Occasionally our clients ask us to design products people can rely on in extreme environments such as potentially explosive, very hot or cold, high humidity, or crawling with pathogens.
A lot of times these products also qualify as “mission-critical,” meaning people’s lives depend on them. Their failure is unacceptable. Extreme conditions like these often present extreme product-development challenges. Here are some of the harshest environments you might come across as a product designer or engineer and the ruggedized solutions and products that stand up to them.
Extreme Environment #1: Explosive Atmospheres
Coal and crude oil deposits often have associated natural gas that poses an explosion hazard. Electronic devices can be risky because they could theoretically create a spark. We designed the Scott Protégé Multi-Gas Monitor to be intrinsically safe in such an environment: in other words, the gas detector is incapable of releasing enough energy to ignite an explosive atmosphere. Making it intrinsically safe requires capping the electrical or thermal energy available from it, which is obviously a challenging requirement for an electronic device.
Not everything can be made intrinsically safe. In a device with a high-power circuit, internal and external shorts caused by internal failures or dust could generate a short circuit. Shorts can lead to sparks or heat rise, which could auto-ignite the atmosphere. Such a device would require another method, such as an explosion-proof (XP) enclosure, to be made safe for use in this environment. This is what we did – designed an XP enclosure – for a different Scott gas monitor. When the atmosphere inside of it was ignited, no spark or substantial temperature rise escaped. Testing that device required igniting them in a controlled environment at UL. (It’s always cool to blow stuff up.)
Of course, getting that crude oil out of the ground safely is only the first challenge; next you have to refine it. Certain parts of a refinery work at such high temperatures and pressures that traditional lubricants burn away instantly. Critical, moving mechanical parts such as ball bearings are often made of graphite, which is self-lubricating and super hard, even at temperatures that would melt tungsten or steel.
Extreme Environment #2: Exceptionally Low Temperatures
Extreme cold is another environment where ensuring safety and function is challenging. Low temperatures can change the properties of materials and make metals and plastics brittle. (Interacting with the device is another factor in the extreme cold – push buttons can become stiff, and you have users wearing bulky gloves. We collaborate with our interaction design colleagues to work around those constraints.)
The cold also wreaks havoc on batteries. This is why photographers shooting in super cold environments bring completely mechanical cameras from the 1960s and ‘70s instead of the amazing modern gear available today. Gordon Wiltsie, for example, took many of his famous shots of Antarctica using the all-mechanical Nikon FM2.
Extreme Environment #3: Wet and Salt-Wet
Water and its sister, humidity, rusts metals, degrades chemicals and erodes material. When mixed with salts, its corrosive abilities multiply. Any product designed for the outdoors – even ones meant to be used in conditions typically considered more recreational than extreme, such as pool- or oceanside – has to contend with wetness and corrosion.
We recently worked on a satellite tracking device, a little box that sits on the outside of a cargo shipping container or large construction equipment, and communicates regularly with a satellite to send GPS coordinates to the owner of the equipment. Ours has an integrated solar panel to help recharge its battery, and it’s designed to survive ten years exposed to sun, wind, rain, cold, and salt water. To make sure they’ll stand up to harsh conditions, we tested those little boxes by freezing them, then dropping them onto concrete over and over, cycling from cold to hot to cold again and then vibrating them to simulate every possible stress they might encounter. Not to mention making them out of UV-resistant plastic.
The Blue Ocean Megaphone we designed for Nielsen-Kellerman is built to hold up to conditions that commonly ruin other megaphones, including water damage, corrosion, cracking, and breaking. It floats when dropped in the water and operates perfectly after being fully submerged. To make certain, we drop-tested it and optimized the horn, can, handle and boot design assembly for waterproofing and sealing.
Cars are another product that cope with the corrosive outdoors, and even their interiors can be affected by the tough environment. For example, humidity may have played a role in degrading the propellant used in the defective Takata airbags now facing a massive recall. To test for potential problems like this one, engineers use controlled environment chambers to cycle through quick changes in temperature and humidity.
Extreme Environment #4: Crawling with Pathogens
By now we know that hospital rooms are crawling with germs that can lead to serious infectious diseases. A 2013 CDC report pinpointed hospitals as the most acute source of antibiotic-resistant germs. To make products safer for hospital use, we ensure they’re wipeable and that the materials are safe for the range of hospital-approved cleaning agents. Still, wiping down surfaces is not 100% effective – germs can survive inside cracks and crevices, and sometimes all wiping does is move the germs from one surface to another. We partnered with Sanosil to help design a different solution: their fogging disinfectant system emits a dry mist containing silver ions and hydrogen peroxide that has been shown to significantly cut a disease’s transmission rate. It is even being used to fight the spread of ebola.
Another challenge is designing medical and surgical products for sterilization by autoclave, a pressure chamber that heats up to 249 degrees Fahrenheit for about 15 to 20 minutes to zap equipment of bacteria, fungi, viruses, and spores. This presents both design and materials considerations. Autoclave temperatures exceed the maximum operating temperatures of many common thermoplastics – they would become liquid at these temps. Commonly used materials such as polypropylene, HDPE and even ABS and PC are softened at these temperatures. More expensive, but high melting point temperature materials such as Radel (PPSU), polysulfones, and PEEK are commonly used when repeated autoclaving is required without loss of mechanical integrity. Since autoclaving is a steam process, there are design constraints as well – as water is likely to condense and could collect inside the product. Design for autoclaving, and even gas sterilization procedures, often requires designing the parts to include drain holes for draining, outgassing and evaporation.
Other common processes for sterilization include ethylene oxide (ETO) gas, and gamma radiation – each with their own material constraints. While these sterilization methods are more typically used for one-time use disposable products, autoclaving is more typically used for products that are intended for a relatively long life of reuse. ETO and gamma processes can allow the use of lower cost, lower temperature materials – but it is still a good idea to check compatibility with the sterilization process of choice.
Extreme Conditions Call for Extreme Creativity
Clients sometimes come to us with a product that is half-developed by the time they realize it won’t be able to stand up to all the challenges posed by a hostile environment. Our breadth of experience allows us to look at a device and intuitively know which direction to go in. We’ve done waterproof, rustproof, shock proof, and explosion proof. We’re experts at sealing and circulating fluid dynamics. We also do a lot of drop and shock testing— the Protégé gas monitor we mentioned above was sealed and drop tested, because a drilling rig can be wet and slippery. And we’ve designed military spec devices that can survive repeated 12 foot drops onto concrete and pelting with hail (or rather, 1/2 inch ball bearings), no problem. (That was fun.)
Designing for both extreme and dangerous environments takes a combination of know-how and creativity. It’s often best to start with the most important constraint (intrinsic safety, for example) and then consider how and whether other constraints (water- or dust-proofing, drop testing) are necessary, and how to incorporate them. These product development scenarios get easier with experience, and we truly enjoy the challenge.