What Should Be Verified Before Approving a Tower-Internals Supplier Drawing for Production?
A purchase order is not the end of tower-internal engineering.
For custom internals, one of the most important steps occurs before production:
drawing approval.
A buyer or EPC should not review only the overall diameter.
The drawing is the final opportunity to catch interface errors before material is cut, welded, molded, or assembled.
Verify the Design Basis
The drawing should match the agreed project data:
- tower diameter;
- process conditions;
- material;
- product type;
- quantity.
If the design basis changes, the drawing may need revision.
Check Overall Dimensions
Verify:
- outside diameter;
- height;
- layer thickness;
- support elevation;
- clearance.
Dimensions should correspond to the actual vessel, not merely an old specification.
Check Segmentation
For components entering through a manway, verify:
- number of segments;
- maximum segment size;
- assembly pattern.
The drawing should make installation practical.
Check Material Specification
“Stainless steel” is not sufficient if the PO requires SS316L.
The drawing or BOM should identify the agreed material grade.
The same applies to:
- PP;
- PVDF;
- ceramic;
- mesh wire;
- fasteners.
Review Interfaces
Confirm how the internal connects to:
- support ring;
- beams;
- feed nozzle;
- adjacent components.
A drawing should answer how the part is actually installed.
Check Flow Openings
For support plates and grids, verify that structural members do not unnecessarily block gas or liquid flow.
For distributors, check:
- branch arrangement;
- outlet layout.
For demisters, check:
- sealing;
- support.
Verify Orientation
Some components have a required orientation relative to:
- inlet nozzle;
- manway;
- adjacent layers.
This should be clearly shown.
Check Installation Details
Useful drawing information includes:
- bolt locations;
- segment markings;
- lifting points;
- assembly sequence.
A production drawing that cannot guide installation is incomplete for many retrofit projects.
Confirm Revision Status
Multiple drawing versions may circulate during a project.
The approved revision should be clearly identified.
Production should not begin from an outdated version.
Use Approval Comments Carefully
If the buyer writes:
“Approved with comments”
the supplier should confirm that all comments are incorporated before fabrication.
Unresolved comments can create disputes later.
Consider Inspection Requirements Before Production
If the project requires:
- dimensional inspection;
- material certificates;
- welding inspection;
- trial assembly;
these requirements should be confirmed before manufacturing begins.
They may affect production planning.
Final Engineering Principle
Drawing approval is an interface-control process.
The objective is not simply to confirm that the product looks correct.
It is to verify that the internal will fit the real tower, connect to surrounding equipment, use the correct materials, pass through the access opening, and perform its intended function.