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There’s a direct and proportional relationship between the reliability of utility poles and the reliability of our grid. It looks something like this:
⇑ pole reliability = ⇑ grid reliability
The grid relies on dependable poles to bring reliable services. With millions of poles supporting our power grid, effective inspection programs and reliable pole inspection routines and software are essential for safety and reliability across the grid.
The Utility Pole Inspection Process
Inspections demand more than just a cursory once-over, and across the country pole owners and utilities are required to inspect their poles at regular intervals. Those intervals can vary by state because decay varies by location—areas with extremely high humidity are more susceptible to rot than low-humidity locations. (The USDA has a really helpful map showing this. See page 5).
Whatever the frequency of the cycle, most inspections follow a similar overall process:
Assessment, Planning, and Sampling
Teams review the pole records and age data they have on hand and prioritize areas based on age, environment, and previous issues. It’s really helpful when teams can see data from vegetation management crews and other projects to assess priority levels.
From there, the inspection team pulls a sampling of poles to inspect (this number is often also regulated by the state).
Getting into the Field
With the jobs organized and the samples mapped out, inspection crews head out into the field to actually inspect. There are different inspection methods each with their own pros and cons (more on this later). Inspectors have to examine both the external and internal state of the pole to maintain pole inspection standards for safety.
Analyze and Engineer
Using the inspection info collected in the field, an engineering team analyzes the data to figure out if poles pass or fail inspection. Poles generally are categorized as:
Serviceable: Most of the wood is completely sound, and early stages of decay haven’t reduced the pole strength. Broken ground wires or loose guy wires can be repaired.
Rejected: Decay, insect damage, or mechanical failure have reduced the structural integrity at the ground line, and the pole is no longer safe. (Or, the pole has a split top, cracking, etc that disqualifies it).
Reinforcement/Replacement: Rejected poles can sometimes be reinforced at the groundline to help support the utility pole using c-trusses, c-wrap, etc. If the pole can’t be reinforced, it’ll have to be replaced.
Remediation
After engineering is complete and issues are remediated, all the utility pole inspection data is compiled for future records and reporting. Pole inspection software helps automate the reporting process and helps teams analyze and track trends over time.
Maintaining Pole Standards with the Right Inspection Method
There are different methods of inspecting poles to meet safety and reliability standards, each with its own pros and cons.
Visual Inspection:
This is the first step for most methods and has the lowest assurance of accuracy. Looking at the pole won’t tell you if the majority of it is defective, since decay generally happens underground. But this step is still crucial to assess the above-ground conditions—the cross arm, hardware, and other physical features.
Pros:
Low barrier to inspection
Doesn’t introduce any future damage
Cons:
Doesn’t give any real confidence in the true condition of the pole
Only a very small piece of the picture
Sounding:
Sounding techniques use a hammer to strike the pole surface and listen to the resulting sounds. Hollow sounds can indicate internal voids or decay pockets not visible from the outside.
Sounding is another non-destructive test that's quick to perform. However, it takes experience to interpret the sounds accurately, and results can be subjective. Sounding works best as a complement to visual inspections.
Pros:
Non-destructive
Rapid testing
Cons:
Hard to interpret/subjective
Boring:
For a more thorough assessment, inspectors may use a drill or increment borer to take core samples from the pole. The samples are examined for decay and used to estimate remaining pole strength.
Drilling provides valuable data on internal pole conditions but damages the pole in the process. Core samples are also localized, so it's possible to miss pockets of decay elsewhere in the pole.
Pros:
More detailed and thorough
More trustworthy results
Cons:
Damages the pole
Can miss results
Excavation:
Some types of decay start underground and work their way up the pole. That's where excavation comes in. Inspectors dig around the pole base to examine the buried portions for signs of decay or insect activity.
Excavation is a valuable part of a complete pole inspection, but it is time-consuming and must be done carefully to avoid damaging the pole. Soil may need to be treated after excavation to prevent future decay.
Pros:
Usually provides a higher degree of certainty about the condition
More detailed results
Cons:
Far more time-consuming and demanding
May damage the pole in the process
Which method best meets pole inspection standards? That depends on a couple of different factors like:
Pole species and class
Age
Climate
Resources allocated
For example, a younger pole may only need a visual inspection and sounding inspection, since not enough time has passed to make decay a real concern. (But have there been intense storms? Unexpected humidity? That could affect decay too!)
Southern pines are pretty popular in our home state of PA, and because these poles are more susceptible to external decay below the groundline, excavation may be the best inspection method, or a combo of all might be necessary to make sure a pole is safe.
Inspection practices that include multiple testing methods help provide the most complete picture of the pole. However, there’s no rulebook for the right method, and utilities' best approach to find that delicate balance between inspection costs and the risks of pole failures.
Reject, Remediate, or Replace?
One of the hardest parts (after the inspection itself) is trying to address failed poles. No one wants to pay for and coordinate an expensive pole replacement process. Too often poles get slotted for replacement because they’re a liability, but then create more of a liability when the attachment transfer process lags and turns into a doublewood issue.
When is a replacement really necessary? When will other remediations suffice? We’re not just talking about financial costs—we’re weighing the safety of homes and businesses that rely on the grid!
When it comes to addressing failures, the right engineering software and process can help ease some of the pain and give confidence in the best options. With integrated pole loading analysis and 3D view in Katapult Pro, designers can view loading results in real-time to make sure remediations are safe and secure. Engineering designs can create complete construction packages for faster fixes, helping office teams communicate clearly and effectively with construction crews.
For more information about Katapult Pro for pole inspections, or to talk to our engineering team about our pole inspection services, give us a shout at hello@katapultengineering.com!