When to use safety wire?

Airplanes undergo a lot of stress. From takeoff to landing and the times in between, there’s stress everywhere. Luckily, there are safety measures in place to ensure an airplane can do its job flight after flight. One such safety measure is small but mighty: safety wire. Also known as locking wire, it is an integral part of aviation maintenance and performance. But what is it and what does it do?

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What is Safety Wire?

Safety wire, as the name suggests is wire. However, there’s a bit more to it than that. Safety wire is used to secure screws, nuts, bolts, studs, and more. These are things that cannot be safely secured by any other practical means. When used properly, the wire will prevent these fasteners from moving. Safety wire is a necessary precaution in areas of the aircraft that undergo a lot of vibration that could potentially cause the loosening of fasteners.

Safety wire is threaded through a hole drilled into the fastener. It is then twisted and anchored to either a second faster or another part, and then twisted again. These twists in the wire are what make it so secure. If done properly, any loosening of the fastener will be counteracted by the tightening of the wire. One way to make sure it’s been installed properly is to see if the twists pass the “righty tighty” test. Does the installed safety wire cause the bolt to tighten, or “tighty”? Then it’s been installed correctly!

However, you must be careful not to over-twist the safety wire. This can make it break more easily when additional stress is added to it. You also don’t want your safety wire to be under twisted either. In general, you want about 6 to 8 twists per inch.

When to Use Safety Wire

Knowing when to use safety wire is crucial in ensuring the safety and longevity of mechanical structures, especially in high-stress environments. Here are some scenarios where safety wire is indispensable:

1. High Vibration Areas

In any application where there is significant vibration, such as in aviation, automotive engines, and industrial machinery, safety wire is essential. The constant motion can cause fasteners to loosen over time, and safety wire acts as a fail-safe to keep components securely in place.

2. Critical Fasteners

For fasteners that are critical to the operation of the equipment—such as those found in control systems, engine compartments, and structural assemblies—using safety wire ensures they remain tightly secured, preventing any catastrophic failures.

3. Emergency Equipment

When securing emergency equipment, such as fire extinguishers and emergency exit mechanisms, you might use a type of safety wire that can break away easily. This ensures that the equipment can be quickly accessed when needed but remains securely in place during normal operations.

4. High-Temperature Environments

In applications like turbines, exhaust systems, or other high-temperature areas, using materials such as stainless steel safety wire ensures that fasteners do not loosen due to thermal expansion and contraction.

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The Different Types of Safety Wire

Because there are different mechanisms that need to be secured, there are different types of safety wire. The most common sizes for safety wire are 0.032 and 0.041 inches in diameter. However, thicker wire will be needed to hold larger screws in place. The most common material for safety wire is stainless steel. Stainless steel is used when you don’t want what it is securing to move.

However, there are times when you do want safety wire to be able to shear or break. For example, you’ll want copper or brass wire when securing emergency equipment such as switch handles, emergency exists, and fire extinguishers. This is because the successful operation of this emergency equipment is dependent on the safety wire being able to break. Copper and brass safety wire, while also more malleable than stainless steel, is usually only 0.015 to 0.020 inches in diameter.  

Safety wire should always be new upon each application since it is single use and disposable. If, upon inspection, you notice safety wire that is loose or missing, be sure to have it replaced as soon as possible.

Precautions to Keep in Mind Before Wiring

Before installing safety wire, you want to make sure that whatever it is securing has been properly assembled first. Safety wire is a failsafe against the vibration and loosening of fasteners, not a replacement for tightening those fasteners.

Make sure you are always using twisting pliers. These special pliers will allow you to grip the two loose ends of a piece of safety wire and twist it properly. However, keep in mind over-twisting will weaken the wire.

General Safety Wire Locking Rules

It is important to remember these rules the next time you are installing safety wire:

• Only use the safety wire once and make sure it isn’t damaged before installation.
• Safety wire should not be chafing or rubbing against any other parts. This can cause it to weaken or even break.
• The length of wire between two fasteners should be as short as possible.
• Fasteners with left-hand and right-hand threads need to be identified before the installation of safety wire.
• The double wire method is the most common and recommended, however the single wire method can be used in hard-to-reach areas.
• The maximum length of a wire should be no more than 23.62 inches, or 600mm.
• Safety wire should be used to secure no more than 3 items together.

Whether you’re doing your own maintenance or maintenance for someone else, it is always a good idea to get a second pair of eyes to look over your work. Installing safety wire is something that aviation maintenance technicians must practice until it becomes second nature. If you’d like to learn more about being an aviation maintenance technician and the different types of maintenance performed on aircraft, contact NCI today!

There has been much discussion revolving around lock wire and safety cable, which reigns supreme. Through our own due diligence, we’ve determined that using lock wire to retain fasteners is time-consuming and error-prone, which makes it costly. Lock wire also requires extensive training and produces sharp ends when cut, which can cause serious injury to the technician.

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Meanwhile, extensive research and testing at GE Aircraft Engine facilities revealed that the use of Bergen Safety Cable instead of lockwire resulted in a 50 percent reduction in installation time with consistently superior quality and lower assembly costs.

In today’s manufacturing environment, speed and quality are everything. Here are a few reasons why Bergen Safety Cable is superior to lock wire.

7 Major Benefits of the Bergen Safety Cable System:

1. Reduction of potential foreign object damage

   When traditional lock wire is removed from an application, it needs to be cut many times in order to be completely removed. This process produces numerous small fragments which are difficult to keep track of. If the scrap material cannot be fully recovered, it can cause serious damage to the aircraft and potentially its passengers as well. This is known as foreign object damage or FOD. However, when Bergen Safety Cable is removed, it produces only two pieces of scrap, making it easy to keep track of and eliminates the potential for FOD.

2. Improved access to tight areas

   The Bergen Safety Cable tool was designed specifically to allow access to restricted areas. The short length of the tool as well as the tool nose, which can be rotated 360 degrees, assists operators working in these tough conditions.

3. Elimination of guesswork

   Using traditional lock wire requires that the operator determine how much wire to use, how many twists per inch, and many other important details. If a step is missed or completed incorrectly using lock wire, the operator must start all over. With Bergen’s Safety Cable system, all the guesswork is eliminated. The operator simply strings the cable through the fastener holes and the safety cable tool does the rest, which results in perfectly wired fasteners every time and increased production.

4. Minimal training required

   The cumbersome nature of applying traditional lock wire can take a very long time to master. With the streamlined method of the Bergen Safety Cable system, a new operator with zero experience can be up and running within 30 minutes.

5. Eliminates injuries

   Traditional lock wire produces very sharp ends when cut, which poses a serious threat of injury to the operator. The fused ends and flexible nature of Bergen Safety Cable removes the risk of injury 100 percent.

6. User-friendly tooling

   The Bergen Safety Cable tool was designed with the user in mind. Our tool utilizes the best principles of ergonomics, which allows the tool to fit comfortably in the operator’s hand.

7. High return on investment

   Using the Bergen Safety Cable system simplifies the task of lock wiring fasteners together. The simplicity translates into time savings, which allows an operator to complete a job in half the time. The time savings allows the operator to move on to the next project faster, which can double production.

Other benefits include reduced inspection time, consistent cable tension on each application, and a material that is lighter than lock wire and traditional safety wire. Choosing to use Bergen Safety has a myriad of significant benefits that our customers agree improve product quality and save them time and money across the board.

If you are looking for more details, kindly visit Monel Wire Mesh Features.