How Should Spare Packing and Spare Tower Internals Be Defined in a Purchase Order?
Many tower projects require spare material.
Unfortunately, the purchase order may simply state:
Include 5% spares.
That sounds clear until someone asks:
Five percent of what?
For packed-tower procurement, spare quantity should be linked to the actual product and maintenance strategy.
Random Packing
For random packing, spares may be defined by:
m³, kg, or percentage of the main packing volume.
The PO should identify which unit controls.
For example:
Main packing: 20 m³Spare packing: 1 m³
is clearer than “5% spare.”
Ceramic Packing
Ceramic packing may justify a separate allowance because of potential:
handling and maintenance breakage.
The spare quantity should still be listed as a separate commercial line.
Structured Packing
Structured packing spares require more thought.
A percentage of volume may not be the most useful spare.
The project may instead require:
one complete layer, selected segments, or specific replacement elements.
Because the packing is cut to fit the tower, spare geometry should be defined.
Demisters
A spare demister could mean:
extra mesh, one segment, or one complete replacement pad.
The purchaser should state which one is required.
Liquid Distributors
Keeping an entire spare distributor may be impractical.
Spare parts may instead include:
orifice components, nozzles, gaskets, bolts, or removable sections.
The maintenance strategy should determine the spare scope.
Hardware
Small items such as:
bolts, clips, washers, and pins
are inexpensive compared with the cost of site downtime.
Providing a defined quantity of spare hardware can be useful.
Identification
Spare material should be clearly marked:
SPARE
and linked to the tower or internal tag.
It should not be mixed accidentally with installation material.
Packaging
Long-term spares may remain in storage for years.
Their packaging may therefore need stronger:
moisture protection, labeling, or crate construction
than material intended for immediate installation.
Documentation
Spare components should appear on:
packing list and BOM.
This helps future maintenance teams identify exactly what was supplied.
Engineering Takeaway
Spare quantity should be a defined procurement item rather than an unexplained percentage.
The appropriate spare basis depends on whether the product is loose packing, custom structured packing, a demister, an internal assembly, or installation hardware.