Ripple effect: How vibrations testing can save millions

When looking at pit-to-port successes at mines, particularly from a cost perspective, the seemingly small changes can make the biggest impact. NAM recently talked to Dialight CEO Fariyal Khanbabi about how vibrations – or lack thereof – can impact other systems, specifically safety through proper lighting.

NAM: Why is vibration such an important consideration when looking at upgrading lighting in metal and mining operations and how can vibration negatively affect lighting?
Fariyal Khanbabi: Vibrations caused by heavy machinery, combined with the harsh environment and exposure to debris on mining sites, can drastically impact the reliability and performance of critical mining equipment such as lighting fixtures.

Any lighting fixture, whether it be LED (light-emitting diode) or conventional HID (high-intensity discharge), is an assembly of parts, where robustness to movement and physical energy needs to be understood and factored into its design. Because these fixtures are often mounted in locations of high or consistent vibration, it’s critical to understand the effects it can have on the fixture drivers, power connections, housing materials and even the brackets and poles on which they are mounted. Otherwise, the fixtures may fall or suffer premature failure. 

This, in turn, can have a negative impact on overall visibility and mine safety – causing extensive downtime and delaying productivity until these fixtures are fixed or replaced. 

What are some pitfalls that you should look for when reviewing vibration certifications and claims? What are some practices that mining site managers, heavy equipment operators and company leaders should undertake and report upon in order to provide the highest confidence in a fixture’s ability to stand up to vibration?
Constant vibration of non-stop heavy machinery can literally shake lighting fixtures apart, rapidly exposing miners to hazards such as injury or even death. Conventional HID sources are especially vulnerable due to the inherent design of the lamps which can be easily and adversely affected by vibration and impact, causing premature failure. But even some LED fixtures, with their solid-state design can suffer the same fate if they aren’t designed to withstand these conditions. 

Mining managers need to insist on installing or upgrading to heavy-duty, industrial-grade lighting fixtures that are tested to withstand high-vibration environments and include built-in shock resistance. Long-life potted drivers and proven mechanical designs can protect against damage from vibration and shock-related failures. 

For example, as part of Dialight’s LED lighting fixture design validation, we subject all fixtures to various sinusoidal vibration tests over a given frequency range (from slow to fast) for a fixed duration. After the initial test, or endurance sweep, an engineer will note any damaged components, including electrical PCBAs, hardware and mounting bracketry and weaknesses uncovered, and resolve it prior to the product’s use. This methodology gives confidence to our customers, who work in harsh, often unpredictable industrial, chemical and mining environments, for the greatest variety of use cases.

What are the differences between resonant dwell tests and endurance sweeps? Are there benefits to performing both tests on equipment?
An endurance sweep subjects equipment such as lighting fixtures to a given frequency range, typically moving from slow to fast, for a fixed duration of time. In this method, acceleration is applied gradually, while held for a period long enough that the equipment has sufficient time to fully distribute the resulting internal loads. Conversely, resonant dwell tests are conducted by vibrating test units at its unique, site-specific frequency where the energy input to the test unit is the greatest. 

While failures found during the resonant dwell test aren’t truly applicable to real world conditions, due to the test featuring environment extremes, both of these various frequency tests check different aspects of vibration, such as g-forces, fixture velocity and kinetic energy. 

Engineering teams use results from both tests when designing fixtures in order to understand and uncover the durability modes at extreme physical energy levels. Knowing these failure modes helps to identify any potential weakness in fixtures that will be used at the work site. In vibration testing, endurance sweeping minimizes the difficulties of asking a customer to apply the resonant dwell test results to their real-world applications. Endurance sweeps give confidence to end users over the greatest variety of use cases.

The volatile combination of vibration, explosive gases and dust in the air, combined with the potential for ignition from an arc or spark from a malfunctioning light – or even just the high heat output from most fixtures will quite literally break down and fry electrical components – resulting in dire consequences. 

What is the difference between shock and vibration? Why is it important to test both? 
Shock is a rapid motion, caused by sudden acceleration or deceleration of the material, such as a crash test performed on a vehicle – a high-level of force is applied to the test unit, in this case a car, for a brief duration. 

Vibration is a mechanical phenomenon whereby oscillations occur around an object’s point of equilibrium. These oscillations may occur periodically or at random and vary in speed.

Classical shock testing has the potential for producing adverse effects on the physical and functional integrity of all materials in a fixture. Durations of shock that correspond with natural frequency periods of the unit will magnify the negative effects on the unit’s overall physical and functional integrity. Vibration testing imparts energy, or stress, on all the mechanical structures according to their mass, distance from center of mass and geometry. This includes the mounting brackets, hardware, enclosure housings, drivers, LEDs and every solder joint in lighting fixtures.

Both tests are important because shock tests determine the upper bound level of acceleration loads applied, while also testing packaging that protects the material’s physical and functional integrity. Vibration testing validates a fixtures overall design and durability.

How does picking equipment properly designed and tested to stand up to vibration help improve the overall operations and productivity of metal and mining applications?
Miners and other heavy industrial organizations depend on lighting every single day to illuminate some of the world’s most dangerous work sites. Sufficient lighting can keep employees safe from poor or collapsed infrastructures, alert site managers of hazardous chemical leaks or spills and warning signs for potential explosions.

The volatile combination of vibration, explosive gases and dust in the air, combined with the potential for ignition from an arc or spark from a malfunctioning light – or even just the high heat output from most fixtures will quite literally break down and fry electrical components – resulting in dire consequences. While choosing inexpensive, subpar lighting fixtures may seem like a money saving opportunity today, it will only lead to more maintenance and safety risks that cost more tomorrow. 

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