Aluminum Extrusion: Staying Cool with Nitrogen

Aluminum is a highly malleable material, which is readily shaped for any number of purposes. The aluminum extrusion process is key to shaping aluminum, and it must be completed in an inert environment to reduce the formation of oxides. Learn why this is important and how facilities can reduce the risks of health hazards in an inert environment. 

How Aluminum Extrusion Works

Billets of aluminum are first heated to above 800 degrees Fahrenheit to become malleable, then coated with a lubricant so the molten metal will not stick to the extruding ram. 

The ram presses the aluminum billet through a die, which is cast in a given shape. As the aluminum passes through the die, liquid nitrogen flows over the metal to prevent oxides from adhering to the aluminum. This also extends the lifespan of the die by cooling it. In some operations, nitrogen gas is used instead of liquid. While the overall purpose is the same -- to keep out oxides, which can cause the extruded aluminum to crack -- the gas does not cool the die. 

The shaped aluminum passes through the die, then exits the press where its temperature is taken. Temperature records help maintain press speeds, for plant efficiency. The extruded aluminum pieces are then transferred to a leadout table and a puller, where the metal is cooled using fans. Some mixtures of aluminum are cooled with water as well as air. 

The cooled and cut aluminum is then stretched via a stretcher, a step that increases the hardness and strength of the finished piece. Finally, extruded aluminum pieces are cut for precision and aged under controlled temperatures via heat treatment. 

The entire process resembles a play-doh modeling kit, where the dough is squeezed through a press and comes out in a tube or a star shape, for instance. 

Extruded aluminum pieces are used in a variety of industries, including railway cars, lightweight automobiles, bridge decking, solar panels, and coaxial cables. 

Whether liquid or gaseous nitrogen is used, there is a risk of a nitrogen leak causing an oxygen deficient atmosphere. Nitrogen is naturally heavier than oxygen, so it displaces the oxygen molecules in the atmosphere. Since nitrogen has no color, odor, or scent, employees are unable to tell there's a leak. A leak poses health hazards in addition to work disruption and revenue losses. Fortunately, there's an easy way to protect facility staff. 

Why Oxygen Sensors Should Be Used With Aluminum Extrusion 

When nitrogen displaces oxygen, oxygen levels start to fall unbeknownst to anyone present. Eventually, oxygen levels will grow dangerously low. In an oxygen deficient environment, employees may start to feel dizzy or confused. Some may sweat, start to cough, or experience rapid breathing and increased heart rate. Death via asphyxiation is a real risk. 

An oxygen sensor provides assurance that there is no leak, since it tracks levels of oxygen in the room 24/7. As long as oxygen levels are above the OSHA threshold of 19.5, the monitor will be silent. If liquid or gas nitrogen starts to leak, leading oxygen levels to fall, the monitor will sound an air horn and flash lights. Staff will understand there is a problem and will have time to evacuate to safety. Staff can also check the monitor face at any time to see oxygen levels at a glance. 

PureAire offers oxygen monitors that feature zirconium sensors, which last long and withstand shifts in barometric pressure and temperature. These monitors can operate for over 10 years with no annual maintenance or calibration. PureAire's monitors work in temperatures from -40 Celsius to 55 Celsius and even function in confined spaces, such as basements or freezers.  Learn more about PureAire's products at www.pureairemonitoring.com. 

How Do Potato Chips Stay So Fresh In The Bag?

Chip bags have all that air in them for a valid reason — and it's not air, anyway, it's nitrogen gas. 

So what is this gas doing in your bag of crisps? First, the gas acts as a preservative so your chips are as crispy when you open the bag as the day they were packaged. Next, the gas also gives the chips a cushion. In what's known as slack fill, chips manufacturers intentionally inflate the package with nitrogen gas to protect it from damage in transit. Without the cushion of nitrogen gas, chips would likely wind up at their final destination as a bag of crumbs, because the chips inside the bag would break through being stacked in transit or packed onto a grocery store shelf. 

Nitrogen gas is piped into the chip bag before packaging. The gas displaces oxygen from the bag, which is then filled with chips and sealed. Without this step, chips would have a much shorter shelf life. Oxygen in the bag would cause the chips to stale and humidity found in air would lead to soggy crisps — no signature crunch.

While nitrogen gas does play an important role in keeping chips fresh and full-sized, there is a danger in using this gas. Not to the chips — since nitrogen lacks odor, color, and flavor—but to the employees in the processing plant. Nitrogen preserves the chips' texture because it displaces oxygen. If nitrogen leaks in the packaging facility, it will displace ambient oxygen — eventually causing levels to fall so low they threaten employee health. 

Workers become confused and dizzy when they breathe air that lacks sufficient oxygen. Oxygen-deficient air also causes respiratory problems and can lead to death via asphyxiation. 

The same properties that made nitrogen a good choice for preservation — lack of color, odor, and taste — mean employees cannot detect a leak until it is too late. 

Fortunately, there's a simple and reliable way to make sure food packaging facilities aren't leaking nitrogen: Using oxygen sensors to measure the amount of oxygen in the air. 

How an Oxygen Deficiency Monitor Protects Food Packaging Plant Workers

An oxygen monitor tracks oxygen levels in the facility, which should be stable as long as there is no gas leak. Since nitrogen gas displaces oxygen, oxygen levels will fall in the event that nitrogen starts to leak. When oxygen levels fall below safe thresholds — which are defined by OSHA as 19.5 percent — the oxygen monitor will sound an alarm. Employees will be able to leave the packaging floor and alert emergency personnel before the situation turns deadly. 

For peace of mind, employees can check the levels of ambient oxygen by looking at the face of the monitor. A silent monitor — with no loud alarms or flashing lights — indicates that all is well. Lights and loud noises mean staff should stop what they are doing and vacate immediately. 

To properly protect employees, one oxygen deficiency monitor should be installed in any room where nitrogen gas is used or stored. Facilities that use nitrogen generators to produce nitrogen on demand also need an oxygen sensor near the generator. 

PureAire's oxygen deficiency monitors are a cost-effective long-term solution to nitrogen leaks in food packaging plants. These monitors provide accurate readouts even when temperatures are as low as -40 Celsius, and operate reliably even in confined spaces, including freezers and basements. 

PureAire's monitors feature a zirconium sensor, which requires no maintenance and no calibration after installation. PureAire's O₂ monitors provide consistent readouts regardless of the weather or barometric pressure, which makes them reliable solutions for safety-minded employers. 

If you are looking for an oxygen monitor that is easy to use, accurate, and built to last, look to PureAire to provide solutions that protect your employees and deliver peace of mind. Browse products at www.pureairemonitoring.com.