Approved for Manufacture: What Must Be Frozen Before Tower Internals Production Starts?

A signed purchase order does not always mean manufacturing should begin.

For custom tower internals, several engineering inputs may still be changing.

Starting production too early can create:

• scrap;
• rework;
• schedule disputes;
• additional cost.

This is why many projects use an Approved for Manufacture, or AFM, milestone.

Commercial Order and Manufacturing Release Are Different

The purchase order can authorize the supplier relationship.

AFM authorizes the supplier to fabricate against a defined technical baseline.

These can happen on different dates.

This is particularly important for custom:

• distributors;
• support grids;
• collectors;
• structured packing;
• demisters;
• gas distributors.

Freeze the Governing Drawings

Before AFM, the supplier should know which drawing revisions control production.

There should not be:

two active GA drawings or unresolved purchaser comments.

The released drawing set should be clearly identified.

Freeze Material

Material must be confirmed before:

raw-material purchasing and cutting.

This includes relevant:

• alloy;
• polymer;
• ceramic grade;
• sheet or wire thickness.

Material substitution discussions should be closed first.

Freeze Tower Interfaces

Critical interface data may include:

• tower ID;
• support-ring elevation;
• nozzle locations;
• manway dimensions;
• beam arrangement.

If any of these remain provisional, fabrication may be premature.

Freeze Functional Parameters

For a distributor, this might include:

• design flow;
• outlet density;
• orifice size.

For a demister:

• thickness;
• wire size;
• density.

For structured packing:

• geometry;
• element height;
• segmentation.

Not every calculation must be reissued.

But the manufacturing-defining parameters need to be stable.

Close Technical Deviations

Any supplier deviation that affects fabrication should already have a disposition.

An unresolved deviation cannot safely coexist with AFM status.

Close Drawing Comments

Comments such as:

“Confirm manway later”

should not remain open if manway size controls segmentation.

Projects should distinguish between:

comments that affect manufacturing and comments that can be closed later.

Confirm Inspection Requirements

Before manufacturing starts, the supplier should know whether the buyer requires:

• hold points;
• witness points;
• PMI;
• NDT;
• water testing;
• trial assembly.

Some inspections can only occur at specific stages.

If the requirement arrives after fabrication, the original inspection opportunity may be lost.

Confirm Documentation Inputs

Certain documentation needs to be prepared during manufacturing rather than reconstructed afterward.

For example:

• material traceability;
• weld records;
• batch records;
• inspection records.

The supplier should therefore know the final documentation requirement before production.

Issue a Formal Release

AFM should ideally be a controlled action:

• drawing stamp;
• email authorization tied to revision;
• project document status.

A vague phone call saying “you can start” provides poor protection for either party.

What Can Still Change After AFM?

Changes may still occur.

But once AFM is issued, a change should enter formal change control.

The project should understand that a late revision may create:

• material waste;
• additional labor;
• delivery impact.

Engineering Takeaway

Approved for Manufacture is the point where the project declares the manufacturing definition sufficiently stable.

Before that milestone, material, geometry, interfaces, critical parameters, deviations, inspection requirements, and governing revisions should be frozen.