Release #5570 Agency Contact: Russ Risko AdSpeak Marketing Communications 215.343.6565

New, Portable, Hydraulically Limited Cable Puller Passes Rugged 16,000-Foot Fiber Cable Field Test

By: Javier Varela, Application Engineer & Rocio Shariatpanahi, SCADA Developer CITI LCC, Charlotte, N.C.

In the late Summer of 2001, CITI, LLC, Charlotte, N.C., was awarded a project by the Richmond County Water Authority to expand its capacity.

Part of the project was to run the fiber optic cables used in the control and monitoring system for the pumping station. Richmond County is located near Rockingham NC - about 60 miles east of Charlotte, and the intake facility is located next to the Beebe River.

CITI provides networking services, primarily. We do everything from laying the cable to the terminations to the installation and testing of the network itself. But we had been involved with the original bid to design the cable-placing project, as the engineers for one of the groups that did the research on the best way to run the cable. So we decided bid on the actual project as well. We've run fiber cable before, but usually in much shorter lengths in rigid conduit, and mostly indoors. But this project called for the outside placement of 16,300 continuous feet of fiber optic cable. For assignments like this we usually call on an electrical contractor. But we didn't this time because we wanted to see if we could do it ourselves.

Getting Started

Key to completing the job was the usual: doing the best job possible at the least possible cost. So, we began to line up the equipment.

The job itself called for placing 16,300 feet of fiber optic cable - more than three miles! -- from an intake facility, or a pump station, to the water treatment plant.

First and foremost was a means of moving the cable across the terrain. While we could have used air compressors to blow the fiber through the ductwork, it's a very expensive alternative. And we might also have purchased the fiber already in the ducts, but you can only get it in maximum lengths of 1000 feet, which would require splices at each connection. And that's what we were trying to avoid (because of signal loss restrictions). We were limited to a single fusion splice, set at the 8100-foot mark, or half way across the run. Usually this gives only a 0.01 db loss across the splice.

So in the end there was really no option to using a capstan unit for fiber optic cable. You have to have a specific bending radius, depending on the size of the cable, and you have to use a specific size of capstan gauged to that bending radius.

A Web search for cable pullers led us to the website for GMP Tools. Ted Clemens, Director of Sales at GMP, told us that GMP had just introduced a portable, hydraulically limited cable puller that would be ideal for this application. What makes the GMP puller unique, he said, is that you can take it to the jobsite, take it off the truck and bring it right to the pulling site. It is well designed for small contractors like us, who don't own or have access to a large utility or line vehicle with a mounted cable-pulling wench and capstan drive. All the new GMP puller requires is a pickup truck and a power source.

And while a lot of products can motivate this device, Clemens suggested a Trac Horse, from Stanley Hydraulic Tools, because of the remote and rugged terrain we would be facing. The Trac Horse is an all-terrain mobile hydraulic power unit capable of powering over 90 hand-held hydraulic tools. Its hydraulic output matches the requirement of the GMP cable puller, with a 1000-pound payload, but just a 4-pound per square inch pound footprint - the equivalent horsepower output to a hundred-cfm air compressor.

Typically, this installation would be performed with a $150,000 line truck with a front-mounted wench, and a 180-cfm air compressor at about $12,000. But the GMP Cable Puller and the Stanley Trac Horse cost around $13,000 each, so the cost-benefits were a 'no-brainer.'

Murphy's Law Kicks In

After GMP engineers Kevin Delaney and Russ Hackius, along with Steve Jones from Stanley Hydraulic Tools, spent some time with us showing us how to set up and use the equipment, we were on our own.

And, as usual, the project looked great on paper, but once we got into the field, it was a totally different story.

To begin with, the terrain was rougher on land than it was on paper. There were some very significant hills to go up and over, and a couple of creeks to traverse. And the vehicles we had - even with four-wheel drive - were not going to be able to cross some areas. We used two Ford 4W-Drive standard pickup trucks (an F350 and X150 dual cab, short bed). But there were some places that were not accessible to even these vehicles. One gulley, for example, had too much slope and depth to get a vehicle across it.

The Trac Horse is basically driven by tank treads that can get you through some rough terrain. We were able to load the GMP cable puller components into the bed of the Trac Horse and walk it out to the location. Then, we set-up the puller and used the hydraulics on the Trac Horse to operate it.

And we took the GMP Cable Puller and the Stanley Trac Horse where others dare not go. There were two creeks that needed to be crossed, for example. We drove around the first, with the Trac Horse and cable puller loaded in the pickup bed. With the second, the water was less than a foot deep, so we crossed it directly with the cable puller loaded in the Trac Horse bed. We did this on September 11th, and the Trac Horse was suddenly pulled out and sent to assist in the rescue efforts resulting from that day's tragic events. After that, we utilized a Stanley portable hydraulic power unit mounted on the pickup.

Murphy's Law was still in charge. We estimated the job at one week; it took us three weeks. The problem was not equipment related, but was that each half of the ductwork for the 16,000 foot run was placed by different contractors, and not both followed the same procedures. The first half, by the contractor's subcontractor, was run over comparatively smooth terrain, but wasn't precisely straight. This caused increased pull friction on the cable. The contractor's half was done correctly. And even though it was laid over uneven terrain, it was an easier pull. In fact, we pulled that last half of the run in the final two days.

How We Did It

Pulling 8,100 feet of fiber optic cable in two days, however, was more a function of the equipment than the ductwork. Aside from the rugged terrain, there were other obstacles to be addressed. The first were the dynamics of the operation. We were to place 16,300 feet of 18-strand fiber optic cable with a single splice halfway between the run.

First the ductwork was set in place. The round Silacore ducts (Duraline) measured by 2.5 inches in diameter. The inside is both ribbed and lubricated to reduce surface tension on the delicate cable being pulled through it coated. Even so, a polywater (a polymer-based lubrication) is fed into the duct to make it slick and easier to pull, further reducing the pulling friction.

The duct also arrives with "pull tape" already set in its interior. This allows you to attached the cable to the tape at one end of the duct, then pull at the other until the cable has passed continuously through the ductwork. With the capstan turning clockwise, you put the pull tape around it, and turn it on. The capstan starts pulling the fiber from the other end.

There are limitations on the amount of pull force you can apply, which are determined by the fiber optic cable. While the pull tape in the duct we used has a maximum pull strength of 1250 pounds, the cable we were running has a pull force of just 600 pounds.

Of course, you can't pull fiber optic cable in a single run of 16,000 feet at 600 pounds. So we broke it up to smaller bites. Pull boxes (drop boxes) were placed about every 3000 feet. But we found out that since the duct was not completely straight over the first 8,100 feet, we had to actually go every 1000 - 2000 feet (depending on the angle and the terrain) to be able to pull the cable. So we actually had to setup and dismantle the cable puller nearly three times what we anticipated.

What we ended up doing is opening the ducts in some key areas (where terrain demanded it?) when there was too much pull friction. We opened the duct to pull the cable, then re-sealed the duct with an insulated sleeve, or plastic coupling.

Pulling It All Together

Because we now had to move the cable puller and power pack every 1,000 feet. Portability became a major issue. We were able to move it from one location to another very quickly. From the time we broke it down and put it on the truck to the time we finished the setup at the next location averaged just 10-12 minutes. And what took the longest time was actually lifting and carrying the hydraulic motor - about 150-175 pounds. The hydraulic connections are plainly labeled for quick assembly.

At first, we were taking the power pack out of the truck and placing it next to the capstan; later we secured the power pack to the truck so it was never moved with the hoses were in front so we could connect it. This further reduced setup time.

Once setup at the pull box, calibration and control came into play.

The foot control allowed us to apply as much force as we as needed. We could gradually increase or decrease the feed without exceeding it's calibration … we couldn't exceed 600 pounds of force which is limited by the cable. We could increase or decrease the cable feed as needed. When we were figure-8'ing cable, for example, we were able to slow down the cable feed without having to stop. Sometimes we encountered major "forces," and we were able to slow down a little bit, and that was very convenient.

To calibrate the puller, we did a dry test at each stop - that is, we ran it without having any load in the motor you press the foot pedal and make sure the turning capstan is turning free, you can load the motor. And at that point you are setup. From the time you connect the hoses, through calibration, to the time you start, on the average was between 10-12 minutes.

As you go from pull box to pull box, you have to pull the cable to that station in a figure-eight. You cannot bend the fiber past a certain angle, or it will break, and this determines the "size" of the figure-8. In this case it was 6-feet in diameter.

As the cable comes out of the duct, with the polymer coating on it, it is very wet and slippery. We have to clean it (by hand, with rags) and figure-8 it at the same time.

This machine is capable of pulling cable at 300-feet/minute. This has to be cleaned and figure-8'ed maintaining that pace, or you'd be stopping and going all the time. If you are moving 8,000 feet of cable a length of 1000 feet, you have to feed all 8,000, and leave 1000 in the duct. The other 7000 feet has to be reeled (on the figure 8).

You try to handle the f/o cable as little as possible. You want to make the turn and leave the fiber in the duct without having so many people handle it.