The strength of a Solar Module Mounting Structure (MMS) depends not only on its primary structural members but also on the quality of its connections. Even if the columns, rafters and purlins are properly installed, poor connections can reduce the stability of the complete structure.
Cleats and Connection Plates are used to connect various structural members together and ensure that loads are transferred safely throughout the Solar MMS.
In this article, we will understand the purpose of Cleats, Connection Plates, their types, applications, installation procedures and inspection requirements.
Project Details
- Project Type
- Ground Mounted Solar Power Plant
- Structure Type
- Fixed Tilt Solar MMS
- Module Configuration
- 2P × 28
- Total Modules
- 56 Nos
- Module Size
- 2382 × 1134 × 35 mm
- Tilt Angle
- 11°
What Is a Cleat?
A Cleat is a fabricated steel component used to connect two or more structural members together.
It provides a secure connection between members while allowing the structural loads to pass safely from one member to another.
What Is a Connection Plate?
A Connection Plate is a flat steel plate used to join structural members using bolts.
Connection Plates improve joint strength and ensure proper alignment between connected members.
Where Are Cleats Used in a Solar MMS?
Cleats are commonly used at the following locations.
- Hat Purlin to Rafter Connection.
- Rafter to Column Connection.
- Front Bracing Connection.
- Rear Bracing Connection.
- Wind Bracing Connection.
- Secondary Structural Connections.
Function of Cleats
The primary functions of Cleats are
- Connect structural members.
- Transfer structural loads.
- Maintain member alignment.
- Improve joint rigidity.
- Reduce stress concentration.
- Provide easy assembly during installation.
Function of Connection Plates
Connection Plates perform the following functions.
- Join two or more steel members.
- Distribute forces over a larger area.
- Improve connection strength.
- Reduce local deformation.
- Facilitate bolted construction.
Load Transfer Through Connections
The load path through a bolted connection is shown below.
Solar Module
↓
Hat Purlin
↓
Cleat
↓
Rafter
↓
Connection Plate
↓
Column
↓
Foundation
Every connection should be capable of safely transferring the applied forces without excessive deformation.
Types of Connections Used
A typical Ground Mounted Solar MMS may include the following bolted connections.
- Hat Purlin to Rafter.
- Rafter to Column.
- Front Bracing to Column.
- Rear Bracing to Column.
- Wind Bracing to Column.
- Wind Bracing to Rafter.
Importance of Bolted Connections
Bolted connections provide several advantages.
- Faster installation.
- Easy replacement.
- No field welding.
- Better quality control.
- Easier maintenance.
- Reduced installation time.
Why Field Welding Should Be Avoided
Most Solar MMS members are supplied with a galvanized coating for corrosion protection.
Field welding can
- Damage the galvanized coating.
- Reduce corrosion resistance.
- Increase maintenance requirements.
- Introduce heat distortion.
Whenever possible, bolted connections should be preferred.
Quality Requirements for Cleats
Every Cleat should satisfy the following requirements.
- Correct dimensions.
- Proper hole locations.
- Burr-free edges.
- Uniform galvanized coating.
- No visible bending.
- No cracks.
Quality Requirements for Connection Plates
Connection Plates should be inspected for
- Correct thickness.
- Correct hole diameter.
- Proper edge distance.
- Galvanized coating.
- Flatness.
- Surface damage.
Installation Procedure
Step 1
Verify the member identification before installation.
Step 2
Position the Cleat correctly.
Step 3
Insert all bolts without tightening completely.
Step 4
Check alignment of connected members.
Step 5
Tighten bolts uniformly.
Step 6
Perform the final torque check.
Quality Inspection Checklist
□ Correct Cleat Position.
□ Correct Connection Plate.
□ Proper Bolt Size.
□ Correct Hole Alignment.
□ Tight Bolt Connections.
□ No Missing Bolts.
□ Galvanized Coating Intact.
□ No Visible Gaps Between Members.
□ No Bent Plates.
Common Installation Mistakes
- Installing the wrong Cleat.
- Using incorrect bolt length.
- Loose bolt tightening.
- Missing washers.
- Misaligned holes.
- Damaged galvanized coating.
- Reusing damaged bolts.
Maintenance Checklist
During periodic inspections, verify
- Loose bolts.
- Corrosion.
- Plate deformation.
- Cracks around bolt holes.
- Missing hardware.
- Water accumulation near connections.
- Damage caused by vibration.
Best Practices
- Use only approved connection hardware.
- Never enlarge bolt holes at site without engineering approval.
- Protect galvanized surfaces during handling.
- Replace damaged connection plates immediately.
- Tighten bolts using calibrated tools.
- Recheck all critical connections after module installation.
Importance of Good Connections
A properly connected Solar MMS provides
- Better Structural Stability.
- Improved Load Distribution.
- Higher Wind Resistance.
- Reduced Maintenance.
- Longer Service Life.
- Improved Safety.
Complete Load Transfer Path
Solar Modules
↓
Hat Purlins
↓
Cleats
↓
Rafters
↓
Connection Plates
↓
Columns
↓
Foundation
↓
Soil
Conclusion
Cleats and Connection Plates are small components, but they play a major role in the overall strength and stability of a Ground Mounted Solar Module Mounting Structure. Proper fabrication, correct installation and regular inspection of these connections help ensure that loads are transferred safely between structural members throughout the service life of the solar plant.
In the next article, we will understand Bolts, Nuts and Washers used in Solar MMS, their purpose, bolt grades, tightening sequence, torque control and quality inspection requirements.