation may include:

• Pressure gauges
• Pressure transmitters
• Temperature indicators
• Temperature transmitters
• Level gauges
• Level transmitters
• Differential pressure indicators
• Flow meters
• Control valves
• Shutdown valves
• Junction boxes
• Cable trays
• Local control panels
• PLC or DCS interface points

For offshore applications, instrumentation must be selected according to hazardous area requirements, environmental protection ratings, material compatibility, and client specifications.

Testing is a major part of DNV-approved skid and modular equipment manufacturing. The objective is to verify that the equipment is safe, compliant, and ready for delivery.

Typical tests and inspections may include:

• Material inspection
• Dimensional inspection
• Welding inspection
• NDT
• Hydrostatic testing
• Pneumatic leak testing where applicable
• Load testing
• Lifting point inspection
• Coating inspection
• Instrument calibration
• Functional testing
• Factory acceptance testing
• Electrical continuity testing
• Earthing verification
• Final visual inspection

The exact inspection and test plan depends on the project specification, equipment type, applicable code, and DNV scope.

The DNV certification or approval process may vary depending on the project. However, a typical process may include the following steps.

The first step is to define the certification scope. This includes clarifying whether DNV approval is required for the complete package, the lifting frame, the offshore container, the portable offshore unit, the pressure equipment, or only selected components.

Clear scope definition avoids misunderstanding during the project and helps determine the applicable standards and documentation requirements.

The applicable DNV standard or service specification must be identified at the beginning of the project. Depending on the equipment type, different DNV documents may apply.

For example, offshore containers, portable offshore units, lifting appliances, marine operations, or project-specific verification scopes may each require different criteria.

The manufacturer or engineering team prepares and submits design documentation for review. This may include:

• General arrangement drawings
• Structural drawings
• Lifting drawings
• Pad eye details
• Center of gravity calculation
• Structural calculations
• Equipment datasheets
• Piping drawings
• Pressure vessel drawings
• Material specifications
• Welding documents
• Inspection and test plan
• Load test procedure
• Coating specification

DNV or the appointed verification body reviews the documents against the applicable requirements.

After design review, manufacturing can proceed under controlled conditions. Depending on the certification scope, DNV or third-party inspectors may witness selected manufacturing, welding, NDT, pressure testing, load testing, or final inspection activities.

Inspection hold points and witness points should be clearly defined in the inspection and test plan.

After fabrication, the package may undergo load testing, pressure testing, leak testing, functional testing, or FAT. Any non-conformities must be corrected before final acceptance.

For lifting-related approval, load testing and inspection of lifting points may be particularly important.

Final documentation is compiled into a manufacturing record book or quality dossier. This may include:

• Approved drawings
• Design calculations
• Material certificates
• Welding records
• NDT reports
• Test reports
• Coating reports
• Calibration certificates
• Inspection release notes
• Load test certificates
• Final certificates
• Operation and maintenance manuals

Upon successful completion, the relevant certificate, approval letter, or verification statement may be issued according to the agreed scope.

Independent design review and inspection help reduce the risk of structural failure, lifting accidents, pressure equipment issues, or manufacturing defects. This is especially important for offshore and marine applications where safety margins are critical.

Improved Safety
Independent design review and inspection help reduce the risk of structural failure, lifting accidents, pressure equipment issues, or manufacturing defects. This is especially important for offshore and marine applications where safety margins are critical.

Higher Client Confidence
DNV approval gives EPC contractors, operators, and end users greater confidence that the equipment has been designed and manufactured according to recognized requirements.

Easier Project Acceptance
Projects with strict offshore or marine specifications often require third-party approval. DNV-certified or DNV-reviewed equipment can support smoother technical approval and handover.

Better Documentation Quality
DNV-related projects require strong documentation control. This improves material traceability, inspection transparency, and long-term maintenance records.

Reduced Offshore Risk
When equipment is properly reviewed, inspected, and tested before delivery, the risk of offshore modification, repair, or rejection is reduced.

Improved Lifecycle Reliability
DNV-approved equipment is designed not only for initial delivery but also for safe handling, installation, and long-term use in demanding environments.

Manufacturing DNV-approved skid and modular equipment requires a disciplined production and quality system.

Important manufacturing requirements include:

• Controlled material procurement
• Certified material traceability
• Approved welding procedures
• Qualified welders
• Controlled fabrication sequence
• Inspection hold points
• NDT coordination
• Dimensional control
• Coating quality control
• Assembly verification
• Pressure testing
• Load testing
• FAT execution
• Non-conformity management
• Final documentation control

The manufacturer must be capable of coordinating engineering, procurement, fabrication, quality control, inspection, testing, and documentation as one integrated process.

DNV-related requirements should be considered from the earliest design stage. Trying to apply DNV approval after fabrication has started may create delays, redesign, rework, or certification problems.

• Early coordination helps define:
• Certification scope
• Applicable standard
• Load cases
• Documentation requirements
• Material requirements
• Welding requirements
• Testing requirements
• Inspection hold points
• Delivery schedule
• Certificate format

This is especially important for fast-track offshore and marine projects where late changes can significantly affect cost and delivery.

For offshore applications, lifting design is often one of the most important parts of the approval process. Skids and modular packages must be safely lifted during transportation, installation, and maintenance.

A proper lifting design must consider:

• Gross weight
• Dynamic amplification
• Sling geometry
• Pad eye strength
• Shackle size
• Weld design
• Load distribution
• Center of gravity
• Skew loading
• Structural load path
• Load testing requirements

Offshore lifting is more demanding than normal onshore handling because dynamic conditions, vessel movement, weather windows, and installation constraints may affect the operation.

If a modular package is transported by sea, marine transportation requirements may also apply. The equipment must be suitable for load-out, sea fastening, vessel motion, acceleration loads, and arrival handling.

• Marine transportation considerations may include:
• Sea fastening points
• Transport frame design
• Center of gravity
• Barge or vessel loading
• Dynamic sea loads
• Stability considerations
• Preservation during transport
• Lifting after transportation
• Protection against marine corrosion

For large or heavy packages, marine warranty requirements may also become part of the project scope.

Offshore platforms and FPSOs require compact, safe, and reliable equipment. DNV-approved modular packages can support offshore project execution by reducing offshore fabrication and increasing pre-delivery readiness.

Typical offshore platform and FPSO packages may include:

• Separator skids
• Scrubber packages
• Fuel gas conditioning skids
• Chemical injection packages
• Produced water treatment units
• Filter separator systems
• Pig launcher and receiver packages
• Drain vessels
• Utility skids
• Heat exchanger packages
• Emission control packages

Because these packages may be installed in space-limited and safety-critical environments, DNV-related design and manufacturing discipline provides significant project value.

DNV-approved skid and modular equipment projects can be technically demanding. Common challenges include:

• Late definition of certification scope
• Incomplete project specifications
• Weight increase during design development
• Center of gravity changes
• Lack of lifting data
• Material certificate limitations
• Welding documentation gaps
• Coating specification conflicts
• Interface changes
• Testing schedule constraints
• Documentation delays

These challenges can be managed with early planning, clear communication, strong engineering control, and experienced project execution.

Successful DNV-approved skid and modular equipment delivery depends on several best practices:

• Define certification scope at the RFQ stage
• Identify applicable DNV standard early
• Freeze critical design inputs before fabrication
• Prepare structural and lifting calculations early
• Control weight and center of gravity throughout the project
• Use certified and traceable materials
• Apply approved welding procedures
• Coordinate inspection hold points
• Perform required testing before shipment
• Maintain complete documentation from the beginning
• Involve DNV or third-party inspector early
• Manage design changes through formal revision control

These practices help reduce rework, avoid approval delays, and improve final project acceptance.