When should legacy equipment be modernized instead of replaced?
When the valuable part of the asset still has useful life and the real constraint can be removed without inheriting unacceptable reliability, safety or support risk. Age alone is a weak decision criterion.
What argues for modernization?
A sound mechanical base, known failure modes, a contained obsolete subsystem, expensive replacement downtime, difficult integration of a new machine, or a targeted capability gap that can be corrected.
What argues for replacement?
Multiple interacting obsolescence risks, structural wear, unavailable safety support, insufficient process capability, poor maintainability or modernization work approaching the cost and disruption of a new asset without delivering comparable life.
What should be compared before CAPEX approval?
Required output, remaining life, spare-parts exposure, maintainability, documentation, interfaces, implementation downtime, commissioning risk and lifecycle cost - not purchase price alone.