4 Advice to Choose a Optical Cable Tractor

5.0 PLOWING VERSUS TRENCHING

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5.01 In general, the most desirable and economical method of cable placement in open or rural areas is plowing. Here there will be fewer obstacles to impede the progress of the plowing equipment.

Advantages of Plowing:

• Speed of installation in open areas
• Less ground disturbance than may be caused by trenching

Disadvantages of Plowing:

• Large size and high cost of equipment
• Requires skilled equipment operators, quality supervision, and equipment in good condition
• Can not be used for all soil and terrain conditions
• Possibility of damaging cables or underground utilities

5.02 In urban or suburban areas where there can be many obstacles such as underground utilities, sidewalk and paved road crossings, trenching has advantages.

Advantages of Trenching:

• Lower cost of equipment
• Digging operation is separate from cable placement
• Better depth control
• Less risk of damaging underground utilities
• Provides the opportunity to place conduit at the same time

Disadvantages of Trenching:

• Slower rate of cable placement than with plow
• Not suitable for all soil and terrain conditions

6.0 PLOWING

6.01 It is important to notify all other utilities that may occupy the same right-of-way (ROW) that a fiber optic cable will be placed. If there is a “1-call-center” or a local utility location and coordination committee active in the area, they should be notified 72 hours before plowing operations begin. This will provide them with enough advance notice to locate and mark their route along the ROW prior to construction.

6.02 The ROW should be staked in advance of plowing. The locations of all underground structures such as culverts, water lines, and other utilities should clearly be marked for the plowing crew. If necessary, obstructions should be uncovered prior to plowing.

6.03 Cable plows are generally of two types: static and vibratory. Either type may be used to install fiber optic cable. Steerable plows, which can be offset to place the cable away from the centerline of the cable plow prime mover, are available in both types.

6.04 Successful and economical plowing of cable depends primarily on having equipment powerful enough for terrain conditions. Local soil conditions and cable depth are the two primary determining factors in the correct size of tractor necessary for plowing. Too much horsepower is better than too little horsepower.

6.05 A crawler tractor is most suitable for static buried cable plowing. A tractor equipped with a torque converter drive should be used whenever it is available. This will permit smoother plowing performance by absorbing the shock loads encountered in the plowing operations.

6.06 The drawbar force for soil penetration by a static plow may reach a magnitude of tens of thousands of pounds. Heavy and large equipment is needed to generate a drawbar force of this magnitude. A plow that vibrates substantially reduces the drawbar force required to plow-in cable when compared with the force necessary to move a static plow of the same size. With drawbar force reduced, the equipment size required for the plow is also reduced.

6.07 The reel carrier should allow for easy installation of the reel using such features as hydraulic lift assistance and should accommodate a reel or reels of adequate size for the intended installation. The cable feed system includes all the components mounted on the tractor which supports and guides the cable as it is fed into the plow chute. Typically, it includes a reel carrier, rollers and/or guide tubes. Use of capstan drive units is recommended. Capstan drive units, which provide pulling force of up to 250 pounds can help prevent excessive pulling, tension at the cable feed tube entry and exits.

6.08 All rollers or guides in the cable feed system which cause a change in the direction of the cable path must conform to the minimum bend radius of the cable being placed. Small diameter rollers (fairleads) can be used to guide the cable over the tractor cab, if the feed chute guide and cable reel are positioned so that the cable cannot be tensioned over the smaller rollers. Fairleads should be designed to prevent the cable from becoming wedged between the vertical and horizontal rollers.

6.09 The cable path inside the feed chute must be clean and free of burrs, sharp edges, stiffeners, or roughness. Welds must be smooth. Gussets on the divider gate in multiple chute designs must not interfere with the smooth passage of the cable. The cable must feed smoothly through the chute and must not exceed the minimum bending radius of the cable.

6.10 Before plowing begins, a means of communications must be established between the equipment operator and the supervisor monitoring the cable placement and route. The communications link must be able to override the equipment noise.

6.11 The starting point for the reel being plowed should be a splice pit or hole excavated to the proper depth. Sufficient slack should be reeled off at this point to reach a splice vehicle or splice location. The plow should start at the required depth from the splice pit.

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6.12 A figure-eight operation is necessary whenever the cable must be pulled through a pipe or conduit. This often occurs at road, river, bridge, or railroad crossings. A figure-eight operation requires that the cable be removed from the reel.

6.13 With the plow stopped, remove the cable from the plow’s chute. Do not raise the plow to the surface when the plow is not moving. Never back up the plow with a cable still in the chute. The cable to the rear of the feed chute must be excavated and slack pulled to prevent kinking the cable over the exit chute before raising the plow.

6.14 The cable remaining on the reel must be laid out in a large figure-eight configuration close to the pullthru location. Keep the cable as clean of debris as possible by not figure-eighting the cable onto sand or dirt which might adhere to the cable. Sand or dirt clinging to the cable can cause increased pulling tensions. Spreading out a sheet of polyethylene before beginning to figure-eight is one method that will help keep the cable reasonably clean. Figure-eighting onto clean pavement or grass will also help lower the possibility of a dirty cable.

6.15 With all the cable off the reel and laying on the ground in a figure-eight, attach the pulling line to the end of the cable. Begin the pull just as before by hand pulling the cable out of the figure-eight and feeding it into the pipe or conduit placed under the obstacle. Once the cable end has entered the pipe or conduit, the cable should be carefully guided from the figure-eight by hand. Radio communications must be maintained to ensure the pull can be quickly stopped if trouble develops with feeding the cable from the figure-eight.

6.16 An alternative to manually figure-eighting the cable off the reel before continuing the pull, is to use a figure-eight machine shown in Figure 5 below. Instead of pulling the cable from the reel and laying it on the ground, the cable is looped over the barrel of the figure-eight machine. Guided by a revolving arm and a series of rollers, the cable can be rapidly removed from the reel as it is wound around the machine’s drum.

6.17 Once the inside end of the cable is freed, it is connected to the pull line and the figure-eight machine reversed. The cable is now removed from the figure-eight machine’s drum as the end winch or capstan pulls the cable through the duct.

6.18 Company practices may prescribe a ripping pass to the depth of the cable burial along the entire route prior to plowing in operations to ensure the route is clear between start and stop locations. The ripping pass is made in the same direction as the cable plowing operation. The ripping pass ensures the route is clear before the fiber optic cable is loaded for plowing.

6.19 When plowing in fiber optic cable a warning tape is placed 12” below the surface of the ground directly above the cable. Both the cable and the warning tape are normally plowed in at the same time.

6.20 The plow movement should be started slowly and its speed gradually increased after all cable slack has been taken up from the delivery system. Plow attitude and depth should be changed gradually. Changes should be made only with the plow underway. Never raise the plow to the surface if the plow is not moving. The cable to the rear of the feed chute must be excavated and slack pulled to prevent kinking the cable over the exit chute before raising the plow. Never back up the plow with a cable still in the chute.

6.21 Each section, after it is plowed in, should be checked with an OTDR for possible increases in attenuation due to pressure or breaks.

6.22 Any cable ends left for future splicing should have their protective caps reinstalled and sealed with tape prior to burial.

7.0 TRENCHING

7.01 Trenching may be chosen to bury fiber optic cable in urban and suburban areas where the high number of obstacles (sidewalk and street crossings) makes plowing impractical.

7.02 The choice of location for trenching in fiber optic cable follows the same set of rules as for plowing. Buried cable should be located where there is the least possibility of it being disturbed. Along roads, the cable should be located so that future surfacing and widening operations will not extend over it. Care should be taken that the route selected will not interfere with the natural drainage of the area and so that the natural drainage does not result in the depth of cable coverage being affected.

7.03 Trenching is normally conducted by using machinery. In some areas however, it may be necessary to hand-dig the trench. For maximum speed, hand digging should be held to a minimum. For maximum trenching speed, never dig a deeper or wider trench than required. However, it is recommended that a 4” wide trench be considered the minimum practical width.

7.04 The backfilling material must conform to local regulations. Clean backfill should be placed from 9” to 12” from the bottom of the trench to provide protection for the cable. On private right-of-way (ROW), the earth should be mounded over the trench to compensate for future settling. The backfilled trench may,in some cases, be satisfactorily packed down by running the tractor or wheel of a truck along the trench line on top of the backfill. When possible the top should be filled with top soil. Rocks and debris should never be left in the bottom of the trench. Surface compression could cause cable damage in the future.

7.05 All permanent pavement and sidewalks must be restored to the satisfaction of proper authorities. When shrubs or other local vegetation must be disturbed it should be set aside and replaced when possible. Where lawn has been removed, it should be replaced or re-seeded.

7.06 Following the installation of the cable, each section should be checked with an OTDR for possible increases in attenuation due to pressure or breaks.

7.07 Any cable ends left for future splicing should have their protective caps reinstalled and sealed with tape prior to burial.

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Outside Plant Construction Guide

Introduction
Review Of Fiber Optic Technology. 
Project Preparation And Guidelines.
Underground Cable Construction.
Underground Cable Installation.
Aerial Cable Installation.
Completing Outside Cable Plant Installation.
  

Underground Cable Installation

Cable Pre-installation Procedures
 
The following items are key considerations in preparation for installing the fiber optic cable when the construction is ready for cable placement. Optical fiber cable should be carefully inspected when received and stored safely onside during storage before installation. All cables should be tested to ensure the cable was not damaged in shipment. All personnel handling cables, on reels, drums or spools (all three names are often used) or during installation, should be properly trained.
 
 
Installation Guidelines
 
Follow the cable manufacturer's recommendations as no one knows how to handle cable as well as the company which made it. Fiber optic cable is often custom-designed for the installation and the manufacturer may have specific instructions on its installation.
 
Check the cable length to make sure the cable being pulled is long enough for the planned cable run. Try to complete the installation in one pull if possible.  Prior to any installation, assess the route carefully to determine the methods of installation and obstacles likely to be encountered.
 
 
Pre-installation Cable Inspection
 

• Always wear protective gloves and safety boots (with steel toe caps) when handling reels – fiber optic cable spools are heavy.
• Check that the cable specified by the order to the supplier has been delivered. This includes cable type, number and types of fiber, length of cable, etc.
• Inspect the cable reel for signs of excessive weathering and/or damage.
• Reels must be transported or stored with their battens intact.
• Do not accept delivery of an optical fiber cable if the reel is visibly damaged.
• The plastic foil wrap must remain in place until cable placement.
• When removing the plastic foil wrap on the cable, do not use sharp tools that could potentially damage the cable jacket.
• Ensure that the cable reel bolts are all tightened.
• Verify that nails, bolts or screws on the inside surface of reel flanges are counter-sunk to avoid damage to the cable during placement.
• When ready to unspool the cable, place the cable reel in line with the intended direction of deployment, in order to prevent the cable from rubbing against the reel flange.
• Cable ends must always be sealed – using pre-formed or heat shrinkable end caps. Tape for sealing cable ends is considered unsuitable.
• Should the reel be rolled for some reason, always do so following the direction of the arrow.
• Reels on site, must be chocked to prevent them from moving or rolling.

 
 
 
Testing Fiber Optic Cable On The Reel
 
All optical fiber cables must be tested while on the reel, prior to deployment. Installing cable is a time-consuming and expensive process so it is important to ensure the cable is good before installation. If there is any sign of damage to the reel of fiber, all fibers may need to be tested. If the cable and reel look undamaged, a sampling of one fiber per buffer tube or ribbon may be adequate.
 

 
Pre-test the cable with a Visual Fault Locator (VFL) and/or an Optical Time-Domain Reflectometer (OTDR). The VFL will show if the fiber is continuous; the OTDR will confirm that the fiber still meets specifications and has no damage. A pigtail with a mechanical splice or a bare fiber adapter can be used to connect bare fibers to the VFL or OTDR.
 
Testing shall be done on fibers in one direction at nm, using a pulse width of 30ns since nm is the wavelength that shows stress losses in the fiber best. OTDR traces must be stored and an electronic copy submitted to the project manager.
 
 
Cable Handling
 
Twisting Cable
 
Do not twist the cable. Twisting the cable can stress the fibers.  Tension on the cable and pulling ropes can cause twisting. Use a swivel pulling eye to connect the pull rope to the cable to prevent pulling tension causing twisting forces on the cable.
 

 
Roll the cable off the spool instead of spinning it off the spool end to prevent  putting a twist in the cable for every turn on the spool. When laying cable out for a long pull, use a "figure-8" on the ground to prevent twisting. The figure 8 puts a half twist in on one side of the 8 and takes it out on the other, preventing twists.
 
 
Cable pay-off - over the top or from the bottom?
 

 
 
For most installers, over the top makes more sense. However, advocates of “from the bottom” when jetting / blowing cable do exist. Ultimately, faced with this choice, a contractor must determine which option is favored by the client.
 
 
Installing Swivel Pulling Eyes:
 
Cable manufacturers install special strength members, usually aramid yarn (Dupont Kevlar), for pulling. Fiber optic cable should only be pulled by these strength members unless the cable design allows pulling by the jacket. Any other method may put stress on the fibers and harm them. Swivel pulling eyes should be used to attach the pulling rope or tape to the cable to prevent cable twisting during the pull.
 
 

 

• Strip the cable jacket and cut back all fibers to the end of the jacket, leaving the aramid strength members only.
• Separate the aramid yarn into two bundles and loop it through the swivel eve in opposite directions.
• Tie knots in each bunch at the eye and loop the strength members back to the cable jacket.
• Tape the strength members along the jacket and up to the pulling eye.

Cables should not be pulled by the jacket unless it is specifically approved by the cable manufacturers and an approved cable grip, often called a “Kellems Grip,” is used. These grips are usually tied to the strength members also.
 

 

Pulling  Rope
 
Special fiber optic pulling tapes should be used if available. An 8mm polyester or polyaramid pull rope must to be used for optical fiber cables that are to be pulled in by hand. When using a hauling winch, a 12,5mm or thicker polyester or polyaramid rope should be used as hauling rope.
 
Ropes manufactured from nylon are not suitable as their stretch factor is too high and they can potentially cut into ducts. Steel hauling rope or galvanised wire must never be used as they can damage ducts and/or cables.
 
 
Duct Fill Ratios for Hauling        


 
Fill ratios are calculated by comparing the area of an inner diameter cross-section of the inner-duct to the outer diameter cross-section area of the fiber optic cable. For optimum hauling performance, it is recommended that the cable-to-duct diameter fill ratio does not exceed 65%, or as per cable spec sheet.
                                                                                                                        
 
How To "Figure 8" Cable for Intermediate Pulls in OSP Installations
 
On very long OSP runs, typically longer than approximately 2.5 miles or 4 kilometers, it may be necessary to use an automated fiber puller at intermediate point(s) for a continuous pull or pull from the middle out to both ends (midspan pull.) When laying loops of fiber on a surface during a pull, use “figure-8” loops to prevent twisting the cable. The figure 8 puts a half twist in on one side of the 8 and takes it out on the other, preventing twists.
 

 
 
Bend Radius
 
Do not exceed the cable bend radius. Fiber optic cable can be broken when kinked or bent too tightly, especially during pulling. If no specific recommendations are available from the cable manufacturer, the cable should not be pulled over a bend radius smaller than twenty (20) times the cable diameter.
 


After completion of the pull, the cable should not have any bend radius smaller than ten (10) times the cable diameter.
 
 
Pulling Tension
 
Excess pulling tension on a fiber optic cable can damage the fibers. Tension limits assume the fiber is being pulled properly using the cable strength members. Fiber optic cable should only be pulled by the cable strength members unless the cable design allows pulling by a grip on the jacket. An approved cable grip, often called a “Kellems Grip,” must be used. These grips are usually tied to the strength members also. Any other method may put stress on the fibers and harm them.
 
Do not exceed the maximum pulling tension rating. Consult the cable manufacturer and suppliers of conduit, innerduct, and cable lubricants for guidelines on tension ratings and lubricant use.
 
When pulling long lengths of cable in conduit or innerduct (up to approximately 3 miles or 5 kilometers in the outside plant, use proper cable lubricants but make certain the lubricant is compatible with the cable jacket.
 

 
If possible, use an automated puller with tension control and/or a breakaway pulling eye.  On very long OSP runs (farther than approximately 2.5 miles or 4 kilometers), midspan pulls are necessary. Pull from the middle out to both ends or use an automated fiber puller at intermediate point(s) for a continuous pull.
 
When laying loops of fiber on a surface during a pull, use “figure-8” loops to prevent twisting the cable.
 
 
 
Cable Pulling
 
Cables may be installed in ducts by pulling or blown in with special equipment. In this section we will cover both techniques, starting with cable pulling.
 
 
Pre-Installation Check
 
Prior to any hauling, the following must be confirmed:
·       Maximum allowable pulling tension for the cable being installed
·       Minimum allowable bending radius during installation for the cable
·       Minimum allowable bending radius after installation for the cable
·       Cable length required for each pull
·       Cable length required at the splicing locations

 
Duct Rodding
 
Rodding is used to clear the duct passage and install the pulling rope, using fiberglass pushrods. An alternative is to use air-blowing device.
 

 
·       Push the rod into the duct until the front end of the rod reaches the adjacent HH / MH.
·       Attach the pulling rope to the end of the rod at the adjacent HH / MH.
·       Next, pull the rod and pulling rope back through the duct

 
If the air pressure method is preferred, the pulling rope will be blown through the duct until it reaches the adjacent HH / MH.
 
 
Duct Testing and Cleaning
 
To clean the duct, attach a cylindrical brush or close-fitting mandrel and a second rope to one end of the installed pull rope and pull this through the duct.
 

 
If the cable sample or mandrel cannot pass through the duct, consult with the Client on whether to switch to an alternative duct or to repair the designated duct.
 
 
Midspan Pulls and Center Pulls
 
Pulling long cable runs may be difficult or impossible due to the friction between the cable and the duct. Lubrication helps but often does not completely resolve this issue. Guides are available from lubricant manufacturers to estimate the lengths possible to pull with proper lubrication. To assist with alleviating this issue, specialized techniques, such as center pulls or midspan-pulls can be used with either the manual pull or winch methods.
 
 
Midspan Pulls
 
Midspan pulls are used to provide a series of shorter, lower-tension pulls in one direction. In a midspan pull, the cable is pulled through duct to a handhole or manhole and the pull is continued until sufficient cable has been pulled for the rest of the length of the pull. Cable that is pulled is laid in a “figure 8” pattern on the ground
 

 
 
Center Pulls
 
In a center pull, the cable is placed in the middle of the pull and pulled off the spool in one direction until the end of the pull is reached. Then the cable is continued to be rolled off the reel into figured 8s on the ground. Then the figured 8 cable is flipped over and the end is pulled in the other direction. Ensure the cable is long enough for the entire pull before beginning the operation.
 
Communication, directed by a team leader with team members positioned at each HH / MH is essential, for that the pulling action to be achieved in a synchronized manner. Communication via the use of either cell phones or two-way radio is desirable.
 

 
 

• In a center pull operation, set up the cable reel near the center of the duct run to be pulled.
• To avoid cable rubbing against drum flanges keep the drum level - orientate the drum so that natural payoff direction is towards the pulling direction. Always use cable jacks or a cable trailer to lift the drum during the hauling process.
• Align the cable drum so that the cable can be routed from the top of the reel into the duct in as straight a path as possible.
• Make use of a flexible cable guide – placed between the HH / MH lid and duct to be used.
• Ensure that there is a swivel between the cable sock and the hauling rope.
• Pull the cable in one direction to the intended HH / MH.
• Uncoil the remaining cable in a figure-eight configuration.
• Flip-over the figure-eight so that the pulling-eye end of the cable is on top. As mentioned previously, this can be accomplished by 3-installers, one at each end of the eight, and one at the center.
• Pull the exposed end of the cable in the opposite direction to complete the pull. Hand-feeding of the cable paying off from the figure-eight is required.
• A warning marker (colored tape or similar material) may be attached to the pull-line at ± 10m in front of the pulling grip to alert observers at HHs / MHs that the cable is approaching.
• Place an end cap on all bare cable ends in HHs / MHs, to prevent moisture and/or dirt intrusion.

 
 
 
 
Pulling Tension
 
The maximum allowable pulling tension on fiber cable can vary and is dependent on the cable construction. The maximum tension for a particular cable can be found on the cable spec sheet.
Except for short runs or hand-pulls, tension must be monitored on the pull rope. The use of a breakaway swivel can be used to ensure that the maximum tension of the cable is not exceeded and should be used as a fail-safe rather than a primary means of monitoring tension.
 
Cable lubricant is recommended for most fiber optic cable pulls as a means of lowering pulling tension.
 
Pulling a new fiber optic cable over an existing one is never recommended due to the possibility of entanglement. Techniques exist to pull into ducts new ducts, especially the thin fiber ducts, that can allow safely adding cables to current conduits.
 
 
 
Access Build (Drops)
 
The final connection to a building, often called the drop, is unique. Drops are often fraught with deployment challenges including multiple tight bends and space constraints. The last phase of an installation is normally the most expensive and time consuming part of any overall fiber project. Careful planning and installation can mitigate the problems.


 
 
 
Introduction to Air-Assisted Installations (Blowing or Jetting)
 
Jetting or blowing (also sometimes referred to as floating) are two air-assisted cableinstallation techniques. Blowing cables does not really blow the cables in the duct, but consists of pushing the cable with a tractor mechanism while blowing compressed air into a preinstalled duct to float the cable in the duct and reduce friction. The air flow to helps “float” the cable inside the duct and reduces friction between the cable and the duct, making it possible to push the cable considerable distances in a duct. This technique provides an efficient, stress-free deployment in far greater distances than possible when pulling cable. Air-blown cable can be use in premises cabling installations as well as OSP.
 

 
Jetting and blowing differ in how pulling force is applied to the cable. Jetting uses a missile at the front end of the cable. A differential pressure across the missile head creates a pulling force on the cable. Blowing does not use a missile - instead, the pulling force on the cable is due to fluid drag of air rushing along the cable - this pulling force is distributed along the cable length. A mechanical pushing device is common in both methods.
 
 
     
 
It is common wisdom that hydraulics can give you higher forces than pneumatics. Mindful of this, a blowing machine with a pneumatic drive is recommended for cables up to 15mm in diameter and a blowing machine with a hydraulic drive is recommended for cables with a diameter in the range from 14 - 32mm.
 
The key parameters when installing fiber cable in ducts are blowing distance and time. to m is a typical blowing length. Typical installation speeds are 40-50 meters per minute under an air pressure of 10 bars (atmospheres). Most routes can be blown with a 10 bar supply.
 
Smaller diameter and lower weight cables make possible larger blowing distances, so blowing cable is perfect for the new generation of microcables. The maximum cable push force will decrease as the duct inside diameter increases, reducing the achievable blowing distances.
 
Blowing distance is directly related to the weight of cable, the pressure used and, friction from the inside of the microduct. Cable can be successfully blown further than 2-km when blowing heads are used in tandem.
 

 
Additional air can also be inserted further down, to achieve more distance.

 

 
 
Preparing For Blowing Cable
 
Survey the complete route prior to blowing in order to determine the location of HHs / MHs and distances between then. Determine where coupling of ducts are necessary. Survey the route for the accessibility of terrain for the use of the intermediate (mid-point) fiber blowing equipment. Identify specified ducts to be utilised. And as always, consider the accessibility of HHs / MHs to the splicing vehicles.
 
 
Jetting / Blowing The Right Cable
 
Choosing the right cable is extremely important for any installation. Strictly speaking, the purpose of the cable is to protect the fibers during installation and the service lifetime. Cables share some but not all characteristics and you need to ensure you install the cable type appropriate for the application.
 
Micro cables are designed with high-density polyethylene (HDPE) outer sheaths to minimize friction with the inner surface of micro ducts. They are also designed with the necessary stiffness properties to resist buckling forces and to negotiate changes in direction.
 
The cable on the drum must be covered until just prior to installation to protect the jacket from heat due to exposure to the sun and getting dirty.
 
 
Air-Assisted Installation Practices
 

 
Consider a very long link installation. Cable reels are typically supplied containing 4-km of cable. Mindful of this, reels are placed midway of a 4-km length. There’s plenty of evidence suggesting that the most efficient cable installation would involve two 2-km jetting shots (A to B followed by A to C). After jetting A to B, a ‘figure-8’ will be created at the midway point, to gain access to the end point of the cable previously on the drum. Next, the figure-8 end will be jetted in the other direction.
 
One ought to be able to install 4-km of cable in one placement of the cable drum and blowing equipment consisting of; 2-km of cable jetting in opposite directions with 2-km of "figure-eighting" in the center. Adding more air blowing to a microduct further down can also increase the achievable distance.  If at some point the cable movement slows down during the blowing process, then instead of taking a 2-km run, the jetting could be reduced to only 1-km. This would call for a second ‘figure-8’ to be made at the 1-km mark.
 
 
 
Duct Integrity Testing (DIT)
 
All team members MUST wear eye protection during DIT testing as small particles can be blown out of ducts through the holes in the DIT catcher.
 
Air Test

• Fit a DIT catcher on the far side and equip personnel with two-way radios.
• Allow the air to flow through duct for at least one minute, to remove all loose particles and/or moisture.
• Now proceed with the sponge test.

 
Foam Sponge Test - cleaning the duct:

• A sponge is typically 100mm in length and 2 x the duct ID.
• Wet the sponge slightly with blowing lubricant.
• Place the tight-fitting foam sponge inside the microduct.
• At a pressure of 10bars, blow the sponge through the microduct.
• If excess water or dirt exits the microduct, repeat the process.

 
Mandrill Test
 
One can test ducts for bends, kinks or blockages that may hinder blowing cable by doing a mandrel test to see if one can blow a sample down the duct.

• The sponge test MUST precede this test - a mandrill can damage a dirty duct.
• Use a 40mm (1.6 inch) long mandrill made from Nylon or Teflon, or a 3m length of cable.
• Use no more than 3-bar of pressure to blow-though the mandrill.
• The mandrill OD, must be no more than 85% of the microduct ID.
• At the receiving end, a DIT catcher must be used.
• Note that a flying shuttle can cause injury and/or damage!
• Always inspect the condition of the emerged mandrill, visible grooves is an indication of duct indents.

 
Pressure Test
 
A pressure test checks for coupler leaks or microduct punctures that could affect blowing cable.

• Fit a high-pressure end-cap to the duct under test on the far-side.
• Gradually build the pressure up to 10 bars (atmospheres.)
• Test all coupling used for this test for leaks, using soap, water and a sponge.
• Connect the air feed and leave this open until the pressure in duct stabilizes at 10 bars.
• Close the air valve on the test assembly and monitor the pressure gauge for 5min.
• Losing 1 bar in 5min is acceptable – any leak greater than that, must be found and fixed.

 
If the duct fails DIT tests, consult with the relevant authority on whether to use an alternative duct or to repair of the designated duct.
 
 
Micro Duct Fill Ratio
 
For optimum jetting / blowing performance, ensure that your cable-to-duct diameter fill ratio does not exceed 76%. This is determined and provided by the microduct supplier. It is wise to always verify this by checking the provided spec sheet.
 
 
Cable Blowing Lubricants
 
Adding a small amount of lubricant to a tight-fitting foam carrier (sponge) before blowing it through the duct, will provide an open and lubricated pathway. It is argued to give better results compared to coating both the duct and cable with lubricant. Odd, huh? Let me try to explain. Lubricant on a cable jacket apparently makes it too "slippery" for optimal laminar-flow jetting.
 

 
Let’s not forget that the air "pushes" on the jacket through friction. A too low friction jacket will not easily be pushed by air. Normally, as little as 0.25 litre of lubricant is required to coat 2km of cable.
 
 
Suggested Air-Assisted Installation Practices       
 

• It is desirable to blow downhill wherever possible.                                  
• DIT results must be available prior to blowing the cable.

• Always measure the cable diameter before jetting, to select the correct spacers for the blowing machine. The cable must lie snug in the V-groove between the drive rollers.      
• To ensure that the cable is not prone to slipping, push and pull the cable through the machine by hand a few times to ensure that the cable is seated properly in the drive rollers. 
• The cable must always enter the jetting machine under no tension and in a straight line.
• The cable must be clean as it enters the blowing equipment to allow for effective gripping of the driving wheels. Contamination of the cable will cause unwanted friction and result in a reduced blowing distance.

• Monitor the speed and torque of the blowing machine as the cable is blown to ensure that the cable jacket is not damaged by the driving wheels.                                                                                   
• One person must control the cable reel and be prepared for emergency stops.
• Always note the meter reading on the cable and zero the blowing machine distance meter, prior to blowing.
• Always establish two-way communication during the fiber deployment process at crucial points along the cable route.
• The blowing machine should have an automatic shut-off feature that controls the push force applied to the cable. With this feature, cable and duct damage can be prevented should the cable stop abruptly within the micro duct.
• Ensure that when connecting the transportation duct to the blowing machine, it is not entangled with the new or existing cable/s.
• The ‘figure-8’ must be laid on a ground sheet and care must be taken to ensure that the cable does not touch the ground as it is fed into the machine.
• To protect the end of the cable and also to guide the cable along its desired route, a bullet must be used.
• As mentioned, blowing lubricant reduces the frictional drag on both cable and in the duct thus increasing the achievable distance.
• To ensure that the blowing equipment remains in good working condition - after a week of continuous blowing - machine maintenance must be performed.

 
Management of Cable Slack
 
When handling cable, always wear; a protective overall, gloves and safety boots.
 
Never exceed the recommended cable bend radius:

• 10 x Cable OD - No Tension (installed)
• 20 x Cable OD -Under Tension(being installed)

 

 
What is the minimum bend radius of your microducts?
Formula:  Radius min =10 x OD
Therefore, if you have microduct has a OD of 10mm, your Radius min =100mm

 

• A total length of 17m (15m for slack and 2m for splicing) of cable slack is traditionally required in a HH or MH housing a splice enclosure. Be sure to consider the accessibility of HHs / MHs to splicing vehicles as additional length of duct may be needed.
• Install slack brackets on HH / MH walls to secure cables. The slack in the HH or MH needs to be tied together using a tie wrap or PVC tape at 1m intervals. The fiber cable slack inside the HH / MH must be coiled in a ‘clock-wise’ direction with minimal back tension.
• Ensure that the slack of one splice closure does not become inter-twined with the slack of other splice closures in the HH / MH.
• Bundle cables together in groups of relevance.
• Do not route cables in such a manner that they block ducts.
• Used ducts must be sealed between cable and duct.
• Cable slack typically adds 2% to the overall distance. Thus a 100-km link is likely to contain as much as ± 102 Km’s of cable.

 
Figure-8-ing
 
The preferred size of a figure-8 is about 5m in length, with each loop about 2.5m in diameter. To start with, set up two traffic cones 5m apart – then pay the cable off the top of the reel and loosely weave it around the cones in a figure-8 pattern - on top of a groundsheet. Large relaxed loops will help prevent the cable from becoming entangled.
 




 
Continue to figure-8 the cable until the remainder of the reel is played off.
 
In order to pull from the figure-8 - it is necessary to flip it over, a task that requires a minimum of three people -one at the centerand one at each end. The required cable end will now be at the top of the figure-8.
 
 
Special Micro Duct Tools and Accessories
 
Acceptable Cable Drum Jacks Must Be Used

 
 

Tools
Ensure that installers are fully educated on the proper use and operation of any tool before starting a job.
 


It is essential to always use the prescribed cutting tools to produce a clean and straight cut to a microduct, before inserting a coupler.

 
Bullet
Fixed to the end of the fiber cable before blowing starts, to guide the cable through the microduct.
 


Sponge
Used for removing dirt and/or moisture from a microduct.




Shuttle
Used to check the microduct for bends, kinks or blockages.




Caps & Plugs
Used for the permanent or temporarily sealing of unused microducts to prevent water and dust from getting into ducts.



 
Use only the prescribed connectors and end-plugs.

Couplers
Used for the air-tight coupling of microducts.
 
 
 

De-bur Tool
Allows for one to round-off a microduct after cutting - before adding a coupler, to produce an air-tight connection.



Locking Tool
Used to firmly lock the microduct into a connector.



Cable Carriers
Parachutes capture the air within a duct, tugging along with it the cable. In the absence of air pressure, they collapse allowing for easy pullback. An alternative is to use an Inflatable Carrier.
 
 

 
 Inflatable Carrier





 
 
(C) The Fiber Optic Association Inc.
 
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