How to Specify Clips, Bolts and Attachment Hardware for Tower Internals
Small hardware is easy to overlook during tower-internals procurement.
Yet missing clips, incompatible bolts, or undefined attachment details can stop installation completely.
For this reason, fasteners and attachment hardware should be treated as a defined part of the procurement scope.
Start with the Scope Boundary
The RFQ should clearly answer:
Who supplies the attachment hardware?
Possible arrangements include:
- all hardware supplied with the internal;
- vessel-side clips already exist;
- supplier provides only removable fasteners;
- field contractor supplies bolts.
Any of these can work.
What creates problems is leaving the responsibility undefined.
Material Compatibility
Bolts, nuts, clips, washers, and tie components may contact:
- the tower shell;
- packing support;
- process liquid;
- corrosive gas.
Their material should therefore be compatible with the surrounding system.
For example, using unspecified carbon-steel fasteners on stainless internals may create corrosion or contamination concerns in some services.
Bolt Grade Matters
Writing only “SS316 bolt” may not always be enough.
Where structural loading is significant, the specification may need to identify:
- fastener material standard;
- strength class;
- thread;
- diameter.
For ordinary light-duty attachment, such detailed control may not be necessary.
Again, the requirement should follow the engineering risk.
Removable or Permanent?
Maintenance philosophy matters.
Some internals need to be removed during:
- inspection;
- cleaning;
- packing replacement.
The fastening method should therefore support the intended maintenance strategy.
A permanently welded connection may be undesirable where routine removal is expected.
Loose Parts Control
Small loose hardware can easily be lost during transport.
The supplier should package and identify:
- bolts;
- nuts;
- washers;
- clips;
- pins.
They can be placed in clearly marked bags or boxes corresponding to the assembly.
The packing list should show them.
Spare Hardware
For site assembly, providing a small quantity of spare fasteners may be useful.
The exact requirement should be agreed in the purchase order.
This is particularly helpful for international projects where replacement hardware may not be immediately available at site.
Galvanic Compatibility
When dissimilar metals are used together in a conductive environment, galvanic corrosion can become a concern.
Procurement should therefore avoid choosing attachment materials solely by cost.
Material combinations should be reviewed where corrosion risk is significant.
Welding Requirements
Some attachment systems involve welding.
The specification should define:
- whether shop welding is permitted;
- whether field welding is permitted;
- welding procedure requirements;
- weld material;
- inspection level.
The supplier should not assume that field welding is acceptable at every site.
Interface Dimensions
Clips and brackets must fit the actual vessel details.
Important dimensions may include:
- support-ring thickness;
- beam width;
- hole diameter;
- bolt spacing;
- clip position.
These should be shown on drawings.
Inspection and Packing
Before shipment, QA should verify:
- required hardware quantity;
- material where specified;
- thread and size;
- part identification;
- packaging.
This is simple but frequently overlooked.
Engineering Takeaway
Fasteners may represent a very small percentage of the order value but can determine whether the entire internal can be installed.
Procurement should define attachment method, hardware material, scope, quantities, and interface details before fabrication.