When machinery fails during a heat wave, the weather usually takes the blame. Here, Chris Johnson, managing director of bearing specialist SMB Bearings, argues that often the real story sits months earlier, in maintenance decisions that went unaddressed.
Heat places additional stress on almost every industrial asset. Bearings, motors, gearboxes and drive systems operate within defined temperature ranges, and rising ambient temperatures reduce their ability to dissipate heat generated during normal operation.
Well-maintained equipment can usually absorb seasonal temperature swings without issue. When machinery struggles after only a few hot days, it’s often worth looking beyond the thermometer for the root cause.
Heat exposes what maintenance misses
One of the most common areas affected is lubrication. Lubricants perform a vital role by creating a protective film between moving surfaces, reducing friction and preventing metal-to-metal contact. As temperatures rise, lubricant viscosity falls, leaving the lubricant thinner and less able to maintain that barrier.
On its own, this rarely causes a problem. Trouble starts when lubrication is already compromised before the heat arrives. Grease may have aged, contamination may have occurred or relubrication intervals may have stretched beyond what the application needs. Equipment running under these conditions can operate for a long time without obvious symptoms, until the lower viscosity of a heatwave makes the underlying issue impossible to ignore.
The result is often an increase in friction, which generates additional heat within the component itself. This can create a cycle where rising temperatures accelerate lubricant degradation, which then increases friction further. Bearings are often among the hardest-working parts in rotating machinery, and their temperatures can climb quickly once lubrication performance starts to slip.
Temperature affects bearing life directly too. Excessive operating temperatures speed up grease oxidation and shorten lubricant service life. Seals can also suffer, raising the risk of contamination reaching the bearing assembly. The bearing may keep turning, but its expected service life can fall considerably.
Misalignment behaves in a similar way. Small alignment issues place extra loads on bearings and shafts. Under normal operating conditions, these forces may remain within acceptable limits and go unnoticed. During periods of elevated temperatures, however, thermal expansion can make those existing alignment problems more pronounced.
Components expand at different rates depending on their material and operating environment. A system that is already slightly misaligned can experience increased vibration and uneven load distribution as temperatures rise. Again, the heat has not created the fault. It has simply magnified a weakness that was already present within the machine.
Vibration is often the earliest warning sign of a problem developing. Many maintenance teams rely on vibration monitoring to identify bearing wear, imbalance and alignment issues before they lead to failure. Minor defects, though, can sit below alarm thresholds for a long time.
Hot weather can change that. Increased operating temperatures often amplify the effects of existing wear, causing vibration levels to rise enough for a fault to become visible. What appears to be a sudden breakdown may actually be the final stage of a deterioration process that has been progressing gradually over many months.
A heatwave is a stress test
The knock-on effect spreads well beyond bearings. Motors, conveyors, pumps and HVAC systems all rely on efficient rotating components. Because bearings support the vast majority of these motor-driven systems, even small increases in friction can affect both reliability and energy efficiency.
That link between temperature and efficiency is easy to overlook. A bearing operating with excessive friction draws more energy. A motor working harder to overcome mechanical resistance generates more heat. Over time, these losses accumulate. During a heatwave, they become far more visible because the system has less opportunity to dissipate excess heat.
Cooling systems provide a useful example. According to the International Energy Agency (IEA), demand for cooling is increasing rapidly as temperatures rise and heatwaves become more frequent. During periods of extreme heat, HVAC systems, industrial fans and ventilation equipment must operate for longer periods to maintain safe working temperatures and protect sensitive equipment.
Bearings in these systems therefore spend more time under load precisely when reliability is most important. If lubrication has deteriorated or wear is already developing, failures often occur when cooling capacity is needed most.
This is why a heatwave can be useful. When equipment struggles under elevated temperatures, maintenance teams have an opportunity to investigate the underlying cause rather than patch the symptom. Rising temperatures, increasing vibration levels and higher energy consumption can all point towards developing issues that would otherwise stay hidden.
Condition monitoring technologies are making this process easier. Temperature sensors, vibration analysis and lubricant monitoring can provide early warning of developing faults before they lead to unplanned downtime. Rather than waiting for a heatwave to expose a problem, manufacturers can identify and address it as part of a proactive maintenance strategy.
The importance of identifying these issues early becomes even clearer when the cost of failure is considered. According to IDS-INDATA, unplanned downtime can cost UK and Europe based manufacturers £157 billion in 2026. Bearing failures may account for only a small component within a machine, but when they bring critical equipment to a standstill, the wider financial consequences can be substantial.
Heatwaves should therefore be viewed as more than just weather events. They provide a real-world test of equipment condition. Machinery that continues to operate reliably during periods of elevated temperatures is often machinery that has been properly maintained throughout the year.
When failures occur, it is tempting to blame the weather. Yet in many cases, the temperature is simply revealing weaknesses that were already there. A bearing that overheats during a heatwave may have been suffering from lubrication issues for months. A motor that begins vibrating excessively may have been operating with a developing alignment problem long before temperatures increased.
If equipment struggles during a few days of hot weather, the temperature may not be the real problem. More often, it is a sign that the machine has been trying to tell you something for quite some time.
To learn more about bearing selection and lubrication best practice, visit SMB Bearings’ website.
