In a fiber optic network installation, one of two methods is used to lay the cable into place: blowing or pulling. This article covers the fiber optic cable blowing procedure from start to finish. You’ll learn how blowing is different from pulling, the equipment needed, and the challenges faced during the process.
What is the fiber optic cable blowing procedure?
In fiber optic cable blowing, high speed air flow is combined with a mechanical pushing force to produce the installation known as blowing or jetting. This is the preferred method used to push fiber optic cable through a pre-installed conduit.
Several hundred meters of cable are pushed into the duct before compressed air is injected into the duct inlet. The fiber optic cable is attached to a blowing head, which has two seals to grip the cable tightly. As the air pressure builds up, the jetting motion pushes the fiber optic cable through the conduit.
How to maximize performance in a fiber optic cable blowing installation
Take the following factors into consideration for a straightforward installation using fiber optic cable blowing:
Friction Reduction
Always opt for a fiber optic cable that has a low coefficient of friction (between the cable outer surface and the duct inner wall). This will reduce the amount of air required to push the cable through the conduit. Blowing lubricants such as oil can also be used to reduce this friction.
Conduit Size
The size of the conduit you’re blowing the cable through is important. Choose a conduit that is slightly larger than the fiber optic cable. This will allow the cable to be blown into place with ease, and less air pressure required.
Air Pressure
A word of warning: too much air pressure from the blowing equipment can damage the fiber optic cable. Use the minimum amount of pressure required to push the fiber optic cable through the conduit.
Temperature
Temperature is an important factor in your installation. If the fiber optic cable is too cold, the cable jacket may become brittle and be more likely to break. Similarly, if the air is too cold, it will condense and freeze, which can also damage the fiber optic cable.
Air Flow
Use an air compressor with a high flow rate. This will help to reduce the pressure drop as the air moves through the system. If you’re not sure, conduct a pressure test before you begin.
Cable length and flexibility
The length of the fiber optic cable will determine the amount of time it takes to install. Bear in mind that some cable manufacturers will specifically advertise their fiber optic cables are ideal for a blowing installation: for example, uni-tube, multi-tube, unarmored, armored, and microduct cables. These will be flexible, making them easier to install than a more rigid design where cable damage can occur.
Duct type
The duct size and type will also have an impact on the ease of installation. It’s easier to install a fiber optic cable in a duct system with a smaller diameter duct rather than a larger diameter duct.
Duct connectors
If the fiber optic cable is being installed in an existing duct, pay attention to the connectors. Make sure they’re sealed tight so air can’t escape. This will also help to reduce the pressure drop and increase the efficiency of the installation.
What’s the difference between blowing and pulling cables?
The fiber optic cable blowing process has a number of advantages over the pulling method and is often the first choice for an installation. Firstly, it causes less damage to the fiber optic cable. Secondly, it is less likely to get stuck in the conduit. And thirdly, it is faster than pulling, meaning savings in manpower and resources.
Although fiber optic cable blowing is often the favored solution, there will be some scenarios when using a pulling eye and a winch is a better fit.
Lack of air pressure
If the fiber optic cable is going to be installed in a long conduit, it may be difficult to generate enough air pressure to accommodate the blowing distance required. In this case, pulling would be a better option.
Installation method around bends
The fiber optic cable blowing method is suitable when you’re installing around obstructions or bends. However, knowing the minimum bend radius of your cable can help you plan accordingly. If you’re not sure, The Network Installers can advise on the best method of installation.
Installation process in live environments
If the fiber optic cable is going to be installed in a live environment, it is often better to pull the cable as this minimizes the risk of disruption to your telecommunications service.
How do you bury fiber optic cable in a blowing installation?
In a fiber optic installation, the cable is typically laid in an underground conduit to protect the cable jacket. So, how does this work in a blowing installation? Simply, the blowing head is inserted into the conduit and the fiber optic cable is fed through it. The air pressure from the compressor pushes the fiber optic cable through the conduit and into place.
How do you pull fiber optic cable through a conduit?
In comparison, if you’re completing a pulling installation, a fiber optic cable is attached to a pulling head, with two seals that grip the cable tightly. The pulling head is inserted into the conduit and the fiber optic cable is fed through it. The air pressure from the compressor pulls the fiber optic cable through the conduit and into place.
Essential fiber optic cable blowing procedure equipment
In order to blow a fiber optic cable, you will need the following:
- An air compressor is used to create the air pressure that will push the fiber optic cable through the conduit.
- A fiber optic cable will be blown through the conduit.
- A blowing head is a device that attaches to the fiber optic cable and allows it to be blown through the conduit.
- A duct is a pipe that the fiber optic cable will be blown through.
- A length of conduit is the length of pipe that the fiber optic cable will be blown through.
Learn more about the fiber optic cable blowing method
If you have any questions about the fiber optic cable blowing procedure as part of a new installation or a cable repair project, please don’t hesitate to contact The Network Installers. We’ll talk you through the best options based on your individual fiber optic network configuration. Get in touch today.
