From US Navy Frigates to Indian Shipyards: Why Modular Skid Delivery Is the New Normal

The US Navy is pushing modular construction to accelerate delivery of its Constellation-class frigates. In India, L&T Shipbuilding has committed 10 billion rupees to expand modular fabrication capacity. And according to SaromGlobal's 2026 commissioning report, leading EPCs now require FAT/SAT test protocols to be planned at the FEED stage — six to nine months before steel is cut.

These are not isolated trends. They are symptoms of a structural shift in how complex equipment reaches the point of use. The common thread: modular skid delivery.

A skid-mounted equipment package — whether it is a reliquefaction system for an LNG carrier, a BOG compressor unit for a gas terminal, a CIP cleaning skid for a food-grade process plant, or a methanol fuel supply system for a dual-fuel vessel — follows the same fundamental delivery logic. It is designed as a self-contained module, fabricated and tested in a controlled workshop environment, transported as a complete unit, and integrated at the final site with minimal field work.

This is not a new concept. But in 2026, it has moved from "preferred approach" to "default expectation" across naval shipbuilding, commercial marine, offshore, and industrial process sectors.

We have been delivering skid-mounted equipment since 2012. Across 70+ skid packages — reliquefaction skids, BOG compressor skids, CIP cleaning skids, methanol fuel skids, LNG bunkering skids, filter skids, hydraulic valve boxes, and TCS (temperature control system) skids — certified by LR, NK, DNV, ABS, BV, and CCS, delivered to shipyards in Korea, Japan, and China, built for five international system integrators and three international engineering companies, we have developed a clear picture of what makes modular skid delivery work and where it breaks down.

What you will take away from this article: a detailed walkthrough of the 8 critical milestones in modular skid delivery — from initial design review to sea trial — with practical lessons from 70+ deliveries, a FAT checklist you can adapt, and a process flow diagram you can share with your project team.

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Table of Contents

1. The Modular Shift: Why 2026 Is a Tipping Point
2. What Is a Modular Skid? Scope and Boundaries
3. The 8 Milestones of Modular Skid Delivery
4. Milestone 1: Design Review — Where 60% of Delivery Risk Is Decided
5. Milestone 2: Procurement — Long-Lead Items That Make or Break Schedules
6. Milestone 3: Fabrication — Workshop Advantages Over Field Assembly
7. Milestone 4: Factory Acceptance Test (FAT) — The Make-or-Break Gate
8. Milestone 5: Packaging and Transport — The Overlooked Risk
9. Milestone 6: Shipyard Installation — From Crane Hook to Bolt-Down
10. Milestone 7: Commissioning and SAT — Proving It Works in Place
11. Milestone 8: Sea Trial — The Final Validation
12. FAT Checklist: What to Inspect Before Shipment
13. Why Modular Delivery Saves 25-40% on Total Installed Cost
14. Classification Society Requirements Across the 8 Milestones
15. Lessons from 70+ Skid Deliveries: What Goes Wrong and How to Prevent It
16. FAQ
17. Conclusion: The 8-Milestone Framework as a Procurement Tool

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1. The Modular Shift: Why 2026 Is a Tipping Point

Three converging forces are making modular skid delivery the default rather than the exception.

Force 1: Naval shipbuilding is going modular at scale.

The US Navy's decision to adopt modular construction for the Constellation-class frigate program is not just a procurement strategy — it is an acknowledgment that traditional stick-built approaches cannot deliver complex warships on the timelines and budgets required. As reported by The War Zone in early 2026, the Navy is restructuring its shipbuilding contracts to incentivize modular block construction, where pre-assembled equipment modules are installed into hull sections before those sections are joined. This approach has been standard practice in Korean and Japanese commercial shipbuilding for decades, but its adoption by the US Navy signals that modular delivery has crossed the threshold from "commercial efficiency tool" to "strategic necessity."

Force 2: Emerging shipbuilding nations are building modular capacity from the ground up.

India's L&T Shipbuilding announced a 10 billion rupee investment to build new modular fabrication facilities (ShipUniverse, 2026). Rather than replicating the traditional build-in-place approach, L&T is designing its new yard around modular construction principles — dedicated skid assembly halls, integrated test bays, and heavy-lift transport corridors. This is significant because it means new entrants to the shipbuilding market are adopting modular delivery as a foundational design principle, not retrofitting it onto existing workflows.

Force 3: Commissioning protocols are shifting left.

Perhaps the most technically significant trend is the upstream migration of FAT/SAT planning. SaromGlobal's 2026 commissioning study documents a clear pattern among leading EPCs and system integrators: test protocols for skid-mounted equipment are now being defined during the Front-End Engineering Design (FEED) stage, six to nine months before fabrication begins. This means the commissioning engineer has a seat at the design review table from day one. The implication for skid fabricators is profound — you are no longer just building to a drawing; you are building to a test plan.

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2. What Is a Modular Skid? Scope and Boundaries

Before walking through the delivery milestones, it is worth defining what we mean by "modular skid" — because the term covers a wide range of equipment complexity.

A modular skid is a self-contained equipment assembly mounted on a structural steel frame (the "skid"), designed to be fabricated, piped, wired, instrumented, and tested as a complete unit in a workshop, then transported and installed at the final site with minimal field work.

The key characteristics that distinguish a modular skid from loose equipment or field-assembled systems:

Self-contained functionality. A skid performs a complete process function — compression, heat exchange, filtration, temperature control, fuel supply — without requiring additional equipment to operate (beyond utility connections).

Workshop-complete. All piping, instrumentation, wiring, and control systems are installed and tested in the fabrication workshop. The goal is to minimize field connections to utility tie-ins (power, cooling water, process inlet/outlet).

Transportable as a unit. The skid is designed from the outset to fit within transport constraints — road clearance, container dimensions, crane capacity at the destination, or hatch/opening sizes on a vessel.

Interface-defined. All connections to adjacent systems are pre-defined with specific nozzle locations, flange ratings, and cable termination points. The interface document is as important as the P&ID.

Equipment Types We Have Delivered as Modular Skids

Skid Type	Application	Typical Complexity	Class Certification
Reliquefaction Skid	LNG/LPG carriers — reliquefy boil-off gas	High — compressors, heat exchangers, control systems	LR, NK, DNV
BOG Compressor Skid	Gas terminals, LNG carriers — compress boil-off gas	High — reciprocating or screw compressors, pulsation dampeners	LR, NK, ABS
CIP Cleaning Skid	Food/pharma/marine — clean-in-place systems	Medium — tanks, pumps, heat exchangers, automated valves	CCS, ASME
Methanol Fuel Skid	Dual-fuel vessels — fuel supply systems	High — pumps, filters, heat exchangers, gas detection	ABS, DNV
LNG Bunkering Skid	LNG-fueled vessels — fuel transfer systems	High — cryogenic components, ESD systems	DNV, BV
Filter Skid	Process filtration — ballast water, fuel, lube oil	Low-Medium — filters, valves, instrumentation	Various
Hydraulic Valve Box	Offshore/subsea — hydraulic control manifolds	Medium — precision machined manifolds, HPU	DNV, ABS
TCS Skid	Temperature control — heating/cooling fluid circuits	Medium — heat exchangers, pumps, control valves	LR, CCS

This range — from relatively simple filter skids to complex reliquefaction systems — means that "modular skid delivery" is not a one-size-fits-all process. But the 8-milestone framework applies across all these equipment types. The depth of work at each milestone scales with complexity, but the sequence is consistent.

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3. The 8 Milestones of Modular Skid Delivery

Every skid delivery — regardless of type, size, or classification society — follows eight sequential milestones. Skip one, and you pay for it downstream. Compress one beyond its natural duration, and quality suffers. Reorder them, and you create rework.

Here is the complete sequence:

Milestone	Duration (Typical)	Key Deliverable	Common Failure Mode
1. Design Review	4-8 weeks	Approved-for-fabrication drawings	Interface dimensions not locked → rework at installation
2. Procurement	6-16 weeks	All long-lead items on site	Late compressor/valve delivery → entire schedule shifts
3. Fabrication	8-16 weeks	Complete skid assembly	Welding sequence errors → distortion, fit-up failures
4. FAT	1-3 weeks	Signed FAT protocol	Insufficient test scope → defects found at SAT
5. Packaging & Transport	1-4 weeks	Skid delivered to site undamaged	Inadequate bracing → transit damage to instruments
6. Shipyard Installation	2-6 weeks	Skid bolted, aligned, connected	Foundation misalignment → pump vibration, pipe stress
7. Commissioning & SAT	2-4 weeks	SAT protocol signed	Missing utilities → commissioning delayed
8. Sea Trial	1-2 weeks	Performance verified underway	Performance deviation under dynamic loads

Total typical duration: 25-55 weeks from design kick-off to sea trial completion.

The range is wide because a simple filter skid can move from design to FAT in 16 weeks, while a reliquefaction system with classification society design review takes 40+ weeks. But the milestone sequence is invariant.

Let us walk through each one.

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4. Milestone 1: Design Review — Where 60% of Delivery Risk Is Decided

The design review milestone is where the majority of downstream risk is either eliminated or embedded. Based on our experience across 70+ skid deliveries, approximately 60% of the issues that cause schedule delays, cost overruns, or rework at the shipyard can be traced back to decisions made — or not made — during design review.

What Happens During Design Review

The design review for a modular skid is not a single meeting. It is a structured sequence of submissions, reviews, and approvals involving three to five parties:

1. The end user / shipowner — defines performance requirements
2. The system integrator / EPC — translates requirements into process design (P&IDs, HMBs)
3. The skid fabricator (us) — develops detailed mechanical design, structural calculations, pipe routing
4. The classification society — reviews and approves drawings against applicable rules (ASME, PED, class rules)
5. The shipyard — confirms interface dimensions, lifting points, foundation details

Key Deliverables

• General Arrangement (GA) drawings — the skid's 3D envelope, nozzle locations, lifting points, weight distribution
• P&ID (Piping and Instrumentation Diagram) — process flow, valve positions, instrument locations
• Interface drawings — connection points to ship systems (pipe flanges, cable glands, support structure)
• Structural calculations — skid frame design for operating loads, transport loads, and seismic/dynamic loads
• Material specifications — confirmed materials for all pressure-retaining components
• Electrical/instrument layouts — cable routing, junction box locations, control panel arrangement

Where Things Go Wrong

Interface lock failures. The most common and most expensive design review failure is leaving interface dimensions "to be confirmed" when moving to fabrication. In a shipyard environment, where the skid must fit into a specific space in the hull with connections to adjacent systems, a 50mm error in nozzle location can mean cutting and re-welding pipe runs on the vessel — work that costs 3-5 times more than workshop correction and delays outfitting by days or weeks.

Weight underestimation. Skid weight determines lifting plan, foundation design, and transport logistics. Underestimating weight at design review (common when instrumentation and cable trays are not fully accounted for) creates problems at every downstream milestone.

Classification society comment loops. If the fabricator submits drawings to class without resolving all design queries first, the comment-response cycle can add 4-8 weeks to the design phase. Our practice: resolve all technical questions with the integrator before class submission, and submit with a clean comment matrix.

Our Approach

We conduct a structured design review in three rounds:

1. Preliminary review (week 2): GA and P&ID review with integrator — focus on process requirements and space constraints
2. Detailed review (week 4): Full drawing package review with integrator + classification society — focus on structural, material, and code compliance
3. Interface freeze (week 6-8): Final interface drawing sign-off with shipyard — all nozzle locations, foundation bolt patterns, and lifting points locked

The interface freeze is a hard gate. No fabrication begins until interfaces are locked. This is non-negotiable because the cost of downstream correction is disproportionate to the cost of spending two extra weeks on design.

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5. Milestone 2: Procurement — Long-Lead Items That Make or Break Schedules

Procurement for a modular skid is not a standard bill-of-materials exercise. It is a logistics puzzle where the longest-lead item sets the pace for the entire project.

The Long-Lead Reality

For complex skids, the procurement timeline is often the single largest component of total project duration. Here are typical lead times for critical components:

Component	Typical Lead Time	Schedule Impact if Late
Reciprocating compressors	16-24 weeks	Entire project delays — cannot start mechanical assembly
Screw compressors	12-20 weeks	Same as above
Special alloy plate/pipe (duplex, titanium, Inconel)	8-16 weeks	Delays pressure part fabrication
Class-approved valves (cryogenic, fire-safe)	10-16 weeks	Delays piping assembly and hydrotesting
Instrumentation packages	8-12 weeks	Delays electrical/instrument fit-out
Heat exchangers (shell & tube, custom)	10-16 weeks	Delays process assembly
Control panels (PLC/DCS)	8-14 weeks	Delays wiring and loop testing

Procurement Strategy

Our procurement approach for skid projects follows three rules:

Rule 1: Order long-lead items before design review is 100% complete. For items like compressors and special alloy materials, we issue purchase orders at the 70-80% design completion stage, based on confirmed process data. The risk of ordering slightly early (and potentially revising specifications) is far lower than the risk of a 16-week compressor delivery holding up a project that has 12 weeks of fabrication ahead.

Rule 2: Maintain approved vendor lists by classification society. Each class society (LR, NK, DNV, ABS, BV, CCS) has different requirements for material and component certification. We maintain vendor lists organized by class, so when a project comes in with, say, NK class, we immediately know which valve suppliers, plate mills, and pipe mills hold NK production agreements. This eliminates 2-4 weeks of vendor qualification at project start.

Rule 3: Incoming inspection is a milestone gate. Every long-lead item receives incoming inspection upon arrival at our workshop — dimensional check, material certificate review (EN 10204 3.1/3.2), surface condition, and for pressure-retaining components, positive material identification (PMI). Items that fail incoming inspection get flagged immediately, not discovered during assembly.

The 600+ PQR Advantage

With over 600 qualified welding procedures (PQRs) covering carbon steel, stainless steel, duplex, super duplex, titanium, nickel alloys, and clad materials, we can accommodate most material specifications without additional welding qualification. This eliminates a common procurement bottleneck — waiting 4-6 weeks for new WPS/PQR qualification when a project specifies an unusual material combination.

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6. Milestone 3: Fabrication — Workshop Advantages Over Field Assembly

This is where the "modular" in modular skid delivery delivers its primary value. Every hour of work done in the workshop is inherently more efficient, more controllable, and more inspectable than the same work done in the field.

Workshop vs. Field: The Numbers

Factor	Workshop Fabrication	Field Assembly
Productivity	Baseline (1.0x)	0.4-0.6x (weather, access, scaffolding)
Welding quality	Controlled environment, fixed stations	Variable — wind, humidity, position
Inspection access	Full 360-degree access, good lighting	Often restricted, requires scaffolding
Tool availability	Full workshop tooling	Limited to what is mobilized
Schedule control	Single management chain	Multiple trades, shipyard coordination
Safety	Controlled environment, ground level	Height work, confined spaces, hot work permits

The productivity multiplier alone — workshop work being 1.7-2.5 times more productive than equivalent field work — is the fundamental economic driver of modular delivery. For a skid that requires 5,000 labor hours of piping, welding, and instrument installation, doing that work in a workshop rather than on a vessel saves 2,000-3,000 labor hours. At loaded labor rates, that is a significant cost differential.

Fabrication Sequence

A typical skid fabrication follows this sequence:

1. Skid frame fabrication (weeks 1-3): Structural steel frame — cutting, welding, NDT, dimensional check, painting
2. Equipment setting (week 3-4): Mount major equipment (vessels, heat exchangers, pumps, compressors) onto the frame
3. Piping fabrication and installation (weeks 4-10): Pipe spool fabrication, fit-up, welding, NDT, support installation
4. Hydrotesting (weeks 8-11): Pressure testing of piping systems and pressure vessels per code requirements
5. Electrical and instrument installation (weeks 8-12): Cable tray, cable pulling, junction boxes, instruments, control panel
6. Insulation and heat tracing (weeks 10-13): If required — thermal insulation, heat tracing, weather protection
7. Touch-up and final inspection (weeks 12-14): Paint touch-up, nameplate installation, final dimensional survey

Quality Milestones During Fabrication

At each stage, there are defined hold points (H) and witness points (W) for the classification society surveyor:

• H — Material verification: Before welding begins on pressure-retaining parts
• W — Fit-up inspection: Before welding of critical joints
• H — NDT (radiography/ultrasonic): After welding, before hydrotest
• H — Hydrotest: Witnessed pressure test per ASME VIII or EN 13480
• W — Dimensional survey: Final check against GA drawings before FAT

These hold points are defined in the Inspection and Test Plan (ITP), which is agreed with the classification society during design review. Skipping or compressing quality milestones is the fastest way to create problems at FAT and beyond.

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7. Milestone 4: Factory Acceptance Test (FAT) — The Make-or-Break Gate

FAT is the single most important milestone in the entire skid delivery process. It is the last opportunity to find and fix problems in a controlled environment before the skid leaves the workshop. Every issue discovered at FAT costs X to resolve. The same issue discovered at the shipyard costs 3-5X. Discovered during sea trial: 10-20X.

What FAT Covers

A comprehensive FAT for a modular skid typically includes:

1. Visual and dimensional inspection
- Overall dimensions vs. GA drawing
- Nozzle locations vs. interface drawing (this is critical — mm-level accuracy)
- Nameplate data vs. data sheets
- Paint condition, weld appearance, general workmanship

2. Pressure and leak testing
- Hydrostatic test: 1.5x design pressure (ASME VIII) or 1.43x (PED)
- Pneumatic leak test: 1.1x design pressure with soap bubble or helium
- Vacuum test (for systems operating below atmospheric)

3. Mechanical testing
- Pump performance: flow rate, head, vibration, bearing temperature
- Compressor performance: capacity, pressure ratio, oil consumption, vibration
- Valve operation: stroke time, seat leakage, actuator function
- Relief valve set pressure: calibrated and locked

4. Electrical and instrument testing
- Continuity and insulation resistance
- Motor rotation direction
- Instrument calibration: pressure transmitters, temperature sensors, flow meters, level switches
- Control loop testing: simulate inputs, verify outputs
- Emergency shutdown (ESD): verify trip functions

5. Functional testing (for complex skids)
- Run the complete system on test fluid (water, nitrogen, or actual process fluid)
- Verify automatic sequences: startup, shutdown, emergency stop
- Verify alarm and trip setpoints
- Data logging: capture performance parameters for baseline

6. Documentation review
- As-built drawings (red-lined if changes from approved drawings)
- Material certificates (EN 10204 3.1/3.2)
- NDT reports
- Hydrotest certificates
- Instrument calibration certificates
- Welding records (WPS, welder qualifications, weld maps)

Who Attends FAT

Typically four parties:
1. Fabricator QA/QC team — hosts the test, provides test procedure, records results
2. Client / system integrator — witnesses tests, reviews documentation, raises punch items
3. Classification society surveyor — witnesses hold-point tests, stamps certificates
4. End user (sometimes) — observes, may raise additional requirements

FAT Duration

Skid Complexity	FAT Duration	Typical Punch Items
Simple (filter, valve box)	1-2 days	5-15 (cosmetic, documentation)
Medium (CIP, TCS)	3-5 days	15-30 (minor mechanical, instrument)
Complex (reliquefaction, BOG compressor)	5-10 days	30-80 (performance tuning, control logic)

The SaromGlobal Insight: Plan FAT at FEED Stage

The SaromGlobal 2026 commissioning report makes a critical observation: FAT/SAT protocols that are developed after fabrication starts — or worse, improvised during FAT — consistently produce more punch items and longer resolution times than protocols developed during FEED. The reason is straightforward: when the test plan is defined early, the fabrication team builds with testability in mind. Instrument taps are located for easy access. Test connections are pre-installed. Temporary supports for test equipment are designed into the frame. When FAT planning is deferred, these considerations are afterthoughts, and the test setup itself becomes a mini-project.

Our practice: we develop the FAT procedure in parallel with detailed design (Milestone 1) and issue it for client review at least 4 weeks before the scheduled FAT date. This gives the client time to add requirements and gives our team time to prepare test setups.

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8. Milestone 5: Packaging and Transport — The Overlooked Risk

This milestone gets the least attention in project planning and causes some of the most expensive surprises. A skid that passes FAT perfectly can arrive at the shipyard with damaged instruments, bent pipe supports, or cracked paint — all because packaging and transport were treated as an afterthought.

Transport Modes and Constraints

Mode	Max Dimensions (typical)	Max Weight	Vibration/Shock Risk
Flat rack container	12m x 2.4m x 2.6m (40ft)	40 tons	Moderate — road + sea
Open-top container	12m x 2.35m x 2.38m	30 tons	Moderate
Breakbulk / project cargo	Custom	100+ tons	Low-Moderate (direct sea)
Road transport (domestic)	Regional limits	Regional limits	High — vibration, bumps
Barge transport	No practical size limit	No practical limit	Low

Packaging Requirements

For skids being transported by sea (which is most marine equipment deliveries):
- Nitrogen purge or desiccant for all sealed cavities (vessels, pipe runs, instrument housings)
- Instrument protection — remove or protect fragile instruments (gauge glasses, sight glasses, control valves with positioners)
- Pipe end protection — blind flanges or plastic caps on all open nozzles
- Bracing — temporary structural bracing to resist transport loads (acceleration: 0.8g longitudinal, 0.5g transverse for sea transport)
- Corrosion protection — VCI paper or coating for exposed machined surfaces
- Lifting lugs — clearly marked, load-rated, certified

The "Last Mile" Problem

The most common transport damage occurs not during the main ocean voyage, but during handling at the destination port and final delivery to the shipyard. Heavy-lift crane operations, transfer to transport trailers, and maneuvering through shipyard roads create shock and vibration loads that can exceed sea transport loads. Our practice: include specific handling instructions and maximum acceleration limits in the shipping documentation, and when feasible, send a supervision engineer for the final lift and positioning at the shipyard.

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9. Milestone 6: Shipyard Installation — From Crane Hook to Bolt-Down

Installation is where the "modular" advantage is either realized or lost. A well-designed skid, built to accurate interface dimensions, with clear installation drawings and a competent installation supervisor, can go from crane hook to bolted-in-place in hours. A poorly designed skid — or one where interfaces were not locked at design review — can take weeks of field modification.

Installation Sequence

1. Foundation check: Verify ship's foundation dimensions, bolt hole positions, and level against installation drawing
2. Rigging and lift: Position skid using shipyard crane per lifting plan
3. Set-down and alignment: Place skid on foundation, check level, adjust shimming
4. Bolt-down: Torque foundation bolts to specification
5. Pipe connections: Connect process piping to ship systems per interface drawing
6. Electrical connections: Connect power cables, instrument cables, communication cables
7. Leak test: Pressure test all field connections
8. Alignment verification: Final alignment check of rotating equipment (pumps, compressors) after bolt-down

The Interface Drawing Is Everything

At this milestone, the quality of the interface drawing from Milestone 1 is directly tested. Every nozzle position, every bolt hole, every cable gland location is either right or wrong. There is no "approximately right" at the shipyard.

In our experience, skid installations that proceed without field modifications (other than shimming and normal pipe-fitting tolerances) have one thing in common: the interface drawing was frozen at Milestone 1 with input from the shipyard, and the fabricator held dimensional tolerance to +/- 3mm on all interface points.

Supervision

For complex skids, we provide installation supervision — typically one mechanical engineer on site for 2-4 weeks during the installation and connection phase. This is not a sales add-on; it is a practical necessity. The person who built the skid understands its internal routing, hidden connections, and critical alignments in ways that shipyard workers, seeing the skid for the first time, cannot.

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10. Milestone 7: Commissioning and SAT — Proving It Works in Place

Commissioning is where the skid transitions from "installed equipment" to "operational system." The Site Acceptance Test (SAT) formally validates that the skid performs to specification in its installed environment — not just on the workshop floor.

Commissioning vs. FAT: What Changes

Parameter	FAT (Workshop)	SAT (Shipyard/Site)
Process fluid	Water or nitrogen (usually)	Actual process fluid (or close substitute)
Utilities	Workshop supplies	Ship/plant utilities (may have limitations)
Control integration	Local control panel only	Integrated with vessel/plant automation system
Operating conditions	Ambient temperature, no motion	Actual environment (heat, cold, vibration)
Interface verification	Simulated	Actual connections to adjacent systems
Emergency systems	Tested in isolation	Tested as part of vessel/plant ESD system

Common Commissioning Issues

Based on our experience, the most frequent commissioning issues are not equipment defects (those are caught at FAT) but integration issues:

1. Utility availability: Ship's cooling water system not ready, or power supply specifications different from what was specified
2. Control system integration: Communication protocol mismatches between skid PLC and vessel automation system
3. Vibration: Equipment that ran smoothly in the workshop develops vibration issues when mounted on a vessel hull (different structural dynamics)
4. Cable routing conflicts: Field cables routed by shipyard workers interfering with skid-mounted instrumentation

Pre-Commissioning Checklist

Before SAT begins, a systematic pre-commissioning check ensures readiness:

• [ ] All construction punch items from installation phase closed
• [ ] Utility connections verified: cooling water, instrument air, electrical power, hydraulic supply
• [ ] Control system communication verified: skid PLC ↔ vessel IAS/AMS
• [ ] Piping flushed and cleaned
• [ ] Instrument calibration verified post-installation
• [ ] Safety systems tested: gas detection, fire detection, ESD
• [ ] Lubrication and consumables charged
• [ ] Operating and maintenance manuals available on board

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11. Milestone 8: Sea Trial — The Final Validation

For marine equipment, sea trial is the ultimate proof of performance. The skid must operate correctly under real-world conditions: vessel motion (roll, pitch, heave), actual cargo or fuel, ambient conditions (temperature, humidity, salt air), and integrated with all vessel systems.

What Gets Tested at Sea Trial

• Performance under motion: Equipment designed for 15-degree roll / 7-degree pitch must function within those parameters
• Dynamic load response: Compressor and pump behavior under varying vessel accelerations
• Control system stability: Automated sequences (startup, shutdown, mode changes) under real conditions
• Noise and vibration: Measured at rated load against specification limits
• Endurance: Typically 4-8 hours of continuous operation at rated conditions

Sea Trial Support

For complex skids (reliquefaction, BOG compression, fuel supply systems), we provide a commissioning engineer for the sea trial period — typically 3-7 days. This engineer is not there to "fix problems" but to:
- Verify performance parameters against the baseline established at FAT
- Assist the ship's crew with initial operation and familiarization
- Document any deviations for warranty records
- Sign off on the final performance acceptance certificate

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12. FAT Checklist: What to Inspect Before Shipment

This checklist is derived from our standard FAT protocol, adapted across 70+ skid deliveries. It can be used as a starting point for any modular skid FAT.

General Inspection

• [ ] Skid dimensions match GA drawing (+/- 3mm on interface points)
• [ ] Nameplate data correct (pressure, temperature, volume, serial number)
• [ ] Paint system complete — DFT measured, no damage, color per specification
• [ ] All nozzle flanges match specification (rating, facing, bolt holes)
• [ ] Lifting lugs present, marked with SWL, NDT completed
• [ ] Earthing/grounding connections installed

Pressure and Leak Testing

• [ ] Hydrostatic test completed — pressure held for required duration (typically 30 min)
• [ ] No visible leaks at flanges, welds, instrument connections
• [ ] Pneumatic leak test completed (if specified)
• [ ] Test records signed by QC and class surveyor

Mechanical Equipment

• [ ] Pump rotation correct / flow and head verified
• [ ] Compressor performance verified (if applicable)
• [ ] Valve operation checked — manual and actuated
• [ ] Relief valve set pressures verified and sealed
• [ ] Vibration within limits (ISO 10816 or vendor specification)
• [ ] Bearing temperatures within limits during run test

Electrical and Instrumentation

• [ ] Motor insulation resistance > 5 MOhm (at 500V DC)
• [ ] Motor rotation direction correct
• [ ] All instruments calibrated — certificates available
• [ ] Control loops verified — input → controller → output
• [ ] ESD function tested — trip setpoints verified
• [ ] Alarm functions tested — high/low/high-high/low-low
• [ ] Local control panel HMI operational — all screens accessible

Documentation

• [ ] As-built drawings (or confirmed "built as designed")
• [ ] Material certificates (3.1/3.2 per EN 10204)
• [ ] Weld maps and NDT reports
• [ ] Hydrotest certificates
• [ ] Instrument calibration certificates
• [ ] Electrical test records
• [ ] ITP with all hold/witness points signed

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13. Why Modular Delivery Saves 25-40% on Total Installed Cost

The economic case for modular skid delivery is well established, but the magnitude of savings is often underestimated because traditional cost comparisons focus on fabrication cost alone, ignoring the total installed cost including field work, schedule impact, and quality costs.

Cost Comparison Framework

Cost Element	Field-Built	Modular Skid	Saving
Direct labor (fabrication)	1.0x	0.6-0.7x	30-40% (workshop productivity)
Materials	1.0x	0.95-1.0x	0-5% (bulk purchasing)
Inspection and testing	1.0x	0.7-0.8x	20-30% (workshop access)
Transport	0x (built on site)	0.05-0.10x	Net cost (offset by labor savings)
Site/shipyard time	1.0x (full duration)	0.2-0.3x (install + connect only)	70-80% less site time
Rework and NCR	1.0x	0.3-0.5x	50-70% fewer quality issues
Schedule (interest/opportunity cost)	1.0x	0.6-0.8x	20-40% shorter schedule

The largest saving is not in fabrication cost — it is in reduced site/shipyard time. For shipbuilding, where berth time costs $15,000-50,000 per day, reducing outfitting time by 2-4 weeks through modular delivery represents a direct financial benefit that dwarfs the transport cost of shipping a skid.

Real Example: Reliquefaction Skid Program

On a multi-vessel reliquefaction skid program we delivered to a Korean shipyard, the shift from mixed field-assembly to full modular delivery (starting from the third vessel) reduced shipyard outfitting time by approximately 3 weeks per vessel. At that yard's daily rate, this translated to a saving that far exceeded the additional transport and packaging costs of shipping complete skid modules from China.

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14. Classification Society Requirements Across the 8 Milestones

Different classification societies have different inspection regimes, but all follow a similar pattern across the 8 milestones. Here is a summary based on our experience with LR, NK, DNV, ABS, BV, and CCS:

Milestone	LR	NK	DNV	ABS	BV	CCS
1. Design Review	Drawing approval	Drawing approval	Drawing approval	Drawing approval	Drawing approval	Drawing approval
2. Procurement	Material certs review	Material certs review	Material certs review	Material certs review	Material certs review	Material certs review
3. Fabrication	H/W per ITP	H/W per ITP	H/W per ITP	H/W per ITP	H/W per ITP	H/W per ITP
4. FAT	Witness hydrotest + function test	Witness hydrotest + function test	Witness hydrotest + function test	Witness hydrotest + function test	Witness hydrotest + function test	Witness hydrotest + function test
5. Transport	Scope varies	Scope varies	Scope varies	Scope varies	Scope varies	Scope varies
6. Installation	Survey at shipyard	Survey at shipyard	Survey at shipyard	Survey at shipyard	Survey at shipyard	Survey at shipyard
7. SAT	Witness (if required)	Witness (if required)	Witness (if required)	Witness (if required)	Witness (if required)	Witness (if required)
8. Sea Trial	Attend (for main machinery)	Attend (for main machinery)	Attend (for main machinery)	Attend (for main machinery)	Attend (for main machinery)	Attend (for main machinery)

Key differences between societies:

• DNV tends to have the most detailed documentation requirements, particularly for risk assessments and failure mode analysis. Expect 30-40% more documentation effort compared to other societies for equivalent equipment.
• ABS is generally the most pragmatic in terms of production surveillance, with clear hold point definitions and efficient survey scheduling.
• LR places particular emphasis on material traceability and welding qualification records.
• NK requires detailed production test procedures submitted well in advance of FAT.
• CCS follows ASME closely for pressure equipment and has specific requirements for Chinese-flag vessels.

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15. Lessons from 70+ Skid Deliveries: What Goes Wrong and How to Prevent It

After delivering 70+ skid packages across eight equipment types, for five system integrators and three engineering companies, to shipyards in three countries, under six classification societies, certain patterns repeat. Here are the most impactful lessons:

Lesson 1: The Interface Drawing Is a Contract

Treat the interface drawing as a contractual document, not a reference sketch. Every dimension, every nozzle position, every flange rating, every bolt hole location must be verified, agreed, and frozen before fabrication starts. We have seen projects where a single mislocated nozzle (30mm off) required a week of pipe modification at the shipyard, costing more than the entire interface drawing effort.

Prevention: Conduct a dedicated interface review meeting with the shipyard (not just the integrator) before freezing the GA drawing. Use a tolerance table: +/- 3mm for interface points, +/- 5mm for non-interface dimensions.

Lesson 2: FAT Is Not a Formality

Some clients treat FAT as a box-checking exercise — send a junior engineer for a day, sign the protocol, move on. This is a mistake. FAT is the cheapest place to find problems. Every hour spent at FAT saves multiple hours at the shipyard.

Prevention: Insist on a detailed FAT procedure (not a generic checklist) issued 4 weeks before FAT. Staff FAT with engineers who will also be present at commissioning — continuity matters.

Lesson 3: Compressor Delivery Sets the Schedule

On skids with reciprocating or screw compressors, the compressor delivery date is the project schedule. Everything else can be accelerated or parallelized; the compressor cannot. We have seen 8-week schedule slippages caused by compressor delivery delays, with no practical mitigation other than waiting.

Prevention: Issue compressor purchase orders at 70% design completion. Accept the risk of minor specification changes rather than the certainty of schedule delay.

Lesson 4: Transport Damage Is Preventable

We have received skids from sub-suppliers with bent pipe supports, cracked instrument housings, and corrosion from inadequate preservation — all transport damage. We have also shipped 70+ skids internationally with zero transport damage claims.

Prevention: Design transport bracing as part of the skid engineering (not an afterthought). Use shipping monitors (shock and tilt indicators). Remove fragile instruments for separate packaging. Nitrogen-purge all sealed systems.

Lesson 5: The Fourth Vessel Is Always Better Than the First

On multi-vessel programs, we consistently see 20-25% improvement in fabrication efficiency from the first vessel to the fourth. This is the learning curve in action — the same workers, the same tools, the same procedures, applied to identical skids. But this improvement only materializes if the design is frozen (no changes between vessels) and the workforce is maintained (no team rotation).

Prevention: For multi-vessel programs, negotiate design freeze after vessel 1 FAT. Keep the same fabrication team throughout the program.

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16. FAQ

What is the typical lead time for a modular skid package from order to delivery?

The total lead time depends on skid complexity and long-lead item availability. For a simple skid (filter, valve box), expect 16-20 weeks from order to ex-works. For medium-complexity skids (CIP, TCS), 24-32 weeks. For complex skids (reliquefaction, BOG compressor, methanol fuel system), 36-52 weeks. The largest variable is compressor or other long-lead equipment delivery, which can be 16-24 weeks alone. We recommend placing long-lead item orders at 70-80% design completion to compress the overall schedule.

What is the difference between FAT and SAT for skid-mounted equipment?

FAT (Factory Acceptance Test) is conducted at the fabricator's workshop before shipment. It verifies the skid's construction quality, pressure integrity, mechanical performance, and control functions in a controlled environment. SAT (Site Acceptance Test) is conducted after the skid is installed at the final site (shipyard, vessel, or plant). It verifies performance with actual process fluids, actual utility connections, and integrated with the site's control and safety systems. FAT catches fabrication defects; SAT catches integration issues.

How does classification society certification work for modular skids?

The classification society (LR, NK, DNV, ABS, BV, CCS, etc.) is involved at every milestone. During design review, they approve drawings and calculations. During procurement, they review material certificates. During fabrication, they conduct hold-point and witness-point inspections per the agreed Inspection and Test Plan (ITP). During FAT, they witness pressure tests and functional tests. The fabricator must hold a valid production agreement with the relevant class society and employ qualified welders per class requirements. We hold production agreements with all six major classification societies.

Can a skid be too large to ship as a single module?

Yes. Transport constraints — road clearances, container dimensions, crane capacity at the destination port or shipyard, and hatch/opening sizes on the vessel — impose practical limits on skid size. Typical maximum dimensions for a single-module shipment are approximately 12m x 4m x 4m (for road transport) or 12m x 2.35m x 2.6m (for containerized shipping). Larger systems are designed as multi-module skids that are assembled and connected on site. The design review (Milestone 1) must account for transport constraints from the outset — the worst outcome is a skid that passes FAT but cannot be shipped through the vessel's access opening.

What certifications does Lmart hold for skid fabrication?

Lmart holds ASME U Stamp (pressure vessels), PED CE marking (European Pressure Equipment Directive 2014/68/EU), ISO 9001 quality management, and production agreements with LR, NK, DNV, ABS, BV, and CCS classification societies. We have over 600 qualified welding procedures (PQRs) covering carbon steel, stainless steel, duplex stainless steel, titanium, and nickel alloys. Our skid workshop is 8,000 square meters with overhead crane capacity up to 50 tons.

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17. Conclusion: The 8-Milestone Framework as a Procurement Tool

Modular skid delivery is not a manufacturing technique. It is a project delivery strategy. The 8-milestone framework — Design Review, Procurement, Fabrication, FAT, Packaging & Transport, Shipyard Installation, Commissioning & SAT, and Sea Trial — provides a structured approach to managing the complexity of delivering pre-assembled equipment packages into demanding environments.

The trends driving this shift are not reversing. The US Navy's adoption of modular construction for frontline warships, India's investment in purpose-built modular fabrication facilities, and the upstream migration of commissioning planning to the FEED stage all point in the same direction: modular skid delivery is the new baseline expectation, not a premium option.

For procurement engineers, project managers, and technical superintendents evaluating skid fabricators, the 8-milestone framework provides a practical checklist for vendor assessment:

1. Does the fabricator have a structured design review process with defined interface freeze points?
2. Does the fabricator manage long-lead procurement proactively, with approved vendor lists by classification society?
3. Does the fabricator have dedicated skid fabrication workshop capacity (not ad hoc floor space)?
4. Does the fabricator develop FAT procedures in parallel with design (not after fabrication)?
5. Does the fabricator have documented transport and packaging procedures for international shipment?
6. Does the fabricator provide installation supervision at the shipyard?
7. Does the fabricator support commissioning and SAT with knowledgeable engineers?
8. Does the fabricator have sea trial support experience for marine equipment?

At Lmart, the answer to all eight is yes — demonstrated across 70+ skid packages, 8 equipment types, 6 classification societies, and deliveries to 50+ countries over 13 years.

Ready to discuss your next skid project?

• Modular Skids & TCS — Product Page
• BOG Compressor Units — Product Page
• Projects & References — 150+ Cases
• Contact Our Engineering Team

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