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Prefabrication in MEP systems
31 October 2018
Shalini John

MEP Prefabrication – Process and Benefits Manufacturing Plant

One of the most impactful advances in construction is the ease, popularity and successful implementation of prefabrication in many disciplines of construction, but none more impressive than in building services or the MEP (mechanical, electrical and plumbing, also known as M&E) sector. Prefabrication refers to the manufacture of building components at an off-site environment, which are then transported and installed on site. Prefabricated units developed through MEP engineering design are manufactured in a several ways. Though panels and modules can be efficiently prefabricated, the prefabrication of complete MEP systems is more complex. A closer look at the process and benefits of prefabrication can help assess its feasibility.

Traditionally, MEP systems construction has been a multi-level process, with service engineers and designers introducing their skills and materials in sequence at the site. Projects suffered from absent and inefficient labour teams, inclement weather, dangerous working conditions, difficulties in maintaining quality control and the resulting rising costs. Construction debris would accumulate, causing air pollution and the presence of potentially toxic materials on site. Also, access to building sites could be restrictive if other buildings exist outside the site boundaries, and so, the different trade contractors would face difficulties to bring in equipment and materials.

The practice of MEP prefabrication provides a feasible alternative to traditional methods. Both MEP components and MEP modules can be manufactured, inspected, labelled and tested offsite, with plumbers, insulators, HVAC engineers and electricians working together at the same to time to completing their installations. Coordination between trades is finished faster and so is installation.

Modular installations constitute an advanced form of prefabrication that can be assembled off site and installed on site. Modular installations that include MEP systems, or MEP modules, enable coordination and provide efficient solutions for the installation of MEP services or MEP components. Typically, a module will have steel frames to support pipes, ducts and cable trays. The frames are generally 6-12 metres in length, with width and height limited by the size of the transport used to move it to the site and the route/roads that are available to the site. These modules are designed at the same time as the MEP coordinated drawing process. Additionally, the method of connecting the modules must be planned and the steel beam weight and size must be calculated for the mounting frame. Modules may be fabricated either in a workshop or factory outside the construction site or in a temporary work area set up on the construction site. Installations are usually performed with the use of duct lifters or chain blocks, although tower cranes have been used to install MEP modules in shafts.

Complete MEP systems can sometimes be difficult to manufacture, due to assembly limitations, inefficient implementation of BIM (building information modelling) and poor standards of off-site manufacturing, but with efficient planning and design, the use of prefabricated MEP systems have several advantages.

The variety of units that can be prefabricated through MEP engineering design can be categorized into 3 main groups: Prefab Components, Sub-assemblies and Integrated Assemblies. They consist of the following elements:

1. Prefab Components
  • Pre-insulated plastic piping
  • Flexible water pipe
  • Prefabricated pre-insulated aircon duct
  • Plug and play cable
  • Flexible sprinkler dropper
2. Sub-assemblies (Including only MEP services)
  • Prefab horizontal module or vertical riser
  • Prefab plant module
  • Prefabricated horizontal or vertical ceiling modules with pipes, cable trays, trunking, etc.
  • Prefabricated plant modules with pump, compressor, etc.
3. Sub-assemblies (Integrated with architectural/structural components)
  • Prefab horizontal module with ceiling board
  • Prefab vertical riser module with catwalk
  • Prefabricated MEP modules integrated with catwalk
  • Riser module with platform
  • Prefabricated horizontal module with ceiling board (and even lighting, exit signs, etc.)
4. Integrated Assemblies
  • Prefab plant room
  • MEP systems integrated into Prefabricated Prefinished Volumetric Construction systems
So, how are MEP modules manufactured?

Produced in a BIM environment, MEP coordinated drawings can be used to generate MEP shop drawings, which then drive modular design. At each project stage, the modules must be manufactured according to the contents of MEP coordinated drawings and the level of detail specified in the BIM model.

Workflow for MEP Shop Drawing Services

1. The architect provides a building layout BIM model to MEP consultants, who develop the concept design and schematic design of the individual trades.

2. The MEP trade engineers (or MEP contractors) and MEP prefabricator develop the MEP coordinated drawings in BIM. These are defined with assemblies, quantity, size, shape, location and orientation. Elevation views of specific locations, such as corridors, turning points in trade routing and the routing of new services can be produced. A lead coordinator can integrate MEP BIM models to create the final MEP coordinated drawings.

3. Consultants, builders and MEP contractors review and approve MEP coordinated drawings.

4. The modules’ supporting frame, flanges and corners, along with other details, are added to the MEP coordinated drawings for fabrication and assembly, which are then known as MEP shop drawings.

During the design stage, MEP engineers and the main contractor introduce their inputs into the design, helping achieve technical clarity early on. Clashes and safety concerns can be eliminated through MEP coordination. Comprehensive MEP systems design must consider maintenance, replacement and upgradation of MEP systems, improving the feasibility of the design and thus construction productivity.

Another process sees the main contractor take care of the design and manufacture, hiring MEP consultants and engineers to design, develop and construct the module, based on client requirements.

It is crucial to take enough time to analyse prefabricated MEP module design options, using BIM software. For example, a vertical riser in a frame travelling through several floors may be more efficient than installing a small assembly for each floor.

Once the MEP module drawing or MEP shop drawings are complete, the design of the modules is ready and can be manufactured. A template or jig is typically utilised at the factory to check module alignments. Shrink wrap or tarpaulin can be used to cover and protect the modules from the effects of weather. When the modules are complete, they can be transported to the site for installation. Castor wheels can be pre-installed to ease transport and handling and can be removed after installation. During installation, pallet jacks and forklifts help lift and move modules into place.

The general process and participants of the prefabrication workflow can be outlined as follows:

  • MEP design services – by consultant or main contractor or MEP module prefabricator
  • MEP coordinated drawings – by MEP shop drawing services provider
  • Prefabrication, commissioning and testing in factory – by MEP module prefabricator
  • Coordinating with site from factory – by MEP module prefabricator or main contractor
  • Installation of MEP modules – by MEP subcontractor
Overall MEP Module Workflow

The overall MEP module workflow, from design to testing of installed MEP modules, is applicable to multiple trades integrated within the modules.

1. Design Phase
  • Design drawing submission (approved by consultant and authorities)
  • MEP Coordinated Drawings (endorsed by MEP trades)
  • Production Drawings Submission (module support strength endorsed by engineers)
  • Materials Submission

The schedule of materials is then approved.

2. Manufacturing Plant
  • Material Procurement
  • Prefabrication of Modules
  • Factory acceptance tests (verified by engineer)
  • Protection of Modules
  • Storage of Modules

The modules are then transported to the site.

3. On Site
  • Visual inspection of delivered modules
  • Modules moved to installation position
  • Marking and setting out of module positions
  • Installation and connection of modules to mains
  • Testing and commissioning for entire service

The prefabrication process is dependent on precisely following the sequence of materials that arrive on site, so it is important to decide on the MEP module components early on. These components should ideally arrive punctually on site, and materials and plans must be approved before mass production.

Benefits of MEP Prefabrication

In many ways, MEP prefabrication, especially MEP modules, has the power to transform building construction. Assembling these modules off site can lead to faster completion times, improved worker safety and cost savings.

Faster Completion – Assembly of components or modules can begin off site, without waiting for the site to become ready or for approvals to be granted.

Cost Savings – Though there may be an initial expense for coordination or for buying of the appropriate lifting equipment, since the quantity of work will be less and the completion of work will be faster, savings in costs are bound to ensue.

Improved Worker Safety – Scaffolding work is at a minimum. Movement, lifting and other labour on the site is drastically reduced, leading to greater worker safety.

No Snags, No Damage of Services – MEP modules are typically installed from the ground up, avoiding many problems with connections. On-site work is reduced to connecting modules to mains, thus cutting down on any potential damages to components.

Easy Installation – With less manpower required, prefabricated MEP modules and components can be installed easily, neatly and more efficiently.

Reduced Environmental Impact – Dust, noise pollution and construction debris are significantly reduced with off-site prefabrication.

Greater Quality Control – Most of the work is carried out in a controlled environment or factory, thereby ensuring quality control.

When MEP modules are delivered to a site on time, factory congestion and potential damages to the modules are reduced. Using BIM technology, on-site installation can be simulated and possible problems with regard to access can be identified. Builders must specify crane capacity, availability of platforms for placing the modules on, delivery routes and other logistics. Large pump skids and modules must be planned for in advance.

Engineers can conduct inspection after delivery to the site and before installation. Supporting rods on modules for installation can be marked on the slab soffit or columns. Finally, the modules are installed and connected to the mains.

A variety of benefits can be enjoyed with MEP prefabrication, namely improved safety, quality, scheduling and costs. This practice also reduces environmental impact, dust and noise pollution and construction debris. Quality control is improved due to controlled factory settings and the sequence of work and logistical coordination is optimized. With a surfeit of options for MEP shop drawing services available worldwide, an overseas BIM services provider who specialises in quality architectural CAD outsourcing services would be a cost-effective solution that can ensure high quality.