What is expected usable life of any 24VDC power supply if continuously being in use in DCS & PLC System ?
Since product datasheets of renowned make power supplies define MTBF more than 3,50,000 to 5,00,000 hrs, but that is not the practical case. Any documented evidence will be helpful.

 

Those numbers indicate that the greatest loss of reliability is outside of the control of the manufacturer, and in the hands of the end user.

 

MTBF is just statistical math, not component wear-out life. In real-world 24/7 DCS panels, top-tier 24VDC supplies usually last 8 to 12 years depending on thermal stress.

The main bottleneck is electrolytic capacitor dry-out (Arrhenius rule: lifespan halves for every 10°C temp rise). Most plants replace them at the 8-year mark during major turnarounds, or when load derating is bad.

What’s the average cabinet temp and load % in your setup?

 

Indeed, even solder connections have a MTBF

 

MTBF is just statistical math, not component wear-out life. In real-world 24/7 DCS panels, top-tier 24VDC supplies usually last 8 to 12 years depending on thermal stress.

The main bottleneck is electrolytic capacitor dry-out (Arrhenius rule: lifespan halves for every 10°C temp rise). Most plants replace them at the 8-year mark during major turnarounds, or when load derating is bad.

What’s the average cabinet temp and load % in your setup?

Average cabinet room temperature is 24-26 Deg.C. Inside cabinet temperature may be around 30 Deg.C. Loading is @20%

 

Average cabinet room temperature is 24-26 Deg.C. Inside cabinet temperature may be around 30 Deg.C. Loading is @20%

With 30°C internal cabinet temp and only 20% load, you're in the sweet spot. Thermal stress on the primary and secondary capacitors is minimal here.

Under these conditions, reputable industrial supplies (like Puls DIMENSION or Phoenix Quint) easily reach 12 to 15+ years of actual service life before capacitor ESR starts degrading significantly.

The main risks at that point won't be thermal wear-out, but rather external transients (lightning/utility surges on the AC input) or dust/humidity accumulation over the years.

If it's a non-critical loop, running them beyond 10 years is common in those benign conditions, but for critical DCS racks, checking AC ripple voltage on the 24V bus during routine shutdowns is the best way to verify health before blindly replacing them.

 

Agreed on Jason's analysis. MTBF is typically published for 25C - reduces substantially when measured at 40C or 60C. The highest internal temperatures typically occur at the transformer (magnetic), but Electrolytic Capacitor degradation the primary factor limiting lifespan. It's impacted by component quality, current loading and/or ambient temperature over time. Extended presence of high input-side harmonic (AC line) can become a factor. Most manufacturers offer various ranges of Power supplies - highest component quality usually available in the higher priced (and longer warranty) models. Your application with 30C and 20% loaded is ideal for very long lifespan of 10-20 years, absent catastrophic events. Measuring for change (increase) in voltage ripple on the DC side is best way to detect degradation in most power supplies. There are some higher end models that may have internal sensing of lifespan, or with communication options, can report information enabling lifespan calculation.