Modular Construction
Modularization Design Guide: Chemical Plant
Grajesh Shah, Hitesh Majmundar
Abstract
In chemical, petrochemical, oil and gas industries, modularization concept is becoming popular and extensively
utilized irrespective to site location and climatic conditions because of its potential to reduce schedule, minimizing
cost, effective utilization of skilled labour for better quality with maximum safe environment, reduction in space
requirements for plant layouts and reduction in installation cost.
The article details about modularization design approaches, consideration for modularization, consideration of
piping design for optimization of modularization project. During modularization, size, weight and the center of
gravity (COG) of the module play’s an important role for finalizing layouts and piping within modules. Also, still
constructability, equipment sizing, equipment layout and piping design are critical factors in modularization.
The article talks about general procedures, criteria and guidance with regards to engineering deliverables for
modularization.
Introduction
M
odule is defined as a structural unit assem- • High density piping areas
bled with equipment, structural steel, piping, • Stringent shutdown constraints
electrical and instrumentation, fireproofing,
painting, insulation, and testing completed as much Modularization Challenges
possible, as shown in Figure 1 Typical Module. The as- •• Unproven process technology
sembly of the modules is generally done away from •• Location limitations
the project site. The assembled modules are transport- •• Meticulous planning, logistics, engineering and
ed to the project site by either one or a combination of procurement
sea, road, rail, waterway, and air modes. •• Early engineering and procurement
•• Identification of pre-select contractor and module
shop
•• Increased cost of engineering
•• Increased shipping costs
•• Increased steel quantities
•• Increased equipment damage potential
•• Additional rigging/lifting requirement
•• Module plan interfaces
Types of Modules
Typical module types include:
•• Mega-modules (over 500 tons; require special
shipping)
•• Large and intermediate modules (require barge or
Fig.1 Typical Module rail)
•• Trackable modules
Requirement of Modularization •• Pre-assembled pipe rack modules (PAR’s)
• Remote site location
•• Pre-assembled unit modules (PAU’s)
• Severe site weather constraints (too hot or too cold)
•• Skid-mounted equipment modules.
• Schedule driven improvement
•• Hybrid modules (partially completed in the shop
• Limited availability of regional skilled labour and fully assembled in the field).
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Modular Construction
PIPE-RACK MODULE STAIR TOWER MODULE
UNIT MODULE SKID MODULE
Modularization Approach
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Modular Construction
Modularization Pros and Cons Design Consideration
Modularization Pros Key design considerations for modularization in-
cludes.
• Streamline field installation.
• Overall module layout from its installation and
• Facilitates remote site locations.
erection sequence point of view to be identified.
• Shortens multiple work fronts.
• Various additional loading consideration and anal-
• Reduces risk of site conditions/weather ysis requirement (lifting analysis, land transporta-
• Breaks projects into manageable parts tion, water transportation, jacking) in addition to
• Improves safety, quality and productivity. the in-place loading and design requirement.
• Shortens duration and reduces field staff. • Space provision for temporary supporting arrange-
• Reduce on-site fabrication. ment during transportation
• Reduce temporary facilities. • Suitable berths need to be investigated, vessel
cranes or shore cranes, tidal windows, ballasting
• Reduce scaffolding.
restrictions, wind effects and limits play an impor-
• Reduce small tools and consumables. tant role in deciding module transportation sched-
• Reduce number of field welds. ule and cost.
Modularization Pros • Schedule for module transportation should be align
with the availability of Barge/SPMT both at fabrica-
• Committed execution sequence.
tion yard and project site.
• Committed module delivery schedule and routes.
• Pipe routing to optimize the numbers of Golden
• Potential for design changes and rework Joints between modules.
• Potential loss or damage during transport
Modular and Stick Built Construction
• Heavier construction cranes
Key Differences in modular and stick-built con-
• More cranes required for large module assembly struction.
and outfitting.
• More planning, communication, organization Stick-Built Construction Modular Construction
• Less flexibility Potentially lower due to
Prerequisite of Modularization efficiencies in produc-
Potentially higher due tion and assembly. Cost
At the start of the project incorporating modulariza- Cost to labor and onsite assessment is neces-
tion, following needs to be identify: work. sary due to potentially
• Items to be modularize. increased steel and
transport costs
• Location of fabrication / module yard and transpor-
tation route to project site Longer construction Potentially shorter time-
• Logistic survey of module transportation routes Time periods due to onsite lines through pre-fabri-
work. cation and planning.
like road, rail, waterways and investigating trans-
portable size of module. Requires skilled labor
Less onsite labor is re-
• Transport vehicle (ship and barges, truck, SPMT, Labor on site, which can
quired, reducing costs.
crane etc.) to establish the modular design basis. increase the costs.
• Early purchase orders of major equipment, pipes, Enhanced safety due to
Higher risk due to pro-
cable trays, instruments Safety
longed onsite activities.
controlled shop condi-
tions.
• Installation methodology of module on site through
jacking / lifting plan Requires more qual-
Easier to manage with
ity personnel onsite
• Scheduling, planning and coordination for the de- Quality quality control in shop
and material control
livery of items to the fabrication yard. settings.
processes.
• Naval architect to get acceleration loads and impact Flexibility High, allowing for Limited, with designs
loads for sea transportation. adjustments during needing to be finalized
construction. early.
• 3D Model set-up as per modularization concep
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Modular Construction
Module Weight Monitoring and Control
It is important to monitor and control weight of modules when pre-fabrication and modularization techniques
are used in project. While calculating module weight, following components weight needs to be considered:
Rotary & Static Equipment empty weight
Equipment weight: Insulation weight
Equipment platforms which are in vendor scope
Dry weight of pipes within module (Including in-line
items)
Piping Weight:
Primary and secondary supports weight
Scaffolding & Insulation weight
Primary Framing, Secondary steel (Temporary)
Grating, Handrails, Chequred plates, Ladders, Platforms
Structural Weight:
etc.
Fireproofing
Cables & Cable Trays
Junction Box
Tracing Panels
Electrical weight:
RCU
Lighting Fixtures
Misc. items (Switch box, Cover of cable tray etc.)
RIO Boxes, Junction Boxes, FO Junction Boxes
Instrumentation weight: Cables, Cable Trays & Its supports
Instrument Air Manifolds, F&G System, Transmitters
To mitigate the risk of exceeding NTE (Not to exceed weight), some contingency needs to be considered
during initial stages of project while capturing module weight. In later stages of the project when available data
gets matured this contingency shall be reduced.
Module Hook–Up/Interface with other Module
The hook up phase involves the physical installation and integration of various components and systems,
such as structural, piping, mechanical, electrical, and instrumentation and control (I&C) installation.
Type of hook-up for
Merit Demerit SNAP
piping
Reduce Labor and Material han- Considerable alignment issues
A “Single Weld Hook-Up” dling costs at site
(SWHU) refers to connecting
pipes between modules with Reduce nos. of Golden Joint End up with double weld hook
a single closure weld, aiming w.r.t. Double Weld Hook-up up if there are alignment related
for a more efficient and cost- issues
effective approach compared Eliminates the need for storage Significant nos. of Golden Welds
to traditional methods that and disposal of test medium and
involve separate hook-up associated testing equipment
spools. Due to less Golden Joints,
Opportunity to reduce the hydro Potential risk to the project sched-
test and pneumatics resting at ule due to inspection of the more
site. Golden Joints and NDT execution.
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Modular Construction
Many merits same as single weld Significant increase in nos. of
hook-up (SWHU) Golden Welds
A “Double Weld Hook-Up”
(SWHU) refers to connecting Possibility of local pocket, if nec-
pipes between modules with essary precautions not considered
a traditional methods that
Address most module out of
involve separate hook-up
Alignment conditions.
spools. Other demerits are same as single
weld hook-up (SWHU)
Increase the nos. of potential
Site Hook up is faster
leakage
Axial Alignment is significant
No NDT & Hydrotest at Site
issue
Hydrotest of complete system
can be carried out at Yard, Overall length of the pipe needs
Flange type Hook Up
which mitigates the need for to be cut
rectification of weld joint
Can not be provided for all the
services
Reduce the Cutting and
Rewelding activities during shut Flange joint required more main-
downs tenance over a longer periods
Module Envelope Plan – Sample
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Modular Construction
Module plan shown above depicts typical modular- • Engage competent staff, subject matter experts, cus-
ization approach adopted on one of the refinery brown tomer technical representatives, and third-party
field Project. Brown field project has its own construc- specialists and encourage early collaboration.
tion challenges and modularization can significantly • For vertical modules needs special attention as they
reduce the production down time but with that it needs need to be designed to meet its lifting during hori-
certain area of attention during its concept, design and zontal position (during land transport), taken up
construction stage. Below are the few attention points from truck and rotated and made vertical up to set
to be taken care at appropriate stages: in final position at site.
• While deciding the number of lift points for each
module, design team, construction & modular
Conclusion: The Optimal Approach
shop team should align for the crane to be used for Both modular and stick-built approaches have their
lifting the module and based on hook capacity nos. own pros and cons. The choice depends on project-
of lift points shall be decided. specific factors like scale, location, complexity, sched-
ule and budget.
• Ensure project standards (such as basis of design,
design criteria, and lifting basis) are aligned with Modularization offers a pathway to faster, safer,
customer expectations, industry codes, and all stake and more cost-effective solutions as the energy indus-
holders to avoid conflicts & rework at later date. try evolves.
• Identify hazards associated with specialized con- In many cases, a hybrid approach—combining
struction, put in place a risk reduction plan, and modular efficiency with stick-built flexibility—deliv-
communicate effectively to the broader team. ers the best results.
Grajesh Shah (BE Mech Engg) has 30 Hitesh Majmundar (BE Civil Engg) has 30
years of experience in the field of Piping years of experience in the field of Civil and
Design. He is working as Head of Piping Structural Design. He is working as Head
Design Department at Worley Vadodara. of Civil and Structural Design Department
He has been involved in FEED and Detail at Worley Vadodara. He has been involved
engineering of various Oil and Gas, Refinery, in FEED and Detail engineering of various
Petrochemical, Chemical, Fertilizer, Utilities Refinery, Petrochemical, Chemical, Fertilizer, Utilities and offsite
and offsite projects. projects.
32 Chemical Industry Digest. April 2025
