Large-Diameter Tower Internals RFQs: What Site Information Should Be Confirmed Before Quotation Becomes Final?

Large-diameter tower internals create a special procurement risk.

A supplier may fabricate a component correctly according to the RFQ and still encounter installation problems because the RFQ was based on nominal equipment dimensions rather than actual site conditions.

This risk becomes greater in retrofit projects.

Nominal ID vs Actual ID

Older vessels may have:

ovality, corrosion, lining, distortion, or previous modifications.

Where fit is critical, the buyer should decide whether field measurement is required.

Manway

Actual clear access should be confirmed.

For large internals, this controls the maximum section envelope.

Support Ring

Important dimensions include:

inside diameter, width, thickness, elevation, and condition.

A replacement support grid or distributor may depend on these details.

Existing Beams

Beam position can interfere with:

distributor arms, collector chimneys, support panels, and demister sections.

Their location should appear on the site drawing.

Nozzles

The supplier should receive accurate:

nozzle position, diameter, orientation, and projection

for any internal that connects to them.

Tower Verticality and Level

For liquid distributors, tower level and internal support elevation can matter.

A new distributor cannot correct severe vessel or support-ring misalignment unless the design specifically accounts for it.

Existing Internals

Some internals may remain in place while others are replaced.

The supplier needs to know what equipment remains and where it is located.

Installation Route

The path from outside the vessel to the final installation position may be more restrictive than the manway itself.

Large projects may need to consider:

platform access, internal ladders, beams, and lifting space.

Photography and Site Survey

For retrofit work, photographs and a focused dimensional survey can reveal conditions that old drawings do not show.

This is often more valuable than adding another page of generic specification text.

Engineering Takeaway

Large-diameter internals should move from preliminary quotation to final fabrication only after critical site geometry has been confirmed.

Field information is particularly important for retrofit towers.