How to Choose the Best Winch for Underground Cable Installation – Expert Tips from Powerhowse Electric
A Q & A with Paul Emerson from Powerhowse Electric, New Zealand about winch selection factors and pulling tension in cable pulling/hauling.
Understanding Winch Selection for Underground Cable Pulls
Polywater® is often asked by its customers about how to better install underground cable. Some of these queries involve selection of the hardware and materials that will make the installation safer and more efficient. Frequent questions involve what materials and winches should be used for a particular cable installation project. Since Polywater is not a winch technology manufacturer, we often rely on our colleagues that are experts in cable hauling technologies and operation. To address the common question of “What is the best winch for underground cable-induct-installation?” we asked Paul Emerson of Powerhowse Electric cable hauling and handling of New Zealand to weigh in.
Meet the Expert: Paul Emerson of Powerhowse Electric
Polywater
Paul, could you give us a brief introduction of Powerhowse Electric and the business you’re in?
Paul Emerson
Certainly. Powerhowse Electric was started about 53 years ago by a guy named Bill Howse. The primary business at that time was making switchboards. Twenty years after the founding, he was approached by a cable hauling company to see if he could make some rollers for a cable installation. He then developed rollers and capstan winches for cable hauling for the electrical industry. These systems have been manufactured over the last 35 years.
Today, Powerhowse specializes in the sale and hire of cable hauling equipment along with materials used to facilitate the installation of cables.
We have three main parts of our business. We manufacture cable hauling equipment here in New Zealand. We have a hire department where we send out a lot of equipment around the country for power projects. And we distribute materials and machinery used in cable installation for companies like Polywater.
New Zealand is a unique market. We have 27 power authorities and a total population of about 5 million. So, we work with everybody in the power sector in New Zealand: power utilities, engineering consultants, civil contractors, hauling contractors and wholesalers.
Common Questions Installers Ask About Cable Hauling Equipment
Polywater
Tell us about some of the common questions you receive from customers about cable hauling equipment, like what type of winch to use and so forth.
Paul
It’s more the other way around. Customers come to us and say, “We’ve got a project.” Then, we will ask a list of questions like, “How big or heavy is your drum? What size cable is it? How heavy is your cable? How many cables are you installing? How many bends in your duct?”
After we get confirmation of their specifics, we’ll go back and make a recommendation. We’ll say, “We expect tensions of X based on the information you have given us. And with that we recommend you use a five-ton winch that we have available, or a three-ton trailerized winch.” The equipment recommendations really depend on the project specifics.
Project-Specific Winch Recommendations: What Factors Matter Most?
Polywater
At what stage does the cable installation contractor get involved in specifying winches and the equipment that is going to be used for a particular project?
Paul
At the beginning. On one side, if the project is with a power utility, the contractor will have a good understanding of what type of cable they’re installing. So, if they’re putting a 220 kV line in the ground, the installation contractor will know that they’re going to need something serious. They need to plan for it, and they probably get specialist equipment built.
On the other side, which is your subdivisions, it’s a bit more relaxed because there’s plenty of equipment available to do that sort of project. So, they will have a look at it and say yes, I can only put two kilo-newtons on the nose or 20 kilo-newtons (kN) on the nose on the cable. And then they understand that: “I can use a winch from Powerhowse or we’ve got our own winch here that we can use.”
| Related Content: Planning Underground Cable-in-Conduit Pulls: Defining a Safety Factor to Maximize Cable Lifespan |
The Role of Cable Tension in Winch Selection
Polywater
You mentioned tension. How does the issue of tension enter into the selection process of a winch?
Paul
Every cable has maximum tension and sidewall bearing pressure that it can withstand without experiencing damage. Pulling a cable over rollers, or into duct, creates friction. Friction creates tension on the cable while it is pulled. If the maximum tension of the cable is surpassed, damage can occur. So, the selection of the winch for a particular job will be based on what tensions are expected to be generated on the cable and what measures can be taken to ensure that the tension does not get too high.
How Duct Bends Affect Cable Tension and Winch Size
Polywater
What are some of the factors that create more tension on the cable that can impact the size and use of a winch?
Paul
Bends create high tensions and sidewall bearing pressure that can exceed the limits of the cable. You need to do something to control the sidewall pressure, so the cable isn’t crushed. The tension on the cable generated in every duct bend grows exponentially which causes the sidewall pressure to grow as well.
Synchronizing Winches with Cable Pushers: Why It Matters
One way to control sidewall bearing pressure is to reduce incoming tension into the bend. A drum drive or cable pusher in combination with the winch can be used to unwind the cable from the drum and push and pull the cable through the bend at a higher velocity. The drum drive will relieve back tension on the cable to reduce the incoming tension to the bend. The drive or pusher and the winch must be synchronized so as not to work against each other. This means that the speed of the winch must have the capability to be finely adjusted to match the payout rate of the cable from the drum.
Anchoring Techniques to Ensure Safe Cable Pulling Operations
Polywater
Are there any other issues that should be discussed with the cable installer when selecting a winch?
Paul
There are many factors that need to be considered. Any time you pull cable, you put something under tension. So, for health and safety measures, anchoring is an important part of that equation.
To anchor the winch, you want an anchor weight twice that of the tension force on the cable. So, if it’s a trailerized winch with an anchor of five tons, the maximum tension that could be hauled would 2.5 tons. If you’re hauling three tons, you would need something like a six-ton digger to anchor it. Then, you chain your winch to the digger and put the bucket down on the digger to act as an anchor. You always want to anchor your winch to create a safety margin to protect the cable and workers.
| Related Content: What’s the Best Way to Lubricate Cable When Installing into Conduit or Duct? |
Best Practices for Calculating Safe Winch Pulling Loads
Polywater
Are there any guidelines or best practices that you use to determine how much power you will need in a specific cable pull?
Paul
A common practice if you’re installing cable in underground ducts is to try to pull the cable at 3 to 1 ratio of the break working load. If your equipment break working load was 1,500 kgs you would need to target a maximum of 500 kgs of tension to have a Safe working Load (SWL). Then you know that would be the maximum you would put on the winch. For overhead the safe working load is 5 to 1. If it’s 1,500 kgs swivel, only 300 kgs of tension should be placed on the winch.
Solving the Biggest Challenges in Underground Cable Installation Projects
Polywater
What would you say is the biggest challenge in setting up a cable pull? What’s the number one pain point?
Paul
There are usually more than one pain point in most installations. The main challenge is coordination between the different parties involved in the installation. The design engineer might want to end an installation in a location that, unknown to him, is not accessible by the winch. The civil contractor installing the conduit might forget to prove it once it is installed to create problems later for the cable installer. The cable installer might not know how to install multiple cables into a single duct to create problems for the joiner contractor. The lack of coordination can cause delays and cost overruns of the project.
Final Thoughts on Winch Use: Physics, Precision, and Safety
Polywater
Are there any final thoughts that you would like to share about winch selection or cable hauling?
Paul
It’s all about controlling tension, right? The winch plays an important role in this control. The winch can be used to control tension generation around bends. It can be synchronized with a drum drive or cable pusher to reduce back tension on the cable. Reduce the tension as much as possible, so you have a safe cable haul and so you’re not damaging the asset or the cable.
“A winch is a winch.” It’s there to do a job, and you know it’s unforgiving. You know, if you put a five-ton winch on a one kV cable and pull at full throttle, around six bends because you think it’s going to be hard to get through, you’re just going to destroy the cable. But if you understand how to use the winch properly, it will make the job much easier. It’s not rocket science, but it is physics.
Polywater
Paul, we want to thank you for the insights you have provided us today. Your expertise and experience in underground cable installation will be very helpful for many of our customers. Especially, those who rely on the optimized performance of their pulling winches.
Paul
Thank you. It was a pleasure talking with you.
